Synthesis of β-lactones. Part 7.1 α-Chloro- and α,α-dichloro-β-lactones by aldolization of carbonyl compounds with lithium ester enolates derived from chlorinated phenyl alkanoates: an unusual course of the Darzens reaction

Abstract

α-Chlorinated β-lactones are obtained in a one-step reaction at a temperature <-78 °C by condensation of ketones or aldehydes with ester enolates derived from phenyl α-chloroalkanoates or α,α-dichloroethanoate. The intermediate O-lithiated phenyl α-chloro-β-hydroxyalkanoates eliminate lithium phenoxide instead of lithium chloride, thus causing the Darzens reaction to take an unusual course. Irrespective of the low diastereoselectivity of this process, it is in many cases superior to other known processes for the synthesis of α-chlorinated β-lactones.