It found that the Ru3(CO)12 coordinated with 2-(diphenylphosphino)benzonitrile (2-DPPBN) to effectively catalyze the [2 + 2 + 2] cyclotrimerization of the trifluoromethyl group substituted internal alkynes in high yields with up to >98% regioselectivity. Isolation of a ruthenacyclopentadiene was successful and confirmed that the complex is a reaction intermediate.
Iron-catalyzed [2 + 2 + 2] intermolecular cycloaddition of trifluoromethyl group substituted unsymmetrical internal alkynes afforded the corresponding trifluoromethyl group substituted benzene derivatives in high yield with excellent selectivity.