Regioselective synthesis of new (imidazo[2,1-b] [1,3]-thiazin-6-yl)-1,2,3-triazole-5-carboxylates as potential antimicrobial agents

Abstract

The paper presents the results of the study on the interaction of azido(benz)imidazo[2,1-b][1,3]thiazines with acetylene carboxylates under non-catalytic conditions according to Huguesgen. It was established that the [3+2]-cyclocondensation of the specified reagents occurs regioselectively upon heating and without the use of a catalyst with the formation of a 1,4-addition product, alkyl 1-((benzo)imidazo[2,1-b][1,3]thiazine-6-yl)-1H-1,2,3-triazole-5-carboxylates 4a–g, the structure of which was thoroughly proved by the methods of 1H (13C) NMR spectroscopy and chromatography-mass spectrometry. All obtained compounds were investigated in vitro experiments for antibacterial and antifungal activity. Based on the results of bioscreening, methyl 1-(2,3-diphenyl-6,7-dihydro-5H-imidazo[2,1-b][1,3]thiazin-6-yl)-1H-1,2,3- triazole-5-carboxylate 4b, ethyl 1-(2,3-diphenyl-6,7-dihydro-5H-imidazo[2,1-b][1,3]thiazin-6-yl)-1H-1,2,3-triazole-5-carboxylate 4c, methyl 1-(3,4-dihydro-2H-benz[4,5]imidazo[2,1-b][1,3]thiazin-3-yl)-1H-1,2,3-triazole-5-carboxylate 4e, tert-butyl 1-(3,4-dihydro-2H-benz[4,5]imidazo[2,1-b][1,3]thiazine-3-yl)-1H-1,2,3-triazole-5-carboxylate 4g showed a bactericidal effect at a concentration of 31.25 g/ml against the bacterium Proteus mirabilis.