- Microwave assisted bi-functional activation of β-bromo-tert-alcohols
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Microwave-assisted dehydration-oxidation of β-bromo-tert-alcohols to afford 2,3-unsaturated ketones in good yield is reported. The reaction of substrates with DMSO in 1:1 ratio (w/v) is promoted by ZnS in a solvent-free condition. A concurrent bi-functional activation of trans-vicinal bromo- and hydroxyl groups with ZnS is elucidated. This is a new observation under microwave and applies to β-bromo-tert-alcohols derived from 1,4-disubstitued-1-cyclohexenes. It is very useful in the synthesis of 2,3-unsaturated ketones derived from monoterpenes which are valuable flavour compounds. [Figure not available: see fulltext.]
- Kannan, Nandini,Rangaswamy, Manjunatha Javagal,Kemapaiah, Bettadaiah Bheemanakere
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p. 1405 - 1410
(2015/11/09)
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- Modified Marko's aerobic oxidation of alcohols under atmospheric pressure with air or molecular oxygen at room temperature
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A modified version of Marko's aerobic oxidation procedure, using highly pure (99.995+%) CuCl with 4,7-diphenyl-1,10-phenanthroline (dpPhen), DBAD, and Cs2CO3 (98% purity) successfully oxidized primary and secondary alcohols to the corresponding aldehydes and ketones in excellent yield at room temperature with either air or molecular oxygen under atmospheric pressure.
- Nishii, Takeshi,Ouchi, Tomomi,Matsuda, Aya,Matsubara, Yuka,Haraguchi, Yuuko,Kawano, Tomomi,Kaku, Hiroto,Horikawa, Mitsuyo,Tsunoda, Tetsuto
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p. 5880 - 5882,3
(2020/07/31)
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- Formation of trans-verbenol and verbenone from α-pinene catalysed by immobilised Picea abies cells
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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.
- Vanek, Tomas,Halik, Jan,Vankova, Radmila,Valterova, Irena
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p. 321 - 325
(2007/10/03)
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- Scope of enantioselective Palladium(II)-catalyzed aerobic alcohol oxidations with (-)-sparteine
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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%.
- Mandal, Sunil K.,Jensen, David R.,Pugsley, Jacob S.,Sigman, Matthew S.
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p. 4600 - 4603
(2007/10/03)
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- Palladium-catalyzed aerobic oxidative kinetic resolution of alcohols with an achiral exogenous base
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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.
- Mandal, Sunil K.,Sigman, Matthew S.
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p. 7535 - 7537
(2007/10/03)
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- Applications of High-Temperature Aqueous Media for Synthetic Organic Reactions
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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.
- An, Jingyi,Bagnell, Laurence,Cablewski, Teresa,Strauss, Christopher R.,Trainor, Robert W.
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p. 2505 - 2511
(2007/10/03)
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- Qualitative determination of the non-volatile reaction products of the α-pinene reaction with hydroxyl radicals
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This work describes the qualitative determination of the non-volatile reaction products (condensables) in the α-pinene/OH/O2/NO reaction.The study was carried out in a fast-flow reactor and the hydroxyl radicals were generated by the H + NO2-reaction.Two collection systems have been checked: a liquid nitrogen trap and an active charcoal trap.It was found that the liquid nitrogen trap was the most suitable technique since heterogenous reactions on the active charcoal surface lead to the formation of products not related to α-pinene/OH reaction.Both dichlorometane and methanol have been tried out as solvents but methanol has to be avoided since it forms a number of unwanted methanol-adducts during the extraction or analysis.The following condensables have been identified as genuine reaction products: pinonaldehyde, campholene aldehyde, trans- and cis-pinocamphone, pinol, trans-carveol, carvotaneacetone, trans-sobrerol and a ketoalcohol 5-(2-hydroxy-2-propyl)-2-methyl-2-cyclohexen-1-one.Some mechanistic aspects of the formation of these products are discussed with special attention for the role of nitric oxide.
