TY - JOUR. T1 - An arene-alkene photocycloaddition-radical cyclization cascade. T2 - The first synthesis of cis,cis,cis,trans-[5.5.5.5]-fenestranes. AU - Wender, Paul A.. AU - Dore, Timothy. AU - DeLong, Mitch A.. PY - 1996/10/21. Y1 - 1996/10/21. N2 - The first cis,cis,cis,trans-[5.5.5.5]-fenestranes have been synthesized in three steps using a novel arene-alkene photocycloaddition-radical cyclization cascade, which creates overall 5 new rings and 8 stereogenic centers. A lead tetraacetate mediated ring expansion of a 5,5-fused ring system, discovered in the course of exploring the chemistry of these new materials, is also described.. AB - The first cis,cis,cis,trans-[5.5.5.5]-fenestranes have been synthesized in three steps using a novel arene-alkene photocycloaddition-radical cyclization cascade, which creates overall 5 new rings and 8 stereogenic centers. A lead tetraacetate mediated ring expansion of a 5,5-fused ring system, discovered in the course of exploring the chemistry of these new ...
The Nazarov cyclization is a common synthetic tool in the synthesis of cyclopentenone rings. The reaction is characterized by a divinyl ketone starting reagent that undergoes a 4π-electron electrocyclization after addition of a Lewis/Brønsted acid; forming the cyclopentadienyl cation that undergoes cyclization. An extension of this methodology involves using a divinyl imine starting reagent. This cyclization is less favoured due to the electron donating ability of the nitrogen atom, causing the pentadienyl cation to be relatively stable and unwilling to undergo cyclization. To improve this cyclization, the imine is replaced with the electron withdrawing nitronate functionality. It is hypothesized that by doing so the addition of an acid will form the cyclopentadienyl cation that will readily undergo Nazarov cyclization. The synthesis of an aryl vinyl silyl nitronate was optimized and the compound was tested with a number of different acid catalysts to determine if the nitronate Nazarov ...
Effect of primary polymer chain rigidity on intramolecular cyclization and intramolecular crosslinking in free-radical crosslinking monomethacrylatedimethacrylate copolymerizations., The effluent analysis of several pyrrone and polyimide precursors during cyclization., Reduction and cyclization to form poly(benzimidazole amide imide) copolymers., Thermal degradation of polymers. Part XIX. The thermal cyclization and characterization of quinazolone pre-polymers, Cationic cyclization of cis-1 4-polybutadiene I. Synthesis and technological evaluation of the polymer, ThreeFourFive-Component Diastereoselective Cyclization of Fischer Carbene Complexes Lithium Enolates and Allylmagnesium Bromide., Evolution of aggregation structure of polyacrylonitrile fibers in the cyclization reaction., Epoxy resins based on aromatic glycidylamines. III. Kinetics of intramolecular cyclization of N N-bis(2-hydroxy-3-chloropropyl)aniline, Cyclization during polyesterification Isolation of an 18-member ring compound from
A proposed universal monoterpene synthases (cyclases) cyclization mechanism topologically requires an isomerization step of the substrate geranyl diphosphate (GPP) to the formation of the proposed universal intermediate linalyl diphosphate (LPP), which has never been directly observed. The study described here was designed to investigate the cyclization mechanism by studying a model enzyme, (4R)-(+)-limonene synthase ((+)-LS), a monoterpene cyclase that produces (+)-limonene by using substrate GPP. The study synthesized two novel difluorinated substrate analogues, 8,9-difluorogeranyl diphosphate (DFGPP) and 8,9-difluorolinalyl diphosphate (DFLPP), which were designed to retard the cyclization step in order to observe the intermediate at the enzyme active site. Both analogues are proved to be substrates for (+)-LS. Compared to GPP, which has a kcat value of 0.0905 +/- 0.0070 s-1, DFGPP has a reduced kcat value at 0.00144 +/- 0.00002 s-1, showing a 69-fold slower rate in the catalytic reaction. ...
