Catalytic Hydrogenation of Substituted Quinolines on Co–Graphene Composites

Abstract

A set of 20 composites was prepared by pyrolysis of Co2+ complexes with 1,10‐phenanthroline, melamine and 1,2‐diaminobenzene. These composites were tested as the catalysts for the hydrogenation of quinolines. As shown by powder X‐ray diffraction and TEM, the composited contained Co particles of several dozen nm sizes. The composition (elements content), Raman spectra X‐ray photoelectron spectra parameters of the composites were analyzed. It was found that there was no distinct factor that controlled the yield of 1,2,3,4‐tetrahydroquinolines in the investigated process. The yields of the respective products were in the range 90–100 %. The three most active composites were selected for scale‐up and hydrogenation of a series of substituted quinolines. Up to 97 % yield of 1,2,3,4‐tetrahydroquinoline was obtained on a 50 g scale. Five representative substituted quinolines were synthesized on a 10–20 grams scale using the Co‐containing composites as the catalysts.

Screening of Palladium/Charcoal Catalysts for Hydrogenation of Diene Carboxylates with Isolated-Rings (Hetero)aliphatic Scaffold

“…The catalytic properties of the composites were tested in the reaction of quinoline hydrogenation because this reaction was widely used for the evaluation of the hydrogenation catalysts [ 11 , 12 , 27 , 28 , 29 , 30 ]. The reaction conditions (T = 50 °C, p(H 2 ) = 30 bar, t = 4 h, Table 2 ) were specially selected in such a manner that complete conversion of quinoline to 1,2,3,4-tetrahydroquinoline was not achieved ( Table 2 ).…”

“…Time, temperature, and duration of the processes are indicated in the text of the paper. After completion of the reaction, the catalyst was separated by centrifugation, the reaction mixture was evaporated, and the organic residue was analyzed by NMR and LC/MS, as reported previously [ 28 , 29 , 30 ].…”

“…Well-known protocols used for the preparation of Pd-containing hydrogenation catalysts were selected in order to evaluate the performance of the commonly used Pd-containing composites in this reaction. The performance of these catalysts was also evaluated by the hydrogenation of quinoline—a well-studied reaction, which can be proposed as a benchmark for the comparison of the catalytic performance in the hydrogenation reaction [ 11 , 12 , 27 , 28 , 29 , 30 ].…”

Redox Behavior of Cobalt–Phosphine Complexes vs Their Catalytic Activity in Organozinc Compound Formation: Background for Mechanistic Investigations

“…Instead of expensive representatives of Group IX (rhodium and iridium), the catalytic systems based on their group-neighbor cobalt were tested in several types of reactions, such as hydrogenation, hydroformylation, borylation, and hydrosilylation . At the same time, Co-containing complexes or Co-based nanosystems were tested in catalytic processes, which typically involved the use of catalysts based on metals of other groups (not Group IX), for example, Pd-catalyzed cross-coupling or hydrogenation of unsaturated organic compounds …”

A Method for the Synthesis of 1,2,3,4‐Tetrahydroquinolines through Reduction of Quinolin‐2(1H)‐ones Promoted by SmI2/H2O/Et3N

“…Compared with the complex cyclization reaction, the method of directly converting nitrogen‐containing heterocycles into 1,2,3,4‐tetrahydroquinoline is more convenient and efficient. The method of straightforward reduction hydrogenation of quinoline derivatives is one of the most studied and reported strategies, including the reduction of quinoline catalyzed by Pd, [8a] Rh, [8b] Co, [8c] Raney Ni, [8d] PtO 2 [8e] and 3,4‐dihydroquinolin‐2(1H)‐one catalyzed by Ru, [9a] BH 3 , [9b] B(C 6 F 5 ) 3 , [9c] DIBAL [9d] and samarium powder, [9e] these reactions require high‐pressure hydrogen, and some reducing agents are explosive, which limits their application. Therefore, a mild, concise, efficient method for synthesis of 1,2,3,4‐tetrahydroquinolines is highly desired.…”