Condensed 1,3,5-Triazines: 1,3,4-Thiadiazolo(3,2-a)-1,3,5-triazines and Isoxazolo(2,3-a)-1,3,5-triazines.

A convenient route is reported for the synthesis of substituted 1,3,4-thiadiazolo[3,2-a]-1,3,5-triazine-5,7-diones and isoxazolo[2,3-a]-1,3,5-triazines. Condensation of the appropriately substituted 2-amino-1,3,4-thiadiazole and 3-aminoisoxazole with phenoxycarbonyl isocyanate provides the desired target compounds in fair yield.