Reductive Coupling of Aryl Halides via C-H Activation of Indene

Main observation and conclusion This paper describes the first case of a reductive coupling reaction with indene, a non-heteroatom olefin used as a reducing agent. The scope of the substrate is wide. The homo-coupling, cross-coupling, and synthesis of 12 and 14-membered rings were realized. The control experiment, indene-product curve and density functional theory calculations showed that the eta(3)-palladium indene intermediate was formed by C-H activation in the presence of cesium carbonate. We speculate that the final product was obtained through a Pd (IV) intermediate or aryl ligand exchange. In addition, we excluded the formation of palladium anion (Pd(0)(-)) intermediates.

Automated summary

This paper presents the first case of a reductive coupling reaction using indene as a reducing agent, showing a broad substrate scope and various types of reactions. The formation of an eta(3)-palladium indene intermediate was confirmed through control experiments and density functional theory calculations, while the formation of palladium anion intermediates was excluded.