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Chemoselective Hydrogenation of α,β‐Unsaturated Nitriles
Authors:Pavel Kukula  Martin Studer  Hans‐Ulrich Blaser
Abstract:The chemoselective hydrogenation of cinnamonitrile to 3‐phenylallylamine proceeds with up to 80% selectivity at conversions of >90% with Raney cobalt and up to 60% selectivity with Raney nickel catalysts. Best results were obtained with a doped Raney cobalt catalyst (RaCo/Cr/Ni/Fe 2724) in ammonia saturated methanol at 100 °C and 80 bar. Major problems are the formation of hydrocinnamonitrile and of secondary amines, and overreduction to 3‐phenylpropylamine. Important parameters are the catalyst type and composition, the solvent type and the presence and concentration of ammonia. The catalytic system tolerates functional groups like OH, OMe, Cl, C?O, but not aromatic nitro groups. Preliminary experiments indicate that other unsaturated nitriles with di‐ or trisubstituted C?C bonds are also suitable substrates.
Keywords:allylamines  chemoselective hydrogenation of unsaturated nitriles  Cr‐modified Raney cobalt  effect of ammonia addition  Raney nickel
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