The iodine-catalyzed Prins cyclization of homoallylic alcohols and aldehydes was investigated under metal-free conditions and without additives. Anhydrous conditions and inert atmosphere are not required. The reaction of 2-(3,4-dihydronaphthalen-1-yl)propan-1-ol and 21 aldehydes (aliphatic and aromatic) in CH2Cl2 in the presence of 5 mol % of iodine gave 1,4,5,6-tetrahydro-2H-benzo[f]isochromenes in 54%-86% yield. Under similar conditions, the Prins cyclization of six alcohols containing an endocyclic double bond (primary, secondary, or tertiary) led to dihydropyrans in 52%-91% yield. The acyclic homoallylic alcohols gave 4-iodo-tetrahydropyran in 29%-41% yield in the presence of 50 mol % of iodine. This type of substrate is the main limitation of the methodology. The relative configuration of the products was assigned by NMR and X-ray analysis. The mechanism and the ratio of the products are discussed, based on DFT calculations.
Title: Metal-mediated Heterocyclization: Synthesis of Heterocyclic Compounds Containing More Than One Heteroatom Through Carbon-Heteroatom Bond Forming Reactions. VOLUME: 14 ISSUE: 8. Author(s):K. C. Majumdar, B. Roy, P. Debnath and A. Taher. Affiliation:Department of Chemistry, University of Kalyani, Kalyani- 741 235, India.. Abstract: Heterocyclic compounds are versatile building blocks in organic synthesis. These are important part in various natural products and bioactive compounds. Several methodologies have been developed to synthesize these heterocyclic compounds. This review article covers an updated (published during 2005 to 2008) summary of transition-metal catalyzed approaches for the syntheses of commonring heterocycles containing more than one heteroatom via the selective formation of carbon-heteroatom bonds. The five-membered ring heterocycles with two nitrogen atoms include imidazoles, pyrazoles, indazoles, imidazoindolones etc. and heterocycles with one nitrogen and one oxygen ...
A highly efficient method for the construction of pyrrolidinyl spirooxindoles with 3-isothiocyanato oxindoles and chalcones via a Michael/cyclization cascade reaction has been developed by using bifunctional cinchona-derived squaramide organocatalysts. A series of complex pyrrolidinyl spirooxindoles could be
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.. ...
The unprecedented combination of a palladium(ii) complex with a chiral Bu-QUOX ligand and a chiral phosphoric acid enables the highly efficient asymmetric oxidative tandem cyclization of N-(2,2-disubstituted hex-5-en-1-yl)acrylamides, providing a straightforward method to access chiral 6,5-bicyclic aza-heter
A cobalt-rhodium heterobimetallic nanoparticle-catalyzed reductive cyclization of 2-(2-nitroaryl)acetonitriles to indoles proceeds without any additives under mild conditions. The catalytic can be reused more than ten times without loss of catalytic activity.. ...
SYNTHESIS OF FUSED PYRAZOLES VIA INTRAMOLECULAR CYCLIZATION OF APPROPRIATELY ortho -SUBSTITUTED NITROARENES AND NITROHETEROARENES
Home » Visible light photocatalysis of radical cation Diels-Alder cycloadditions: preparation of tris(2,2-bipyrazyl)ruthenium(II) bis(tetrakis(3,5-bis(trifluoromethyl)phenyl)borate ...
ESI Induced Gas-Phase Nazarov Cyclization of (2E)-3-(2-Methoxyphenyl)-1-(thiophen-2-yl)-prop-2-en-1-one and its Oxygen Analogue ...
