Preparation of isomeric trifluoromethylbenzylamines

The production of tyramine via the selective hydrogenation of 4-hydroxybenzyl cyanide over a carbon-supported palladium catalyst

The selective production of primary amines is a problem that plagues heterogeneously catalysed nitrile hydrogenation reactions. Whilst the target amine tyramine (HOC₆H₄CH₂CH₂NH₂) is biochemically available through the action of enzymes, synthetic routes to this species are not widely reported. Here, a heterogeneously catalysed method is proposed that utilises a Pd/C catalyst to effect the selective hydrogenation of 4-hydroxybenzyl cyanide within a three-phase reactor. The aforementioned selectivity issues are overcome by adjustment of various experimental parameters (hydrogen supply, agitation rate, temperature, use of an auxiliary agent) that result in improved catalytic performance, such that the desired tyramine salt (tyramine hydrogen sulphate) can be produced in quantitative yield. Accordingly, through consideration of the interconnectivity of hydrogenation and hydrogenolysis processes, a selective synthetic strategy is achieved with the findings suitable for extension to other substrates of this nature.

Tyramine hydrogen sulphate is produced via the heterogeneously catalysed selective hydrogenation of 4-hydroxybenzyl cyanide within a three-phase reactor.

Selective Hydrogenation of Nitriles to Primary Amines Catalyzed by a Polysilane/SiO2-Supported Palladium Catalyst under Continuous-Flow Conditions

Hydrogenation of nitriles to primary amines with heterogeneous catalysts under liquid‐phase continuous‐flow conditions is described. Newly developed polysilane/SiO₂‐supported Pd was found to be an effective catalyst and various nitriles were converted into primary amine salts in almost quantitative yields under mild reaction conditions. Interestingly, a complex mixture was obtained under batch conditions. Lifetime experiments showed that this catalyst remained active for more than 300 h (TON≥10 000) without loss of selectivity and no metal leaching from the catalyst occurred. By using this continuous‐flow hydrogenation, synthesis of venlafaxine, an antidepressant drug, has been accomplished.

Preparation of N-Alkylbis(3-aminopropyl)amines by the Catalytic Hydrogenation of N-Alkylbis(cyanoethyl)amines

An improved process for the preparation of N-alkylbis(3-aminopropyl)amines is described. These triamines are of interest as monomers for the condensation polymerization with esterified carbohydrate diacids (aldaric acids) to generate the corresponding poly(4-alkyl-4-azaheptamethylene aldaramides). The triamine synthesis is comprised of two efficient steps and requires no chromatographic purification. Bisconjugate addition of alkylamines to acrylonitrile followed by catalytic hydrogenation of the N-alkylbis(cyanoethyl)amines over Raney nickel yields the target N-alkylbis(3-aminopropyl)amines. Much less solvent was used in the bisconjugate addition step then previously reported, and in the second step, a relatively low-pressure catalytic hydrogenation (50 psi of hydrogen) was employed using Raney nickel as the catalyst in a 7 N methanolic ammonia solvent system to afford the N-alkylbis(3-aminopropyl)amines of high purity in nearly quantitative yield.