Substrate‐Controlled Regioselectivity Switch in a Three‐Component 1,3‐Dipolar Cycloaddition Reaction to Access 3,3′‐Pyrrolidinyl‐Spirooxindoles Derivatives

The additive‐free 1,3‐dipolar cycloaddition reaction of isatin‐derived azomethine ylides with α‐cyano‐α,β‐unsaturated compounds was developed, which enabled diversity‐oriented synthesis of a series of novel and structurally complex 3,3′‐pyrrolidinyl‐spirooxindoles derivatives containing four contiguous and two quaternary stereogenic centers in high yields (up to 92%) and excellent diastereoselectivities (up to >25:1 dr). The reaction displays switchable regioselectivity depending on the steric effect of the substrates.