Preparation of some perhydrothiazolo[3,2-a] [1,3,5] triazine-2,4-diones

2-Dialkylamino-δ²-thiazolines were found to react with aryl isocyanates to give 1,3-diaryl-8a-dialkylaminoperhydrothiazolo3,2-a ] 1,3,5]triazine-2,4-diones (IIa-c), while p-toluenesulphonyl isocyanate gave a 1:1 adduct (VII). No reaction was observed with alkyl or aryl isothiocyanates.