Copper-Catalyzed Synthesis of Tetrasubstituted Olefins with Bicyclo[1.1.0]butanes and α-Diazo-Esters

BCBs (bicyclo[1.1.0]butanes) serve as useful building blocks in organic synthesis due to their unique reactivity caused by the ring-strain. Herein, a copper-catalyzed olefination with BCBs and α-diazo-esters is disclosed, which generates tetrasubstituted olefins in a moderate <i>Z</i>/<i>E</i> ratio and pure <i>Z</i>-isomers are isolated in moderate yields. The reaction enjoys advantages such as mild reaction conditions, simple reaction protocol, good functional group tolerance, and low catalyst loading. As for disubstituted BCBs, various aryl groups and an aliphatic group are well tolerated. The synthetic utility of the present method is showcased by several transformations, which furnish structurally diverse tetrasubstituted olefins.