Effet de solvant sur le bilan stéréochimique de la réaction de darzens—I

摘要: Abstract The reaction of benzaldehyde with ethyl chloracetate is stereoselective in benzene—NaH ethanol-sodium ethylate but non-stereoselective HMPT—NaH. intermediate threo- and erythro-halohydrins (ethyl-2-chloro-3-hydroxy-3-phenyl-propionates) are cyclized under Darzens' conditions. In HMPT each halohydrin gives the corresponding glycidate, while benzene or ethanol, erythro-halohydrin trans-glycidate threo-isomer partly cis-glycidate reverts to starting materials. Evidence for these pathways has been obtained from cyclizations performed C6D5CHO.