Determining small molecule-target protein interaction is essential for the chemical proteomics. One of the most important keys to explore biological system in chemical proteomics field is finding first-class molecular tools. Chemical probes can provide great spatiotemporal control to elucidate biological functions of proteins as well as for interrogating biological pathways. The invention of bioorthogonal chemistry has revolutionized the field of chemical biology by providing superior chemical tools and has been widely used for investigating the dynamics and function of biomolecules in live condition. Among 20 different bioorthogonal reactions, tetrazine ligation has been spotlighted as the most advanced bioorthogonal chemistry because of their extremely faster kinetics and higher specificity than others. Therefore, tetrazine ligation has a tremendous potential to enhance the proteomic research. This review highlights the current status of tetrazine ligation reaction as a molecular tool for the chemical

Determining small molecule-target protein interaction is essential for the chemical proteomics. One of the most important keys to explore biological system in chemical proteomics field is finding first-class molecular tools. Chemical probes can provide great spatiotemporal control to elucidate biological functions of proteins as well as for interrogating biological pathways. The invention of bioorthogonal chemistry has revolutionized the field of chemical biology by providing superior chemical tools and has been widely used for investigating the dynamics and function of biomolecules in live condition. Among 20 different bioorthogonal reactions, tetrazine ligation has been spotlighted as the most advanced bioorthogonal chemistry because of their extremely faster kinetics and higher specificity than others. Therefore, tetrazine ligation has a tremendous potential to enhance the proteomic research. This review highlights the current status of tetrazine ligation reaction as a molecular tool for the chemical

TY - JOUR. T1 - Carbene and silicon routes as methods for the generation and dipolar cycloaddition reactions of methyl nitrile ylide. AU - Padwa, Albert. AU - Gasdaska, John R.. AU - Tomas, Miguel. AU - Turro, Nicholas J.. AU - Cha, Yuan. AU - Gould, Ian. PY - 1986. Y1 - 1986. N2 - Methyl nitrile ylide was generated by both a photochemical and desilylation route and has been characterized by UV spectroscopy and by its kinetic and cycloaddition behavior. The dipole is formed by the addition of singlet methylene to acetonitrile and shows a strong transient absorption at 280 nm which is quenched by the addition of standard dipolarophiles. The relative rates of formation of 1,3-dipolar adducts and the relative rates of quenching of the transient absorption are in excellent agreement. Generation of the dipole from a silylthioimidate followed by dipolar cycloaddition also gave rise to related cycloadducts. The ratio of cycloadducts obtained from an unsymmetrically substituted dipolarophile was found ...

The 1,3-dipolar cycloaddition reaction of cyclopropanes and nitrones to give tetrahydro-1,2-oxazine has been studied with density functional theory calculations at the B3LYP/6-31+G(d,p) level of theory. Realistic substituents were modelled including those at the 2-, 3-, 4-, and 6-positions of the final oxazine ring product. The strained σ bond of the cyclopropane was found to play the role of an alkene in a conventional [3+2] dipolar cycloaddition. Two distinct, but similar, reaction mechanisms were found â€" an asymmetric concerted pathway and a stepwise zwitterionic pathway. The reaction barriers of the two pathways were nearly identical, differing by less than ~1 kcal/mol, no matter what the substituents were. The effect of a Lewis acid catalyst was examined and found to have a very large effect on the calculated barriers through coordination to the carbonyl oxygen atoms of the diester substituents on the cyclopropane. The reaction barrier was found to decrease by as much as ~19 ...

If you have a question about this talk, please contact .. The development of bioorthogonal reactions made it possible to visualize and study biomolecules in their native cellular context and contributed to advanced targeted drug delivery strategies. In our research group we are interested in developing novel bioorthogonal chemistry and apply this in the targeting of specific cell types. We recently added non-strained, highly soluble and stable vinylboronic acids (VBA) as reactants to the bioorthogonal toolbox which react with tetrazines in an inverse-electron demand Diels-Alder reaction. We have observed exceptional high reaction rates between non-strained vinylboronic acids (VBAs) and dipyridyl tetrazines relative to that of tetrazines lacking such dative coordinating ligand. As VBAs are mild Lewis acids, we hypothesize that coordination of the pyridyl to the boronic acid promotes the tetrazine ligation. In the current presentation, we explore the scope and molecular origins of the observed VBA ...

Taking the 266 nm excited pyrimidine (uracil or thymine) with cyclopentene as model reaction systems, we have examined the photoproduct formation dynamics from the [2 + 2] photocycloaddition reactions of triplet pyrimidines in solution and provided mechanistic insights into this important DNA photodamage reaction. By combining two compliment methods of nanosecond time-resolved transient IR and UV-vis laser flash-photolysis spectroscopy, the photoproduct formation dynamics as well as the triplet quenching kinetics are measured. Characteristic IR absorption bands due to photoproduct formation have been observed and product quantum yields are determined to be similar to 0.91% for uracil and similar to 0.41% for thymine. Compared to the measured large quenching rate constants of triplet uracil (1.5 x 10(9) M(-1)s(-1)) or thymine (0.6 x 10(9) M(-1)s(-1)) by cyclopentene, the inefficiency in formation of photoproducts indicates competitive physical quenching processes may exist on the route leading to ...

Lawrence Scott and Marina Petrukhina discuss their new book on fullerene fragments and other open geodesic polyaromatic molecules .

A stereoselective total synthesis of (+)-$\alpha$-herbertenol starting from the allyl alcohol 12, readily available in three steps from the monoterpene (R)-limonene, is described. Claisen rearrangement of the aryl allyl ether 10 and concomitant cyclisation furnished a 5:3 mixture of the tricyclic compounds 13 and 14. Degradation of the isopropenyl group followed by cleavage of the central ring and functional group manipulation transformed 13 into (+)-$\alpha$-herbertenol (1b).. ...

TY - JOUR. T1 - Synthesis, spectroscopy, and applications of small nitrile oxides. AU - Pasinszki, Tibor. AU - Westwood, Nicholas P.C.. PY - 2011/6. Y1 - 2011/6. N2 - Small covalent nitrile oxides are important transient species in organic synthesis and widely used especially for dipolar cycloaddition reactions. Due to their instability, their isolation and characterization are challenging. This review focuses on the generation, spectroscopy, structural properties, and synthetic application of small nitrile oxides, XCNO, where the X substituent group is smaller than five atoms, viz. X= hydrogen, halogen, pseudohalogen, alkyl, vinyl, ethynyl, or nitro.. AB - Small covalent nitrile oxides are important transient species in organic synthesis and widely used especially for dipolar cycloaddition reactions. Due to their instability, their isolation and characterization are challenging. This review focuses on the generation, spectroscopy, structural properties, and synthetic application of small ...

In 1908, Ciamician discovered that upon exposure of carvone to sunlight for one year, carvone camphor resulted.[2] After this finding was confirmed in the 1950s, a flurry of research identified the synthetic value of the photochemical [2+2] cycloaddition between enones and alkenes for the construction of complex molecular frameworks.[3][4] In spite of the stepwise, radical mechanism, both stereoselective intra- and intermolecular variants have emerged. Cyclic enones must be used to prevent competitive cis-trans isomerization. [2+2] Photocyclization may produce two constitutional isomers, depending on the orientation of substituents on the alkene and the enone carbonyl group. When the enone carbonyl and substituent of highest priority are proximal, the isomer is termed "head-to-head." When the enone carbonyl and substituent are distal, the isomer is called "head-to-tail." Selectivity for one of these isomers depends on both steric and electronic factors (see below). (1) ...

Green Chem., 2013, 15,2384-2388 DOI: 10.1039/C3GC41126E, Communication Dwun Kit Jonathan Yeung,a Tao Gao,b Jiayao Huang,a Shaofa Sun,b Haibing Guob and Jian Wang*a * Corresponding authors a Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore E-mail: [email protected] ; Fax: (+)65-6516-1691 b HuBei Collaborative Innovation Center of Non-power Nuclear Technology, Hubei University of Science and Technology, Hubei Province, China Received 12 Jun…

Intramolecular transannular dipolar cycloaddition was investigated as a key step in a synthetic approach to the core of the sarain alkaloids; although the use of an azomethine ylide was unsuccessful with the chosen aldehyde substrate, cycloaddition with a nitrone did give the alternative regioisomeric bridge

A new method of adding fluorescent labels to the middle of oligonucleotides is reported. Diets-Alder cycloaddition was used to add five fluorescent maleimides to an oligonucleotide containing a 2-deoxyuridine modified at the 5-position with a spaced furan. This is a new approach to internal oligonucleotide chemistry that opens Lip a large range of possibilities for further conjugation.. ...

