34182-03-1Relevant academic research and scientific papers
Chemoselective activation of trimethylsilyl enol ether functionalities in the presence of silyl-protected alcohols by trimethylsilyl-nonaflyl exchange
Boltukhina, Ekaterina V.,Sheshenev, Andrey E.,Lyapkalo, Ilya M.
experimental part, p. 3507 - 3515 (2011/12/04)
Trimethylsilyl enol ethers bearing trialkylsilyl-protected hydroxy groups were converted into synthetically valuable bifunctional alkenyl nonaflates under the action of nonafluorobutane-1-sulfonyl fluoride combined with potassium fluoride in the presence
Formation of trans-verbenol and verbenone from α-pinene catalysed by immobilised Picea abies cells
Vanek, Tomas,Halik, Jan,Vankova, Radmila,Valterova, Irena
, p. 321 - 325 (2007/10/03)
Both enantiomers and the raceinate of α-pinene were transformed by Picea abies cells immobilised on alginate. The main products were cis- and trans-verbenol, the later being further transformed to verbenone. The enantiomeric purity of each product more or less corresponded to that of the substrate. Transformation by free cells was faster than that by the immobilised cells. The ratio of products differed to some extent between the transformation by tree and immobilised cells.
Scope of enantioselective Palladium(II)-catalyzed aerobic alcohol oxidations with (-)-sparteine
Mandal, Sunil K.,Jensen, David R.,Pugsley, Jacob S.,Sigman, Matthew S.
, p. 4600 - 4603 (2007/10/03)
Evaluation of the substrate scope for Pd(II)/ (-)-sparteine catalyzed aerobic oxidative kinetic resolution of secondary alcohols is disclosed. An improved system is found with use of tert-butyl alcohol solvent in which benzylic and aliphatic alcohols as well as alcohols containing olefins are effectively oxidatively resolved. For substrates that successfully undergo oxidative kinetic resolution, krel values are generally between 10 and 20. Successful scale-up of various substrates to 10-mmol scale is described. Extension to oxidative desymmetrization of 1,3-meso-diols is successful with enantiomeric excesses ranging from 78 to 85%.
Palladium-catalyzed aerobic oxidative kinetic resolution of alcohols with an achiral exogenous base
Mandal, Sunil K.,Sigman, Matthew S.
, p. 7535 - 7537 (2007/10/03)
Substitution of exogenous (-)-sparteine for a more practical achiral base in the aerobic oxidative kinetic resolution of secondary alcohols is described. Carbonate bases are the most effective of those screened and allow for effective kinetic resolution of benzylic, allylic, and aliphatic substrates. The procedure was also successfully extended to the oxidative desymmetrization of meso diols.
One-pot transformation of silyl enol ethers into 1,3-dienes: In situ generation of alkenyl nonaflates and subsequent Heck reactions - Scope and limitations
Lyapkalo, Ilya M.,Webel, Matthias,Reissig, Hans-Ulrich
, p. 3646 - 3658 (2007/10/03)
Palladium-catalysed reactions between methyl acrylate and the isolated alkenyl nonaflates 2a, 2d and 2e proceed without difficulties, furnishing the desired 1,3-dienes 3, 14 and 15 in good yields. The use of other alkenyl nonaflates and olefins in this Heck reaction was also examined. The main purpose of this study was the development of an in situ generation of the required alkenyl nonaflates 2 from the corresponding silyl enol ethers 1 and their one-pot transformation into 1,3-dienes. Thus, the previously described fluoride-promoted exchange of the trimethylsilyl substituent of typical enol ethers 1 for a nonafluorobutylsulfonyl group was directly combined with the palladium-catalysed coupling step. This sequence allowed the efficient transformation of a variety of silyl enol ethers 1 into highly substituted 1,3-dienes in a practical one-pot procedure. The scope and limitations, together with the chemo- and stereoselectivity, of this process are discussed. A particular intriguing example involves a one-pot synthesis of silyl enol ether 1j by means of a Diels-Alder reaction, subsequent nonaflation and a Heck reaction with tert-butyl acrylate, furnishing the highly functionalised 1,3-diene 30 in good overall yield. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
Asymmetrization of all-cis-3,5-dihydroxy-1-(methoxycarbonyl)cyclohexane and of the 4-methyl and 4-ethyl substituted homologues
Zhao, Yurui,Wu, Yusheng,De Clercq, Pierre,Vandewalle, Maurits,Maillos, Philippe,Pascal, Jean-Claude
, p. 3887 - 3900 (2007/10/03)
Enantiomerically pure mono acylated derivatives of cis,cis-3,5-dihydroxy-1-(methoxycarbonyl)cyclohexane 1, all-cis-3,5-dihydroxy-4-methyl-1-(methoxycarbonyl)cyclohexane 2 and all-cis-3,5-dihydroxy-4-ethyl-1-(methoxycarbonyl)cyclohexane 3 were obtained upon lipase catalyzed asymmetrization. PPL-catalyzed transesterification of 1 with vinyl acetate led in high yield to the (S)-monoacetate (+)-13. With substrates 2 and 3 this process was slower and gave the (R)-monoacetates (-)-14 and (-)-15; the best results were obtained with SAM II lipase. On the other hand, enantiotoposelective hydrolysis of their diacetates and especially dibutyrates gave useful results only for the 4-substituted substrates and produced the (S)-monoesters. Copyright (C) 2000 Elsevier Science Ltd.
