Single-Atom Fe-Catalyzed Acceptorless Dehydrogenative Coupling to Quinolines.

A single-atom iron catalyst was found to exhibit exceptional reactivity in acceptorless dehydrogenative coupling for quinoline synthesis, outperforming known homogeneous and nanocatalyst systems. Detailed characterizations, including aberration-corrected HAADF-STEM, XANES, and EXAFS, jointly confirmed the presence of atomically dispersed iron centers. Various functionalized quinolines were efficiently synthesized from different amino alcohols and a range of ketones or alcohols.

Rhodium-Catalyzed Regioselective [4 + 2] Cycloaddition of Ynamines and 2-(Cyanomethyl)phenylboronates.

A rhodium-catalyzed [4 + 2] cycloaddition of ynamines and 2-(cyanomethyl)phenylboronates has been developed, leading to efficient and excellent regioselective synthesis of valuable indole-linked aromatic compounds in a concise and flexible approach. Interestingly, this strategy was successful in the construction of C···N axially chiral indoles with high enantiocontrol by the introduction of a new phosphoramidite ligand (Xie-Phos).

Cobalt-Catalyzed Synthesis of Alkenes and Vinyl Sulfones Via Dehydrogenative Coupling of Alcohols and Sulfones.

A novel protocol to access vinyl sulfones and internal/terminal olefins via cobalt-catalyzed acceptorless dehydrogenation coupling (ADC) has been established. This system enables the divergent synthesis of three kinds of olefin compounds through the coupling of alcohols and sulfones under oxidant-free conditions. The broad applicability of this procedure is demonstrated by over forty olefin products, including pharmaceutical-related compounds and complex substrates, in a one-pot process.

Cobalt-Catalyzed Acceptorless Dehydrogenation of Primary Amines to Nitriles.

The direct double dehydrogenation from primary amines to nitriles without an oxidant or hydrogen acceptor is both intriguing and challenging. In this paper, we describe a non-noble metal catalyst capable of realizing such a transformation with high efficiency. A cobalt-centered ,bidentate complex was designed and employed as a metal-ligand cooperative dehydrogenation catalyst.

Sustainable Aerobic Allylic C-H Bond Oxidation with Heterogeneous Iron Catalyst.

Emerging techniques are revolutionizing the realm of chemical synthesis by introducing new avenues for C-H bond functionalization, which have been exploited for the synthesis of pharmaceuticals, natural compounds, and functional materials. Allylic C-H bond oxidation of alkenes serves as possibly the most employed C-H bond functionalization reaction. However, sustainable and selective approaches remain scarce, and the majority of the existing conditions still hinge on hazardous oxidants or costly metal catalysts.

Tandem Electro-Thermo-Catalysis for the Oxidative Aminocarbonylation of Arylboronic Acids to Amides from CO and Water.

Direct CO electroreduction to valuable chemicals is critical for carbon neutrality, while its main products are limited to simple C /C compounds, and traditionally, the anodic O byproduct is not utilized. We herein report a tandem electrothermo-catalytic system that fully utilizes both cathodic (i.e.

Direct C-C Double Bond Cleavage of Alkenes Enabled by Highly Dispersed Cobalt Catalyst and Hydroxylamine.

The utilization of a single-atom catalyst to break C-C bonds merges the merits of homogeneous and heterogeneous catalysis and presents an intriguing pathway for obtaining high-value-added products. Herein, a mild, selective, and sustainable oxidative cleavage of alkene to form oxime ether or nitrile was achieved by using atomically dispersed cobalt catalyst and hydroxylamine. Diversified substrate patterns, including symmetrical and unsymmetrical alkenes, di- and tri-substituted alkenes, and late-stage functionalization of complex alkenes were demonstrated.

Divergent Synthesis of Alcohols and Ketones via Cross-Coupling of Secondary Alcohols under Manganese Catalysis.

A homogeneous manganese-catalyzed cross-coupling of two secondary alcohols for the divergent synthesis of γ-disubstituted alcohols and β-disubstituted ketones is reported. Employing the well-defined Mn-MACHO as the catalyst, this novel protocol has a broad substrate scope with good functional group tolerance and affords a diverse library of valuable disubstituted alcohols and ketones in moderate to good yields. The strong influence of the reaction temperature on the selective formation of alcohol products was theorized in preliminary DFT studies.

Atomically Dispersed Co-N/C Catalyst for Divergent Synthesis of Nitrogen-Containing Compounds from Alkenes.

