Three-Component GaHal₃-Promoted Reactions of Substituted Methylidenemalonates and Donor–Acceptor Cyclopropanes with Propargyl Halides: Cascade Diastereoselective Construction of Five-Membered Lactones

Abstract

A new cascade three-component process for high trans,trans-diastereoselective assembly of five-membered (1-halovinyl)lactones has been developed. The process is based on reactions of substituted methylidenemalonates and cyclopropanedicarboxylates with 3-haloprop-1-ynes in the presence of GaHal₃ and involves the intermediate in situ generation of 1,2-zwitterionic gallium complexes with [Ga(L)₃]³⁺[GaX₄^-]₃ composition. Chloro, bromo, and iodo derivatives can be obtained successfully. Mechanistic and stereochemical aspects of the process we developed have been studied and considered in detail.