Copper–cobalt coordination polymers and catalytic applications on borrowing hydrogen reactions

A porous copper–cobalt polymer was synthesized and achieved applications for the N-alkylation of sulfonamides with alcohols, and carboxamides with alcohols.

Co-N-Si/AC Catalyst for Aerobic Oxidation of Benzyl Alcohols to Esters under Mild Conditions

A stable, earth-abundant, reusable cobalt-based heterogeneous catalyst is developed for the oxidative esterification of alcohols under ambient conditions, featuring broad substrate scope, providing good to excellent product yields. This protocol enables easy recyclability of the catalyst, measured up to five times without significant loss of efficiency. The active sites of Co-N-Si/AC are proposed to be Co-N species.

The preparation of a Co@C3N4 catalyst and applications in the synthesis of quinolines from 2-aminobenzyl alcohols with ketones

A Co@C₃N₄ composite was synthesized through Co-doping of C₃N₄ and revealed high catalytic activity for the synthesis of quinolines.

Recent advances in sustainable synthesis of N-heterocycles following acceptorless dehydrogenative coupling protocol using alcohols

In this review, we have summarized various aspects of homogeneous and heterogeneously catalyzed recent advancements in the synthesis of heterocycles following the ADC approach.

Acceptorless dehydrogenative coupling with Ru-based catalysts for the synthesis of N-heteroaromatic compounds

A summary of recently developed ruthenium catalysts for the synthesis of N-heteroaromatic compounds via acceptorless dehydrogenative coupling (ADC) and the related auto-transfer-hydrogenative (ATH) reaction.

Direct synthesis of novel quinoxaline derivatives via palladium-catalyzed reductive annulation of catechols and nitroarylamines

A palladium-catalyzed new hydrogenative annulation reaction of catechols and nitroarylamines, allowing straightforward access to two classes of novel quinoxaline derivatives, has been demonstrated.

Retracted: Synthesis of 2-Arylisoindoline Derivatives Catalyzed by Reusable 1,2,4-Triazole Iridium on Mesoporous Silica through a Cascade Borrowing Hydrogen Strategy

Covalent attachment of a 1,2,4-triazole iridium complex to mesoporous MCM-41 generated a heterogeneous catalyst that was found to be effective in the synthesis of 2-aryl isoindolines, quinolines, cyclic amines, and symmetrical secondary amines through a cascade borrowing hydrogen strategy. Interestingly, the supported heterogeneous iridium catalyst prepared from the 1,2,4-triazole iridium complex and mesoporous MCM-41 exhibited high catalytic activity in the preparation of 2-aryl isoindoline derivatives and symmetrical secondary amines. The catalyst system is highly recyclable for at least five times. Besides the important effect of the triazole, iridium sites grafted on siliceous supports can act as multifunctional catalytic centers and thus greatly enhance the catalytic activity of the catalysts. Furthermore, mechanistic experiments revealed that the reaction is initiated by an initial alcohol dehydrogenation and promoted by an iridium hydride intermediate. Importantly, the direct detection of a diagnostic iridium hydride signal confirmed that the synthesis of 2-aryl isoindolines occurs by a borrowing hydrogen process. This work provides an efficient example of isoindolines synthesis through a borrowing hydrogen strategy.

Ruthenium(ii)/acetate catalyzed intermolecular dehydrogenative ortho C-H silylation of 2-aryl N-containing heterocycles

The first application of a RuHCl(CO)(PPh3)3-OAc catalytic system on the selective intermolecular mono C-H silylation of 2-aryl N-heterocycles using HSiEt3 as the silylating reagent has been described. This protocol features good functional group tolerance and high regioselectivity, and has potential for gram scale-up, which provides a convenient and practical pathway for the synthesis of versatile organosilane compounds. This catalytic system can also be applied to the silylation of challenging sp3 C-H bonds.

Thienylbenzotriazole promoted highly active gold nanoparticles supported on N-doped graphene as efficient catalysts in water and a mechanism exploration

Gold nanocomposite catalyzed alkylation of ketone with alcohol, alcohol and alcohol, particularly for amine and amine in water.

Immobilization of manganese dioxide nanoparticles on modified poly 2,4-dichlorostyrene microspheres: a highly efficient and recyclable catalyst for borrowing hydrogen reactions

Modified poly 2,4-dichlorostyrene microspheres were designed and synthesized, and were proved to be an effective carrier to synthesize supported manganese dioxide nanoparticles.

Direct α-C-H amination using various amino agents by selective oxidative copper catalysis: a divergent access to functional quinolines

Herein, we present, for the first time, direct dehydrogenative α-C-H amination of tetrahydroquinolines (THQs) using various amino agents by selective aerobic copper catalysis, which enables divergent access to 2-aminoquinolines, the core structures of numerous functional products. In which, the catalyst system preferentially oxidizes the tetrahydroquinolines between two amino reactants, and the presence of TEMPO significantly enhances the capability of the first oxidation of THQs and makes it a kinetically controlled process, thus favoring the C-N bond-forming step. The developed chemistry features broad substrates, excellent functional tolerance, high chemo-selectivity, and no need for pre-preparation of specific aminating agents, which offers a practical way for diverse and atom-economic synthesis of 2-aminoquinolines that are difficult to prepare or inaccessible with the existing C-H amination approaches.

