Synthesis of 3-aryl-3-trimethylsilylcyclopropenes and their dibenzoyl derivatives. Possible cyclopropenyl anion precursors?†

Abstract

3-Aryl-3-trimethylsilylcyclopropenes (1) were synthesized by a four-step reaction sequence starting from known benzoyl trimethylsilanes. These cyclopropenes were thermalized on a gas chromatography column and the products were collected and identified. Their 1,2-dibenzoyl derivatives (2) were prepared in a two-step transformation beginning with 3-aryl-1,2,3-tris(trimethylsilyl)cyclopropenes (5), the ultimate intermediates in the syntheses of 1. These compounds (2) are rare examples of isolable cyclopropenes with electron withdrawing groups at the vinyl positions. Fluoride-induced desilylation reactions of electron deficient cyclopropenes also are described and a carbon-centered electrophile has been successfully used to trap a putative cyclopropenyl anion.