TY - JOUR. T1 - The retro Diels-Alder reaction as a valuable tool for the synthesis of heterocycles. AU - Stájer, Géza. AU - Csende, Ferenc. AU - Fülöp, Ferenc. PY - 2003/9/1. Y1 - 2003/9/1. N2 - Applications of the retro Diels-Alder reaction (cycloreversion) under mild conditions for the laboratory preparation of heteromonocycles or condensed-ring heterocycles are reviewed. A new method utilizes diendo- or diexo-3-aminonorbornene-2-carboxylic acids and their derivatives for the formation of heterocyclic ring systems which are difficult to access by other routes or which can be prepared only in complicated multi-step procedures. The synthesis of substituted 1,3-dienes (e.g. furan derivatives) and O,N- or N,N-heterocycles (oxazoles, isoxazoles, pyrazoles, imidazoles, triazoles, pyrimidinones, oxazinones, pyridazinones etc) are discussed.. AB - Applications of the retro Diels-Alder reaction (cycloreversion) under mild conditions for the laboratory preparation of heteromonocycles or ...

PENTALENIC ACID; (2-CHLOROETHYL)NITROSOUREAS; 1,3-DICARBONYL COMPOUNDS; 1,4-DIAZABICYCLO<2.2.2>OCTANE; 2+2 PHOTOCYCLOADDITION; 2-CYCLOHEXENONE; 2-PYRIDINONE DERIVATIVES; 3-METHYLADENINE DNA GLYCOSYLASE; 4-HYDROXYCINNAMAMIDE DERIVATIVES; 5-FLUOROURACIL; 9-ALKOXYPURINES; ABSORPTION; ACID DERIVATIVES; ACYCLIC NUCLEOSIDES; AGENTS; ALKYLATING-AGENTS; ALKYLTRANSFERASE; ALPHA,BETA-UNSATURATED KETONES; AMIDE CONFORMERS; ANALOGS; ATASE; BREAST; CALCIUM-CHANNEL; CELL-LINES; CHLOROETHYLNITROSOUREA; CLEAVAGE; COLON; CROSS-LINK; DACARBAZINE; DERIVATIVES; DNA-DAMAGE; DOUBLE MICHAEL REACTION; ETHERS; FACILE; HERPES-SIMPLEX VIRUS; HETEROCYCLIC ENAMINES; HUMAN-TUMOR-CELLS; HYPOIODITE; INACTIVATION; INHIBITORS; ISOMERS; LUNG-TUMORS; MALIGNANT-MELANOMA; MALONONITRILE; MAMMALIAN O-6-ALKYLGUANINE-DNA ALKYLTRANSFERASE; MECHANISM; METHYLATING AGENTS; METHYLENE-COMPOUNDS; MGMT; MICE; MOLECULES; N-ISOPROPYLIDENEHYDRAZINOCARBONYL DERIVATIVES; NITROSOUREA; NMR; NUCLEAR MAGNETIC-RESONANCE; O-6-METHYLGUANINE; ...

Cathodic reduction of the nitro moiety and subsequent intramolecular cyclization affords different substituted 2,1-benzisoxazoles and quinoline N-oxides.

Sonification of N-benzyl-N-(methoxymethyl)-N-[(trimethylsilyl)methyl]amine (5a) in the presence of LiF led to the formation of the reactive azomethine ylide 1d, which was intercepted by cyclic thioketones to give spirocyclic 1,3-thiazolidines. In the case of 2,2,4,4-tetramethylcyclobutane-1,3-dithione, the 1:1- and 1:2-cycloadduct, respectively, was formed as the major product depending on the ratio of the starting materials. With 1,3-thiazole-5(4H)-thiones, 1d undergoes stereoselective [2+3]-cycloadditions with the C=S group to yield spirocyclic 1:1-adducts. In the case of the 1,3-dipole generated from N-benzyl-N-(methoxymethyl)-N-[1-(trimethylsilyl)ethyl]amine (5b), the [2+3]-cycloaddition proceeded in a non-regioselective manner leading to a mixture of regio- and diastereoisomers. ...

An organocatalytic asymmetric [3 + 2] cycloaddition of oxindole-based azomethine ylides with 3-nitro-2H-chromenes has been developed. This reaction provides a facile approach to densely functionalized polycyclic spirooxindole-chromane adducts featuring four contiguous stereogenic centers, including two tetrasubstit

Organic chemists have long recognized the important role that reaction media play in controlling rates, product distributions and stereochemistry. Recently, much effort has been directed towards the use of organized media to modify reaftivity as compared to that in isotropic liquids. Judicious selection of a given organized system for a given application requires sufficient understanding of the properties of the organized media themselves and those of the substrate interactions therein. The multimolecular aggregation of hydrophobic solutes in water could prove to be of immense value to the organic chemist. The aggregation of simple olefinic systems in water would enable photocycloaddition to compete efficiently with the various other modes of dacay of the short-lived excited state. Investigations of a few systems (dimerization of coumarins, stilbenes and alkylcinnamates) in our laboratory have been successful and they bring to light the significance of the hydrophobic effect. One of the most ...

The title compound, N,N-dibenzyl-1-(1-[(4-methyl-2-phenyl-4,5-dihydrooxazol-4-yl)methyl)]-1H-1,2,3-triazol-4-yl)methanamine was synthesized in high yield by 1,3-dipolar cycloaddition reaction of 4-(azidomethyl)-4-methyl-2-phenyl-4,5-dihydrooxazole and N,N-dibenzylprop-2-yn-1-amine in toluene at reflux. The structure of this product was established on the basis of NMR spectroscopy (1H, 13C), Elemental Analysis and MS data.

Vishwakarma Singh and co-workers from IIT Bombay have published in Organic and Biomolecular Chemistry on an oxidation of a phenol that yields a Diels-Alder substrate that dimerizes on itself and when the dimer is heated reforms the dienone substrate that undergoes an intramolecular Diels-Alder reaction. So the sequence goes like so: intermolecular Diels-Alder to retro-Diels-Alder…

Almost all successful syntheses of bicyclic beta-lactams involve the early synthesis of the monocyclic azetidin-2-one ring. Of the numerous methods developed to achieve this, the [2+2] cycloaddition of chlorosulphonyl isocyanate (CSI) to functionalised alkenes has proven to be particularly useful. In general, addition is performed on alkenyl acetates providing C-4 acetoxyazetidinones, which have found widespread use since the 4-acetoxy substituent can be replaced with various nucleophiles in an elimination/addition sequence. However, there are few functionalised alkenes which directly introduce the C-4 carbon substitution required for carbapenem synthesis upon cycloaddition with CSI. Earlier investigations within this group have shown that allylsilanes undergo regioselective cycloaddition with CSI to yield C-4 silylmethyl substituted beta-lactams.133,137 The regiochemistry of cycloaddition is controlled by the beta-effect of silicon, i.e., silicons ability to stabilise the development of ...

B. R. Buckley and H. Heaney: Mechanistic Investigations of Copper(I)- Catalyzed Alkyne-Azide Cycloaddition Reactions.- J. D. Crowley and D. A. McMorran:

The intermediate [Zn(4-PTZ)2(H2O)4] (4-PTZ=5-(4-pyridyl N-oxide)tetrazolate) (1) in the synthesis of 4-H-PTZ (2) from cycloaddition reaction of 4-cyanopyridine N-oxide with NaN3 in water catalyzed by ZnCl2 was structurally characterized. The catalysis role of Zn2+ in the synthesis of tetrazole stems from the formation of tetrazolate zinc complex 1. © 2004 Elsevier B.V. All rights reserved ...

Rh-Catalyzed [5+1] and [4+1] Cycloaddition Reactions of 1,4 Enyne Esters with CO : A Shortcut to Functionalized Resorcinols and Cyclopentenones ...

We systematically studied the heats of formation (HOFs) for a series of 3,3′-azobis-1,2,4, 5-tetrazine derivatives by den... ...

It seemed plausible that the biosynthesis of Bistellettadine A (9) was proceeding by intermolecular dimerization of the monomeric carboxylic acid corresponding to 7. Barry B. Snider of Brandeis University found (Org. Lett. 2010, 12, 828. ) that that intermolecular dimerization did proceed efficiently, but to give a 5:4 mixture of diastereomers. In contrast, the linked diester 7 cyclized with exclusive diastereocontrol. The product 8 was readily carried on to Bistellettadine A 9. This raises the possibility that a chiral template, attached either covalently or through salt formation, could be designed that would direct the absolute configuration of the cycloaddition.. ...

