Stereoselective functionalization of 1-alkoxy-2-(phenylethynyl)cyclopropanes via lithiation and subsequent reactions with electrophilic reagents

Abstract

trans-1-Alkoxy-2-(phenylethynyl)cyclopropanes undergo lithiation at the hydrogen atom in the α-position to the triple bond on treatment with BuLi in THF at–(65—70) °C. The resulting organolithium derivatives react with acetaldehyde, acetone, dimethyl disulfide, and methyl chloroformate giving the corresponding alcohols, sulfides, and esters with the yields up to 69% with complete retention of cyclopropane ring stereoconfiguration. The obtained methyl 3-alkoxy-2,2-dimethyl-1-(phenylethynyl)cyclopropanecarboxylates and the corre-sponding acid readily undergo ring opening with addition of water molecule or HCl.