Alkene functionalization with a single-atom catalyst (SAC) which merges homogeneous and heterogeneous catalysis is a fascinating route to obtain high-value-added molecules. However, C-N bond formation of alkene with SAC is still unexplored. Herein, a bimetal-organic framework-derived Co-N/C catalyst with an atomically dispersed cobalt center is reported to show good activity of chemoselective aziridination/oxyamination reactions from alkene and hydroxylamine, and late-stage functionalization of complex alkenes and diversified synthetic transformations of the aziridine product further expand the utility of this method.

Interheteromolecular Hyperconjugation Boosts (De)hydrogenation for Reversible H Storage.

Interheteromolecular hyperconjugation is ubiquitous in organic systems, affecting bond length, dipole moments, conformations and so on, while its effect on (de)hydrogenation reactivity in a heterogeneous thermo-catalytic system has rarely been explored. Herein, the N-heterocycles containing a benzene ring and aliphatic chain [N-ethylcarbazole (NEC) and N-propylcarbazole (NPC)] were utilized to study the correlation between interheteromolecular hyperconjugation and catalytic (de)hydrogenation. Density functional theory calculations, variable-temperature H nuclear magnetic resonance spectroscopy, and catalytic experiments showed that the presented hyperconjugation between NEC and NPC weakened the electron cloud density of aromatic rings and thus facilitated the reactivity with hydrogen featuring unpaired electrons.

Core-Shell Nano-Cobalt Catalyzed Chemoselective Reduction of N-Heteroarenes with Ammonia Borane.

An easily prepared core-shell heterogeneous nanocobalt catalyst was reported, which could achieve selective reduction of N-heteroarenes with ammonia borane under mild conditions and ambient atmosphere. Various quinoline, quinoxaline, naphthyridine, isoquinoline, acridine, and phenanthroline derivatives were hydrogenated with high selectivity and efficiency. Notably, substrates bearing sensitive functional groups under molecular hydrogen reduction conditions, such as cyano, ester, and halogens were well tolerated by the catalytic system.

Asymmetric Construction of α,γ-Disubstituted α,β-Butenolides Directly from Allylic Ynoates Using a Chiral Bifunctional Phosphine Ligand Enables Cooperative Au Catalysis.

A highly efficient construction of chiral γ-substituted α-allyl-α,β-butenolides with up to >99% enantiomeric excess from readily available allylic ynoates is realized. In this asymmetric gold catalysis, the cationic gold(I) catalyst featuring a bifunctional phosphine ligand enables a four-step cascade which permits the conversion of a diverse array of allylic ynoates into valuable chiral α,γ-disubstituted α,β-butenolides.

Molecular oxygen-mediated oxygenation reactions involving radicals.

Molecular oxygen as a green, non-toxic and inexpensive oxidant has displayed lots of advantages compared with other oxidants towards more selective, sustainable, and environmentally benign organic transformations. The oxygenation reactions which employ molecular oxygen or ambient air as both an oxidant and an oxygen source provide an efficient route to the synthesis of oxygen-containing compounds, and have been demonstrated in practical applications such as pharmaceutical synthesis and late-stage functionalization of complex molecules. This review article introduces the recent advances of radical processes in molecular oxygen-mediated oxygenation reactions.

Palladium-Catalyzed Dearomative syn-1,4-Oxyamination.

A palladium-catalyzed dearomative syn-1,4-oxyamination protocol using non-activated arenes has been developed. This one-pot procedure utilizes arenophile chemistry, and the corresponding para-cycloadducts are treated with oxygen nucleophiles via formal allylic substitution, providing direct access to syn-1,4-oxyaminated products. The reaction conditions permit a range of arenes, as well as different O-nucleophiles, such as oximes and benzyl alcohols.

Palladium-Catalyzed Dearomative syn-1,4-Carboamination with Grignard Reagents.

A protocol for palladium-catalyzed dearomative functionalization of simple, nonactivated arenes with Grignard reagents has been established. This one-pot method features a visible-light-mediated [4+2] cycloaddition between an arene and an arenophile, and subsequent palladium-catalyzed allylic substitution of the resulting cycloadduct with a Grignard reagent. A variety of arenes and Grignard reagents can participate in this process, forming carboaminated products with exclusive syn-1,4-selectivity.

A Stable Nanocobalt Catalyst with Highly Dispersed CoN Active Sites for the Selective Dehydrogenation of Formic Acid.

Novel nanostructured catalysts with highly dispersed cobalt have been synthesized by the pyrolysis of metal phenanthroline complexes. Materials with significantly different properties were obtained by simply tuning the metal/ligand ratio. The catalytic potential of this class of compounds is shown by the first example of the dehydrogenation of formic acid under the catalysis of atomically dispersed cobalt.

