Another Role of Copper in the Simmons–Smith Reaction: Copper-catalyzed Nucleophilic Michael-type Cyclopropanation of α,β-Unsaturated Ketones

Abstract Cyclopropanation was performed using the Furukawa procedure with CH2I2/Et2Zn and α,β-unsaturated ketones. The reaction was performed in the presence of a copper salt. The reactivity was highly dependent on the substrate structure, and cyclopropanated products were obtained in better yields than those achieved using the original Simmons–Smith conditions with a Zn–Cu couple in some cases. Stereospecificity was observed in a certain case; however, the synthesis of an asymmetric version with a chiral ligand was not successful.