This video was recorded at CHEM 125b: Freshman Organic Chemistry II. Cyclic conjugation that arises when p-orbitals touch one another can be as important for transition states as aromaticity is for stable molecules. It is the controlling factor in "pericyclic" reactions. Regiochemistry, stereochemistry, and kinetics show that two new sigma bonds are being formed simultaneously, if not symmetrically, in the 6-electron Diels-Alder cycloaddition. Although thermal dimerization of thymine residues in DNA is forbidden, photochemistry allows the 4-electron cycloaddition. "Electrocyclic" ring opening or closing chooses a conrotatory Möbius pathway, or a disrotatory Hückel pathway, according to the number of electron pairs involved and whether light is used in the process. Dewar benzene provides an example of a very unstable molecule that can be formed photochemically and then persists because of unfavorable orbital overlap in the transition state for ring opening ...

TY - JOUR. T1 - Intramolecular nitrile oxide-alkene cycloaddition of sugar derivatives with unmasked hydroxyl group(s). AU - Shing, Tony Kung Ming. AU - Wong, Wai F.. AU - Cheng, Hau M.. AU - Kwok, Wun S.. AU - So, King H.. PY - 2007/3/1. Y1 - 2007/3/1. N2 - (Chemical Equation Presented) Intramolecular nitrile oxide-alkene cycloaddition (INOC) of sugar derivatives with one to four free hydroxyl group(s) is reported. The INOC reaction, using chloramine-T, in the presence of silica gel, to generate nitrile oxides from oximes, proceeded smoothly to afford five- or six-membered carbocycles in good to excellent yields. This new methodology alleviates protection/deprotection steps and makes the synthetic route shorter and more efficient.. AB - (Chemical Equation Presented) Intramolecular nitrile oxide-alkene cycloaddition (INOC) of sugar derivatives with one to four free hydroxyl group(s) is reported. The INOC reaction, using chloramine-T, in the presence of silica gel, to generate nitrile oxides from ...

The Diels-Alder reaction is one of the most powerful synthetic tools in organic chemistry, and asymmetric Diels-Alder catalysis allows for rapid construction of chiral carbon scaffolds. For this reason, considerable effort has been invested in developing efficient and stereoselective organo- and biocatalysts. However, Diels-Alder is a virtually unknown reaction in Nature, and to engineer an enzyme into a Diels-Alderase is therefore a challenging task. Despite several successful designs of catalytic antibodies since the 1980s, their catalytic activities have remained low, and no true artificial Diels-Alderase enzyme was reported before 2010.. In this thesis, we employ state-of-the-art computational tools to study the mechanism of organocatalyzed Diels-Alder in detail, and to redesign existing enzymes into intermolecular Diels-Alder catalysts. Papers I-IV explore the mechanistic variations when employing increasingly activated reactants and the effect of catalysis. In particular, the ...

A series of novel purine-based fluoroaryl triazoles were synthesized using the Cu(I) catalyzed 1,3-dipolar cycloaddition reactions (click reactions), and assayed for their neuroprotective effects using fluorescence electron microscopy. Among these triazoles, o-fluorophenylmetyl-triazole, 7, has comparable neuroprotective effect as that of Flavopiridol (1) and Roscovitine (2), the state of the art CDK inhibitors, against the Aß induced neurotoxicity. These results are substantiated using computer docking methods (DarwinDock/GenDock), which predict that Roscovitine and the triazole 7 bind to the ATP-binding site of CDK5/p25 with comparable binding energies, whereas the corresponding pentafluorophenylmethyl-triazole, 9, has dramatically reduced binding energy (in accordance with its lack of neuroprotection). These combined experimental and theoretical studies support the involvement of CDK5/p25 in the neuronal cell cycle re-entry.

In the structures a, b and c the first two are dipolar (1,2-dipoles; curiously, no actual 1,3 dipoles make it since they apparently do not contribute significantly) and c is neutral. There is no mention (I might have missed it) in the quoted article about the individual contributions of the three structures to the overall dipole moment. My experience is that once a dipole moment reaches about 6D, solvation of that state starts having a very significant impact on its energy, indeed its geometry (even if the solvent is merely a typical organic solvent such as dichloromethane). In a recent study which will be published shortly, we compared two ion pairs in the isobornyl chloride system. In the gas phase, one ion pair had a dipole moment of ~32D (!), and this was a great deal higher (~20 kcal or more) than another in energy with a dipole moment of "only" 14D. But once solvation is applied, the two become equal in energy. Geometry re-optimization was critical. OK, these are "extreme" dipoles, and the ...

To quote Yogi Berra, Deja Vu all over again! This was a hot topic in the 1970s, but then the debate was whether semi-empirical methods could handle this hot potato. I think we can say the DFT methods eventually won that one. But in 1991, I note we too were fretting on the theme of Transition state structure in cycloaddition reactions as a function of ring size and geometry, namely how many electrons could be involved in a pericyclic reaction before it turns stepwise? We decided then the transition (for a neutral hydrocarbon it has to be said) was somewhere between 10 and 14. I think that may well still be the modern view. For systems where zwitterions are more heavily stabilized, it is no surprise that it comes earlier. I do note that although the bibliography in Fernandez, Sierra and Torres article is extensive, it does not cite our article. A related question might be whether these higher electron systems (4n+2, n=2,3) might ever sustain Möbius topologies. Thus again for a hydrocarbon (DOI: ...

Angewandte Chemie DOI: 10.1002/ange.200903427 Strained Molecules Foregoing Rigidity to Achieve Greater Intimacy** Alexander S. Filatov, Edward A. Jackson, Lawrence T. Scott, and Marina A. Petrukhina* Interactions between the surfaces of planar and nonplanar molecules have generated considerable interest in materials chemistry[1, 2] as critical elements for understanding twodimensional supramolecular assembly, molecular and chiral recognition, and heterogeneous catalysis. Carbon-rich balland bowl-shaped polyaromatic molecules, such as fullerenes and fullerene fragments or buckybowls, figure prominently in these studies. Fullerenes have been found to form solid constructs with planar metalloporphyrins with remarkably close contacts but without the need for matching their convex and concave faces.[3] Molecular self-organization of nonplanar polyaromatic bowls on a planar metal surface introduces the interesting additional factor of symmetry mismatch.[4] Studies of ordered structures formed by ...

A three-component reaction of an alpha ,alpha -disubstituted alpha -isocyanoacetamide, an aldehyde and an amino alc. afforded 5-iminooxazolines, which, upon sapon., cyclized under acidic conditions to provide the macrocyclodepsipeptides in good overall yields. [on SciFinder (R)]. Keywords: Alcohols Role: RCT (Reactant) ; RACT (Reactant or reagent) (amino; prepn. of iminooxazolines via ammonium chloride-promoted three-component reaction of isocyanoacetamides ; aldehydes and amino alcs.); Peptides Role: SPN (Synthetic preparation) ; PREP (Preparation) (depsipeptides ; macrocyclic; prepn. of macrocyclodepsipeptides via cyclization of iminooxazolines); Aldehydes Role: RCT (Reactant) ; RACT (Reactant or reagent) (prepn. of iminooxazolines via ammonium chloride-promoted three-component reaction of isocyanoacetamides ; aldehydes and amino alcs.); Ugi reaction (prepn. of isocyanoacetamides via Ugi reaction of ketones ; ammonium formate and isocyanoacetates); Ketones Role: RCT (Reactant) ; RACT (Reactant ...

Abstract. An efficient chiral Lewis acid-catalyzed inverse-electron-demand Diels-Alder reaction of N-sulfonyl 1-aza-1,3-dienes is based on the combination of Ni(II)-DBFOX complex as catalyst and the use of a metal-coordinating (8-quinolyl)sulfonyl moiety. The reaction provides highly functionalized piperidine derivatives in good yields with excellent endo-selectivity, and good enantioselectivities.. ...

The central themes of our research program are the development of methodology to accomplish the synthesis of optically pure materials and the subsequent application of the new methodology to the total synthesis of biologically significant natural products. At the present time there are several different approaches to a variety of targets in progress in our laboratories. The first is the transfer of chirality from optically active hydroxylamines (e.g.,1) employing intra-and intermolecular nitrone /alkene cycloaddition reactions in the chirality transfer step. Particular targets for this chemistry are several unusual alpha-amino acids (2) as well as alkaloids related to pretazettine (3). The synthesis of pretazettine is also being addressed in a different approach involving a chiral ring expansion of allylic alcohol (4). Recently, significant progress has been realized in the synthesis the alkaloid gelsemicine (7) based on the Diels-Alder reaction of chiral maleimides such as (5). It has been ...

3,6-Bis(2,4-dimethyl-1H-pyrrol-1-yl)-1,2,4,5-tetrazine/ACM30169256 can be provided in Alfa Chemistry. We are dedicated to provide our customers the best products and services.

