Asymmetric Synthesis of 2′‐Trifluoromethylated Spiro‐pyrrolidine‐3,3′‐oxindoles via Squaramide‐Catalyzed Umpolung and 1,3‐Dipolar Cycloaddition

The introduction of a trifluoromethyl group into the 2′‐position of spiro‐pyrrolidine‐3,3′‐oxindoles is described. By using 1 mol% of a quinine‐derived squaramide as catalyst, the 2,2,2‐trfluoroethylamine (CF₃CH₂NH₂)‐derived ketimine is transformed initially into a trifluoromethylimine through an umpolung reaction. The subsequent 1,3‐dipolar cycloaddition gives the pharmaceutical important target compounds in excellent yields, enantioselectivities and diastereoselectivies.