- Vinckier, C.,Compernolle, F.,Saleh, A. M.
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p. 501 - 514
(2007/10/03)
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- Al-NiCl(2°)6H2O-THF: A new, mild and neutral system for selective reduction of organic functional groups
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A mild and neutral reducing system consisting of Al-NiCl(2°)6H2O-THF has been developed and reacted with a series of organic compounds containing different functional groups in order to evaluate its synthetic utility. It was observed that this system very efficiently reduces the α-enones to the saturated ketones, aromatic aldehydes and ketones to the corresponding alcohols, nitriles and nitroarenes to amines, acid anhydrides and acid chlorides to aldehydes, disulphides to thiols and epoxides to the corresponding alcohols. On the other hand isolated double bonds, carboxylic acids, esters, lactones, primary, benzyl and allyl halides, aliphatic aldehydes and ketones and aliphatic nitro compounds were found to remain inert to this system. Furthermore, the reducing properties of Al-NiCl(2°)6H2O in several other organic solvents were also studied.
- Sarmah,Barua
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p. 8587 - 8600
(2007/10/02)
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- Pheromone Synthesis, CIV.- Synthesis of the Enantiomers of α-Phellandren-8-ol (p-Mentha-1,5-dien-8-ol), a Monoterpene from Bark Beetles
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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.
- Mori, Kenji,Igarashi, Yasuhiro
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- Stereocontrolled Regiospecificity of the Water Loss from trans-Sobrerol Radical Cation upon Electron Ionization
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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.
- Selva, Antonio,Ferrario, Francesco,Ventura, Paolo,Pellegata, Renato
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p. 523 - 529
(2007/10/02)
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- Monoterpenoid Chemistry - Part 3. Stereoselective Synthesis of the Major Oxygenated Metabolites of trans-Sobrerol
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The stereoselective synthesis of the major oxygenated metabolites of trans-sobrerol (1) in optically active and/or racemic form is described.
- Pellegata, Renato,Dosi, Ivana,Ventura, Paolo,Villa, Maurizio,Lesma, Giordano,Palmisano, Giovanni
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- Metal Catalysed Rearrangements in Monoterpene Series: Thallium(III) Oxidation of Δ3-Carene
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The action of Tl(III) acetate on Δ3-carene has been studied and its mode of action correlated with that of other soft acids like Hg(II) and Pb(IV) acetates.
- Pandita, K.,Thappa, R. K.,Agarwal, S. G.,Dhar, K. L.,Atal, C. K.
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p. 763 - 765
(2007/10/02)
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- Selectivity and Reactivity in Some Oxidations with Pentavalent and Hexavalent Chromium Reagents: A Short Synthesis of Norbisabolide
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Selective oxidative cyclization of the t-hydroxyolefin (5) with pyridinium chlorochromate leads to a simple synthesis of norbisabolide (4).On the other hand, α-terpineol (7) on treatment with chromium(V) reagent undergoes facile oxidative cleavage followed by cyclization to give homoterpenyl methyl ketone (8).
- Kuchibhotla, Uma,Chakraborty, T. K.,Chandrasekaran, S.
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p. 1216 - 1218
(2007/10/02)
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- The Conjugate Addition of a Silyl Group to Enones and its Removal with Copper(II) Bromide: A Protecting Group for the αβ-Unsaturation of αβ-Unsaturated Ketones
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Silyl-lithium reagents mixed with copper(I) salts react with enones, including esters and aldehydes, to give β-silyl carbonyl compounds in good yield.The β-silylketones can be used in synthesis without risk to the silyl group and the enone group can be restored by bromination-desilylbromination with copper(II) bromide.The principle is illustrated with syntheses of carvone and dihydrojasmone.
- Ager, David J.,Fleming, Ian,Patel, Shailesh K.
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p. 2520 - 2526
(2007/10/02)
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