Chiral Rhodium(III) Complex-Catalyzed Cascade Michael-Alkylation Reactions: Enantioselective Synthesis of Cyclopropanes

Chiral Rh­(III) complex
catalyzed highly efficient enantioselective cyclopropanation of α,β-unsaturated
2-acyl imidazoles or pyridine with 2-bromomalonate is developed to
generate corresponding multisubstituted cyclopropanes in 70–99%
yields with 93→99% enantioselectivity. The proficiency of the
process is also demonstrated in gram scale reaction maintaining same
reactivity and selectivity level in lower catalyst loading. Moreover,
the developed methodology is applicable in challenging synthesis of
biscyclopropane scaffold with 97% ee in a single operation.