Tailoring Ni based catalysts by indium for the dehydrogenative coupling of ethanol into ethyl acetate

Exploring stable and robust catalysts to replace the current toxic CuCr based catalysts for dehydrogenative coupling of ethanol to ethyl acetate is a challenging but promising task.Herein,novel NiIn based catalysts were developed by tailoring Ni catalysts with Indium(In)for this reaction.Over the optimal Ni0.1Zn0.7Al0.3InOx catalyst,the ethyl acetate selectivity reached 90.1%at 46.2%ethanol conversion under the conditions of 548 K and a weight hourly space velocity of 1.9 h^(-1)in the 370 h time on stream.Moreover,the ethyl acetate productivity surpassed 1.1 g_(ethyl acetate)g_(catalyst)^(-1)h^(-1),,one of the best performance in current works.According to catalyst characterizations and conditional experiments,the active sites for dehydrogenative coupling of ethanol to ethyl acetate were proved to be Ni4In alloys.The presence of In tailored the chemical properties of Ni,and subsequently inhibited the C-C cracking and/or condensation reactions during ethanol conversions.Over Ni4In alloy sites,ethanol was dehydrogenated into acetaldehyde,and then transformed into acetyl species with the removal of H atoms.Finally,the coupling between acetyl species and surface-abundant ethoxyde species into ethyl acetate was achieved,affording a high ethyl acetate selectivity and catalyst stability.

Sustainable electrochemical cross‐dehydrogenative coupling of4‐quinolones and diorganyl diselenides

An environmentally friendly method for the synthesis of 3‐organylselenyl quinolones through theelectrochemical cross‐dehydrogenative coupling of 4‐quinolones and diorganyl diselenides wasdeveloped.As a green,atom economic and self‐separating process,the present reaction requiresneither external oxidants nor electrolytes,forming a recyclable catalytic system.

Synergism of Plasma and Catalyst on the Dehydrogenative Coupling of Methane

At atmospheric pressure and ambient temperature, pulse corona induced plasma was used as a new method for dehydrogenative coupling of methane. The synergism of plasma and catalyst on dehydrogenative coupling of methane was investigated. Experimental results have revealed that the synergism does exist, when positive corona within a suitable power range and an intermediate pulse repetition frequency (PRF) for a loaded 7-Mn2O3/7-A12O3 catalyst were chosen. In respect to the mechanism approach, a tentative model for general pathway was proposed to explain the role of plasma and catalyst partaking in the process of methane decomposition and C2 products formation.

Enones from aldehydes and alkenes by carbene-catalyzed dehydrogenative couplings

Enones are widely explored in synthetic chemistry as fundamental building blocks for a wide range of reactions and exhibit intriguing biological activities that are pivotal for drug discovery.The development of synthetic strategies for highly efficient preparation of enones thereby receives intense attention,in particular through the transition metal-catalyzed coupling reactions.Here,we describe a carbene-catalyzed cross dehydrogenative coupling(CDC)reaction that enables effective assembly of simple aldehydes and alkenes to afford a diverse set of enone derivatives.Mechanistically,the in situ generated aryl radical is pivotal to“activate”the alkene by forming an allyl radical through intermolecular hydrogen atom transfer(HAT)pathway and thus forging the carbon-carbon bond formation with aldehyde as the acyl synthon.Notably,our method represents the first example on the enone synthesis through coupling of“non-functionalized”aldehydes and alkenes as coupling partners,and offers a distinct organocatalytic pathway to the transition metal-catalyzed coupling transformations.

Copper-Catalyzed Hydrogen Production through the Dehydrogenative Coupling of Methanol and Diamine

A hydrogen storage system was developed via heterogeneous catalysis,employing the dehydrogenative coupling of methanol and N,N′-dimethylethylenediamine to efficiently produce high-purity H_(2).In this process,the Cu/ZnO/Al_(2)O_(3) catalyst displayed superior activity in hydrogen production,with Cu+identified as the major active site through comprehensive characterization.

