Abstract
Reaction of 6-amino-1, 3-diethyluracil (Ib) with dimethylformamide-thionyl chloride afforded 5, 7-diethyl-3-dimethylaminoisothiazolo [3, 4-d] pyrimidin-4, 6 (5H, 7H)-dione (IVb) and three minor products (VIb, VIIb, VIIIb). Similar reactions of five 6-aminouracils or 6-amino-1-benzyl-cytosine (XV) with N-formyl-sec-amine-thionyl chloride afforded corresponding 3-aminoisothiazolo [3, 4-d] pyrimidine derivatives (IVa-i or XVI). When 6-amino-1, 3-diethyl-2-thiouracil (Ij) was allowed to react similarly, IVb was obtained as a major product and the yield of the expected 5, 7-diethyl-3-dimethylaminoisothiazolo-[3, 4-d] pyrimidin-4 (5H)-one-6 (7H)-thione (IVj) was very low.
