Efficient Methods for the Synthesis of Benzopyrano[3,4-c]pyrrolidines by Catalyzed 1,3-Dipolar Cycloaddition of Azomethine Ylides with 3-Substituted Coumarins

Abstract

With triethylamine as a catalyst, the 1,3-dipolar cycloaddition of azomethine ylides with 3-substituted coumarins proceeded smoothly under mild conditions to afford the desired products benzopyrano[3,4-c]pyrrolidines in good to excellent yields.

Keywords:

• Azomethine ylide
• benzopyrano[3,4-c]pyrrolidine
• coumarin
• 1,3-dipolar cycloaddition

ACKNOWLEDGMENTS

We are grateful for the financial support from the National Natural Science Foundation of China (20902083), the Province Natural Science Foundation of Zhejiang (Y4090082), and Zhejiang Normal University.

Notes

^a Reactions performed with 0.3 mmol 1a and 0.6 mmol 2a, 0.06 mmol base, in 2.5 ml solvent at room temperature.

^b Reactions performed with PhCH˭NCH₂COOEt (2b).

^c Isolated yield.

^d No reaction.

^e Reflux.

^a Reactions performed with 0.3 mmol 1a and 0.6 mmol 2a, 0.06 mmol triethylamine, in 2.5 mL ethanol at room temperature for 12 h.

^b Isolated yield.

^c No reaction.