Catalytic asymmetric Darzens reaction promoted by a chiral phase-transfer catalyst derived from cinchonine is described. The desired α,β-epoxy ketones were obtained by use of α-chloro acyclic and cyclic ketones as substrates with moderate to high enantiomeric excesses under mild reaction conditions. This methodology can be quite an effective protocol for practical asymmetric synthesis.
Darzens Reaction Rate Enhancement Using Aqueous Media Leading to a High Level of Kinetically Controlled Diastereoselective Synthesis of Steroidal Epoxyketones
作者:Bo Li、Chunbao Li
DOI:10.1021/jo501500v
日期:2014.9.5
been used in aqueous Darzensreactions. The Darzensreactions were much faster in water than in organic solvents. This aqueous rate enhancement occurred for Darzensreactions between enantiopure steroidal haloketones and aldehydes, yielding enantiopure spiroepoxides with a high level of kinetically controlled diastereoselectivity. Chromatography was avoided in the purifications of the steroidal spiroepoxides
A New Method for the Synthesis of Unsymmetrical Bis-Aldols by the Samarium(II) Iodide-Mediated Aldol Reaction of Aldehydes with Aryl or Alkyl Oxiranyl Ketones
作者:Teruaki Mukaiyama、Hidehiro Arai、Isamu Shiina
DOI:10.1246/cl.2000.580
日期:2000.5
Unsymmetrical alkyl or aryl 2-hydroxy-1-(1-hydroxyalkyl)alkylketones (bis-aldols) were synthesized by the samarium(II) iodide-mediated aldol reaction of aldehydes with alkyl or aryl oxiranyl ketones. Bis-aldols were formed via the aldol reaction of aldehydes with samarium enolates generated by epoxy-fragmentation of oxiranyl ketones using two moles of samarium(II) iodide.
不对称的烷基或芳基 2-羟基-1-(1-羟基烷基) 烷基酮 (双-羟醛) 是通过碘化钐 (II) 介导的醛与烷基或芳基环氧乙烷基酮的羟醛反应合成的。双羟醛是通过醛与通过使用两摩尔碘化钐 (II) 对环氧乙烷基酮进行环氧裂解而生成的钐烯醇化物的羟醛反应形成的。
Michael-type addition of hydroxide to alkynylselenonium salt: practical use as a ketoselenonium ylide precursor
A novelsyntheticmethod of ketodiphenylselenonium ylide from alkynylselenonium salt is described. A reaction of alkynylselenonium salt, hydroxide ion, and aldehyde in the presence of silver triflate and triethylamine gave oxiranylketones just as a trans-isomer in moderate to good yields, whereas benzoyl aziridine derivatives were obtained from the reaction with sodium p-toluenesulfonamide instead
Enantioselective Epoxidation of α,β-Enones by Electrophilic Activation with a BINOL-Zinc Catalyst
作者:Ana Minatti、Karl Heinz Dötz
DOI:10.1002/ejoc.200500606
日期:2006.1
affords, in situ, a catalyst for homogeneous epoxidation of (E)-α,β-enones to the corresponding trans-epoxy ketones. tert-Butyl hydroperoxide (TBHP) and cumene hydroperoxide (CMHP) are effective terminal oxidants for this process. Enantiomeric excesses of up to 96 % can be achieved conveniently at room temperature. Mechanistic investigations point towards an electrophilicactivation of the substrates