Unique reactivity of Grignard reagents towards cyclopropenyl-carboxylates—highly selective carbon–carbon bond cleavage

Abstract

An unexpected highly selective reaction of Grignard reagents is described: Instead of generating the normal tertiary alcohols from the reaction with the ester functionality, its treatment with doubly activated cyclopropenyl-carboxylates leads to the deprotonation and highly regio- and stereoselective cleavage of the less substituted carbon–carbon single bond of the carbocycles with the Grignard reagent attacking the less substituted sp²carbon atom. Subsequent reaction with different electrophiles affords multi-substituted stereodefined 2-(1-alkenyl)malonate-type derivatives as single stereoisomers, which are otherwise very difficult to make.