Reactions with hydrazidoyl halides. IV. Synthesis of thiazolo[3,2-a]benzimidazoles,imidazo[2,1-6]thiazoles and pyrazolo[4,3-b]thiazines

Hydrazidoyl halides were condensed with 2-mercaptobenzimidazole yielding 4a-c and 7a,b which were cyclized to the corresponding 2-arylhydrazonothiazolo3,2-a]benzimidazol-3-ones 5a,b and 3-substituted 2-arylazo thiazolo3,2-a]benzimidazoles 8a,b respectively. Imidazo2,1-b]thiazoles were obtained by the reaction of hydrazidoyl halides with 2-mercapto-4,5-dihydroimidazole. Also, hydrazidoyl halides 6a,b were reacted with 3-amino-4-mercapto-5-phenylpyrazole to give pyrazolo4,3-b]thiazines 15a,b . The structures of the products were assigned on the basis of their elemental analysis and spectral data.