Cycloadditionsreaktionen von Heterokumulenen, IX. 1:1-, 2:1- und 3:1-Addukte aus der Umsetzung von Isothiocyanaten mit 3-Dimethylamino-2,2-dimethyl-2H-azirin (Cycloaddition reactions of heterocumulenes, IX. 1:1-, 2:1-, and 3:1-Adducts from the reaction of isothiocyanates with 3-dimethylamino-2,2-dimethyl-2H-azirine) ...

Gilvocarcin V (GV) and ravidomycin (RMV) exhibit excellent antitumor activities in the presence of near-UV light at low concentration maintaining a low in vivo cytotoxicity. Although, the exact molecular mechanism for in vivo actions of these antibiotics has yet to be determined, a [2+2] cycloaddition reaction of the vinyl side chain with DNA thymidine residues in addition to the inhibition of topoisomerase II and DNAhistone H3 cross-linking are reported for the GVs mechanism of action. Such activities have made these molecules interesting candidates for the biosynthetic investigation to generate analogues with improved activity/solubility. Previous biosynthetic studies have suggested that the GV biosynthetic pathway involves a number of synchronously occurring transformations leading to the oxidative C-C bond cleavage and other intriguing biosynthetic reactions, such as the vinyl side chain formation, methylations, Cglycosylation and dehydrogenation. Although gene inactivation results identified many

One-pot synthesis of 3-vinyl substituted indoles containing 1,2-amino alcohol fragment at the nitrogen atom was performed by the reactions of 1-(oxiran-2-y

The development of RGD-based antagonist of αvβ3 integrin receptor has enhanced the interest in PET probes to image this receptor for the early detection of cancer, to monitor the disease progression and the response to therapy. In this work, a novel prosthetic group (N-(4-fluorophenyl)pent-4-ynamide or FPPA) for the (18)F-labeling of an αvβ3 selective RGD-peptide was successfully prepared. [(18)F]FPPA was obtained in three steps with a radiochemical yield of 44% (decay corrected). Conjugation to c(RGDfK(N3)) by the Cu(II) catalyzed Huisgen azido alkyne cycloaddition provided the [(18)F]FPPA-c(RGDfK) with a radiochemical yield of 29% (decay corrected), in an overall synthesis time of 140 min ...

Kendall Houk and co-workers have reported in JACS on a biosynthetic study of heronamide A using DFT calculations to study the [6+4] cycloaddition. JACS paper

Monty Liong is the author of this article in the Journal of Visualized Experiments: Reversibly छोटे अणुओं या Biosensor अनुप्रयोगों के लिए बहु घटक संरचनाएं स्थिर microfluidic पर चिप कब्जा cycloaddition के रिएक्शन

Get this from a library! Bioconjugation protocols : strategies and methods.. [Sonny S Mark; Christof M Niemeyer] -- Contemporary approaches to the synthesis of chemically modified biomacromolecules (proteins, nucleic acids, lipids, and carbohydrates) not only require efficient means to control conjugation and the ...

Photo-mediated copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) "click" reactions for forming polymer networks as shape memory materials Journal Article ...

Download summary (PDF). 1. Professor Alexandru T. Balabans 75th anniversary. Download Art 1 (PDF). 1.-bis Addendum to Professor Balabans List of Publications. Download Art 1-bis (PDF). 2. Horia PETRIDE, Oana COSTAN, Cristina FLOREA and Silvia UDREA. Competitive amide hydrolysis in mono- and diformylated ethylenediamines. Download Art 2 (PDF). Key words: amides, hydrolysis. 3. Florea DUMITRAŞCU, Constantin DRĂGHICI, Daniela VULUGA and Miron Teodor CĂPROIU. New pyrazoles by 1,3-dipolar cycloaddition reactions between sydnones and activated alkynes. Download Art 3 (PDF). Key words: sydnones, pyrazoles, 1,3-dipolar cycloaddition, regioselectivity, NMR spectroscopy. 4. Rodica Daniela BĂRĂŢOIU, Anca Elena BARBU, Lucia MUTIHAC, Miron Teodor CĂPROIU, Constantin DRĂGHICI, Radu SOCOTEANU and Titus CONSTANTINESCU. 4-(3-(phtalhydrazide)azo)N-phenylaza-15-crown-5. Synthesis and properties. Download Art 4 (PDF). Key words: luminol, N-phenylaza-15-crown-5, luminol derivative, 1H- and 13CNMR spectra ...

Three synthetic methodologies are studied in details in this dissertation. For 1,5-hydride shift of alkenyl sulfoximine methodology, the reaction mechanism was studied using deuterium labeling. An uncommon 6-endo-trig 1,5-hydride shift process was discovered. The scope and limitation were studied using N-alkyl, N-allyl, and N-benzyl-substituted S-alkenyl sulfoximines. N-H-S-alkyl sulfoximines, four- and six-membered heterocyclic rings and a new class of chiral dienes were obtained. In [4+3] cycloaddition and ring opening chapter, we demonstrated an ene-like reaction using a symmetric oxyallylic cation can provide α-substituted cyclopentenones. Enantio pure products are potentially accessible by this method. [4+3] Cycloaddition of the symmetric oxyallylic cation with substituted furans, and the ring-opening process of the resulting 8-oxabicyclo[3.2.1]oct-6-en-3-one were also studied. The reaction conditions and scope were investigated. An acid-catalyzed mechanism was proposed for the ...

There is a growing interest in sustainable heterogeneous catalysts based on organic polymers. Here, we describe a series of polyimidazolium salt catalysts, prepared from the direct reaction of arene- bridged bis- and tris-alkyl halides with trimethylsilylimidazole. The polyimidazolium salts were characterized by spectroscopic and analytical techniques and it was found that their morphology and porosity could be controlled by adjusting the steric parameters of the spacer in the alkyl-halide starting materials. Moreover, the polymers are excellent heterogeneous organocatalysts for the cycloaddition of CO2 to epoxides to afford cyclic carbonates at atmospheric pressure under solvent-free conditions. The polymer catalysts exhibit long-term stability and may be recycled and reused at least.. Keywords: carbon dioxide ; cyclic carbonates ; cycloaddition ; organocatalysis ; polyimidazolium. ...

The electronic structure and the participation of the simplest azomethine imine (AI) in [3+2] cycloaddition (32CA) reactions have been analysed within the Molecular Electron Density Theory (MEDT) using Density Functional Theory (DFT) calculations at the MPWB1K/6-311G(d) level. Topological analysis of the electron localisation function reveals that AI has a pseudoradical structure, while the conceptual DFT reactivity indices characterises this three-atom-component (TAC) as a moderate electrophile and a good nucleophile. The non-polar 32CA reaction of AI with ethylene takes place through a one-step mechanism with moderate activation energy, 8.7 kcal·mol−1. A bonding evolution theory study indicates that this reaction takes place through a non-concerted [2n + 2τ] mechanism in which the C-C bond formation is clearly anticipated prior to the C-N one. On the other hand, the polar 32CA reaction of AI with dicyanoethylene takes place through a two-stage one-step mechanism. Now, the activation energy is only

Retro-Diels-Alder Reaction. relationship blogs: Rigby, J. Stille Reaction: Farina, Vittorio; Krishnamurthy, Venkat; Scott, William J. Vilsmeier Reaction of nt many Carbocycles and Heterocycles: Jones, Gurnos; Stanforth, Stephen P. Cycloaddition cars: Rigby, J. Carbon-Carbon Bond-Forming Reactions Promoted by Trivalent Manganese: Melikyan, Gagik G. Asymmetric Epoxidation of Allylic Alcohols: The Katsuki-Sharpless Epoxidation Reaction: Katsuki, Tsutomu; Martin, Victor S. Wallquist, Olof( in permission); McLoughlin, Jim I. airplanes with Samarium(II) Iodide: Molander, Gary A. Ketene Cycloadditions: Hyatt, John; Raynolds, Peter W. Carbonyl Methylenation and Alkylidenation having successful requirements: Pine, Stanley H. Anion-Assisted geopolitical airplanes: Wilson, Stephen R. Baeyer-Villiger Oxidation of Ketones and Aldehydes: Krow, Grant R. Mitsunobu Reaction: Hughes, David L. Pauson-Khand Cycloaddition Reaction for Synthesis of Cyclopentenones: Schore, Neil E. Oxidation of Alcohols to Carbonyl ...

