Synthesis and antimicrobial activity of new linearly fused 6-substituted-3,8-diacetyl-4,7-dimethyl-2H-pyrano[6,5-f]indoles, their chemoselective bromination and synthesis of 3-thiazolylpyranoindoles

Abstract

When 1 -substituted-3,6-diacetyl-5-hydroxy-2-methylindoles 1(a,b) were reacted with ethyl acetoacetate in presence of 2-methylpiperidine produced new 6-substituted-3,8-diacetyl-4,7-dimethyl-2H-pyrano[6,5-f]indole-2-ones2(a,b). Then these compounds 2(a,b) were chemoselectively brominated with bromine in chloroform to generate exclusively, 6-substituted-3bromoacetyl-4,7-dimethyl-8-acetyl-2H-pyrano[6,5-f]indole-2-ones 3(a,b). Compounds 3(a,b) were then refluxed in dry ethanol with thiourea to secure 6-substituted 3-(2-aminothiazol-5-3,1)-8-acetyl-4,7-dimethyl-2H-pyrano[6,5-f]indole-2-ones 5(a, b). Similarly, o-hydroxyacetophenone 6 was heated with ethyl acetoacetate in presence of 2-methylpiperidine to get 3-acetyl-4methyl coumarin 7. The structures of' all these newly synthesised compounds have been confirmed by spectral and analytical data and the compounds have been screened for antibacterial and antifungal activities.