Loading...
  • formation
  • Reaction initiation through single-electron oxidation alleviates chemoselectivity problems that can arise from conventional Lewis acid initiated methods for electrophile formation. (docme.ru)
  • This process has been utilized for bimolecular carbon-carbon bond formation, but these reactions proceed efficiently only with electron-rich arenes, and either require high temperatures with ketone nucleophiles or dicarbonyl/Lewis acid mixtures, or the addition of pregenerated nucleophiles such as enolsilanes after cation formation. (docme.ru)
  • Although the Hofmann-Löffler-Freytag reaction was to become a general and expeditious process for the formation of pyrrolidines, it was not until about 25 years after Hofmann's work that further examples of the reaction appeared in the literature. (wikipedia.org)
  • Wynberg proposed that this reaction proceeded via the formation of a thiolate-alkylammonium tight ion pair and activation of the enone electrophile by a hydrogen bond from the catalyst's hydroxyl group. (hammersmithendocrinology.org)
  • After the failure of several endgame strategies we considered a radical cyclization approach to D-ring formation. (blogspot.com)
  • As the rate of reaction is influenced by the concentration of base, the formation of a hypervalent intermediate is generally accepted, but the question, whether the subsequent decomposition involves a rotationally hindered diradical or a concerted symmetry-allowed non-linear cheletropic pathway has not yet been answered. (organic-chemistry.org)
  • 7 , 12 , 15 , 19 , 20 , 22 Second, reaction of a metal ion such as Hg(II) with the thiol ester formally creates a highly reactive trivalent sulfur species, and thus ester (and lactone) formation proceeds very rapidly at room temperature or below. (orgsyn.org)
  • The second aspect studied in this thesis is based on physicochemical studies of short RNA molecules utilizing NMR based pH titration and alkaline hydrolysis reactions ( Paper IV - V ). The NMR based ( 1 H and 31 P) pH titration studies revealed the effect of guaninyl ion formation, propagated electrostatically through a single stranded chain in a sequence dependent manner. (diva-portal.org)
  • The internucleotidic phosphodiesters, which were influenced by guaninyl ion formation, were hydrolyzed at a faster rate than those sequences where such guaninyl ion formation was prevented by replacing G with N 1-Me -G. (diva-portal.org)
  • While photoredox-catalyzed radical formation combined with nickel catalysis has recently flourished as an elegant solution for C-C bond formation from various functional groups, including native carboxylic acids ( 3 ) and easily oxidized C-H bonds ( 4 ), the widespread availability of olefinic building blocks and natural products has triggered remarkable advances on radical hydroalkylation reactions. (sciencemag.org)
  • With more polarized enol ether derived radical cations, the cyclizations work best for the formation of furanose derivatives where the rate of five-membered ring formation precludes elimination reactions triggered by the radical cation. (wustl.edu)
  • This previously has only rarely been possible because aryne formation is typically rate-limiting, making it challenging to probe the kinetics of subsequent trapping reactions. (rsc.org)
  • pH-rate profiles of CPS and β -LS supported the importance of a Tyr-Glu dyad in β -lactam formation and suggested its reverse protonation in β -LS. (pubmedcentralcanada.ca)
  • Catalysis
  • Although the aldehyde was known in the literature, we found the reported 20% yield of the product to be an unbreakable barrier for the classic Claisen rearrangement despite our best attempts at catalysis and variation of reaction conditions. (blogspot.com)
  • oxidation
  • Long-term stability of macrocycles derived from DFS and their stability toward oxidation further supports DFS as a promising method for modification of peptide-based ligands, cyclization of genetically-encoded peptide libraries, and discovery of bioactive macrocyclic peptides. (rsc.org)
  • The anodic coupling of olefins with amine trapping groups to form proline and pipecolic acid derivatives with a quaternary α carbon atom (see scheme) was successful despite the significantly lower oxidation potential of the product relative to that of either functional group in the substrate: owing to the very fast cyclization, the oxidation potential of the substrate is lower than that of the product. (wustl.edu)
  • ligands
  • The turnover rates are strongly dependent on the type of β-diketiminate used, where ligands with electron-withdrawing substituents, i.e., trifluoromethyl groups, provided complexes that efficiently catalyze the addition of CCl₄ or toluenesulfonyl chloride to styrene. (rero.ch)
  • yield
  • However, the authors reported that substituents on the triple bond of 7 affect the yield of the following cyclization step, since increased conjugation enhances the reaction rate and also increases the product yield. (organic-chemistry.org)
  • Under these conditions the reaction was complete within 10 minutes at room temperature to provide 2 in 77 % yield as a single diastereomer. (docme.ru)
  • Although we were able to achieve some degree of asymmetric induction using phenylalanine, the yield of the reaction remained low despite optimization efforts. (blogspot.com)
