Synthesis of Activated Cyclopropanes via an MIRC Strategy: an Enantioselective Organocatalytic Approach to Spiro Cyclopropanes

An efficient cyclopropanation, by a Michael-initiated ringclosing (MIRC) reaction of 2-arylidene-1,3-indandiones and 2-arylidene malononitriles, has been developed by using different α-monohalogenated methylene active compounds with triethylamine. The first enantioselective cyclopropanation to spirocyclopropanes derived by the reaction of 2-aryl-idene-1,3-indandiones and dimethyl bromomalonate with a commercially available α,α-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.