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-j 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-j. Simplified workup and purification procedures for these compounds are also described.