Synthesis and antimicrobial evaluation of novel polyheterocyclic ring systems derived from 2-oxo-2H-pyrimido[2,1-b]benzothiazole-3-carbonitrile

摘要

New functionalized triheterocyclic ring systems, pyrazolo[4',3':5,6]pyrimido[2,1-b]benzothiazol-4(1H)-ones 4a, b, pyrano[3',4':5,6]pyrimido[2,1-b][1,3]benzothiazol-5-one 6, and pyrido[3',4':5,6]pyrimido[2,1-b][1,3]benzothiazoles 8,9 were efficiently synthesized via the reaction of 2-oxo-2H-pyrimido[2,1-b]benzothiazole-3-carbonitrile (3) with hydrazines, acetylacetone, malononitrile, and cyanoacetamide, respectively. Hydrolysis of 3 with PPA afforded 2-oxo-2H-pyrimido[2,1-b]benzothiazole-3-carboxamide (10). The reactions of 3 with a variety of alpha-aminoazoles afforded the tetra- and penta-heterocyclic ring systems 11-14. The mechanism and the regioselectively of the studied reactions have been discussed. The prepared compounds were screened for their antimicrobial activity against a panel of bacteria and fungi strains and some derivatives showed promising antimicrobial activity.