5‐Cyano‐6‐aryluracil and 2‐thiouracil derivatives as potential chemotherapeutic agents. IV

A series of 5‐cyano‐6‐aryluracils and 2‐thiouracils 1a‐h has been prepared and alkylated to 1,3‐dialkyluracils 2a‐d and 2‐alkylthiouracils, 3, 4 and 6 , by electrophilic substitution with alkyl halides. Reaction of 1b with dibromoethane and 1,3‐dibromopropane gave the corresponding bicyclic products, 7‐aryl‐6‐cyano‐2,3‐dihydrothiazolo[3,2‐ a ]pyrimidin‐5‐ones 5a,b and 8‐aryl‐7‐cyano‐3,4‐dihydro‐2 H ‐pyrimido[2,3‐ b ][1,3]thiazin‐6‐ones 5c‐g . Nucleophilic substitution on 6 with hydrazine led to 7 which on refluxing with formic acid gave 5‐aryl‐6‐cyano‐8‐methyl‐ s ‐triazolo[3,4‐ b ]pyrimidin‐7‐ones ( 9 ), while with acetic and propionic acids only 2‐acylhydrazino‐3‐methyl‐4‐oxo‐5‐cyano‐6‐arylpyrimidines 8a,b were isolated. The hydrazine 7 undergoes cyclization with acetylacetone and methyl dimethylmercaptoacrylate providing 2‐(pyrazol‐1‐yl)‐3‐methyl‐4‐oxo‐5‐cyano‐6‐substituted pyrimidines 10 , and 11 . Some of the compounds were screened for antibacterial‐, antifungal‐ and antiviral activities and a few of them showed significant chemotherapeutical activities.