Synthesis of terpene diamines based on camphor-derived dinitriles

Diamines are useful as additional ligands in enantioselective hydrogenations. A new route for synthesizing such a rigid diamine from naturally available camphor via camphor oxime/camphor furoxan/deoxygenation in large scale was developed. The resulting dinitriles were subjected to hydrogenation with Raney Ni or other heterogenous catalysts. In most cases, the reduction resulted in complex mixtures. The best results were obtained with Raney Ni in THF/H₂O in strongly basic media (NaOH), which affords compound 5b only in good yield. Homogenous catalyst like Grubbs 2nd generation reduced only the less hindered CN group to yield an amino nitrile.