Efficient Route to Highly Functionalized Chalcone-Based Pyranocoumarins via Iodine-Promoted Michael Addition Followed by Cyclization of 4-Hydroxycoumarins

Abstract

Molecular iodine is used as an efficient promoter in the regioselective synthesis of highly functionalized chalcone-based pyranocoumarin derivatives using 4-hydroxycoumarin in acetic acid solvent at 100 °C. Under optimized reaction conditions, our protocol (Michael addition followed by intermolecular cyclization) has tolerance for many functional groups and gave products in good to excellent yields (75–98%) within 1–2 h.

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GRAPHICAL ABSTRACT

Keywords:

• Annulation reaction
• chalcones-based pyranocoumarins
• 4-hydroxycoumarin
• Michael addition
• molecular-iodine promoter

ACKNOWLEDGMENTS

We thank the Department of Science and Technology, New Delhi, for financial support and the Department of Chemistry, Indian Institute of Technology Roorkee for the Ministry of Human Resource Development fellowship to B. V. B.

Notes

Note. MgO, ZnO, CuO, LaCl₃, BiNO₃, SnCl₄, SnCl₂·2H₂O, TaCl₅, LaCl₃, CuBr₂, and TiCl₄: no product obtained.

^a Isolated yield.

^b No reaction (NR).