Fig. 2. Scope for asymmetric synthesis of trisubstituted allenes 3 catalyzed by CPA catalyst (S)-B2.

Unless otherwise noted, reactions were performed with 1 (0.15 mmol), 2 (0.1 mmol), (S)-B2 catalyst (0.01 mmol) and 3 Å MS (100 mg) in CCl₄ (0.5 mL) at room temperature for 24 h. Yields were isolated yields of allenes 3. Dr values were determined by crude ¹H NMR analysis. Ee values were determined by HPLC analysis on a chiral stationary phase. Ar = 3,5-dimethoxyphenyl.