I. The acid catalyzed reactions of certain 1,5-epoxyolefins. The monoxides of a number of 1,5-dienes were prepared and treated with a variety of acidic reagents known to induce cyclization of the parent diolefins. In all cases the major reaction observed was the isomerization of the epoxide to a carbonyl function. No cyclic products were observed. These results are discussed in terms of the general requirements for cyclization.. II. The alkylative cyclization of 1,5-hexadiene The alkylation of 1,5 -hexadiene with t-butyl chloride in the presence of aluminum trichloride was studied. The major monomeric reaction products were cyclic, and both the t-butylcyclohexane and neopentylcyclopentane skeletons were identified among them. Formation of the latter ring system appeared to be slightly favored over formation of the six-membered ring. This preference is undoubtedly due to both steric and electronic factors.. III. The acid catalyzed cyclization of cis, cis- and trans, trans-2,6-octadiene. Both cis, ...
In organic chemistry, an electrocyclic reaction is a type of pericyclic rearrangement where the net result is one pi bond being converted into one sigma bond or vice versa. These reactions are usually categorized by the following criteria: Reactions can be either photochemical or thermal. Reactions can be either ring-opening or ring-closing (electrocyclization). Depending on the type of reaction (photochemical or thermal) and the number of pi electrons, the reaction can happen through either a conrotatory or disrotatory mechanism. The type of rotation determines whether the cis or trans isomer of the product will be formed. The Nazarov cyclization reaction is a named electrocyclic reaction converting divinylketones to cyclopentenones. A classic example is the thermal ring-opening reaction of 3,4-dimethylcyclobutene. The cis isomer exclusively yields cis,trans-2,4-hexadiene whereas the trans isomer gives the trans,trans diene: This reaction course can be explained in a simple analysis through the ...
A novel cascade reaction involving oxidative dearomatization/semipinacol rearrangement of indol-2-yl cyclobutanols is explored with N-sulfonyloxaziridine (Davis oxaziridines) as oxidant, generating various 2-spiroquaternary 3-oxindoles in modest to good yields. This method might be useful in the synthesis of indole-based alkaloids bearing 2-spiroquaternary carbon centers. PTS=p-toluenesulfonic acid monohydrate. ...
Significant advances in metal-catalyzed reactions, especially cyclizations, have dramatically improved the efficiency of organic synthesis over the last three decades. To date these transformations are widely used in the area of synthesis of both natural products and therapeutic agents. "Science of Synthesis: Metal-Catalyzed Cyclization Reactions" presents the most commonly used and significant metal-catalyzed reactions for modern organic synthesis. The basic principles, the current state of the art, scope, limitations, and mechanism of these reactions are also discussed. Typical examples of target synthesis are provided to help inspire further applications ...
Thieme eBooks, Significant advances in metal-catalyzed reactions, especially cyclizations, have dramatically improved the efficiency of organic synthesis over the last three decades. To date these transformations are widely used in the area of synthesis of both natural products and therapeutic agents. Science of Synthesis: Metal-Catalyzed Cyclization Reactions presents the most commonly used and s...
Synthesis of Novel Steroid-Peptoid Hybrid Macrocycles by Multiple Multicomponent Macrocyclizations Including Bifunctional Building Blocks MiBs. . Biblioteca virtual para leer y descargar libros, documentos, trabajos y tesis universitarias en PDF. Material universiario, documentación y tareas realizadas por universitarios en nuestra biblioteca. Para descargar gratis y para leer online.
Chen, H. [陳浩國]. (2009). Silver catalyzed enyne cyclization reactions. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_ ...
The importance of dynamics in simple reactions is made yet again in a recent study by Doubleday and Houk in 1,3-dipolar cycloadditions.1 They looked at the reaction of acetylene or ethylene with either nitrous oxide, diazonioazanide, or methanediazonium. The transition state for these 6 reactions all show a concerted reaction. The transition vector has three major components; (a) symmetric formation/cleavage of the two new σ bonds, (b) bending of the dipolar component, or (c) symmetric bending of the hydrogens of ethylene or acetylene.. Classical trajectories were traced from the transition state back to reactant and forward to product. In the approach of the two fragments, the dipole bend vibrates, but then after the TS, it needs to bend quickly to close the 5-member ring. This means that the bending mode effectively has to "turn a corner" in phase space, and without energy in this mode, the molecules will simple bounce off of each other. Analysis of the reactants indicates significant ...
