DBU-mediated annulation of 2-aryl-3-nitro-2H-chromenes with 1,3-cyclohexanediones for the synthesis of benzofuro[2,3-c]chromenone derivatives

Abstract

The DBU-mediated annulations of 2-aryl-3-nitro-2H-chromenes with 1,3-cyclohexanediones have been developed. This reaction involves a highly efficient domino sequence consisting of regioselective intermolecular Michael addition, intramolecular nucleophilic addition and aromatization as key unit steps. The reaction appears to be general for a variety of 2-aryl-3-nitro-2H-chromenes and tolerates the presence of aromatic moieties with electron-withdrawing and electron-donating substituents. This transformation provides a straightforward synthetic protocol for constructing benzofuro[2,3-c]chromenone derivatives.

Keywords: 1,3-cyclohexanediones; 2-Aryl-3-nitro-2H-chromene; Annulation; Benzofuro[2,3-c]chromenone; DBU (1,8-diazabicyclo[5.4.0]undec-7-ene).