Boric Acid–Catalyzed One-Pot Access to 7-Aryl-benzopyrano[4,3-b] benzopyran-6,8-diones Under Aqueous Micellar Conditions

Abstract

A mild protocol for the synthesis of 7-arylbenzopyrano[4,3-b]benzopyran-6,8-diones by three-component reaction of 4-hydroxycoumarin, aromatic aldehyde, and 5,5-dimethylcyclohexane-1,3-dione (dimedone) with boric acid catalyst under aqueous micellar conditions is described. Good to excellent yield, high selectivity, tolerance of several common functional and protecting groups, and green features including avoidance of organic solvent in the reaction as well as isolation stage and use of nontoxic water-compatible mild Lewis acid catalyst are key attractive features of the protocol.

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GRAPHICAL ABSTRACT

Keywords:

• 4-Hydroxycoumarin
• aromatic aldehyde
• dimedone
• H₂O-SDS
• H₃BO₃

ACKNOWLEDGMENT

The authors (S. R. and P. M.) are thankful to the University Grants Commission (UGC), New Delhi, India, and the Council of Scientific and Industrial Research, New Delhi, India, respectively, for financial assistance by way of research fellowships. We are grateful to the Department of Science and Technology–Funding for Infrastructure in Science and Technology and UGC-Special Assistance Program (SAP) programs for providing infrastructural facilities to the Department of Chemistry, University of Kalyani.

Notes

^a Reactions were performed on 1-mmol scale at 70–80 °C.

^b Isolated yields after column chromatoghaphy/recrystallization.

^c The reaction was carried out under refluxing conditions.

^a Reaction conditions: H₃BO₃ (20 mol%), SDS–water (3 mL, 0.3 g SDS), 70–80 °C.

^b Refers to isolated yield upon recrystallization; known compounds showed physical and spectral features in good agreement with those reported in the literature.