Alkyl-Aryl Coupling Catalyzed By Tandem Systems of Pincer-Ligated Iridium Complexes and Zeolites

Organometallic-catalyzed alkane dehydrogenation to give olefins has been known since 1979, and was extensively developed over the years since then. Dehydrogenation catalysts in tandem with olefin metathesis catalysts were reported to afford catalytic systems for the metathesis of alkanes or alkyl-groups. Now we report a different tandem dehydrogenation-based system, in which the net reaction is the formation of an alkyl-aryl bond, with liberation of H₂, from the coupling of alkyl-H and aryl-H units. In view of the importance of alkyl-aryl bonds in organic chemistry coupling reactions of this type have great potential applicability. No hydrogen acceptor is required so the system is highly atom-economical. Our approach to the development of a system for the catalysis of alkyl-aryl coupling was based on pincer-iridium-catalyzed acceptorless dehydrogenation of an alkyl group, followed by Friedel-Crafts coupling of the resulting olefin with arene，as show in the scheme below. Further dehydrogenation can give us more unsaturated products, such as dihydro-methylnaphthalene and methylnaphthalene.