Synlett, 2009, 1208-1218. Anodic electrochemistry is a powerful tool for generating radical cation intermediates and initiating new cyclization reactions. Like most electrochemical reactions, the transformations involve umpolungs. In this review, recent studies examining the intramolecular coupling of radical cations derived from enol ethers, vinyl sulfides, and ketene acetals with carbon, oxygen, and nitrogen trapping groups are discussed to highlight their synthetic potential.. ...
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
Autor: Glas, Adrian et al.; Genre: Zeitschriftenartikel; Im Druck veröffentlicht: 2015-01; Keywords: cyclic peptides; hydrophobic cross-links; ring-closing metathesis; protein-protein interactions; Pseudomonas aeruginosa; Titel: Constraining Peptide Conformations with the Help of Ring-Closing Metathesis
TY - JOUR. T1 - Synthetic studies of cis-3a-aryloctahydroindole derivatives by copper- catalyzed cyclization of N-allyltrichloroacetamides. T2 - Facile construction of benzylic quaternary carbons by carbon-carbon bond-forming reactions. AU - Iwamatsu, Sho Ichi. AU - Matsubara, Kouki. AU - Nagashima, Hideo. PY - 1999/12/24. Y1 - 1999/12/24. N2 - Cyclization of N-(2-aryl-2-cyclohexen-1-yl)trichloroacetamides by a copper catalyst was investigated. It is crucially important for successful cyclization under mild conditions that alkoxycarbonyl groups are introduced to the nitrogen atom of the N-allyltrichloroacetamides as well as that CuCl- (bipyridine) is used as the catalyst. Three compounds, N-(2-phenyl-2- cyclohexen-1-yl)-, N-[2-(3,4-dimethoxyphenyl)-2-cyclohexen-l-yl]-, and N-[2- (3,4-methylenedioxyphenyl)-2-cyclohexen-1-yl]trichloroacetamides, where the Cbz or MeO2C- group was attached to the nitrogen atom, were instantly converted to the corresponding trichlorinated cis-3a-aryloctahydroindol-2- ...
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 ...
The enantiopure γ-amino alcohols 7 and 18 are prepared by using the diastereoselective michael addition of lithium N-benzyl ( R )-α-methylbenzylamide to α,β-unsaturated esters as a key step. The michael addition of 7 or 18 to an alkynone 8 followed by an intramolecular cyclization afford the cyclic enzmine 10 or 20. which are subjected to the diastereoselective hydrogenation, and the subsequent transformations provide 6-epi-alkaloid 223A and alkaloid 223A, respectively ...
Photochemical cleavage reactions have found a widespread used in biological applications that require the photorelease of biologically active molecules such as proteins, peptides, neurotransmitters, and nucleotide phosphates. This research focuses on the design of photoremovable protecting groups which can be utilized to release these biomolecules by photolysis. These biomolecules are attached to the photoremovable protecting group at the sites of functional groups that are present within these substrates. Such functional groups are carboxylates, phosphates, thiolates, or phenolates, which upon exposure to light, are released as anions of varying basicities. The photochemical reaction involved is an electrocyclic ring closure between aromatic groups that are bridged by a carboxamide linkage. The key intermediate produced by electrocyclization is thought to have zwitterionic character. This zwitterionic intermediate is believed to expel the leaving group as the anion. One of the aromatic groups attached
The research developed in this Doctoral Thesis comprises from the preparation of polyaromatic compounds to the synthesis of natural product derivatives, highlighting the proficiency of homogeneous gold catalysis for the construction of molecular diversity.. A novel approach for the synthesis of a new trindane-based crushed fullerene C60 was developed by a threefold palladium-catalyzed cross-coupling of four suitably functionalized C15 trindene fragments. The trindane C15 skeleton of the central motif was constructed through a triple gold(I)-catalyzed oxidative cyclization.. The scope of the intramolecular gold(I)-catalyzed formal [2+2+2] cycloaddition reaction was extended to O-protected homopropargylic and allylic oxo-1,5-enynes. Under the optimized reaction conditions, the cyclization of (Z)- and (E)- isomers takes place with moderate to excellent yield and increased selectivity in most of the cases, providing access to octahydro-1H-indenes skeletons.. The mastery of gold(I) complexes for the ...
