Oxidant-free, three-component synthesis of 7-amino-6 H -benzo[ c ]chromen-6-ones under green conditions.

An oxidant-free three-component synthesis of biologically significant 7-amino-6 H -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 6 H -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.
Competing Interests: There are no conflicts to declare.
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