A Novel Bifunctional Phosphine Catalyst for Aza-Morita-Baylis-Hillman Reactions

Significance

The development of a series of novel bifunctional phosphine catalysts derived from l-threonine is described. Amongst these new structures, phosphine-sulfonamide 1 was found to efficiently promote the aza-Morita-­Baylis-Hillman reaction between 2-naphthyl ­acrylate and various aromatic and heteroaromatic imines. The desired products were obtained in high yields and high enantioselectivities. Rationale for the high enantioface differentiation is a transition state in which the imine approaches the hydrogen bonding stabilized phosphonium enolate from the sterically less congested bottom side and is attacked on the si-face. Especially noteworthy are the high selectivities achieved with ortho-­substituted aryl imines.