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-1H-pyrazole (4a) or 3-amino-1,2,4-(1H)-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.