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.

Automated summary

This paper reports an effective ligand-free Pd-catalyzed carbonylation of o-bromoaryl iodides with alkynes to obtain indenone compounds. The reaction shows good tolerance towards functional groups on o-bromoaryl iodides and alkynes. By introducing Mo(CO)6 as a carbonyl source, the reaction becomes safer and more operable. Mechanistic investigations reveal a sequential process of oxidative addition, alkyne insertion, carbonyl insertion, and reductive elimination to produce the desired carbonylation products.