Phosphine‐Catalyzed Annulations between Modified Allylic Derivatives and Polar Dienes and Substituent Effect on the Annulation Mode

In this work, the phosphine‐catalyzed annulation reactions between modified allylic derivatives and polar 1,1‐dicyano‐1,3‐dienes have been studied. In the catalysis of PPh 3 (20 mol%), a [4+1] annulation reaction is realized between a series of 1,1‐dicyano‐2,4‐diaryl‐1,3‐dienes and ethoxycarbonyl‐activated allylic acetate, producing polysubstituted cyclopentenes in modest to excellent yields. It is also observed that the substituents of both 1,3‐dienes and allylic derivatives have a significant influence on the annulation mode: under the catalysis of PPh 3 or PBu 3 (20 mol%), regioselective [3+2] annulation products are formed from differently substituted substrates.