Synthesis of 2,3‐dichloroquinoxalines via Vilsmeier reagent chlorination

A convenient and high‐yielding synthesis of 2,3‐dichloroquinoxalines from the corresponding 2,3‐dihydroxyquinoxalines has been developed. Treatment of a slurry of the 2,3‐dihydroxyquinoxaline 1a , 1b , 1c , 1d , 1e , 1f , 1g , 1h , 1i , 1j with N , N ‐dimethylformamide in the presence of excess thionylchloride in 1,2‐dichloroethane results in the rapid and high‐yielding formation of the 2,3‐dichloroquinoxaline derivatives 2a , 2b , 2c , 2d , 2e , 2f , 2g , 2h , 2i , 2j . Simplified workup and purification procedures for these compounds are also described. J. Heterocyclic Chem., 46 , 317 (2009).