Transition-metal-catalyzed additions of C–H bonds to C–X (X = N, O) multiple bonds via C–H bond activation

Chemical transformations via catalytic C–H bond activation have been established as one of the most powerful tools in organic synthetic chemistry. Transition-metal-catalyzed addition reactions of C–H bonds to polar C–X (X = N, O) multiple bonds, such as aldehydes, ketones, imines, isocyanates, nitriles, isocyanides, carbon monoxide and carbon dioxide, have undergone a rapid development in recent years. In this review, recent advances in this active area have been highlighted and their mechanisms have been discussed.