Enantioselective Nucleophilic Addition of Trimethylsilylacetylene to N-Phosphinoylimines Promoted by C2-Symmetric Proline-Derived β-Amino Alcohol

Both C-2- and C-3-symmetric proline-derived beta-amine alcohol ligands were designed, synthesized, and successfully applied to the enantioselective direct addition of trimethylsilylacetylene to N-phosphinoylimines. Aromatic, heteroaromatic, and aliphatic N-(diphenylphosphinoyl) imines and several N-(diethoxyphosphoryl) imines were tested, and optically active propargylic amides in good yields (up to 92%) and excellent enantioselectivities (up to 95%) were obtained by the simple experimental procedure. The convenience, mild conditions, and easy deprotection of the phosphonamide products made the present method very attractive. Furthermore, the Michael-type addition process of C=N alkynylation was studied and proposed on the basis of React P-31 NMR investigation.