Synthesis, antimicrobial and antioxidant activities of some indole analogues containing naphthyridine and pyrimidonaphthyridine systems

Abstract

2-Amino-4-(2'-methoxynapthalen-6'-yl)-6-(4-subtituted phenyl)-pyridin-3- carbonitriles 2a-c have been prepared by cyclocondensation of substituted chalcones 1a-c with malanonitrile in the presence of ammonium acetate. The compounds 2a-c on cyclocondensation with (5'-substituted 2'-phenyl-1H-indol-3'- yl)-acrylonitriles 3a-c afford the key intermediates 4-amino-5-(2'- methoxynaphthalen-6'-yl)-7-aryl-2-(5'-substituted 2'-phenyl-1H-indol-3'-yl)-1,8- naphthyridin-5-carbonitriles 4a-i. Compounds 4a-i when subjected to annulations using simple and inexpensive reagents such as formic acid, carbon disulfide and formamide afford title compounds 5a-i, 6a-i and 7a-i, respectively. The structures of all these previously unknown compounds have been established on the basis of spectral and analytical data. All synthesized compounds have been screened for their antimicrobial and antioxidant activities. Compounds 2b, 5d and 6a exhibit maximum zone of inhibition against the microorganisms E. coli, A. flavus and A. terrus whereas compound 7c shows maximum zone of inhibition against microbes E. coli, S. aureus, A. oryzae and A. niger. Compounds 4h, 5g, 5h, 6g and 6h exhibit good radical scavenging activity as compared to the standards.