Synthesis of some novel pyrazolo[1,5‐ a ]pyrimidine, 1,2,4‐triazolo[1,5‐ a ]pyrimidine, pyrido[2,3‐ d ]pyrimidine, pyrazolo[5,1‐ c ]‐1,2,4‐triazine and 1,2,4‐triazolo[5,1‐ c ]‐1,2,4‐triazine derivatives incorporating a thiazolo[3,2‐ a ]benzimidazole moiety

E ‐3‐( N,N ‐Dimethylamino)‐1‐(3‐methylthiazolo[3,2‐ a ]benzimidazol‐2‐yl)prop‐2‐en‐1‐one ( 2 ) was synthesized by the reaction of 1‐(3‐methylthiazolo[3,2‐ a ]benzimidazol‐2‐yl)ethanone ( 1 ) with dimethylformamide‐dimethylacetal. The reaction of 2 with 5‐amino‐3‐phenyl‐1 H ‐pyrazole ( 4a ) or 3‐amino‐1,2,4‐(1 H )‐triazole ( 4b ) furnished pyrazolo[1,5‐ a ]pyrimidine and 1,2,4‐triazolo[1,5‐ a ]pyrimidine derivatives 6a and 6b , while the reaction of enaminone 2 with 6‐aminopyrimidine derivatives 7a,b afforded pyrido[2,3‐ d ]pyrimidine derivatives 9a,b , respectively. The diazonium salts 11a or 11b coupled with compound 2 to yield the pyrazolo[5,1‐ c ]‐1,2,4‐triazine and 1,2,4‐triazolo[5,1‐ c ]‐1,2,4‐triazine derivatives 13a and 13b . Some of the newly synthesized compounds exhibited a moderate effect against some bacterial and fungal species.