A series of 3-(9-hydroxy-3-methoxy-7-aryl-6,7,9,10-tetrahydro-5H-benzo[h]thiazolo[2,3-b]quinazolin-9-yl)2 H-chromen-2-ones (5a-j) were synthesized by one-pot multicomponent reaction of 6-methoxy-1-tetralone, aryl aldehydes, and thiourea followed by cyclization with 3-(2-bromoacetyl)-2H-chromen-2-one in the presence of a Bronsted solid acid catalyst, poly(4-vinylpyridinium)hydrogen sulfate [P(4-VPH)HSO 4 (0.015 g), under solvent-free conditions at 120 degrees C. All the synthesized compounds were characterized by spectral studies and screened for their in vitro antibacterial activity against S. Atreus and B. thuringiensis (gram positive), and E. coil and K. pneurnoniae (gram negative) bacterial strains. On comparing with the standard drug gentamicin, compounds derived from 4-methoxy and 3,4,5-trimethoxy benzaldehyde, i.e. 5g and 5h, showed broad spectrum antibacterial activity and the remaining compounds showed weak to moderate activity.