The application of a supported palladium catalyst for the hydrogenation of aromatic nitriles

The production of tyramineviathe selective hydrogenation of 4-hydroxybenzyl cyanide over a carbon-supported palladium catalyst

“…Transmission electron microscopy revealed a mean Pd particle size of 2.5 nm. 21 The reactor was charged with catalyst and solvent. The mixture was then heated and reduced under hydrogen for 1 hour prior to substrate addition via a syringe.…”

“…20 In 2016 McMillan and co-workers reported on the hydrogenation of aromatic nitrile compounds over a carbon-supported Pd catalyst. 21 Hydrogenation of benzonitrile to form benzylamine was readily achieved but this was subsequently followed by a hydrogenolysis reaction to produce toluene. Co-adsorption studies of benzonitrile and benzylamine provided evidence for site-selective chemistry over this particular Pd/C catalyst, with specic sites associated with the hydrogenation and hydrogenolysis pathways.…”

“…Chemically, following on from the early work of Buck using a platinum oxide catalyst, 22 there are surprisingly few accounts for the synthesis of this trace amine. [23][24][25] Thus, this work seeks to use a potential synthesis route to a biologically relevant primary amine to additionally explore the factors that inuence hydrogenation and hydrogenolysis steps over the same carbonsupported Pd catalyst used by McMillan et al 21 In this way, the selected reaction system will provide new information on the correlation between molecular structure and selectivity issues connected with the hydrogenation of substituted phenethylamines.…”

The hydrogenation of mandelonitrile over a Pd/C catalyst: towards a mechanistic understanding

“…However, based on previous investigations by McMillan and co-workers into the hydrogenolysis of benzylamine, where the loss of ammonia was shown to be facilitated by a hydrogenolytic step, it is proposed that for the mandelonitrile system, it is a corresponding hydrogenolysis mechanism which facilitates the loss of water. 19,20 Thus, with reference to Scheme 2, two possible routes to the desired product may be considered. 25 Moreover, Scheme 2 highlights that the order in which the hydrogenation and hydrogenolysis steps take place dictates the intermediate species observed.…”

“…17,18 Despite this, production of the hydrogenolysis product under mild conditions has been reported, for example, by Maschmeyer et al, 17 through the study of benzonitrile over a Pd/C catalyst. Whilst there are several instances where hydrogenolytic removal of a functional group is undesirable, such as the hydrogenolysis of benzylamine to yield toluene, 19,20 there are occasions where no hydrogenolysis of the amine functionality is observed. 21 Adding a further degree of complication, there are instances where the selective hydrogenolysis of one functional group in the presence of another is required.…”