Molecular complexity is one of the key reasons why fragment-based lead discovery should work. As described in 2001 by Mike Hann and colleagues at GlaxoSmithKline, the idea is that very small, simple molecules are likely to be able to bind to many different sites on many different proteins; think of the water molecule as being an extreme example of this. As molecules become larger and more complex, they are less likely to bind to any given site on a protein, though if they are complementary to a site the potency will be greater. Similarly, more complex molecules are more likely to have a single binding mode than smaller, less-decorated molecules, which could assume multiple orientations at a single site. These intuitive ideas were supported by a simple computational model that suggested that there is an optimum complexity where molecules would be simple enough that they would bind to several different targets (and thus be useful in a screening collection) while still being complex enough to bind ...
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.
While considering the increasing environmental pollution and its intensive impact on living systems, developing chemical processes using more environmentally acceptable chemicals, catalysts, solvents, atom-efficient methods and energy-efficient technologies eliminating waste production as well as employing renewable raw materials are experiencing a profound challenge to meet sustainability criteria [1,2]. In addition, the environmental risks posed by the toxic and volatile organic solvents have become a major concern. The reason is that the organic transformations employ higher consumption of solvents than the reagents and the employed solvents are difficult to recycle [3]; for the process to be in line with the green chemistry principles, the first task is to replace the toxic catalysts and hazardous organic solvents with green ones.. Performing organic reactions in water has attracted much attention over the past decades due to its numerous advantages such as being considerably safe, nontoxic, ...
Close The Infona portal uses cookies, i.e. strings of text saved by a browser on the users device. The portal can access those files and use them to remember the users data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser. ...
TY - JOUR. T1 - Acetyl cation facilitated cyclizations of olefinic aldehydes. III. factors determining regiochemistry in acroleins. AU - Andersen, Niels H.. AU - Ladner, David W.. AU - Moore, Ana L. PY - 1978/1/1. Y1 - 1978/1/1. UR - http://www.scopus.com/inward/record.url?scp=84918114464&partnerID=8YFLogxK. UR - http://www.scopus.com/inward/citedby.url?scp=84918114464&partnerID=8YFLogxK. U2 - 10.1080/00397917808063571. DO - 10.1080/00397917808063571. M3 - Article. AN - SCOPUS:84918114464. VL - 8. SP - 437. EP - 448. JO - Synthetic Communications. JF - Synthetic Communications. SN - 0039-7911. IS - 7. ER - ...
Department of Chemistry, UBC Faculty of Science. Vancouver Campus. 2036 Main Mall. Vancouver, BC Canada V6T 1Z1. Tel: 604.822.3266. Fax: 604.822.2847. ...
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.
Hoffmann, R.; Tantillo, D. J. Angew. Chem. Int. Ed. 2003, 42, 5877-5882: Breaking Down Barriers: The Liaison Between Sigmatropic Shifts, Electrocyclic Reactions and 3-Center Cations. Ponec, R.; Bultinck, P.; Van Damme, S.; Carbo, R.; Tantillo, D. J. Theor. Chem. Acc. 2005, 113, 205-211: Geometric and Electronic Similarities between Transition Structures for Electrocyclizations and Sigmatropic Hydrogen Shifts. Tantillo, D. J. Annu. Rep. Prog. Chem., Sect. B 2006, 102, 269-289: Reaction Mechanisms. Part (ii) Pericyclic Reactions. Tantillo, D. J.; Lee, J. K. Annu. Rep. Prog. Chem., Sect. B 2007, 103, 272-293: Reaction Mechanisms. Pericyclic Reactions. Lee, J. K.; Tantillo, D. J. Annu. Rep. Prog. Chem., Sect. B 2008, 104, 260-283: Reaction Mechanisms. Pericyclic Reactions. Nouri, D. H.; Tantillo, D. J. Tetrahedron 2008, 64, 5672-5679: Sigmatropic Shifts and Cycloadditions on Neutral, Cationic, and Anionic Pentadienyl + Butadiene Potential Energy Surfaces. Tantillo, D. J. Angew. Chem. ...