The Prato reaction is a particular example of the well-known 1,3-dipolar cycloaddition of azomethine ylides to olefins. In fullerene chemistry this reaction refers to the functionalization of fullerenes and nanotubes. The amino acid sarcosine reacts with paraformaldehyde when heated at reflux in toluene to an ylide which reacts with a double bond in a 6,6 ring position in a fullerene via a 1,3-dipolar cycloaddition to yield a N-methylpyrrolidine derivative or pyrrolidinofullerene or pyrrolidino[[3,4:1,2]] [60]fullerene in 82% yield based on C60 conversion. In one application a liquid fullerene is obtained when the pyrrolidone substituent is a 2,4,6-tris(alkyloxy)phenyl group although a small amount of solvent is still possibly present. This reaction was derived from the work of Otohiko Tsuge on Azomethine Ylide Chemistry developed in the late 1980s. Tsuges work was applied to fullerenes by Maurizio Prato, thus gaining the name. It is known that the Prato reaction is very useful to functionalize ...

I. INTRODUCTION Because of the aromatic character of 2-pyrones, they enter into [4+2] cycloadditions less readily than most cyclic conjugated dienes. Nevertheless, the ability of these heteroaromatic compounds to act as dienes in [4+2] cycloadditions was reported by Diels and Alder only three years after they first reported the [4+2] cycloaddition between dienes and dienophiles which bears their names. 1 In the decades following the first report of 2-pyrones acting as dienes, this methodology was occasionally employed by synthetic chemists, but up until the early 1970s the use of this methodology was largely confined to synthesizing aromatic products (1 and 4). Lankford, P. ; Miller, R. ; Murray, C. ; Yang, D. C. J. Am. Chem. Soc. 1990, 112, 3642. 38. Davies, H. M. ; Matasi, J. ; Hodges, L. ; Huby, N. J. ; Houser, J. H. J. Org. Chem. 1997, 62, 1095. 39. Griesbeck, A. G. J. Prakt. Chem. 1993, 335, 489. 40. Wender, P. ; Eissenstat, M. ; Filosa, M. P. J. Am. Chem. Soc. 1979, 101, 2196. 41. Davies, ...

Isoxazole and its derivatives represent one of the important classes of heterocyclic compounds. These derivatives are employed in the area of pharmaceuticals and demonstrate therapeutic properties such as anti-tumor (Kang et al., 2000), hypoglycemic (Conti et al., 1998), anti-mycobacterial (Changtam et al., 2010) and anti-inflammatory activity (Kwon et al., 1995). In addition, isoxazole derivatives serve as versatile building blocks in organic synthesis (Abbiati et al., 2003). With this extensive background of isoxazole derivatives, we have synthesized the title compound to study its crystal structure.. In the molecular structure of the title compound (Fig. 1), the dihedral angle between the phenyl ring (C9/C10/C11/C12/C13/C14) and isoxazole ring (C1/C3/C4/N5/O6) is 1.14 (9)°. The isoxazole moiety is in a syn-periplanar conformation with respect to the phenyl ring, as indicated by the torsion angle value of 0.5 (2)°. The bond lengths and angles agree with those reported for a related structure ...

The conjugation of maleimide reporter groups to 5′‐diene‐modified oligonucleotides via aqueous Diels‐Alder cycloaddition is described

Site-Specific Surface Functionalization via Microchannel Cantilever Spotting (µCS): Comparison between Azide-Alkyne and Thiol-Alkyne Click Chemistry ...

Pt(II) based anticancer drugs-cisplatin, carboplatin, and oxaliplatin-are widely used in the treatment of a variety of cancers. Unfortunately, the clinical efficacy of these drugs is currently hindered by the development of undesirable side effects and resistance during treatment. The molecular mechanisms underlying these effects are still unclear. For decades, research has focused on DNA as the main cellular target of Pt(II) compounds. However, there is increasing interest in proteins as alternative targets of Pt(II) and contributors to cytotoxic and resistance mechanisms of cisplatin. In this work, I utilize Pt(II) compounds that have been functionalized to participate in the azide-alkyne cycloaddition click reaction to study protein targets of platinum reagents. First, I describe the use of an azide-modified Pt(II) compound to fluorescently label and isolate Pt(II)-bound bovine serum albumin in vitro. Additionally, we discover that Pt(II) compounds form monofunctional adducts on BSA that ...

Synthesis provides the opportunity to design and prepare specific molecules whilst exploring novel processes that further develop the field of organic chemistry. In this context, our programme has concentrated on new and selective carbon-carbon bond forming strategies for the preparation of functionalised synthetic Intermediates. A summary of projects currently under investigation is outlined below:. Alkynylboronate Cycloadditions. Aromatic boronic acids and esters are extremely useful and versatile substrates in modern organic chemistry. We have developed a strategically novel approach to these compounds through cycloaddition reactions of alkynylboronates. To date, this approach has allowed us to generate boronic esters that are connected to benzene, quinone, pyridine, pyrazole, isoxazole and pyridazine scaffolds.. [3 + 3] Annelation Reactions. We have designed an efficient method for the synthesis of piperidines and pyrans by the addition of conjunctive reagents to aziridines and epoxides. ...

Cyclic polyene with six carbon atoms (benzene) is very stable, whereas cyclic polyene with four carbon atoms (cyclobutadiene) is extremely unstable. The electron-withdrawing pentafluorophenyl group of a substituted cyclobutadiene lowers the energy of the lowest unoccupied molecular orbital, greatly increasing its reactivity as a diene in Diels-Alder reactions with acetylene, ethylene and even benzene. Here we show that the reaction with benzene occurs cleanly at the relatively low temperature of 120 °C and results in the formal fragmentation of benzene into C2H2 and C4H4 units, via a unique Diels-Alder/retro-Diels-Alder reaction. This is a new example of the rare case where breaking the C-C bond of benzene is possible with no activation by a transition metal.

The retro-Diels-Alder reaction (rDA) is the microscopic reverse of the Diels-Alder reaction-the formation of a diene and dienophile from a cyclohexene. It can be accomplished spontaneously with heat, or with acid or base mediation. With an appropriate driving force, the Diels-Alder reaction proceeds in reverse, providing diene and dienophile from starting cyclohexene derivatives. As early as 1929, this process was known and applied to the detection of cyclohexadienes, which released ethylene and aromatic compounds after reacting with acetylenes through a Diels-Alder/retro-Diels-Alder sequence. Since then, a variety of substrates have been subject to the rDA, yielding many different dienes and dienophiles. Additionally, conducting the rDA in the presence of a scavenging diene or dienophile has led to the capture of many transient reactive species. (1) The retro-Diels-Alder reaction proper is the microscopic reverse of the Diels-Alder reaction: a concerted (but not necessarily synchronous), ...

Reactant 1, transition states, and products 2 and 3 were optimized at SMD(H2O)/M06-2X/def2-TZVPP//B3LYP-D3(BJ)//6-31+G(d,p). Geometries and relative energies are shown in Figure 1. The reaction1 → 2 is a formal [6+4] cycloaddition, and the reaction 1 → 3 is a formal [4+2] cycloaddition. Interestingly, only a single transition state could be located TS1. It is a bispericyclic TS (see Chapter 4 of my book), where these two pericyclic reaction sort of merge together. After TS1 is traversed the potential energy surface bifurcates, leading to 2 or 3. This is yet again an example of a single TS leading to two different products. (See the many posts I have written on this topic.) The barrier height is 27.6 kcal mol-1, with 2 lying 13.1 kcal mol-1 above 3. However, the steepest descent pathway from TS1 leads to 2. There is a second transition state TScope that describes a Cope rearrangement between 2 and 3. Using the more traditional TS theory description, 1 undergoes a [6+4] cycloaddition to form 2 ...

With the above synthetic considerations as a backdrop, the use of the arene-alkene cycloaddition in complex molecule total synthesis can now be examined. The emphasis here will be on the meta cycloaddition process since it has received the most study. It will become apparent, however, that even this reaction has received relatively little attention in synthesis in spite of its enormous potential. This situation is likely to change riqiidly as recent theoretical and synthetic advances are assimilated. [Pg.657] ...

Which of the following is an ideal Click reaction 1) Cyannohydrin formation from acetaldehyde 2) Diels Alder cyclo addition 3) Attack of triplet

Shu XZ, Li XX, Shu DX, Huang SY, Schienebeck CM, Zhou X, Robichaux PJ, Tang WP. Rhodium-Catalyzed Intra- and Intermolecular 5+2 Cycloaddition of 3-Acyloxy-1,4-enyne and Alkyne with Concomitant 1,2-Acyloxy Migration. Journal of the American Chemical Society. 2012 ;134:5211-5221. ...

