Light‐Induced Nickel‐Carboxylate Facilitates C–O Coupling

The combination of photocatalysis and nickel catalysis has been effectively utilized in the esterification of carboxylic acids with aryl halides. In this work, we present an approach where the esterification of carboxylic acids with aryl halides is achieved without an external photocatalyst. An air‐stable Ni(II) complex and mild organic base are employed in the protocol, allowing for the esterification of aryl bromides and less reactive aryl chlorides with carboxylic acids. The method is also compatible with a variety of carboxylic acids, including formic acid and N ‐protected amino acid derivatives. Mechanistic investigations indicate that the carboxylic acid likely coordinates with nickel, and the homolysis of the NiO bond is the key step for couplings before undergoing a Ni(I)−Ni(III) catalytic cycle.