First, NICS(0) values for a series of related intermolecular anionic attack at alkynes show some interesting trends (Table 1). Two of the transition states look like they might be aromatic: the TSs for the 3-exo-dig and the 5-endo-dig reaction have NICS(0) values that are quite negative. However, given the geometry of these TSs, particularly the close proximity of the σ bonds to the ring center, one might be concerned about contamination of these orbitals. So, NICS(0)MOzz computations, which look at the tensor component perpendicular to the ring using just the π-MOs, shows that the 3-exo-dig is likely non-aromatic (NICS(0)MOzz is near zero), the TS for the 4-endo-dig reaction is antiaromatic (NICS(0)MOzz very positive) and the TS for the 5-endo-dig reaction is aromatic (NICS(0)MOzz is very negative. So this last reaction is the first example of an aromatic transition that is not for a pericyclic reaction ...
Close The Infona portal uses cookies, i.e. strings of text saved by a browser on the users device. The portal can access those files and use them to remember the users data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser. ...
TrendTerms displays relevant terms of the abstract of this publication and related documents on a map. The terms and their relations were extracted from ZORA using word statistics. Their timelines are taken from ZORA as well. The bubble size of a term is proportional to the number of documents where the term occurs. Red, orange, yellow and green colors are used for terms that occur in the current document; red indicates high interlinkedness of a term with other terms, orange, yellow and green decreasing interlinkedness. Blue is used for terms that have a relation with the terms in this document, but occur in other documents ...
The 1,3-dipolar cycloaddition of acyclic 2-diazo-1,3-dicarbonyl compounds (DDC) and thioketones preferably occurs with Z,Econformers and leads to the formation of transient thiocarbonyl ylides in two stages. The thermodynamically favorable further transformation of C=S ylides bearing at least one acyl group is identified as the 1,5-electrocyclization into 1,3-oxathioles. However, in the case of diazomalonates, the dominating process is 1,3-cyclization into thiiranes followed by their spontaneous desulfurization yielding the corresponding alkenes. Finally, carbocyclic diazodiketones are much less reactive under similar conditions due to the locked cyclic structure and are unfavorable for the 1,3-dipolar cycloaddition due to the Z,Z-conformation of the diazo molecule. This structure results in high, positive values of the Gibbs free energy change for the first stage of the cycloaddition process ...
As many of you know Derek Lowes In The Pipeline blog sometimes features "Things I Wont Work With". One particular entry describes selenophenol (PhSeH) in all of its stinky glory. After the failure of several endgame strategies we considered a radical cyclization approach to D-ring formation. Attempts to install various radical precursors at the anomeric position were surprisingly unsuccessful except for one, PhSeH. Completion of the synthesis seemed so close at the time that we decided to go ahead and use PhSeH. Unfortunately, installation of the selenoacetal required the use of PhSeH as a solvent in the presence of ZnI2. We attempted to use PhSeH in quantities up to a 1:1 solvent mixture with MeCN with no success, leaving no option other than using PhSeH as the solvent. The selenoacetal was installed on a model substrate (the Claisen rearrangement yield problem had not been solved at this point) followed by installation of an alkynoate. Treatment of the alkynoate model substrate with Bu3SnH ...
