Mukaiyama aldolisation reactions of α,β-epoxyaldehydes in aqueous media
摘要:
The Mukaiyama aldolisation reaction in aqueous media of cis and trans alpha,beta-epoxyaldehydes with tert-butyldimethylsilyl ketene acetal in the presence of Lewis's acids was studied. Sc(OTf)(3) gave the best results in terms of selectivity. The same reaction of cis and trans alpha., beta-epoxyaldehydes with the enoxysilane of ethyl pyruvate resulted in epoxy Substituted ulosonic derivatives issued from a double sequential condensation of the pyruvate on the epoxy derivatives. (c) 2005 Elsevier Ltd. All rights reserved.
aldolisation reaction of lithium ester enolates with chiral α,β-epoxyaldehydes 2a–2f has been investigated. The reaction proceeds with diastereofacial preference in favour of the anti isomer (anti:syn ≈ 4:1) and can be greatly enhanced in the case of cis α,β-epoxy-aldehydes 2a–2c by a synergic effect of temperature and enolate excess (anti:syn 13:1). The Felkin-Ahn model can explain the results obtained