A highly enantioselective asymmetric Darzens reaction catalysed by proline based efficient organocatalysts for the synthesis of di- and tri-substituted epoxides

Abstract

A new class of easily available and readily tunable proline based chiral organocatalysts was found to efficiently catalyse an unprecedented highly enantioselective asymmetric Darzens reaction of α-chloroketones and substituted α-chloroketones with various aldehydes, which directly produces optically active di- and tri-substituted chiral epoxides with higher product yields (up to 97%) and excellent ee's (up to 99%) under mild reaction conditions.

An Overview of Saturated Cyclic Ethers: Biological Profiles and Synthetic Strategies

“…The essential factor for high diastereoselectivity and yield might be attributed to the formation of a metal-cation-mediated rigid structure during the reaction [28]. Because researchers are still developing new chiral organocatalysts, the substitute scope of the highly enantioselective asymmetric Darzens reaction is expanding [47]. Moreover, shorter reaction times were achieved by using aqueous media in the presence of a Li + -containing base, a phase-transfer catalyst and granular polytetrafluoroethylene under mechanical stirring [48].…”

Catalytic Asymmetric Darzens and Aza‐Darzens Reactions for the Synthesis of Chiral Epoxides and Aziridines

“…Very recently, the group of Siva has developed an unprecedented highly enantioselective asymmetric DR catalyzed by proline based chiral organocatalysts. [40] The authors prepared novel ortho-and para-substituted chiral organocatalysts from the pentaerythritol core and L-proline for the asymmetric DR of a-halogenated carbonyl compounds and a series of aromatic, heteroaromatic, and aliphatic aldehydes (Scheme 15). The parasubstituted catalyst 40 resulted more efficient than the corresponding ortho-substituted, probably due to the steric hindrance between the catalysts and substrates.…”