Synthesis of trifluoromethylated allenes via visible light-promoted bis(trifluoromethylation) of 1,3-enynes

A visible light-promoted/copper-mediated 1,4-bis(trifluoromethylation) method of easily available 1,3-enynes to construct allenic Csp2−CF3 bonds has been described. The reaction proceeded under mild conditions, has broad substrate scope and good functional group tolerance. Photocatalyst is not required in this protocol, and O2 plays an important role in facilitating the trifluoromethyl group transfer and improving the yield. Mechanistic studies revealed that a radical process is involved in the reaction.