Efficient Methods for the Synthesis of Benzopyrano[3,4-c]pyrrolidines by Catalyzed 1,3-Dipolar Cycloaddition of Azomethine Ylides with 3-Substituted Coumarins. - Fan, Li-Ping; Yang, Wei-Jun; Xu, Dong-Cheng; Li, Xin-Sheng; Xie, Jian-Wu (Synthetic Communications, 2011)