Rh(II)-Catalyzed Reactions of Diazoesters with Organozinc Reagents
作者:Robert Panish、Ramajeyam Selvaraj、Joseph M. Fox
DOI:10.1021/acs.orglett.5b01836
日期:2015.8.21
Rh(II)-catalyzed reactions of diazoesters with organozinc reagents are described. Diorganozincreagents participate in reactions with diazo compounds by two distinct, catalyst-dependent mechanisms. With bulky diisopropylethyl acetate ligands, the reaction mechanism is proposed to involve initial formation of a Rh-carbene and subsequent carbozincation to give a zinc enolate. With Rh2(OAc)4, it is proposed that initial
A highly enantioselective 1,3-dipolarcycloaddition of α-substituted diazoesters with exocyclic enones was achieved with chiral scandium(III)/N, N’-dioxide complex as the catalyst. This protocol provided a facile and efficient route to optically active 1-pyrazoline-based spirochromanones and others with good outcomes (up to 97% yield, 98% ee with >95:5 dr). Moreover, enantioenriched 2-pyrazoline-based
Phase-transfer-catalysed asymmetric synthesis of tetrasubstituted allenes
作者:Takuya Hashimoto、Kazuki Sakata、Fumiko Tamakuni、Mark J. Dutton、Keiji Maruoka
DOI:10.1038/nchem.1567
日期:2013.3
Allenes are molecules based on three carbons connected by two cumulated carbon–carbon double bonds. Given their axially chiral nature and unique reactivity, substituted allenes have a variety of applications in organic chemistry as key synthetic intermediates and directly as part of biologically active compounds. Although the demands for these motivated many endeavours to make axially chiral, substituted
A new chiral Brønsted acid derived from carboxylic acid and a chiral oxazaborolidinium ion (COBI), as an activator, is introduced. This acid was successfully applied as a catalyst for the highly enantioselective protonation/nucleophilicaddition of diazoesters with carboxylic acids.
Desymmetrizing Asymmetric Ring Expansion of Cyclohexanones with α-Diazoacetates Catalyzed by Chiral Aluminum Lewis Acid
作者:Takuya Hashimoto、Yuki Naganawa、Keiji Maruoka
DOI:10.1021/ja202070j
日期:2011.6.15
in a 2:1 ratio was found to promote novel catalytic asymmetric ring expansion of cyclohexanone with α-substituted α-diazoacetates to give seven-membered rings with an all-carbon quaternary center. Application of this strategy to 4-substituted cyclohexanones opened up a novel way for the catalytic desymmetrizing asymmetric construction of cycloheptanones bearing remote α,δ-chiral centers.