Ruthenium nanoparticle catalyzed selective reductive amination of imine with aldehyde to access tertiary amines

Reductive amination is one of the most frequently used transformations in organic synthesis. Herein, we developed a novel ruthenium nanoparticle embedded ordered mesoporous carbon catalyst (Ru-OMC) and a new hydrosilylation process for the synthesis of tertiary amines. We present a direct reductive amination of imines (C[double bond, length as m-dash]N bond) with aldehydes (C[double bond, length as m-dash]O bond) using hydrosilane as the reducing reagent under mild conditions. Moreover, the Ru-OMC catalysts can be reused for up to 14 runs without noticeably losing activity.

Copper-catalysed dehydrogenative α-C(sp3)–H amination of tetrahydroquinolines with O-benzoyl hydroxylamines

A copper-catalysed dehydrogenative α-C(sp³)–H amination of tetrahydroquinolines with O-benzoyl hydroxylamines has been demonstrated, which enables direct access to 2-alkylaminoquinolines in efficient manner.

Transition-metal-catalyst-free synthesis of anthranilic acid derivatives by transfer hydrogenative coupling of 2-nitroaryl methanols with alcohols/amines

A transition metal catalyst-free synthesis of anthranilic acid derivatives, featuring operational simplicity, broad substrate scope, good functional tolerance, high step efficiency, is presented.

Straightforward synthesis of quinolines from enones and 2-aminobenzyl alcohols using an iridium-catalyzed transfer hydrogenative strategy

Synthesis of quinolines via transfer hydrogenative coupling with high step- and atom efficiency, mild conditions and operational simplicity.

Transfer hydrogenative para-selective aminoalkylation of aniline derivatives with N-heteroarenes via ruthenium/acid dual catalysis

By ruthenium/acid dual catalysis, a novel transfer hydrogenative para-selective aminoalkylation of aniline derivatives with N-heteroarenes has been demonstrated.

Preparation of pyridyltriazole ruthenium complexes as effective catalysts for the selective alkylation and one-pot C–H hydroxylation of 2-oxindole with alcohols and mechanism exploration

Pyridyltriazole-ligated ruthenium(ii) complexes have been designed and synthesized, which were characterized by X-ray crystallography.

Iodine-mediated regio- and stereoselective iodothiocyanation of alkynes in aqueous ethanol

Iodothiocyanation of alkynes with ammonium thiocyanate (NH₄SCN) and molecular iodine (I₂) has been described under transition-metal-free conditions in green aqueous ethanol. A series of β-iodo vinylthiocyanates were obtained from functional alkynes in good to excellent isolated yields. The synthetic protocol has the advantages of operational simplicity, broad substrate scope, good stereo-selectivity, the use of easily available starting materials.

Hydrogen-Transfer-Mediated α-Functionalization of 1,8-Naphthyridines by a Strategy Overcoming the Over-Hydrogenation Barrier

A general catalytic hydrogen transfer-mediated α-functionalization of 1,8-naphthyridines is reported for the first time that benefits from a hydrogen transfer-mediated activation mode for non-activated pyridyl cores. The pyridyl α-site selectively couples with the C8-site of various tetrahydroquinolines (THQs) to afford novel α-functionalized tetrahydro 1,8-naphthyridines, a class of synthetically useful building blocks and potential candidates for the discovery of therapeutic and bio-active products. The utilization of THQs as inactive hydrogen donors (HDs) appears to be a key strategy to overcome the over-hydrogenation barrier and address the chemoselectivity issue. The developed chemistry features operational simplicity, readily available catalyst and good functional group tolerance, and offers a significant basis for further development of new protocols to directly transform or functionalize inert N-heterocycles.

Selective synthesis of nitrogen bi-heteroarenes by a hydrogen transfer-mediated direct α,β-coupling reaction

By an external hydrogen transfer-mediated activation mode, we herein demonstrate a new palladium-catalyzed direct α,β-coupling of different types of N-heteroarenes. Such a selective coupling reaction proceeds with the advantages of operational simplicity, high atom-economical efficiency, and use of safe and abundant i-propanol as the activating agent, offering a practical way to access nitrogen bi-heteroarenes. Preliminary exploration has revealed that the obtained bis-1,10-phenanthroline 2qq' as a ligand is capable of improving a copper catalyst for C-C bond formation. The work reported in this paper has built an important basis for the creation of extended π-conjugated systems that are of high significance in biological, medicinal, materials and synthetic organic chemistry as well as catalysis.