Stereoselective Synthesis of CF₃-Containing Spirooxindoles via 1,3-Dipolar Cycloaddition by Dipeptide-Based Phosphonium Salt Catalysis

Reported here is an alternative method for asymmetric synthesis of the CF3-substituted 3,2 '-pyrrolidinyl spirooxindoles via 1,3-dipolar cycloaddition by employing dipeptide-based chiral phosphonium salt as a phase-transfer catalyst. Under the optimal reaction conditions, a variety of CF3-substituted 3,2 '-pyrrolidinyl spirooxindole derivatives were readily prepared in high yields as a single diastereomer with high enantiomeric access (>20:1 dr and up to 94% ee).