One-pot and solvent-free synthesis 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 and their antibacterial evaluation

A series of 3-(9-hydroxy-3-methoxy-7-aryl-6,7,9,10-tetrahydro-5 H -benzo[ h ]thiazolo[2,3- b]quinazolin-9-yl)-2H -chromen-2-ones (5a–j) were synthesized by one-pot multicomponent reaction of 6-methoxy-1-tetralone, aryl aldehy- des, and thiourea followed by cyclization with 3-(2-bromoacetyl)-2H-chromen-2-one in the presence of a Brønsted solid acid catalyst, poly(4-vinylpyridinium)hydrogen sulfate [P(4-VPH)HSO4 ] (0.015 g), under solvent-free conditions at 120 °C. All the synthesized compounds were characterized by spectral studies and screened for their in vitro antibacterial activity against S. aureus and B. thuringiensis (gram positive), and E. coli and K. pneumoniae (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.