Rare‐Earth‐Metal‐Catalyzed Kinetic Resolution of Chiral Aminoalkenes via Hydroamination: The Effect of the Silyl Substituent of the Binaphtholate Ligand on Resolution Efficiency

The kinetic resolution of α‐substituted aminopentenes via intramolecular hydroamination was investigated using various 3,3′‐silyl‐substituted binaphtholate yttrium catalysts. High efficiencies in the kinetic resolution were observed for methyl‐, benzyl‐, and phenyl‐substituted substrates utilizing the cyclohexyldiphenylsilyl‐substituted catalyst 2c with resolution factors reaching as high as 90(5) for hex‐5‐en‐2‐amine (3a). Kinetic analysis of the enantioenriched substrates with the matching and mismatching catalyst revealed that the efficiency of catalyst 2c benefits significantly from a favorable Curtin–Hammett pre‐equilibrium and by a large k(fast)/k(slow) ratio. Other binaphtholate catalysts were less efficient due to a less favorable Curtin–Hammett pre‐equilibrium, which often favored the mismatching substrate‐catalyst combination. Cyclization of the matched substrate proceeds generally with large trans‐selectivity, whereas the trans/cis‐ratio for mismatched substrates is significantly diminished, favoring the cis‐cyclization product isomer in some instances.