Platinum aldimines

Hydrogenation of a mixture of amines and aldehydes or ketones results in the formation of unsymme-trical secondary amines. The hydrogenation of the intermediate aldimine or ketimine can be carried out by heterogeneous catalytic hydrogenation over metal catalysts such as platinum, palladium, nickel or Raney nickel. The overall reaction can be regarded as an alkylation of the amino compounds, and also as a reductive amination of the aldehyde or ketone (Scheme 3). 

Tanaka et al. have reported platinum-catalyzed site-selective silylation of aromatic aldimines with hexamethyldisilane [91]. This silylation reaction proceeds exclusively at the position ortho to the imino group. In the case of the reaction of an imine having an electron-withdrawing group at the para position, the yield of the desired silylated product improves (Eq. 45). The key to this site selectivity is the coordination of the imino nitrogen with the platinum atom. 

Mann G, John KD, Baker RT. Platinum catalyzed diboration using a commercially available catalyst diboration of aldimines to a-aminoboronate esters. Org Lett. 

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