Principal Investigator：MATSUDA Akira, Project Period (FY)：1994 - 1995, Research Category：Grant-in-Aid for General Scientific Research (B), Research Field：Chemical pharmacy

To an ice-cooled solution of butyl (p-tolylsulfonylimino)acetate (22.2 g, 78.4 mmol) in dry benzene (36 mL) was added freshly distilled and dried (CaCl2) cyclopentadiene (5.18 g, 78.5 mmol). When the exothermic reaction began to subside, the reaction mixture was kept at room temperature for 12 hours and was then concentrated in vacuo. The oily residue was taken up in Et2O (50 mL) and washed with 5% NaHCO3 solution, dried (MgSO4), and the solvent was removed under reduced pressure. The residue, which solidified upon standing, was crystallized from Et2O-hexane (1:5), yielding 23.0 g (84%) of butyl 2-(p-tolylsulfonyl)-2-azabicyclo[2.2.1]hept-5-ene-exo-3-carboxylate as a colorless solid, mp 53-55°; IR (nujol) 1740, 1600 cm−1; Anal. Calcd for C18H23NO4S: C, 61.88; H, 6.64; N, 4.01. Found: C, 61.97; H, 6.59; N, 3.83. [1H NMR data was reported for the methyl ester, but not for the title compound. Methyl carboxylate analog: 1H NMR (CDCl,/sub,3,/sub,) δ 0.93 (t, J = 5 Hz, 3H), 2.5 (s, 3H), 3.33 (m, ...

The backbone of diene precursor in the proposed biogenesis of methyl isosartortuoate through a Diels-Alder reaction has been constructed via dehydration to establish the conjugated system; and double cyclization by using Horner-Wittig-Emmons reaction and the chiral epoxy ring opening. (C) 2004 Published by Elsevier Ltd ...

Free Essay: Introduction A Diels-Alder reaction is a reaction in which a conjugated diene bonds with an alkane to produce a cyclohexane molecule. This...

In the alignments below, two upper-case letters are aligned, and two lower-case letters are NOT aligned. The superposition files are re-constructed from the corresponding alignments by minimizing the overall RMSD. In a PDB-format superposition file, the first domain is represented by chain S and the second domain is represented by chain A. The coordinates of the first domain are transformed, while the coordinates of the second domain are the same as in the original PDB file. ...

Evaluation of biofilm formation on novel copper-catalyzed azide-alkyne cycloaddition (CuAAC)-based resins for dental restoratives Journal Article ...

Title:Synthesis of Pyrimidine Derivatives from Three-component Reaction of Malononitrile, Aldehydes and Thiourea/Urea in the Presence of High Surface Area and Nanosized MgO as a Highly Effective Heterogeneous Base Catalyst. VOLUME: 11 ISSUE: 7. Author(s):Zahra Hassani. Affiliation:Department of New Materials, Institute of Science and High Technology and Environmental Sciences, Graduate University of Advanced Technology, Kerman, Iran.. Keywords:High surface area, nanosized MgO, Pyrimidine derivatives, Three-component reaction.. Abstract:The three-component reaction of malononitrile, aldehydes and thiourea/urea, is applied to the formation of pyrimidine derivatives. The reaction occurs at best in EtOH at reflux, in the presence of high surface area and nanosized MgO. This methodology is more convenient to compare with alternative ways because it needs shorter reaction times, allows straightforward product isolation, and provides higher yields.. ...

Title:Organocatalyzed Transient Dienamine-Mediated Diels-Alder Reactions between α,β-Unsaturated Ketones and Alkenes. VOLUME: 15 ISSUE: 5. Author(s):Iosune Arrastia, Ana Arrieta and Fernando P. Cossio*. Affiliation:Donostia International Physics Center, San Sebastian/Donostia, Donostia International Physics Center, San Sebastian/Donostia, Donostia International Physics Center, San Sebastian/Donostia. Keywords:Organocatalysis, diels-Alder reactions, cycloadditions, michael additions, pericyclic reactions, stepwise mechanisms.. Abstract:Organocatalyzed (4+2) cycloadditions (Diels-Alder reactions) are reviewed in this manuscript. Among the different catalytic alternatives, reactions involving α,β-unsaturated ketones and alkenes are considered. In these processes, substituted cyclohexanones are obtained via HOMO activation generated by amine organocatalysis that generate transient dienamine species. Both concerted and stepwise mechanisms are described. In most cases, excellent regio-, ...

Huge advances have been made in the field of palladium catalyzed C-H activation in the past decade. The application of palladium catalyzed C-H activation to form complex, multifunctional substrates, especially directly C-H alkynylation are positively exploring. We have recently successfully elucidated a series of palladium catalyzed C-H alkynylation from commercial available material. These transformations included synthesis of highly substituted cyclopentadiene fused chromones from cascade reactions of coumarins with alkynes and C¿H/N¿H dual activation to synthesize benzazepines from isatin and alkynes; Recent years have witnessed an explosive growth in the field of iminium and enamine catalysis. Primary and secondary amines as catalysis in the cycloaddition transformation of biological and pharmaceutical compounds via the iminmium activation model have been greatly explored. We have successfully explored a series of enamine catalyzed [3+2] cycloaddition. These pioneering works consisted by ...

The 1,3-dipolar cycloaddition of trifluoromethylated propargylic alcohols 1 with azides in the presence of catalytic [Cp*RuCl2], afforded exclusively 4-trifluoroniethyl-1,4,5-trisubstituted-1,2,3-triazoles 2 in high yields. (c) 2008 Elsevier Ltd. All rights reserved ...

Interdisciplinary Nanoscience Center - INANO-Fysik, iNANO-huset, Interdisciplinary Nanoscience Center, Science and Technology, Aarhus ...

The development of eco-friendly and environmentally benign catalytic systems is one of the main themes of modern organic synthesis. Ammonium chloride (NH4Cl) is a very inexpensive and readily available catalyst; it has been reported as a catalyst for the synthesis of various heterocyclic compounds (Shaabani et al. 2003; Dabiri et al. 2009; Fortenberrya et al. 2013; Foroughifarab et al. 2011; Maleki and Salehabadi 2010; Shaabani et al. 2008; Hussein 2015). There are many bioactive molecules which possess various heteroatoms such as nitrogen, sulfur and oxygen, always taken the attention of chemists over the years mainly because of their biological significance. Pyrano derivatives have well-known biological effects, such as analgesic and anti-inflammatory activities (El-Zohry et al. 2008a). Indolinone and spiro-indoline derivatives have possessed broad-spectrum therapeutic activities such as anticonvulsants (Ragavendran et al. 2007; Azam et al. 2009; Sridhar et al. 2002), antibacterial (Rahman et ...

The endolexo selectivity of Diels-alder reactions in water and methanol is studied with semiempirical methods using the SCRF approach and a combined quantum chemical (transition state) and molecular mechanics (solvent molecules) method (QC/MM) to determine the effect of protic solvents on the transition slate energies. Evidently, the number of hydrogen bonds that causes strong Coulomb interaction, discriminates heals of formation of transition stales. The results indicate that the s-cis/s-trans conformation of acrylates controls the endolexo selectivity. Copyright (C) 1996 Elsevier Science Ltd ...

The Huisgen 1,3-dipolar cycloaddition of azides and acetylenes catalyzed by Cu(I) salts, leading to 1,2,3-triazoles, is one of the most versatile "click reactions". We have developed a series of optimized protocols and new applications of this reaction starting from several substrates, comparing heterogeneous vs homogeneous catalysis, conventional heating vs microwave irradiation or simultaneous microwave/ultrasound irradiation. Both non-conventional techniques strongly promoted the cycloaddition (bromide → azide → triazole), that could be conveniently performed in a one-pot procedure. This was feasible even with such bulky molecules as functionalized β-cyclodextrins (β-CD), starting from 61-O-tosyl-β-CD or from heptakis[6-O-(tert-butyldimethylsilyl)]-21-O-propargyl-β-CD. "Greener" heterogeneous catalysis with charcoal-supported Cu(II) or Cu(I) (prepared under ultrasound) was advantageously employed. Keywords: Click chemistry; Microwave; Huisgen cyclization; Heterogeneous catalysis; ...