Cu_(1)-B dual-active sites catalysts for the efficient dehydrogenative coupling and CO_(2)electroreduction

Dual-active sites(DASs)catalysts have positive potential applications in broad fields because of their specific active sites and synergistic catalytic effects.Therefore,the controllable synthesis and finely regulating the activity of such catalysts has become a hot research area for now.In this work,we developed a pyrolysis-etching-hydrogen activation strategy to prepare the DASs catalysts involving single-atom Cu and B on N-doped porous carbon material(Cu_(1)-B/NPC).Numerous systematic characterization and density functional theoretical(DFT)calculation results showed that the Cu and B existed as Cu-N4 porphyrinlike unit and B-N_(3)unit in the obtained catalyst.DFT calculations further revealed that single-atom Cu and B sites were linked by bridging N atoms to form the Cu_(1)-B-N6 dual-sites.The Cu_(1)-B/NPC catalyst was more effective than the single-active site catalysts with B-N_(3)sites in NPC(B/NPC)and Cu-N4 porphyrin-like sites in NPC(Cu_(1)/NPC),respectively,for the dehydrogenative coupling of dimethylphenylsilane(DiMPSH)with various alcohols,performing the great activity(>99%)and selectivity(>99%).The catalytic performances of the Cu_(1)-B/NPC catalyst remained nearly unchanged after five cycles,also indicating its outstanding recyclability.DFT calculations showed that the Cu_(1)-B-N6 dual-sites exhibited the lowest energy profile on the potential energy surface than that of sole B-N_(3)and Cu-N4 porphyrin-like sites.Furthermore,the rate-limiting step of dehydrogenation of DiMPSH on Cu_(1)-B-N6 dual-sites also showed a much lower activation energy than the other two single sites.Benefitting from the superiority of the Cu_(1)-B-N6 dual-sites,the Cu_(1)-B/NPC catalyst can also be used for CO_(2)electroreduction to produce syngas.Thus,DASs catalysts are promising to achieve multifunctional catalytic properties and have aroused positive attention in the field of catalysis.

Iron-mediated cross dehydrogenative coupling(CDC) of terminal alkynes with benzylic ethers and alkanes

Iron-mediated sp-sp3 C-C bond formation through the cross dehydrogenative coupling(CDC) of terminal alkynes with benzylic ethers or alkanes has been developed.The inexpensive iron salt is used as the catalyst to make this transformation environmentally benign.Iron-mediated sp-sp3 C-C bond formation through the cross dehydrogenative coupling(CDC) of terminal alkynes with benzylic ethers or alkanes has been developed.The inexpensive iron salt is used as the catalyst to make this transformation environmentally benign.

Metal-Free 12-Catalyzed Highly Selective Dehydrogenative Coupling of Alcohols and Cyclohexenones

The l2 catalyzed highly selective oxidatve condensation of cydohexenones and alcohols for the synthesis of aryl atkyl ethers has been described. DMSO is employed as the mild terminal oxidant. This novel methodology offers a metal-free reaction condition, operational simplicity and broad substrate scope to afford valuable products from inexpensive reagents. Various meta-substituted aromatic ethers which are hardly synthesized from the reported methods requiring meta-substituted phenols, are efficiently prepared by the present protocol.

Domino Cross Dehydrogenative Coupling of 2-Aryl Acetals with Ketones Using DDQ as Oxidant and Reactant Precursor

A novel domino cross dehydrogenative coupling of 2-aryl acetals with unmodified ketones has been developed, using DDQ as both the oxidant and reactant precursor.

Non-equilibrium Plasma Dehydrogenation Coupling of Methane

A few factors effecting the reaction of plasma dehydrocoupling of methane have been investigated. The experiment shows that plasma power load, i.e. the ratio of methane flow to plasma power, is the most important factor effecting methane dehydrocoupling. The products of the reaction are mainly acetylene, ethylene, ethane and unreacted methane etc. If oxygen with a suitable molar ratio is introduced into plasma region at a reasonable position, the selectivity of C2 hydrocarbons can be increased greatly.

