Synthesis of 2-Aryl Naphthoquinones by the Cross-Dehydrogenative Coupling Involving an NHC-Catalyzed endo-Stetter Reaction.

An N-heterocyclic carbene (NHC)-catalyzed intramolecular Stetter reaction proceeding via the endo-fashion was the key step for the transition-metal-free and mild cross-dehydrogenative coupling of 2-cinnamoyl benzaldehydes allowing for the synthesis of 2-aryl naphthoquinones. In this transformation, the carbene generated from the triazolium salt using Na2CO3 catalyzes the intramolecular Stetter reaction, which was followed by air oxidation to reinstall the C-C double bond.