Hydrogen Transfer Strategy Research Articles

Hydrogen-transfer strategy in lignin refinery: Towards sustainable and versatile value-added biochemicals.

Lignin, the most prevalent natural source of polyphenols on Earth, offers substantial possibilities for the conversion into aromatic compounds, which is critical for attaining sustainability and carbon neutrality. The hydrogen-transfer method has garnered significant interest owing to its environmental compatibility and economic viability. The efficacy of this approach is contingent upon the careful selection of catalytic and hydrogen-donating systems that decisively affect the yield and selectivity of the monomeric products resulting from lignin degradation. This paper highlights the hydrogen-transfer technique in lignin refinery, with a specific focus on the influence of hydrogen donors on the depolymerization pathways of lignin. It delineates the correlation between the structure and activity of catalytic hydrogen-transfer arrangements and the gamut of lignin-derived biochemicals, utilizing data from lignin model compounds, separated lignin, and lignocellulosic biomass. Additionally, the paper delves into the advantages and future directions of employing the hydrogen-transfer approach for lignin conversion. In essence, this concept investigation illuminates the efficacy of the hydrogen-transfer paradigm in lignin valorization, offering key insights and strategic directives to maximize lignin's value sustainably.

Iridium-Catalysed Transfer Hydrogenation of 1,8-Naphthyridine with Indoline: Access to Functionalized N-Heteroarenes

An iridium-catalysed hydrogen transfer strategy, enabling straightforward access to tetrahydro pyridine derivatives from aryl-1,8-naphthyridines and indolines, was developed. This method proceeds with unprecedented synthetic effectiveness including high step-economic fashion together with the advantages of having no by-product and no need for external high-pressure H2 gas, offering an important basis for the transformation of 1,8-naphthyridines and indolines into functionalized products.

Hydrogen Transfer Coupling with 100% Atom Economy: Synthesis of 2-Indolyltetrahydronaphthyridine Derivatives.

An iridium-catalyzed hydrogen transfer strategy, enabling straightforward access to tetrahydropyridine derivatives from aryl-1,8-naphthyridines and indolines was developed. This method has unprecedented advantages, including high step economy. In addition, it does not produce any byproducts or require an external high-pressure H2 gas source. The method offers an important platform for the transformation of 1,8-naphthyridines and indolines into functionalized products.

Synthesis of Quinazolinones Via a Tandem Hydrogen-Transfer Strategy Catalyzed by N,S Co-doped Carbon-Anchored Co Nanoparticles

Synthesis of Quinazolinones Via a Tandem Hydrogen-Transfer Strategy Catalyzed by N,S Co-doped Carbon-Anchored Co Nanoparticles

Direct synthesis of quinazolinones via the carbon-supported acid-catalyzed cascade reaction of isatoic anhydrides with amides and aldehydes

A novel catalytic system is reported for the construction of quinazolinones via the carbon-supported acid-catalyzed cascade coupling of isatoic anhydrides with amides and aldehydes. Subsequent selective hydrosilylation of the quinazolinones using a hydrogen-transfer strategy was also explored to provide dihydroquinazolines with structural diversity. The developed methodology proceeds with a broad substrate scope, excellent functional group tolerance, and utilizes a reusable catalyst and air as a green oxidant.

Hf-MOF catalyzed Meerwein−Ponndorf−Verley (MPV) reduction reaction: Insight into reaction mechanism

Hf-MOF-808 exhibits excellent activity and specific selectivity on the hydrogenation of carbonyl compounds via a hydrogen transfer strategy. Its superior activity than other Hf-MOFs is attributed to its poor crystallinity, defects and large specific surface area, thereby containing more Lewis acid-base sites which promote this reaction. Density functional theory (DFT) computations are performed to explore the catalytic mechanism. The results indicate that alcohol and ketone fill the defects of Hf-MOF to form a six-membered ring transition state (TS) complex, in which Hf as the center of Lewis stearic acid coordinates with the oxygen of the substrate molecule, thus effectively promoting hydrogen transfer process. Other reactive groups, such as –NO2, C = C, -CN, of inadequate hardness or large steric hindrance are difficult to coordinate with Hf, thus weakening their catalytic effect, which explains the specific selectivity Hf-MOF-808 for reducing the carbonyl group.

