Synthesis of new 4-alkylthiazolo{[}5,4-d] pyrimidine-1-oxides

6-Chloro-1-methyluracil 1 was treated with various butyl and benzyl mercaptans to give 6-substituted-1-methyluracils 2a-d which were nitrated to yield the corresponding 5-nitro derivatives 3a-d. These were cyclized to 2-substituted-4-methyithiazolo{[}5,4-d] pyrimidine-5,7(4H)-dione-1-oxides 4a-c. On the other hand, the reaction of 6-chloro-5-nitro-1-propyluracil 6 with the above mentioned reagents afforded 6-substituted-5-nitro-1-propyluracils 7a-d which were cyclized similarly to give the corresponding 2-substiluted-4-propylthiazolo{[}5,4-d]pyrimidine-5,7 (4H)-dione-1-oxide derivatives 8a-d. The structures of these compounds were elucidated by H-1 nmr, uv, mass spectra and elemental analysis.