Intramolecular hydroamination/cyclization of aminoalkenes catalyzed by diamidobinaphthyl magnesium- and zinc-complexes

Reaction of 2 equiv of n-Bu2Mg and Et2Zn with the chiral l-proline-derived axial chiral tetraamines (S,S,S)-1 and (R,S,S)-1 gave the chiral bimetallic complexes [M2{(S,S,S)-DABN(MeProline)2}{R}2] (M=Mg, R=n-Bu ((S,S,S)-2); M=Zn, R=Et ((S,S,S)-3)) and [M2{(R,S,S)-DABN(MeProline)2}{R}2] (M=Mg, R=n-Bu ((R,S,S)-2)); M=Zn, R=Et ((R,S,S)-3)). The magnesium complexes showed moderate to high catalytic activity in the intramolecular hydroamination/cyclization of aminoalkenes, though enantiomeric excess was limited to 14% ee due to protolytic ligand exchange processes. The zinc complexes were less reactive and generally required higher reaction temperatures of 60–100 °C, but achieved slightly higher enantiomeric excess of up to 29% ee.