A Highly Stereoselective Synthesis of Optically Active Trisubstituted 1,2-Ethylenediamines:  The First Example of Grignard Addition to N-Diphenylphosphinoyl Ketimines Derived from Amino Acids

The efficient synthesis of optically active trisubstituted 1,2-ethylenediamines is described. Addition of aryl and/or alkyl Grignard reagents to α-amino N-diphenylphosphinoyl ketimines derived from α-amino acids was demonstrated to afford the desired trisubstituted 1,2-ethylenediamines in good yields and with high diastereoselectivities. Subsequent removal of the diphenyphosphinoyl group from the adduct was smoothly accomplished in reasonable yield without racemization under newly developed reductive conditions.