Convenient One‐Pot Protocol for an Exclusive Synthesis of 4‐Cyano/ethoxycarbonyl‐2,2‐dimethyl‐2H‐chromene and/or 3‐Cyano/ethoxycarbonyl‐2‐isopropyl‐benzo[b]furan from a Single Oxo‐ylide

Abstract

[{2‐(Fluoroaryloxy)‐2‐methyl‐propanoyl}‐(cyano/ethoxycarbonyl) methylene]triphenylphosphoranes underwent microwave‐assisted tandem intramolecular Wittig and Claisen rearrangement and internal cyclization reactions to afford fluoro‐substituted 2,2‐dimethyl‐2H‐chromenes and/or 2‐isopropyl‐benzo[b]furans in good yield. Upon controlled microwave irradiation in the presence of Nafion H catalyst in xylene, the oxo‐ylides selectively formed 4‐cyano/ethoxycarbonyl‐2,2‐dimethyl‐2H‐chromenes. Microwave irradiation of the same oxo‐ylide in the presence of K₂CO₃ as catalyst or in a polar solvent–like sulfolane resulted in the exclusive formation of the corresponding fluoro‐substituted 3‐cyano/ethoxycarbonyl‐2‐isopropyl‐benzo[b]furans.

Keywords:

• 3‐cyano‐2‐isopropyl‐benzo[b]furans
• 4‐ethoxycarbonyl‐2,2‐dimethyl‐2H‐chromene
• intramolecular Wittig and Claisen rearrangement reactions
• Nafion H

Acknowledgments

The authors are thankful to J. S. Yadav, Director, Indian Institute of Chemical Technology. V. V. V. N. S. R. R is thankful to the Council of Scientific and Industrial Research, New Delhi, for the financial support.

Notes

IICT Communication No. 041018.