Asymmetric catalytic n -phosphonyl imine chemistry: The use of primary free amino acids and Et ₂AlCN for asymmetric catalytic strecker reaction

(Figure presented) The new asymmetric catalytic Strecker reaction of achiral N-phosphonyl imines has been established. Excellent enantioselectivity (95.2-99.7% ee) and yields (89-97%) have been achieved by using primary free natural amino acids as catalysts and Et ₂AlCN as nucleophile. This work also presents the novel use of nonvolatile and inexpensive Et ₂AlCN in asymmetric catalysis. The N-phosphonyl protecting group enabled simple product purification to be achieved simply by washing the crude products with hexane, which is defined as the GAP chemistry (GAP: Group-Assistant-Purification).(17)It can also be readily cleaved and recycled under mild condition to give a quantitative recovery of N,N′- bis(naphthalen-1-ylmethyl)ethane-1,2-diamine. A new mechanism was proposed for this reaction and was supported by experimental observations.