Exploratory and Mechanistic Studies of the Trimerization Reaction of Benzoylacetylenes in the Presence of a Secondary Amine

A variety of benzoylacetylenes are trimerized to give the corresponding 1,3,5-tribenzoylbenzenes when heated with a catalytic amount of diethylamine. A large amount of diethylamine gives γ-(diethylamino)propenoylbenzene at the expense of 1,3,5-tribenzoylbenzene, verifying a Michael-addition/trimerization/elimination-type mechanism for the formation of the benzene ring.