Palladium-Catalyzed Carbonylative Cross-Coupling of Aryl Iodides and Alkenyl Bromides with Benzyl Halides under Reductive Conditions

A direct and convenient method for the palladium-catalyzed reductive cross-coupling of aryl iodides or alkenyl bromides and secondary benzyl halides under ambient CO pressure to generate a diverse array of aryl/alkenyl alkyl ketones has been developed. This strategy successfully achieves a three-component carbonylative reaction with Zn as the reducing agent for C-C bond formation, overcoming the well-known homocoupling of aryl or alkenyl halides, direct cross-coupling between two different electrophiles and other carbonylative coupling reactions. In addition, this method avoids use of preformed organometallic nucleophiles, such as organo-magnesium, zinc and boron reagents. This approach enables the construction of valuable aryl alkyl/alkenyl ketone derivatives (60 examples, 56-95% yields). Reactivity studies indicate that in situ formed benzylic zinc reagents are intermediates in the catalytic system.