Simple inorganic base cesium hydroxide is found to be the best catalyst for aerobic annulation reaction of o-phenylenediamine and α-hydroxy-2-phenylacetophenone in constructing the quinoxaline skeleton, i.e., catalytic amount of cesium hydroxide can catalyze the reaction efficiently under mild conditions of room temperature in air atmosphere. This method is extendable to a series of vicinal diamines and α-hydroxyl ketones, thus having a relatively broad substrate scope. As no transition metal catalyst is required and cesium hydroxide highly water-soluble, cesiume can be effectively removed by washing with water, the prodcuts can be obtained without cesium and transition metal residue contamination. This reaction requires no other stoichiometric oxidants but the readily available and convenient air as the oxidant, and the only byproduct is water, hence a transition metal-free, mild and efficient, green and practical approach for efficient construction of the quinoxaline derivatives is provided.

Key words: transition metal-free, cesium hydroxide, catalysis, quinoxaline skeleton, air, room temperature