The dissertation herein describes the first total synthesis of the complex Daphniphyllum alkaloid, (-)-calyciphylline N. This alkaloid was chosen as the target in our synthetic program due its unprecedented structure, the inherent challenges associated with its synthesis, and limited reports of synthetic studies towards members of this family of natural products. An initial unsuccessful approach is discussed, followed by a revised, ultimately successful approach. Highlights of the synthesis include a substrate controlled, intramolecular Diels-Alder reaction to build the bicyclo[2.2.2]octane core and set four contiguous stereocenters, a transannular enolate alkylation to secure ring D, a highly efficient Stille carbonylation/Nazarov cyclization sequence to construct ring E with concomitant activation of a hindered silyl group towards Fleming-Tamao oxidation, and an unprecedented, homogeneous hydrogenation of an exceptionally hindered diene ester to complete the eastern hemisphere, a structural motif that

The effect of blocking groups and stereochemistry of the substituents on the regio- and stereoselectivity in intramolecular nitrone-alkene cycloaddition (INAC) of hept-6-enoses are reported. L-ribo-Hept-6-enose 12 and D-lyxo-hept-6-enose 15, both containing a 2,3-O-isopropylidene blocking group, and L-xylo-hept-6-enose 23 and D-arabino-hept-6-enose 30, both with a 2,3-O-trans-diacetal blocking group, were prepared from D-ribose and D-arabinose, respectively. With N-alkyl hydroxylamine, lactols 12 and 15 underwent an INAC reaction to give cis-fused isoxazolidines exclusively whereas lactols 23 and 30 gave a mixture of cis-, trans-fused isoxazolidines (cyclohexanols) and bridged isoxazolidines (cycloheptanols). With the 2,3-O-trans-diacetal protecting group, the bridged bicyclo[4.2.1]isoxazolidines (cycloheptanols), via the endo mode of INAC cyclization, were synthesized for the first time from unbranched sugar derivatives 23 and 30. The stereochemical outcomes of these reactions were rationalized on the

The Chemical Biology product line incorporates techniques and strengths of chemistry to address fundamentally important questions in biology, medicine, and drug discovery. With chemical biology products from Sigma-Aldrich portfolio, you have solutions, expertise and industry leadership to help advance your research and bridge the gap between chemistry and biology.. The portfolio features a market leading range of innovative products for conjugation strategies such as azide-alkyne cycloaddition chemistry as well as synthetic intermediates and building blocks for the synthesis of biomolecules such as peptides, carbohydrates and oligonucleotides.. And were now proud to bring the purity and consistency of Novabiochem reagents to peptide and DNA synthesis, along with a steady stream of new offerings ...

A. C. Cardiel, M. C. Benson, L. M. Bishop, K. M. Louis, J. C. Yeager, Y. Tan, R. J. Hamers. "Chemically Directed Assembly of Photoactive Metal Oxide Nanoparticle Heterojunctions via the Copper-Catalyzed Azide-Alkyne Cycloaddition "Click" Reaction." ACS Nano 2012, 6, 310-318. This article was also featured in C&EN on Jan. 23, 2012 in the News of the Week section (Volume 90, Issue 4, p. 8).. ...

Synthesis of Methyl 2-Bromo-2 oxoccyclopent-1-enecarboxylate." Rama Rao Tata and Michael Harmata. Org. Synth. 2018, 95, 425-438.. "Synthesis of 3-Arylsulfonyl-3-Pyrrolines from Allenyl Sulfonamides by Silver Ion Catalysis." Rama Rao Tata, Chencheng Fu, Steven P. Kelley, and Michael Harmata. Organic Letters 2018, 5723-5726.. "Synthesis of (Z)-2-[(tert-Butyldimethylsilyl)oxy]-3-(phenylthio)acrylaldehyde." Michael Topinka and Michael Harmata. Synthesis 2018, 4476-4482.. "Derivatives of Alkyl 2-Hydroxy-3-oxocyclopent-1-enecarboxylates and Intermolecular [4+2] Cycloadditions of Cyclopentadienones Prepared Therefrom." Aswin Garimalla and Michael Harmata. Synthesis 2018, 4483-4489.. "Sulfinate Allenyl Carbenoids: Synthesis of 2,​5-​Dihydrofurans by Domino Rearrangement and Cyclization." Rama Rao Tata and Michael Harmata. European Journal of Organic Chemistry 2018, 372-375.. "(4+3)-Cycloaddition Reactions of N-Alkyl Oxidopyridinium Ions." Chencheng Fu, Nestor Lora, Patrick L. Kirchhoefer, Dong ...

For a seminal work in HOMO activation via enamineintermediates, see: a) List B., Lerner R. A., Barbas III C. F. J.,Proline-Catalyzed Direct Asymmetric Aldol Reactions, J. Am.Chem. Soc., 2000, 122, 2395-2396. For a review in enamineactivation, see: b) Mukherjee S., Yang J. W., Hoffmann S.,List B., Asymmetric Enamine Catalysis, Chem. Rev. 2007,107, 5471-5569. For a seminal work in HOMO-activation viadienamine intermediates, see: c) Bertelsen S., Marigo M.,Brandes S., Dinér P., Jørgensen K. A., Dienamine Catalysis:Organocatalytic Asymmetric γ-Amination of α,β-UnsaturatedAldehydes, J. Am. Chem. Soc. 2006, 128, 12973-12980.For reviews in dienamine activation, see: d) Ramachary D. B.,Reddy Y. V., Dienamine Catalysis: An Emerging Technologyin Organic Synthesis, Eur. J. Org. Chem., 2012, 865-887. e)Parra A., Reboredo S., Alemán J., Asymmetric Synthesis ofCyclobutanes by a Formal [2+2] Cycloaddition Controlled byDienamine Catalysis, Angew. Chem. Int. Ed. 2012, 51, 9734-9735 ...

Glyconanomaterials, Nanoantibiotics, Surface Functionalization, Graphene chemistry. Our research lies at the interface of Organic Chemistry, Nanomaterials and Nanomedicine, We develop new conjugation reactions that are general, efficient, can accommodate ligand diversity, maintain ligand bioaffinity, and give bioactive and stable interfaces. We have studied extensively the reactivities of perfluoroaryl azides as highly reactive singlet nitrene precursors as well as electron-deficient azides in metal catalyst-free cycloaddition reactions. We use these reactions to functionalize surfaces and nanomaterials, and synthesize antibiotic-conjugates and glyconanomaterials to target bacteria. Graphene functionalization is another focus of our research. We developed robust chemistry to functionalize pristine graphene, and to synthesize graphene composite materials for catalysis applications.. ...

A free platform for explaining your research in plain language, and managing how you communicate around it - so you can understand how best to increase its impact.

The catalytic performance of triazolyl-based molecular gels was investigated in the Huisgen 1,3-dipolar cycloaddition of alkynes and azides. Low-molecular-weight gelators derived from l-valine were synthesized and functionalized with a triazole fragment. The resultant compounds formed gels either with or without copper, in a variety of solvents of different polarity. The gelators coordinated CuI and exhibited a high catalytic activity in the gel phase for the model reaction between phenylacetylene and benzylazide. Additionally, the gels were able to participate in autocatalytic synthesis and the influence of small structural changes on their performance was observed. [-] ...

20 Jul 2016 that N-heterocycles 1 bearing a propargylic ester moiety at position 2 (eq 1), undergo, . in CH2Cl2 for 20 min at 25 °C and then adding the substrate (0.2 mmol); bConversion .. 2013, 135, 7926. (c) Álvarez, E.; Miguel, D.;.. ...

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The self-dimerization of 3-oxidopyrylium leading to stereocontrolled formation of highly functionalized cyclo-octanoids is described. Different functionalities were introduced on the dimer (3) and the stereochemical outcome was determined by single-crystal X-ray analysis. It is noteworthy that the hydrogenation of 3 in ethanol solvent gave the transannulated product 5, whereas the expected dihydro product 4 was obtained when the reaction was run in nonnucleophilic solvents. The mechanistic pathway is discussed ...

Prof. Aiwen Lei and coworkers, Wuhan University, Hubei, have developed a silver catalyst "click reaction" for the synthesis of pyrrole, by cycloaddition. This system benefits from readily-available starting materials, low catalyst loading (0.1 eq), short reaction times (2 h) and excellent chemo-selectivity. And, works for both internal and alkyl substituted terminal alkynes in the presence of many functional groups. The extremely mild conditions used, makes this reaction synthetically attractive ...

A series of different, but commonly used, organic reactions were used to validate the MFD technology up to this point. These include heterocyclic ring formation, amidation, simple phenolic allylation and Diels-Alder reactions. The reactions were performed on different scales ranging from analytical quantities in the order of 2 ml per run, up to a full capacity of 4 kilos per day of final crystalline product. Both high conversion and purity of the product in a reliable fashion could be achieved, using MFDs, which are capable of operating across a broad range of scales.. The performance of MCF microwave reactor devices based on a different geometry than the MFD has been evaluated using an Emrys Optimser laboratory microwave reactor. Here a small Teflon insert with 4 metres of MCF, coiled around it, was placed inside the microwave cavity. Microwave irradiation was used to control the temperature inside the fluid bulk flowing through the capillaries, thus initiating the reaction. The formation of ...

Green-emitting, azide activated fluorescent probes used for detection alkyne-containing targers via a copper-catalyzed click reaction (CuAAC).

