Synthesis of Indenones Via Palladium-Catalyzed Carbonylation with Mo(CO)6 as a CO Surrogate

Transition-metal-catalyzed carbonylation of alkynes has emerged as a powerful engine for the synthesis of indenone compounds. Herein, we reported the development of an effective Pd-catalyzed ligand-free carbonylation of o-bromoaryl iodides with alkynes to afford indenone compounds. A broad range of functional groups on o-bromoaryl iodides and alkynes were tolerated in this protocol, giving carbonylation products. Furthermore, considering the factors of safety and operability, Mo(CO)6 was introduced into the reaction as a carbonyl source. Mechanistic investigations suggested that the reaction proceeded through sequential oxidative addition, alkyne insertion, carbonyl insertion, and reductive elimination steps to produce the observed carbonylation indenone products. Moreover, the indenones obtained with Mo(CO)6 as a CO surrogate can be functionalized to form synthetic useful derivatives via an environmentally friendly way.