  • This brominative cyclization does not always proceed in good yield, but has been used for the biomimetic construction of marine natural products. (paperplane.io)
  • amine
  • http://onlinelibrary.wiley.com/doi/10.1002/cber.19110440309/abstract;jsessionid=88DB9E8643AD7A2A200A0D7E1EDBE471.d01t01 Pictet, Spengler The reaction is a cyclization between an amine that carries an aromatic ring, and an aldehyde, usually catalyzed by acid (Scheme 1911 Pictet Spengler 2). (openwetware.org)
  • The Hofmann-Löffler reaction (also referred to as Hofmann-Löffler-Freytag reaction, Löffler-Freytag reaction, Löffler-Hofmann reaction, as well as Löffler's method) is an organic reaction in which a cyclic amine 2 (pyrrolidine or, in some cases, piperidine) is generated by thermal or photochemical decomposition of N-halogenated amine 1 in the presence of a strong acid (concentrated sulfuric acid or concentrated CF3CO2H). (wikipedia.org)
  • chemistry
  • The development of a strategy for conducting Pd(0)-catalyzed reactions on the chips should greatly expand the synthetic chemistry available for building chip-based libraries. (wustl.edu)
  • During efforts to develop chip-based Heck reaction chemistry, it was discovered that normal solution-phase Heck reactions can be dramatically accelerated using electrochemistry. (wustl.edu)
  • We show that this strategy, rather undocumented in the field of synthetic organic chemistry, can be used in a radical chain reaction to enable notoriously intractable transformations. (sciencemag.org)
  • By enabling the buildup of large molecular libraries, the advent of transition metal-catalyzed aryl-aryl, aryl-alkenyl, and aryl-akynyl cross-coupling reactions has been driving a whole segment of bioorganic chemistry toward aromatic frameworks. (sciencemag.org)
  • Asymmetric Pictet -Spengler Reactions Employing N,N-Phthaloyl Amino Acids as Chiral Auxiliary Groups** H e r b e r t Waldmann,' G u n t h e r Schmidt, H e n n i n g H e n k e , and Michael B u r k a r d 1 Ti(OnPr), The Pictet-Spengler reaction is one of the most important methods in heterocyclic and natural product chemistry. (docme.ru)
  • substituents
  • The reaction barriers of the two pathways were nearly identical, differing by less than ~1 kcal/mol, no matter what the substituents were. (ebscohost.com)
  • The reaction is accelerated by electron-donor substituents at 4-position of benzamidoxime and by electron-acceptor substituents at 4'-position of benzoyl. (cas.cz)
  • The dependence of the rate constants vs σ values of the substituents fulfils the two-parameter Hammett equation at a 99% probability level. (cas.cz)
  • In contrast, complexes with electron-donating substituents on the β-diketiminate promoted efficient ATR cyclization of N -allyl- N -phenyltrichloroacetamide and 2,2,2-trichloroethyl ether. (rero.ch)
  • alcohol
  • Best reaction conditions for ring opening of 16 to succinates or propionates17 were achieved using alcohol/silica gel, while cyclization of 17 to benzoxazinones 18 was easily done with HCl/alcohol. (edu.mx)
  • benzaldehyde
  • 12. Avoid sequences that may lead to unwanted reaction at other sites of the molecule b CH3 Toluene Therefore b to be adopted as nitration of benzaldehyde may lead to side reaction i.e. (slideshare.net)
  • Heck Reaction
  • Pd(0) was generated at preselected sites on an electrochemically addressable chip and then utilized to effect a Heck reaction. (wustl.edu)
  • Catalytic
  • Unlike most mediated electrochemical reactions, the electrolysis in this case was not used to convert a stoichiometric process into a catalytic one by recycling the metal. (wustl.edu)
  • 11 , 29 The rate of the reaction is very slow, but can be enhanced by the addition of a catalytic amount of gaseous Hydrogen Chloride or Hydrogen Bromide . (paperplane.io)
  • acids
  • Moreover, the authors expanded the reaction scope to obtain 1,2,3-trisubstituted indoles by switching the order of addition of the two boronic acids. (organic-chemistry.org)
  • Transition-metal free reactions of boronic acids: cascade addition - ring-opening of furans towards functionalized γ-ketoaldehydesS. (hammersmithendocrinology.org)
  • Biocompatibility of this reaction makes it attractive for derivatization of proteins and peptide libraries comprised of 20 natural amino acids. (rsc.org)
  • Reactions of O,O-dialkyldithiophosphoric acids with non-activated a-olefins. (ebscohost.com)
  • Asymmetric PictetЦSpengler Reactions Employing N N-Phthaloyl Amino Acids as Chiral Auxiliary Groups. (docme.ru)
  • enhances
  • Particularly important is the observation that, relative to bimolecular addition reactions, appending nucleophilic groups to the ether enhances the range of the benzylic groups that can serve as cation precursors. (docme.ru)
  • alkene
  • In 1878, the structure of piperidine was still unknown, and A. W. Hofmann made attempts to add hydrogen chloride or bromine to it in the belief that the compound possessed unsaturation (i.e. he performed standard alkene classification test reactions). (wikipedia.org)
  • reagents
  • Over the last several years the need to improve efficiency and minimize waste has spurred chemists to develop new catalysts for a wider range of reactions that was previously only achievable using stoichiometric reagents. (ebscohost.com)
  • mmol
  • We resorted to setting up many 2 mmol scale reactions in parallel, but this was a cumbersome and not very efficient work around the issue. (blogspot.com)