Endo and exo cycloaddition products (15)( 16) were obtained when (14) was cyclized by the catalysis of BF_3.Et_2Oat room temperature.

• Lewis acid(BF3.；Et2O)催化化合物(14)进行IMDA反应，分离得到endo和exo两种环合产物，(15)和(16)；