Visible-Light-Induced In Situ Generation of Fischer-Type Copper Carbene Complexes from Acylsilanes and Its Application to Catalytic [4 + 1] Cycloaddition with Siloxydienes.

A novel methodology for in situ generation of Fischer-type metal-carbene complexes was developed. Photoirradiation to a mixture of an acylsilane and a cationic copper complex cleanly gave a Fischer-type copper-siloxycarbene complex, which was detected by spectroscopic methods. This carbene complex reacted with siloxydienes in a [4 + 1] cycloaddition manner to give cyclopentene derivatives. It is noteworthy that this reaction proceeds with a catalytic amount of copper through in situ generation of a Fischer-type copper-siloxycarbene complex intermediate.