Selective hydrodeoxygenation of lignin model compound (3,4-dimethoxybenzyl alcohol) by Pd/CNX catalyst

Upgrading of lignin derived bio-oil is an essential step for producing sustainable bio-based chemicals and fuel. Taken into account that α hydroxyl is the abundant functional group in lignin, high effective and selective catalytic alcoholysis for cleaving the Cα-OH linkages would be desirable. However, an in-depth understanding of the reaction mechanisms involved in the cleavage of Caromatic-Cα and Cα-O bonds over a novel catalyst is still needed. Herein, we report an efficient liquid-phase hydrogen transfer strategy for the selective hydrodeoxygenation of a non-phenolic lignin model compound, 3,4-dimethoxybenzyl (veratryl) alcohol, under mild conditions. By employing iso-propanol as solvent and H-donor, and palladium nanoparticles immobilized on nitrogen-doped carbon (Pd/CNX) as efficient multifunctional catalyst, veratryl alcohol dehydroxylation exhibited almost 100% conversion along with very high selectivity for 1,2-dimethoxy-benzene (46%) and 3,4-dimethoxytoluene (54%). Compared with other Pd catalysis, the Pd/CNX has excellent catalytic performances and exhibits higher selectivity for 3,4-dimethoxytoluene under incorporation with 1% HCOOH at 220 °C. The proportion of Pd (0) significantly increases in Pd/CNX catalyst when introduced into N precursor because of its highly dispersed Pd NPs and preventing the reoxidation of Pd (0). The dehydrogenation reaction occurred through the hydrogen generation of a secondary alcohol. Then, the Cα-OH and Caromatic-Cα bonds of veratryl alcohol were selectively cleaved by catalytic transfer hydrogenolysis. The alcoholysis mechanism is supported by dispersion-corrected density functional theory computations.

Iron(0)-Catalyzed Transfer Hydrogenative Condensation of Nitroarenes with Alcohols: A Straightforward Approach to Benzoxazoles, Benzothiazoles, and Benzimidazoles.

The iron-catalyzed hydrogen transfer strategy has been applied to the redox condensation of o-hydroxynitrobenzene with alcohol, leading to the formation of benzoxazole derivatives. A wide range of 2-substituted benzoxazoles were synthesized in good to excellent yields without the addition of an external redox agent. A series of control experiments provided a plausible mechanism. Furthermore, the reaction system was successfully extended to the synthesis of benzothiazoles and benzimidazoles.

Metal-free chemoselective reduction of nitroaromatics to anilines via hydrogen transfer strategy

A novel protocol for chemoselective reduction of aromatic nitro compounds to aromatic amines has been established. The metal-free reduction goes through a hydrogen transfer process. Various easily reducible functional groups can be well tolerated under the optimized reaction conditions.

One-pot synthesis of secondary amine via photoalkylation of nitroarenes with benzyl alcohol over Pd/monolayer H1.07Ti1.73O4·H2O nanosheets

The photoalkylation of nitroarenes with benzyl alcohols in one pot at room temperature and 1 atm N2 was achieved over the Pd/H1.07Ti1.73O4·H2O nanosheets. The sample shows efficient photocatalytic activity with high conversion of nitrobenzene (99%) and selectivity of secondary amine (85%). This flexible photocatalytic system is also applicable to other nitroarenes with high efficiency. Results of in situ FTIR, DRS, and in situ ESR revealed that the benzyl alcohol and nitrobenzene molecules can bind with the surface Lewis and Brønsted acid sites in the catalyst via the HO⋯Ti and NO2⋯HOTi species. The formation of surface coordination species results in not only the activation of reactant molecules via surface electron transfer, but also the expanded visible light absorption of the catalyst. Moreover, in situ ESR suggested that the surface coordination can also facilitate the formation of oxygen vacancies in catalysts, which can greatly promote the exposure of Lewis sites and enhance the activation of reactant molecules. Finally, a possible hydrogen transfer strategy over the sample is proposed on a molecular level.

Exploring Tandem Ruthenium-Catalyzed Hydrogen Transfer and SNAr Chemistry.