A novel strategy to obtain side chain modified poly(oxindole biphenylylene) (POXI) by photoinduced copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction is described. In the first step, an alkyne-functionalized poly(oxindolebiphenylylene) (POXI-alkyne) is synthesized by superacid-catalyzed condensation of isatin with aromatic hydrocarbons. Subsequently, poly(ethylene glycol) methyl ether (Me-PEG), 1-pyrenemethanol (Py-OH) and 1,3-dibromopropane (DBP) are functionalized by azide groups via simple nucleophilic substitution reaction. Visible-light-induced CuAAC reaction between POXI-alkyne and the corresponding azide functionalized click components employing dibenzoyldiethylgermane (DBDEG) as photoactivator resulted in the formation of POXI-PEG, POXI-Py and insoluble network, respectively. Successful modification of POXI was confirmed by the spectral, (1H NMR, FT-IR, Fluorescence), chromatographic (GPC) and thermal (DSC) investigations ...

Development of high throughput assays is a crucial step in developing more efficient techniques that aid in many important areas of research today such as drug development or identification of protein structure function relationships. Integration of high throughput assays into more research efforts could drastically decrease the time and cost it takes for a new drug to hit the market. Protein Kinase A (PKA) is an extensively studied protein as it is highly upregulated in cancer and is a hot spot for drug targeting. In this work, azide-tagged PKA is covalently attached to magnetic beads using azide-alkyne cycloaddition, a well-known click chemistry reaction that selectively and covalently links two compounds. Modified PKA is attached to magnetic beads and the activity of the covalently bound PKA is determined. Significant levels of PKA activity can open the door to development of more efficient drug screening processes. It is anticipated that the azide-PKA conjugated beads will have significantly more

Herein, four new H-shaped triphenylene discotic liquid crystal tetramers have been designed and synthesized using a copper-free [3+2] cycloaddition reaction between the triphenylene dimer and diazide compounds. To probe the molecular self-assembly and mesophase properties, the length and rigid spacers in diazide have been tailored.

The Diels-Alder reaction is one of the most powerful synthetic tools in organic chemistry, and asymmetric Diels-Alder catalysis allows for rapid construction of chiral carbon scaffolds. For this reason, considerable effort has been invested in developing efficient and stereoselective organo- and biocatalysts. However, Diels-Alder is a virtually unknown reaction in Nature, and to engineer an enzyme into a Diels-Alderase is therefore a challenging task. Despite several successful designs of catalytic antibodies since the 1980s, their catalytic activities have remained low, and no true artificial Diels-Alderase enzyme was reported before 2010.. In this thesis, we employ state-of-the-art computational tools to study the mechanism of organocatalyzed Diels-Alder in detail, and to redesign existing enzymes into intermolecular Diels-Alder catalysts. Papers I-IV explore the mechanistic variations when employing increasingly activated reactants and the effect of catalysis. In particular, the ...

Principal Investigator：FUKUZUMI Shunichi, Project Period (FY)：1997 - 1998, Research Category：Grant-in-Aid for Scientific Research (B), Section：一般, Research Field：工業物理化学

An atom- and step-economical C(sp3)-H addition of N,N-dimethyl anilines to various sterically demanding 1,1- and 1,2-disubstituted alkenes has been achieved by using a simple β-diketiminato ligand supported scandium dialkyl complex in combination with a borate compound. The corresponding C(sp3)-C(sp3) bond forming reaction occurs with excellent regioselectivities to give a

1）Su, Y., Petersen, J. L.,Gregg, T. L.,Shi, X.*, "Ambient 1,2,3-Triazole Ring Opening through Intermolecular Radical Addition to Vinyl-Triazole." Org. Lett., 2015, 17, 1208-1211.； 2）Dong, B.‡, Su, Y.‡, Ye, X., Petersen, J. L., Shi, X.*, "Synthesis and Characterization of Fluorescent-Active Triazole-Gold Complexes." Sci. China Chem., 2015, 58, 1-4.； 3）Su, Y., Lu, M., Dong, B., Chen, H.*, Shi, X.* "Silver Catalyzed Alkyne Activation: the Surprising Ligand Effect" Adv. Syn. Cat., 2014, 356, 692-696.； 4）Su, Y., Zhang, Y., Akhmedov, N. G., Petersen, J. L., Shi, X.*, "Ambient Intermolecular [2 + 2] Cycloaddition: An Example of Carbophilicity and Oxophilicity Competition in Au/Ag Catalysis." Org. Lett., 2014, 16, 2478-2481.； 5）Xi, Y.‡, Su, Y.‡, Yu, Z., Dong, B., McClain, E. J., Yu, L.*, Shi, X.*, "Chemoselective Carbophilic Addition of α-Diazoesters through Ligand-Controlled Gold Catalysis." Angew. Chem. Int. Ed., 2014, 53, 9817-9821； 6) Su, Y.‡, Sun, X.‡, Wu, G., Jiao, ...

LI-COR now offers a portfolio of Click Chemistry reagents for copper-catalyzed and copper-free methods. These products offer researchers flexibility to choose the correct reagent for a diverse array of applications. LI-COR Click Chemistry reagents include IRDye® 800CW, IRDye 680RD, and IRDye 650 infrared fluorescent dyes labeled with DBCO, azide, or alkyne groups. Click Chemistry utilizes pairs of reagents that exclusively react with each other and are effectively inert to naturally-occurring functional groups such as amines. Unlike affinity interactions such as streptavidin-biotin, Click Chemistry forges covalent bonds between the reacting partners to deliver stable bioconjugates.. Click Chemistry reactions can be categorized into two separate groups, copper-catalyzed or copper-free. Copper-catalyzed Click Chemistry is used for initiating reactions between azides and alkynes. These reactions are also known as Copper-Catalyzed Azide-Alkyne Cycloaddition (CuAAC). Although they initiate and ...

TY - JOUR. T1 - Total synthesis of (+)- and (-)-galanthamine. AU - Kato, Tomoaki. AU - Tanimoto, Hiroki. AU - Yamada, Hisako. AU - Chida, Noritaka. PY - 2010/12/1. Y1 - 2010/12/1. N2 - The stereoselective total synthesis of (+)-galanthamine [(+)-1], an antipode of the natural product, and (-)-galanthamine [(-)-1] starting from D-glucose is described. The cyclohexene unit in (+)-1 was prepared in an optically active form from D-glucose using Ferriers carbocyclization reaction, and the benzylic quaternary carbon was stereoselectively generated via chirality transfer by Johnson-or Eschenmoser-Claisen rearrangement. The dibenzofuran skeleton was effectively constructed by the bromonium ion-mediated intramolecular dealkylating etherification. After the introduction of a carbon-carbon double bond, the Pictet-Spengler type cyclization, followed by reduction of an amide function afforded (+)-1. Starting from D-glucose, (-)-galanthamine [(-)-1] was also totally synthesized.. AB - The stereoselective ...

Rhodium-Catalyzed Intermolecular Alkyne Cyclotrimerization Route to a Functionalized CycloparaphenyleneRhodium-Catalyzed Intermolecular Alkyne Cyclotrimerization Route to a Functionalized Cycloparaphenylene ...

The use of functionalised recombinant spider silk as a sustainable advanced biomaterial is currently an area of intense interest owing to spider silks intrinsic strength, toughness, biocompatibility and biodegradability. This paper demonstrates, for the first time, the site-specific chemical conjugation of different organic ligands that confer either antibiotic or fluorescent properties to spider silk. This has been achieved by the incorporation of the non-natural methionine analogue L-azidohomoalanine (L-Aha) using an E. coli methionine auxotroph and subsequent copper catalysed azide-alkyne cycloaddition (CuAAC) or click chemistry functionalisation of 4RepCT3Aha. The 4RepCT3Aha protein can be modified either prior to, or post fibre formation increasing the versatility of this approach as demonstrated here by the formation of silk fibres bearing a defined ratio of two different fluorophores uniformly distributed along the fibres. Silk decorated with the fluoroquinone family broad spectrum ...

In this study, a novel approach was developed to synthesize aminophenylboronic acid functionalized magnetic nanoparticles (NPs) via Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry. Firstly, azide-functional Fe3O4 NPs were obtained by a two-step chemical modification process. Then, an alkyne-phenylboronic acid molecule was connected onto the surface of magnetite by the CuAAC reaction. The morphology, structure and composition of the synthesized nanocomposites were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), vibrating sample magnetometer (VSM), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectrometry (XPS). Five proteins, including ovalbumin (OB), transferrin (Trf), as glycoprotein templates and lysozyme (Lyz), bovine serum albumin (BSA), horse heart cytochrome c (Cyt C) as nonglycoprotein templates are chosen as target proteins. The as-prepared [email protected] NPs with a mean diameter of 23.2 nm showed a ...