Reactions of arylglyoxals with tetrasulfur tetranitrides (S4N4): Formation of 2-aroyl-5-arylimidazoles and 2-aroyl-5-aryloxazoles

Treatment of arylglyoxal monohydrates with tetrasulfur tetranitride in p-dioxane at reflux afforded 2-aroyl-5-arylimidizoles and 2-aroyl-5-aryloxazoles in 10 to 31% and 17 to 32% yields, respectively. With non-hydrate of arylglyoxals, yields of the latter increase somewhat, whereas essentially no changes in yields of the former were observed. A mechanism is proposed for the formation of the products.