Applications of High-Temperature Aqueous Media for Synthetic Organic Reactions
An, Jingyi,Bagnell, Laurence,Cablewski, Teresa,Strauss, Christopher R.,Trainor, Robert W.
, p. 2505 - 2511 (2007/10/03)
Preparative organic synthesis was investigated in aqueous media at temperatures up to 300°C. Experiments were conducted with a recently disclosed pressurized microwave batch reactor (MBR) or in conventionally heated autoclaves. Thirty-six examples are presented. Among these, methods were developed for a Fischer synthesis, an intramolecular aldol condensation that was scaled up, decarboxylation of indole-2-carboxylic acid, Rupe rearrangement of 1-ethynyl-l-cyclohexanol, isomerization of carvone to carvacrol, and conversion of phenylacetylene to acetophenone. The applicability of high-temperature water was also demonstrated for biomimetic processes important in food, flavor, and aroma chemistry and for tandem reactions such as formation of 2-methyl-2,3- dihydrobenzofuran from allyl phenyl ether. When addition of acid or base was necessary, less agent was usually required for high-temperature processes than for those at and below boiling, and the reactions often proceeded more selectively. In some instances the requirement was orders of magnitude lower, with obvious consequences for safe, economic processing and for lowering costs of effluent disposal. The diversity of reactions indicates that high-temperature aqueous media could play an increasingly important role in the development of new preparative processes.
Pheromone Synthesis, CIV.- Synthesis of the Enantiomers of α-Phellandren-8-ol (p-Mentha-1,5-dien-8-ol), a Monoterpene from Bark Beetles
Mori, Kenji,Igarashi, Yasuhiro
, p. 93 - 96 (2007/10/02)
Enantiomerically pure (R)-α-phellandren-8-ol (p-mentha-1,5-dien-8-ol, 1a) was synthesized from (R)-carvone (2).Similarly (S)-1a was synthesized from (S)-2.
Stereocontrolled Regiospecificity of the Water Loss from trans-Sobrerol Radical Cation upon Electron Ionization
Selva, Antonio,Ferrario, Francesco,Ventura, Paolo,Pellegata, Renato
, p. 523 - 529 (2007/10/02)
Water loss from trans-sobrerol upon electron impact ionization selectively involves the tertiary OH group, predominantly occuring by a stereocontrolled H-transfer from C(5) position in a rate-determining step process, as proved by 18O and deuterium labelling.Monomethyl ethers behave accordingly.Ionic structures of the water-loss product or products are investigated by metastable ion and collision activation mass-analysed ion kinetic energy spectroscopy, using model ions generated from some substrates, which are chemically related to trans-sobrerol in condensed phase, i.e. α-pinane epoxide, cis-sobrerol and pinol.A substantial conversion of cis-sobrerol molecular ions to ionized pinol by loss of water has been demonstrated.
Monoterpenoid Chemistry - Part 3. Stereoselective Synthesis of the Major Oxygenated Metabolites of trans-Sobrerol
Pellegata, Renato,Dosi, Ivana,Ventura, Paolo,Villa, Maurizio,Lesma, Giordano,Palmisano, Giovanni
, p. 71 - 78 (2007/10/02)
The stereoselective synthesis of the major oxygenated metabolites of trans-sobrerol (1) in optically active and/or racemic form is described.
