Synthesis of Activated Cyclopropanes by an MIRC Strategy: An Enantioselective Organocatalytic Approach to Spirocyclopropanes

An efficient cyclopropanation, by a Michael-initiated ring-closing (MIRC) reaction of 2-arylidene-1,3-indandiones and 2-arylidene malononitriles, has been developed by using different alpha-monohalogenated methylene active compounds with triethylamine. The first enantioselective cyclopropanation to spirocyclopropanes derived by the reaction of 2-arylidene-1,3-indandiones and dimethyl bromomalonate with a commercially available alpha,alpha-L-diarylprolinol as the organocatalyst and K2CO3 as the additive has been accomplished. The spirocyclopropanes were isolated in high yield and up to 85% ee. Notably, the asymmetric one-pot sequential approach to spirocyclopropanes proved to be a feasible process.