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.
[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]
GRAPHICAL ABSTRACT
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).