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.