Transfer Hydrogenation Of Nitrobenzene Research Articles

Synergic catalytic effect of Co nanoparticles and graphitic N on carbon aerogels towards transfer hydrogenation of nitrobenzene

Synergic catalytic effect of Co nanoparticles and graphitic N on carbon aerogels towards transfer hydrogenation of nitrobenzene

Synthesis of p-aminophenol by transfer hydrogenation of nitrobenzene with formic acid as a hydrogen source

Synthesis of p-aminophenol by transfer hydrogenation of nitrobenzene with formic acid as hydrogen source.

Oxygen vacancy-rich BiOBr microflowers for enhancing photocatalytic reduction of nitrobenzene under visible light

BiOBr has successfully been used as a photocatalyst in the selective oxidations of alcohols and amines into carbonyl compounds, however its utilization in the photocatalytic reduction reactions, especially the transfer hydrogenation of nitrobenzene (NB) to valuable organic products such as aniline, azoxybenzene, and azobenzene has rarely been reported. For the first time, we reveal the feasibility of using oxygen vacancy-rich BiOBr flower-like microsphere (BBr_OV) as a photocatalyst and hydrazine monohydrate as a green hydrogen source for such reaction. The existence of OV is probed by high-resolution transmission electron, electron paramagnetic resonance and X-ray photoelectron studies. The NB reduction activity is boosted from ~29% for pristine BiOBr microplate to ~90% for the BiOBr enriched with oxygen vacancies. Detailed characterizations disclose that the enhanced photocatalytic performance is attributed to synergistic roles of oxygen defective and hierarchical flower-like structure, endowing the BBr_OV with efficient NB adsorption/activation, enlarge surface area, improved optical absorption, and increased charge carrier generation/separation efficiency. This work not only reveals a new application of OV-rich BiOBr in the photocatalytic transfer hydrogenation of nitroarene, but also highlights the promoting catalytic effect derived from rich OV surfaces.

Special direct route for efficient transfer hydrogenation of nitroarenes at room temperature by monatomic Zr tuned α-Fe2O3

Determining the route of a heterogeneous catalytic reaction is an important step in studying the reaction mechanism as well as improving reaction activity. As for the widely reported transfer hydrogenation of nitroarenes to aniline, many reported works have made simple judgements about the reaction route based on the “direct route” and “condensation route” proposed by Haber in 1898. Herein, detailed mechanistic experiments and DFT calculations helped us identify a special direct reduction route that goes through Ph-NO2 → Ph-NHOH → Ph-NH2 without the widely recognized Ph-NO intermediate for the transfer hydrogenation of nitroarenes to anilines by monatomic Zr tuned α-Fe2O3. In this catalytic system, Zr0.025Fe0.975Oy-350 can achieve complete transfer hydrogenation of nitroarenes at room temperature, where the parent α-Fe2O3 is inactive. Accompanying spectroscopic characterizations and calculations illustrate that the incorporation of Zr into the crystal lattice of α-Fe2O3 can effectively reduce the electron cloud density of surface iron species. The resulting special Fe(3+α)+-O(2+β)--Zr(4-γ)+ structure has greatly enhanced Lewis acidity, that promotes the decomposition of N2H4·H2O to form active [H] for the reduction of nitroarenes. Moreover, the structure is also beneficial for the adsorption of nitroarene with weakening of the NO bond. The present work can be extended to the application of non-noble metal oxides in the transfer hydrogenation of nitrobenzene under mild condition, and provides a significant method for exploring the reaction process of a heterogeneous catalytic reaction.

Tuning product selectivity in nitrobenzene reduction over a single Bi2MoO6 photocatalyst in one pot: Mechanisms and roles of reaction compositions

Poor product selectivity of metal oxide photocatalysts is one of crucial issues limiting their application in photocatalytic organic synthesis particularly when multiple parallel reactions as well as several intermediates and products are involved, as in the reduction of nitrobenzene (NB) in this present study. Accordingly, catalyst modification is often needed. Herein, we first demonstrate that without catalyst modification it is feasible to control product selectivity over a single bismuth molybdate photocatalyst to selectively prepare three different valuable compounds including aniline (AN), azobenzene (AZO) and azoxybenzene (AZX) with high efficacy. Two widely used bismuth molybdate photocatalysts, namely Bi2MoO6 and Bi4MoO9, were studied and compared. Bi2MoO6 offers better visible-light-driven photocatalytic performance than Bi4MoO9 partly due to its narrow band gap energy and efficient charge carrier separation and transfer as evidenced from UV–vis DRS, EIS, and transient photocurrent studies. The roles of hydrazine hydrate, alcohol solvent, and KOH additive on the transfer hydrogenation of NB were examined and their concentrations were optimized to solely obtain the three different products with excellent selectivity (>98%). Based on UV–vis DRS and Mott-Schottky analysis, the band energy level of Bi2MoO6 and plausible reactions at solid–liquid interface are proposed. The capability to control product selectivity over a single photocatalyst in one pot demonstrated in this work would make the process more practical especially for continuous flow photochemical systems.

