Synthesis of pyrano[3,2-c]chromene-2,5-diones from 4-hydroxycoumarins and aminocrotonates under solvent-free conditions

Abstract

A new one-pot approach was developed for the construction of pyrano[3,2-c]chromene-2,5-diones by reacting 4-hydroxycoumarins with ethyl 3-oxo-3-phenylpropanoates in the presence of ammonium salts or aminocrotonates under solvent-free conditions. The title compounds were formed by intramolecular cyclization through new C–C and C–O bonds. Structure assignment of compound 3e was confirmed by single crystal X-ray analysis.