Synthesis and biological evaluation of some cyanopyridines and isoxazoles

4-Oxo-3,4-dihydro-5H-thiazolo [2,3-a] benzimidazole (2) on treatment with aromatic aldehydes, malononitrile and ammonium acetate yielded 2-amino-3-cyano-4-aryl benzimidazolo [1,2-b] thiazolo [4,5-b] pyridines (3). The same compound (2) reacted with various aromatic aldehydes to afford 2-arylidene-3-oxo-3,4-dihydrothiazolo [2,3-a] benzimidazoles (4a-l) which on cyclization with hydroxylamine hydrochloride in presence of sodium acetate furnished the corresponding 9-aryl isoxazolo [3,4-d] thiazolo [2,3-a] benzimidazoles (5a-l). Compounds (4a-l) exhibited significant activity against Mycobacterium tuberculosis H(37)Rv. All compounds have also been screened for antimicrobial activity.