One-pot and solvent-free synthesis of 3-(9-hydroxy-3-methoxy-7-aryl-6,7,9,10-tetrahydro-5$H$-benzo[$h$]thiazolo[2,3-$b$]quinazolin-9-yl)-2$H$-chromen-2-ones and their antibacterial evaluation

Authors: RAVIBABU VELPULA, JANARDHAN BANOTHU, RAJITHA GALI, YAKAIAH SARGAM, RAJITHA BAVANTULA

Abstract: 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)-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)-2$H$-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 $^{\circ}$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.

Keywords: Quinazolinethiones, thiazoloquinazolines, poly(4-vinylpyridinium)hydrogen sulfate, one pot and solvent-free method, antibacterial activity

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