Nickel-catalyzed reductive formylation of aryl halides via formyl radical

Aromatic aldehydes are the most fundamentally important compounds used in organic synthesis. The development of new synthetic methods for introduction of a formyl group into an organic scaffold is highly desirable. In this report, a nickel-catalyzed reductive coupling between aryl halides and α-chloro N-methoxyphthalimide has been documented for the synthesis of a diverse array of aromatic aldehydes. Because of mild reductive coupling conditions, excellent functional group tolerance, especially for substrates containing free -OH and -NH2, was observed. Due to the simple operation mode, a large library of aromatic aldehydes can be quickly constructed by this process. Moreover, the present protocol is amenable for late-stage functionalization of bioactive compound. A combined computational and experimental investigation suggested the reaction may undergo a reaction mechanism of active Ni(I) catalyst formation and the formation of key formyl radical intermediate under zinc reductive conditions.