A novel process for the synthesis of p‐aminophenol by transfer hydrogenation of nitrobenzene using formic acid as hydrogen source

Abstractp‐Aminophenol (PAP) was synthesized via the transfer hydrogenation of nitrobenzene (NB) over a Pd/AC + SO42−/ZrO2 catalyst using formic acid as the hydrogen source. Pd loading had an obvious effect on the reaction, with an optimal loading of 7 wt.%. The average Pd crystallite size was 3–4 nm, and both Pd0 and Pd2+ species were present on the catalyst surface. The relative proportions of Pd0 and Pd2+ affected the synthesis of PAP, with higher Pd2+ concentrations increasing the PAP selectivity. The reaction conditions for PAP synthesis were optimized, and an NB conversion of 69.6% with 38.1% PAP selectivity was obtained. After the same catalyst sample was used four times, the NB conversion decreased from 69.6% to 61.3%, and PAP selectivity decreased from 34.7% to 21.5%. These changes were attributed to the loss of Pd and S from the catalyst.

Monodisperse CuPt alloy nanoparticles assembled on reduced graphene oxide as catalysts in the transfer hydrogenation of various functional organic groups

We present herein a new nanocatalyst, namely binary CuPt alloy nanoparticles (NPs) supported on reduced graphene oxide (CuPt‐rGO), as a highly active heterogeneous catalyst for the transfer hydrogenation (TH) protocol that is demonstrated to be applicable over the reduction of various unsaturated organic compounds (olefins, aldehydes/ketones and nitroarenes) in aqueous solutions at room temperature. CuPt alloy NPs were synthesized by the co‐reduction of metal (II) acetylacetonates by borane‐tert‐butylamine (BTB) complex in hot oleylamine (OAm) solution and then assembled on reduced graphene oxide (rGO) via ultrasonic‐assisted liquid phase self‐assembly method. The structure of yielded CuPt NPs and CuPt‐rGO nanocatalyst were characterized by TEM, XRD and ICP‐MS. The activity of Cu7Pt3‐rGO nanocatalysts were then tested for the THs that were conducted in a commercially available high‐pressure tube using water as sole solvent and ammonia borane as a hydrogen donor at room temperature. The presented catalytic TH protocol was successfully applied over nitroarenes, olefines and aldehydes/ketones, and all the tested compounds were converted to corresponding reduction products with the yields reaching up to 99% under ambient conditions. Moreover, the Cu7Pt3‐rGO nanocatalyst was also reusable in the TH by providing 99% yield after five consecutive runs in TH of nitrobenzene as an example.

Bifunctional Pincer Catalysts for Chemoselective Transfer Hydrogenation and Related Reactions

A comparative study on the chemoselective transfer hydrogenation of nitroarenes to anilines and related processes using FA as the hydrogen source is described; these processes are catalyzed by a series of pincer catalysts equipped with different functional groups in the secondary coordination sphere. Some new (4 and 5) as well as previously reported (1–3) catalysts belonging to the family of bifunctional PC(sp3)P pincer complexes were employed in this study The reported compounds exhibited remarkably different catalytic activity behavior, depending on the nature of the functional groups. Transfer hydrogenation of nitrobenzene with FA as a hydrogen source was probed using iridium complexes 3 or 4 as a catalyst. Under the same conditions, the analogous palladium complex was found to be useful for the selective amidation of aniline with light carboxylic acids.

Nitrogen-Doped Activated Carbon as Metal-Free Catalysts Having Various Functions

Nitrogen-doped carbon materials have been gaining increasing interest as metal-free catalysts. In this article, the authors have briefly introduced their recent studies on the utilization of nitrogen-doped activated carbon (N-AC) for several organic synthesis reactions, which include base catalyzed reactions of Knoevenagel condensation and transesterification, aerobic oxidation of xanthene and alcohols, and transfer hydrogenation of nitrobenzene, 3-nitrostyrene, styrene, and phenylacetylene with hydrazine. Doped-nitrogen species existed on the AC surface in different structures. For example, pyridine-type nitrogen species appear to be involved in the active sites for Knoevenagel condensation and for the oxidation of xanthene, while graphite-type nitrogen species appear to be involved for the oxidation of alcohols. Being different from these reactions, both surface nitrogen and oxygen species are involved in the active sites for the hydrogenation of nitrobenzene. N-AC was practically inactive for the transfer hydrogenation of vinyl and ethynyl groups, but it can catalyze those hydrogenation reactions assisted by co-existing nitrobenzene. Comparison of N-AC with conventional catalysts shows that N-AC can alternate with conventional solid base catalysts and supported metal catalysts for the Knoevenagel condensation and oxidation reactions.

One-pot synthesis of N,N-dimethylaniline from nitrobenzene and methanol

A route for the direct synthesis of N,N-dimethylaniline from nitrobenzene and methanol was developed through the sequential coupling of the hydrogen production from methanol, hydrogenation of nitrobenzene to produce aniline, and N-methylation of aniline over a pretreated Raney-Ni® catalyst (at 443 K in methanol). A high yield of N,N-dimethylaniline up to 98% was obtained by the proposed methodology. In this process, aniline was produced from in-situhydrogenation of nitrobenzene with hydrogen generated from methanol, or transfer hydrogenation of nitrobenzene with methanol as donor, while methanol acted as a hydrogen source, alkylating reagent and solvent, simultaneously. Additionally, a plausible mechanism of this one-pot reaction process has been described.