Oxidant-free,three-component synthesis of 7-amino-6H-benzo[c]chromen-6-ones under green conditions |
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Authors: | B. S. Vachan,Aishwarya Ramesh,Muthu Karuppasamy,Isravel Muthukrishnan,Subbiah Nagarajan,J. Carlos Mené ndez,C. Uma Maheswari,Vellaisamy Sridharan |
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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.Three-component synthesis of 7-amino-6H-benzo[c]chromen-6-ones was achieved under oxidant-free green conditions. |
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