Functionalization of the C-H Bond of N-Heteroaromatics Assisted by Early Transition-Metal Complexes

This review focuses on direct C-H bond functionalization reactions of N-heteroaromatic compounds by group 3 and 4 organometallic complexes. Early transition-metal-carbon and -nitrogen bonds are highly reactive to C-H bond activation via a sigma-bond metathesis pathway to form new organometallic species. By further inserting other unsaturated molecules into the new metal-carbon bond, C-H bond functionalized products are selectively obtained. To clarify the reaction mechanism, we categorize the reaction by the chelation size of the metallacycle intermediate generated from the organometallic species with N-heteroaromatic compounds, and include both stoichiometric and catalytic reactions with their reaction mechanism.