Abstract 5-Amino-3-methylisothiazole-4-carbonitrile 2 was prepared by oxidation of 3-amino- 2-cyano-thiocrotonamide 1. A series of 4-amino-3-methylisothiazolo [5, 4-d] pyrimidines 6 was derived from 2 by reaction with orthoesters followed by cyclization with primary amines. Hydrolysis of 2 to the corresponding amide 10 followed by cyclization with orthoesters gave the corresponding 5H-isothiazolo [5, 4-d] pyrimidin-4-ones 11. Reactions of 2 and 10 with ...