A hydrogen-transfer strategy for the catalytic functionalization of benzylic alcohols via electronic arene activation, accessing a diverse range of bespoke diaryl ethers and aryl amines in excellent isolated yields (38 examples, 70% average yield), is reported. Taking advantage of the hydrogen-transfer approach, the oxidation level of the functionalized products can be selected by judicious choice of simple and inexpensive additives.

An efficient route for the synthesis of benzimidazoles via a hydrogen-transfer strategy between o-nitroanilines and alcohols

[1,1′-Bis(diphenylphosphino)ferrocene]dichloropalladium(II) has been used as an efficient catalyst for the synthesis of 2-substituted benzimidazoles via a hydrogen-transfer strategy. Various 2-substituted benzimidazoles were synthesized in good to excellent yields (up to 97%). The reaction shows good functional group tolerance. And no additional additive, oxidant, or reductant was required for the reaction.

ChemInform Abstract: Ruthenium‐Catalyzed Selective Imine Synthesis from Nitriles and Secondary Alcohols under Hydrogen Acceptor‐ and Base‐Free Conditions.

Abstract22 examples

ChemInform Abstract: Catalytic Dehydrogenative Aromatization: An Alternative Route to Functionalized Arenes

AbstractReview: 36 refs.

ChemInform Abstract: Convenient Synthesis of Quinolines from α‐2‐Nitroaryl Alcohols and Alcohols via a Ruthenium‐Catalyzed Hydrogen Transfer Strategy.

A new and straightforward method for convenient synthesis of quinolines via a ruthenium-catalyzed hydrogen-transfer strategy has been demonstrated. By employing a commercially available ruthenium catalyst system, different α-2-nitroaryl alcohols were efficiently converted in combination with a variety of alcohols into various substituted products in reasonable to good yields upon isolation. The synthetic protocol is operationally simple with a broad substrate scope, and there is no need for the use of specialized reducing agents, making it a practical approach for versatile preparation of various quinoline derivatives.

ChemInform Abstract: Efficient Synthesis of Quinoxalines from 2‐Nitroanilines and Vicinal Diols via a Ruthenium‐Catalyzed Hydrogen Transfer Strategy.

AbstractA great variety of quinoxalines are simply synthesized.

Efficient synthesis of quinoxalines from 2-nitroanilines and vicinal diols via a ruthenium-catalyzed hydrogen transfer strategy

An efficient synthesis of quinoxalines from 2-nitroanilines and biomass-derived vicinal diols is demonstrated via a hydrogen transfer strategy.

Supported gold-catalyzed and ammonia-promoted selective synthesis of quinazolines in aqueous media

A highly efficient and selective synthesis of 2,4-disubstituted quinazolines via a hydrogen-transfer strategy was developed under the catalysis of nano-Au/TiO2 and the assistance of nitrogen source-promotion.

Convenient Synthesis of Quinolines from α‐2‐Nitroaryl Alcohols and Alcohols via a Ruthenium‐catalyzed Hydrogen Transfer Strategy

AbstractA new and straightforward method for convenient synthesis of quinolines via a ruthenium‐catalyzed hydrogen‐transfer strategy has been demonstrated. By employing a commercially available ruthenium catalyst system, different α‐2‐nitroaryl alcohols were efficiently converted in combination with a variety of alcohols into various substituted products in reasonable to good yields upon isolation. The synthetic protocol is operationally simple with a broad substrate scope, and there is no need for the use of specialized reducing agents, making it a practical approach for versatile preparation of various quinoline derivatives.

Palladium-catalyzed one pot 2-arylquinazoline formation via hydrogen-transfer strategy.

The palladium catalytic system was first applied to 2-arylquinazoline synthesis via hydrogen transfer methodology. Various (E)-2-nitrobenzaldehyde O-methyl oximes reacted easily with alcohols or benzyl amines to provide N-heterocyclic compounds in good to high yields. Similarly, the heterocyclic products could be prepared by the reaction of 1-(2-nitrophenyl)ethanone, urea and benzyl alcohols. In these reactions, the nitro group was reduced in situ by hydrogen generated from the alcohol dehydrogenation step.