Nickel-Catalyzed Dehydrogenation of N-Heterocycles Using Molecular Oxygen

Abstract

Herein, an efficient and selective nickel-catalyzed dehydrogenation of five- and six-membered N-heterocycles is presented. The transformation occurs in the presence of alkyl, alkoxy, chloro, free hydroxyl and primary amine, internal and terminal olefin, trifluoromethyl, and ester functional groups. Synthesis of an important ligand and the antimalarial drug quinine is demonstrated. Mechanistic studies revealed that the cyclic imine serves as the key intermediate for this stepwise transformation.

Photocatalytic Aerobic Dehydrogenation of N-Heterocycles with Ir(III) Photosensitizers Bearing the 2(2′-Pyridyl)benzimidazole Scaffold

“…More recently, several groups have described methodologies to prepare different aromatic N-heterocycles (N-heteroarenes) from partially saturated precursors through either catalytic dehydrogenation or catalytic acceptorless dehydrogenation. , Nevertheless, both strategies require high temperatures and/or harsh reaction conditions and, in some cases, harmful solvents and high catalyst loadings.…”

Syntheses of 1H‐Indoles, Quinolines, and 6‐Membered Aromatic N‐Heterocycle‐Fused Scaffolds via Palladium(II)‐Catalyzed Aerobic Dehydrogenation under Alkoxide‐Free Conditions

“…Recently, transition-metal-catalyzed aerobic dehydrogenation with the help of alkoxides has been developed (Scheme 1). In the presence of these bases, transition metals such as Ru, [14] Ni, [15] and Pd [16] can catalyze the aerobic dehydrogenation of N-heterocycles with a wide range of scopes. The base-metal-catalyzed aerobic dehydrogenation provided N-heterocycles in good yields with high catalytic efficiency using easily accessible reagents.…”

Accelerating H2 Evolution by Anodic Semi‐dehydrogenation of Tetrahydroisoquinolines in Water over Co3O4 Nanoribbon Arrays Decorated Nickel Foam

“…Thus, we speculated that the oxidation of 1 a primarily depended on the Co 3 O 4 electrocatalyst, not the NF substrate, which was different from the previous reports. [33,34] Thus, it could be deduced that Co 3 O 4 could also effectively catalyze dehydrogenation of N-heterocycles, and the Ni foam here was mainly functioned as the substrate providing a high specific surface area to immobilize the Co 3 O 4 nanoribbon arrays. Subsequently, we examined the effect of potential on the semi-dehydrogenation reaction.…”

“…[28][29] However, most reported thermo-, photo-and electrocatalytic synthetic routes should operate in organic solvents, and usually resulted in the complete dehydrogenation products. [30][31][32][33][34] Recently, Zhang group employed Ni 2 P or NiO as the electrocatalyst to achieve the aqueous semi-dehydrogenation of tetrahydroisoquinolines (THIQs) by coupling with effective HER or nitrate reduction reaction, which made a breakthrough in achieving value-added product dihydroisoquinolines (DHIQs). [27,35] Considering the positive function of DHIQ in pharmaceutical chemistry, [36][37] it is highly desirable to develop more readily available electrocatalysts especially based on other earth-abundant metal elements, which could integrate the selective oxidation from THIQs to DHIQs with HER in water.…”