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).