As many of you know Derek Lowes In The Pipeline blog sometimes features "Things I Wont Work With". One particular entry describes selenophenol (PhSeH) in all of its stinky glory. After the failure of several endgame strategies we considered a radical cyclization approach to D-ring formation. Attempts to install various radical precursors at the anomeric position were surprisingly unsuccessful except for one, PhSeH. Completion of the synthesis seemed so close at the time that we decided to go ahead and use PhSeH. Unfortunately, installation of the selenoacetal required the use of PhSeH as a solvent in the presence of ZnI2. We attempted to use PhSeH in quantities up to a 1:1 solvent mixture with MeCN with no success, leaving no option other than using PhSeH as the solvent. The selenoacetal was installed on a model substrate (the Claisen rearrangement yield problem had not been solved at this point) followed by installation of an alkynoate. Treatment of the alkynoate model substrate with Bu3SnH ...
Practice solving Monosaccharides - Cyclization problems. Master even the most complex scientific problems with our step-by-step explanation videos.
... Solstice-TDS 2016.1 Product Release: Beaverton, Ore., June 23, 2016 - Test Systems Strategies, Inc. (
Iwata, C.; Takemoto, Y.; Kubota, H.; Yamada, M.; Uchida, S.; Tanaka, T.; Imanishi, T., 1989: Synthetic studies on spirovetivane phytoalexins. III. A total synthesis of (+or-)-lubiminol
Joint first authorship. • Ali Nakhi, Md Shafiqur Rahman, Guru Pavan Kumar Seerapu, Rakesh Kumar Banote, Kummari Lalith Kumar, Pushkar Kulkarni, Devyani Haldar, Manojit Pal. Transition metal free hydrolysis/cyclization strategy in a single pot: synthesis of fused furo N-heterocycles of pharmacological interest. Organic & Biomolecular Chemistry, 2013.. • Dhilli Rao Gorja, Soumita Mukherjee, Chandana Lakshmi T. Meda, Girdhar Singh Deora, Ankit Jain, Girish H Chaudhari, Keerthana S. Chennubhotla, Rakesh Kumar Banote, PushkarKulkarni, Kishore V. L. Parsa, K. Mukkanti, Manojit Pal. N-Indolylmethyl substituted olanzapine: Their design, synthesis and pharmacological evaluation as PDE4B inhibitors. Organic & Biomolecular Chemistry, 2013.. • P. Mahesh Kumar, K. Siva Kumar, Chandana L. T. Meda, G. Rajeshwar Reddy, Pradeep K. Mohakhud, K. Mukkanti, G. Rama Krishna, C. Malla Reddy,D. Rambabu, K. Shiva Kumar, K. Krishna Priya, Keerthana Sarma Chennubhotla, Rakesh Kumar Banote, Pushkar Kulkarni, Kishor ...
Total syntheses of circumdatin F and circumdatin C, which both possess a 3H-quinazolin-4-one as well as a 1,4-benzodiazepin-5-one moiety, are described. A tripeptide derivative was synthesized as a key intermediate and dehydrated to a benzoxazine by reaction with triphenylphosphine, iodine, and a tertiary amine. The natural products were attained via rearrangements to an amidine intermediate, deprotection with 45% HBr in acetic acid, and cyclization on silica gel.. ...
We are pleased to welcome Raul all the way from Ruben Martins group at ICIQ! He will be collaborating with Mingyu on alkynes of fun chemistry!
Disclosed herein is an improvement in a method for distinguishing cells in a biological sample by staining with a dye, wherein the improvement comprises employing as the dye a compound of the formula ##STR1## wherein G is O or S; R1, R3, and R5 are independently selected from the group consisting of hydrogen, alkyl, aryl, aralkyl, amino, styryl, bis(diaryl)vinylene, and ##STR2## wherein R is hydrogen or alkyl; Z represents the elements necessary to complete a basic heterocyclic ring system of the type used in cyanine dyes; n is 0 or 1; R2 is hydrogen or, taken together with either R1 or R3, represents the elements needed to complete an aromatic or a carbocyclic ring system; R4 is hydrogen or, taken together with either R3 or R5, represents the elements needed to complete an aromatic or a carbocyclic ring system; and X- is an anion.