A new synthesis of 1,3-thiazines and their transformation into 1-substituted-6-alkyluracils by extrusion of carbonyl sulfide

A simple synthesis of 5-acyl-4-hydroxy-3,6-dihydro-2H-1,3-thiazine-2,6-diones from malonic acid, potassium thiocyanate and acid anhydrides is described. A new, general, regioselective method for the synthesis of 1-substituted-6-alkyluracils by the reaction of these thiazines with primary alkyl and arylamines is reported.