Synthesis of novel acyclonucleosides. Reactions of 1‐(1‐bromo or 3‐bromo‐2‐oxopropyl)pyridazin‐6‐ones

Reaction of 1‐(3‐bromo‐2‐oxopropyl)pyridazin‐6‐ones 1 and 2 with sodium azide at room temperature gave the corresponding 1‐(3‐azido‐2‐oxopropyl)pyridazin‐6‐ones 3 and 4 , whereas reaction of 1‐(1‐bromo‐2‐oxo‐propyl)pyridazin‐6‐ones 5 and 6 with excess sodium azide afforded 4‐azido‐5‐chloropyridazin‐6‐one 7 and 4,5‐diazido‐3‐nitropyridazin‐6‐one 8 by dealkylation. Some 1‐(2‐hydroxypropyl)pyridazin‐6‐ones 9, 10, 11 were synthesized from the corresponding 1‐(2‐oxopropyl) derivatives 1, 2, 3 . 4,5‐Dichloro‐1‐(2,3‐dihydroxypropyl)‐pyridazin‐6‐one 13 was also prepared from compound 9 via the corresponding 2,3‐epoxypropyl derivative 12 . Treatment of compound 5 with thiourea gave 4,5‐dichloro‐1‐(2‐amino‐4‐methylthiazol‐5‐yl)pyridazin‐6‐one 14 . Reaction of compounds 1 and 2 with thiourea at 20° afforded the corresponding 3‐formamidinylthio‐2‐oxo‐propyl derivatives 15 and 16 , whereas treatment of compound 1 with thiourea at 45° gave 4,5‐dichloro‐1‐[(2‐aminothiazol‐5‐yl)methyl]pyridazin‐6‐one 17 . Compound 17 was also prepared from compound 15 by refluxing in ethanol.