Asymmetric Hydrogenation of Acetophenone Catalyzed by Chirally Modified Ruthenium Nanoparticles Supported on Carbon Nanotubes

Abstract

Different types of carbon nanotubes as carriers were used to prepare ruthenium nano-catalysts loaded outside (named as Ru/CNTs) and inside (named as Ru@CNTs) the tube. The catalysts were modified in situ with chiral ligands (1S, 2S)-DPEN (1S, 2S)-DPEN = (1S, 2S)-1,2-diphenyl-1,2-ethanediamine). In the presence of TPP (TPP = triphenylphosphine) as the stabilization, the catalytic asymmetric hydrogenation of acetophenone was carried out with the modified catalysts. A novel approach to prepare the inside-loaded catalysts of Ru@CNTs was explored in the preparation. The catalyst can efficiently prevent the Ru nanoparticles from oxidizing in the air in this approach. The catalysts were well characterized by means of TEM, XRD, XPS, BET and H 2 Pulse Chemisorption. The effect of the diameter of carbon nanotubes on the particle size of ruthenium nanoparticles loaded on the tubes was also well studied. When Ru@CNTs (8 %, S) ("S" abbreviated from "short", the same below) was used in the asymmetric hydrogenation of acetophenone, 100 % conversion of acetophenone achieved, and the ee value reached 76.4 %. Under the same reaction conditions, 100 % conversion of acetophenone as well as the highest ee value of 80.8 % were obtained when Ru/CNTs (8 %, S) was applied in the reaction.

Stable Co/N-Doped Carbon Nanotubes as Catalysts for Oxygen Reduction

“…Carbon nanotubes (CNTs) have become excellent catalyst carriers because of their unique cavity structure, large S BET , strong metal–carrier interaction, and unique catalytic properties derived from radial conduction. , Compared with conventional carbon black, CNTs have been confirmed to promote the dispersion of active metal particles through strong interactions and to ensure faster electron conduction, which is expected to become an important basis for improving the performance of catalysts and to have broad prospects in the future . In the past few decades, driven by the rapid development of metal–organic frameworks (MOFs), the structure and composition of M–N–C catalysts have been shown to be precisely controlled through properly designing MOF precursors, thus significantly improving the ORR activity. − Wan et al synthesized three-dimensional (3D) hierarchical Co/N-CNT–Zn/Co by pyrolysis of bimetallic Co- and Zn-zeolitic imidazolate, showing high ORR activity and excellent durability in alkaline media.…”

Chiral carbon nanostructures: a gateway to promising chiral materials

“…The prepared GO-BINOL Ti catalyst showed good reactivity (99%) and moderate enantioselectivity (45% ee) in the following asymmetric addition reactions. 347 In 2020, Bolin's group 348 reported externally loaded ruthenium nanocatalysts (called Ru/CNTs) and internally loaded ruthenium nanotubes (called Ru @ CNTs) based on different carbon nanotube supports, as shown in Fig. 34c.…”

“…(c) Externally loaded ruthenium nanocatalysts prepared using carbon nanotubes as carriers. 348 Copyright 2020, Wiley. (d) Aim of the work: application of CDs-1 in iminium-ion and enamine-mediated amino catalytic processes in aqueous media.…”

Designing Sites in Heterogeneous Catalysis: Are We Reaching Selectivities Competitive With Those of Homogeneous Catalysts?

“…484 For instance, a catalyst consisting of Ru NPs supported on CNTs could be made enantioselective for the asymmetric hydrogenation of acetophenone by adding (1S,2S)-1,2-diphenyl-1,2-ethanediamine to the reaction mixture as a chiral modifier. 485 In another example, the synthesis of iodomethyl dihydrobenzofuran promoted by a Pd/SiO 2 catalyst was made enantioselective via the addition of a chiral sulfinamide phosphine modifier. 486 Ir NPs can also be made enantioselective for the hydrogenation of ketones via the addition of a chiral secondary phosphine oxide.…”

“…There are a few other examples of the use of adsorbed molecular modifiers to control enantioselectivity in heterogeneous catalysis . For instance, a catalyst consisting of Ru NPs supported on CNTs could be made enantioselective for the asymmetric hydrogenation of acetophenone by adding (1S,2S)-1,2-diphenyl-1,2-ethanediamine to the reaction mixture as a chiral modifier . In another example, the synthesis of iodomethyl dihydro­benzofuran promoted by a Pd/SiO 2 catalyst was made enantioselective via the addition of a chiral sulfinamide phosphine modifier .…”