Homogeneous Catalysis for Sustainable Hydrogen Storage in Formic Acid and Alcohols.

Hydrogen gas is a storable form of chemical energy that could complement intermittent renewable energy conversion. One of the main disadvantages of hydrogen gas arises from its low density, and therefore, efficient handling and storage methods are key factors that need to be addressed to realize a hydrogen-based economy. Storage systems based on liquids, in particular, formic acid and alcohols, are highly attractive hydrogen carriers as they can be made from CO or other renewable materials, they can be used in stationary power storage units such as hydrogen filling stations, and they can be used directly as transportation fuels.

Conversion of Simple Cyclohexanones into Catechols.

A novel I2-catalyzed direct conversion of cyclohexanones to substituted catechols under mild and simple conditions has been described. This novel transformation is remarkable with the multiple oxygenation and dehydrogenative aromatization processes enabled just by using DMSO as the solvent, oxidant, and oxygen source. This metal-free and simple system demonstrates a versatile protocol for the synthesis of highly valuable substituted catechols and therefore streamlines the synthesis and modification of biologically important molecules for drug discovery.

Rh-Catalyzed N-O Bond Cleavage of Anthranil: A C-H Amination Reagent for Simultaneous Incorporation of Amine and a Functional Group.

A novel Rh(III)-catalyzed C-H bond amination with the simultaneous release of a formyl group at distal positions is realized employing anthranil as a new type of C-H amination reagent. This chemistry provides an efficient protocol for the synthesis of 2-acyl diarylamines, which are important structural motifs in many bioactive compounds. This new type of C-H amination reagent possesses the advantages of high atom economy, avoids the use of external oxidants, and enables further transformation of the amination products.

Rh-Catalyzed Direct Amination of Unactivated C(sp(3) )-H bond with Anthranils Under Mild Conditions.

C-N Bond formation is of great significance due to the ubiquity of nitrogen-containing compounds. Here, a mild and efficient Rh(III) -catalyzed C(sp(3) )-H aryl amination reaction is reported. Anthranil is employed as the nitrogen source with 100 % atom efficiency.

NHPI and palladium cocatalyzed aerobic oxidative acylation of arenes through a radical process.

The NHPI and palladium cocatalyzed radical oxidative acylation of arenes with aldehydes and alcohols as acyl equivalents via selective C-H functionalization has been described. Molecular oxygen, the most environmentally friendly oxidant, was used as the terminal oxidant in this catalytic cycle.

Cationic Cobalt(III)-Catalyzed Aryl and Alkenyl C-H Amidation: A Mild Protocol for the Modification of Purine Derivatives.

A cationic cobalt(III)-catalyzed direct C-H amidation of unactivated (hetero)arenes and alkenes by using 1,4,2-dioxazol-5-ones as the amidating reagent has been developed. This transformation proceeds efficiently under external oxidant-free conditions with a broad substrate scope. Moreover, 6-arylpurine compounds, which often exhibit high potency in antimycobacterial, cytostatic, and anti-HCV activities, can be smoothly amidated, thus offering a mild protocol for their late stage functionalization.

Metal-free nitrogenation of 2-acetylbiphenyls: expeditious synthesis of phenanthridines.

An intermolecular nitrogenation reaction toward the synthesis of phenanthridines has been developed. This metal-free protocol provides a novel nitrogen-incorporation transformation using azides as the nitrogen source. Phenanthridines, which are of great interest in pharmaceutical and medicinal chemistry, are synthesized efficiently in one step.

From ketones to esters by a Cu-catalyzed highly selective C(CO)-C(alkyl) bond cleavage: aerobic oxidation and oxygenation with air.

The Cu-catalyzed aerobic oxidative esterification of simple ketones via C-C bond cleavage has been developed. Varieties of common ketones, even inactive aryl long-chain alkyl ketones, are selectively converted into esters. The reaction tolerates a wide range of alcohols, including primary and secondary alcohols, chiral alcohols with retention of the configuration, electron-deficient phenols, as well as various natural alcohols.

Copper-catalyzed aerobic oxidative C-C bond cleavage for C-N bond formation: from ketones to amides.

A novel copper-catalyzed aerobic oxidative C(CO)-C(alkyl) bond cleavage reaction of aryl alkyl ketones for C-N bond formation is described. A series of acetophenone derivatives as well as more challenging aryl ketones with long-chain alkyl substituents could be selectively cleaved and converted into the corresponding amides, which are frequently found in biologically active compounds and pharmaceuticals.