Cobalt‐Catalyzed Annulation of o‐Phenylenediamines and Internal Alkynes: Efficient Synthesis of Quinoxaline Derivatives

A cobalt‐catalyzed annulation of o‐phenylenediamines and internal alkynes for the synthesis of quinoxalines is developed. This method provides a variety of quinoxalines in good to high yields under a simple and mild reaction conditions with molecular O2 as a terminal oxidant. Preliminary mechanistic studies show that a novel reaction mechanism is involved in the current reaction, which is different from the previous reported dicarbonyl compound mechanism via the oxidation of the alkyne. A cobalt‐catalyzed annulation of o‐phenylenediamines and internal alkynes for the synthesis of quinoxalines is reported. This method provides a series of quinoxalines in good to high yields under a simple and mild reaction conditions.