A convenient route for synthesis of new benzimidazole-based heterocycles

Reaction of 2-bromo-1-(1-methyl-1H-benzo[d]imidazole-2-yl) ethanone (1) with dimethylsulfide afforded the corresponding sulfonium bromide derivative 2. Coupling of compound 2 with diazotized aromatic amines or with the corresponding N-nitrosoacetanilide derivatives afforded the corresponding hydrazonoyl bromides derivatives 5a-c in good yields. Reaction of 2-bromo-1-(1-methyl-1H-benzo[d]imidazole-2-yl)ethanone (1) with potassium thiocyanate afforded the corresponding 1-(1-methyl-1H-benzo[d]imidazole-2-yl)-2-thiocyanatoethanone (6) that reacts with diazotized aromatic amines or with the corresponding N-nitrosoacetanilide derivatives to afford the corresponding iminothiadiazole derivatives 8a-c. Compounds 8a-c were converted into the corresponding N-acetylthiadiazole, N-nitrosothiadiazole, and thiadiazolone derivatives 9a-c ,10a-c and 11a-c , respectively upon treatment with acetyl chloride , sodium nitirite in presence of acetic acid and refluxing in ethanolic HCl respectively. Reaction of compound 6 with aromatic amines afforded the corresponding arylaminothiazole derivatives 14a-c. Coupling of compound 6 with diazotized anthranilic acid (or methyl antharanilate) and with diazotized anthranilonitrile afforded the corresponding thiadiazolo [3,2-a] quinazoline imine derivative 21a and thiadiazolo [3,2-a] quinazolinone derivative 21b, respectively.