Ashraf A, Shafiq Z, Mahmood K, Yaqub M, Rauf W. Regioselective, one-pot, multi-component, green synthesis of substituted benzo[c]pyrazolo[2,7]naphthyridines.
RSC Adv 2020;
10:5938-5950. [PMID:
35497456 PMCID:
PMC9049208 DOI:
10.1039/c9ra09148c]
[Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 01/19/2020] [Indexed: 11/21/2022] Open
Abstract
An efficient and environmentally benign synthetic protocol has been developed for the synthesis of benzo[c]pyrazolo[2,7]naphthyridine derivatives through regioselective multi-component “on-water” reaction of isatin, malononitrile and 3-aminopyrazole. The Knoevenagel condensation of isatin with malononitrile resulted in the formation of arylidene, which subsequently underwent Michael addition with 3-aminopyrazole followed by basic hydrolysis, cyclization, decarboxylation and aromatization to give the target naphthyridines in good to excellent yields. The one-pot multi-component protocol was also employed to obtain the said naphthyridines in a lower yield (10–15%) than obtained by basic hydrolysis of spiro-intermediates. The present study shows attractive features such as the use of water as a green solvent, short reaction time, reduced waste products and transition metal free C–C and C–N bond formation. The structures of the synthesized derivatives were established through FTIR, 1H-NMR, 13C-NMR spectroscopy and ESI-mass spectrometry.
An efficient and environmentally benign synthetic protocol has been developed for the synthesis of benzo[c]pyrazolo[2,7]naphthyridine derivatives through regioselective multi-component “on-water” reaction of isatin, malononitrile and 3-aminopyrazole.![]()
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