cyanoborohydride patent

[PolytheneSam]

This patent looks interesting.

Patent US3873621

Compounds in which an aldehyde or ketonic functional group are to be reductively aminated are first converted to imines by an appropriate secondary or primary amine, or ammonia, which, in those cases, is included in the reaction mixture.  Compounds in which the functional group to be reduced is an imine, substituted imine or imino ester are protonated by the reaction medium prior to reduction.

http://www.geocities.com/dritte123/PSPF.html

The hardest thing to explain is the obvious