Vachan BS, Ramesh A, Karuppasamy M, Muthukrishnan I, Nagarajan S, Menéndez JC, Maheswari CU, Sridharan V. Oxidant-free, three-component synthesis of 7-amino-6
H-benzo[
c]chromen-6-ones under green conditions.
RSC Adv 2019;
9:32946-32953. [PMID:
35529159 PMCID:
PMC9073129 DOI:
10.1039/c9ra07108c]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 10/03/2019] [Indexed: 01/24/2023] Open
Abstract
An oxidant-free three-component synthesis of biologically significant 7-amino-6H-benzo[c]chromen-6-ones was established involving a Sc(OTf)3 catalyzed three-component reaction between primary amines, β-ketoesters and 2-hydroxychalcones under green conditions. In this strategy, both the B and C rings of 6H-benzo[c]chromen-6-ones were constructed simultaneously starting from acyclic precursors by generating four new bonds including two C-C, one C-N and one C-O in a single synthetic operation. The mechanism of this sequential cascade process involves the initial formation of a β-enaminone intermediate followed by Michael addition with 2-hydroxychalcone, intramolecular cyclization, dehydration, lactonization and aromatization steps. Unlike the related literature approaches, this reaction delivered the products without the addition of any external oxidants to achieve the key aromatization step.
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