Bifunctional Phosphonium Salt‐catalyzed Enantioselective [4+2] Annulation of Isoindigos with Allenes: Access to Complex Heterocycles with Centerpiece of 4H‐Pyrans

Abstract Structurally fused heterocycles encompassing 4 H ‐pyran centerpiece are prevalent scaffolds with promising biological activities, but have daunting synthetic challenges. Herein, we presented a regio‐ and stereoselective [4+2] annulation of isoindigo derivatives with allenes by bifunctional phosphonium catalysis. This protocol provides a complementary way for accessing complex heterocyclic compounds. magnified image