Recent Advances in Transition Metal‐Catalyzed Hydrogenation of Nitriles

Abstract

Amines are important building blocks possessing various applications in agrochemicals, the fine chemical industry, pharmaceuticals, materials science and biotechnology. The catalytic hydrogenation of nitriles is an important reaction for the one‐step synthesis of diverse amines. However, significant amounts of side product formation during the course of the reaction is a major issue. In recent years, an enormous amount of work has been reported using both homogeneous and heterogeneous transition metal complex catalysts for the selective reduction of nitriles. Transition metal catalysts are the most crucial factor that controls the selectivity in this reaction. Therefore, transition metal catalysts are the central point of this review. We have also briefly discussed the effect of reaction parameters, selectivity to different substrate structures and reaction mechanisms. This review provides an overview of recent developments in transition metal‐catalyzed nitrile reduction along with examples which highlight its vast potential in organic transformations.magnified image

Catalytic Hydrogen Production by Ruthenium Complexes from the Conversion of Primary Amines to Nitriles: Potential Application as a Liquid Organic Hydrogen Carrier

“…[21,22] The futureo fl iquid organich ydrogen carriers (LOHC) depends on ar eversiblec hemical reactionb ased on the release and uptake of hydrogen. [30][31][32][33][34][35] Nitriles are versatile intermediates in organic synthesis owing to their direct conversion into av arietyo ff unctionalg roups.C onventional organic procedures requiren ucleophilic displacemento fs uitable leaving groups producing stoichiometrica mounts of waste and with limited selectivity. [28] The acceptorless dehydrogenation of primary amines generates the corresponding nitrile and two moles of hydrogen.…”

Hydrogen

“…Recent advances in transition metal catalyzed nitrile hydrogenation have been reviewed. 85 A challenge in the selective hydrogenation of nitriles to amines is the generation of secondary and tertiary amines produced from the condensation and reduction of the intermediate imines with the product amines. 87 The selectivity toward primary amines can be increased by inclusion of ammonia in the reaction to intercept self-condensation of the products.…”

Mesoporous Metal–Metalloid Amorphous Alloys: The First Synthesis of Open 3D Mesoporous Ni‐B Amorphous Alloy Spheres via a Dual Chemical Reduction Method

“…Amines are important intermediates in the synthesis of many compounds and fine chemicals. Catalytic hydrogenation of nitriles with hydrogen and catalysts is a practical, green, and atom‐economical method for the synthesis of primary amines . However, obtaining good selectivity is challenging because nitriles are readily hydrogenated to secondary and tertiary amines .…”

“…However, obtaining good selectivity is challenging because nitriles are readily hydrogenated to secondary and tertiary amines . Past reports show that homogeneous catalysts are most successful in obtaining high selectivity for primary amines, but applications of conventional homogenous catalysts are limited by the difficulty to collect/recover them after the reaction. Hence, heterogeneous non‐noble metal catalysts tend to be more desirable when economics is a concern.…”