Tungstophosphoric Acid–Catalyzed Imino-Diels–Alder Reaction: An Efficient One-Pot Synthesis of Pyrano- and Furanoquinoline Derivatives

Abstract

Tungstophosphoric acid has been found to be an efficient catalyst for the synthesis of pyranos- and furanoquinolines through the Imino-Diels–Alder reaction involving one-pot coupling of benzaldehydes, anilines, and 3,4-dihydro-2 H-pyran or 2,3-dihydrofuran. The products are formed at room temperature in excellent yields in a short period of time.

Keywords:

• Imino-Diels–Alder reaction
• pyrano- and furanoquinolines
• tungstophosphoric acid

ACKNOWLEDGMENTS

The authors thank the Council of Scientific and Industrial Research and the University Grants Commission, New Delhi for financial assistance.

Notes

^a The reaction of benzaldehyde, aniline, and 3,4-dyhydro-2H-pyran was conducted using different amounts of PTA in MeCN at room temperature.

^a The ratio of 4 and 5 was determined by ¹H NMR spectra of the crude products, and their structures were determined from the spectra (¹H NMR and MS) and analytical data of the pure compounds.

Part 176 in the series “Studies on novel synthetic methodologies.”