Electrode material promoted dehydrogenative homo-/cross-coupling of weakly activated naphthalenes

Herein,we reported an electrochemical dehydrogenative homo-/cross-coupling of weakly activated naphthalene in the exogenous transition metal-and oxidants-free manner.Benefiting from the microscopic interaction between the reactants and the carbon plate anode,the electropolymerization of aromatic rings was suppressed.And a series of binaphthyl and naphthalene-aryl privileged scaffolds were obtained in 28%–90%yields by homo-or cross-coupling.This C(sp2)-H activation strategy featured atom and step economy as well as the ready scalability.

Recent advances in direct dehydrogenative biphenyl couplings

Biphenyl moiety represents a unique structural motif of many natural and unnatural products with biological interests, and dehydrogenative couplings of two aryl C–H bonds under oxidative conditions is unambiguously the most efficient and direct preparation of these compounds. However, higher oxidation potential of benzene derivatives makes such oxidative couplings much more difficult than other arenes. Only very limited advances have been achieved on direct formation of the crucial C–C bond between two phenyl derivatives by dehydrogenative phenyl coupling in the last two decades. This article briefly summarized and commented a number of representative recent achievements in this attractive field, including homo-, cross-and intramolecular rearrangement and couplings, as well as their applications in organic synthesis.

Thermocatalytic Dehydrogenation-Enabled Arene-Alkane Couplings

Comprehensive Summary The direct use of non-prefunctionalized arene and alkane as the starting materials to construct Caryl−Calkyl bond is an unfulfilled target and approaches to this challenge rarely surface in methodology studies.Current methods for thermocatalytic arene-alkane couplings(AAC)occur with specific substrates and/or inconvenient reagents.Herein,we report a one-pot relay bicatalysis system for AAC involving(pincer)Ir-catalyzed alkane transfer dehydrogenation and Fe(OTf)3-catalyzed olefin hydroarylation.This system exhibits broad scope and is particularly effective for alkylation of arenes with arylalkanes to form 1,1-diarylalkanes with high chemo-and regioselectivity,making it potentially useful for late-stage alkylation of complex molecules.Experimental mechanistic data provide a view into the factors controlling the regioselectivity.Finally,the strategy of dehydrogenation-enabled arene-alkane couplings has been successfully extended to a tandem catalysis by using a heterogeneous olefin hydroarylation catalyst.

Scalable Cu(Ⅱ)-mediated intramolecular dehydrogenative phenol-phenol coupling:Concise synthesis of enantiopure axially chiral homo-and hetero-diphenols

An intramolecular dehydrogenative homo-and hetero-coupling of phenols has been successfully developed for quick preparation of enantiopure axial diphenols under mild Cu(Ⅱ)-mediated conditions,using((4 S,5 S)-2,2-dimethyl-1,3-dioxolane-4,5-diyl)dimethanol as the chiral auxiliary.The commercially available(R)-α-met hylbenzy la mine was identified as the best amine ligand for Cu(Ⅱ) in the reactions.A variety of homo/hetero bis-dihydroxylbenzoate substrates were examined,affording the corresponding axially chiral diphenols with satis factory to excellent diastereomeric ratios,and a representative scalable preparation was also attempted.A formal synthesis of natural product(+)-deoxyschizandrin has been achieved in this work using one axially chiral diphenol as the synthetic intermediate.

Oxidative intramolecular coupling of 2,3-disubstituted phenyl acrylic acids and derivatives promoted by di-tert-butylperoxide

Polymethoxy-substituted phenanthrene-9-carboxylic acids or their methylate are key intermediates for the synthesis of tylophora alkaloids and their analogs. An intramolecular oxidative coupling reaction of unfunctionalized 2,3-disubstituted phenyl acrylic acids and derivatives promoted by di-tert-butylper- oxide gave above intermediates in high yields. The mild reaction conditions and easy purification procedures of this method provide a new approach for the synthesis of phenanthrenes.

Palladium-Catalyzed Intramolecular Dehydrogenative Arylboration of Alkenes

The palladium-catalyzed borylative cyclization via C—H activation has been developed.By this chemistry,the indole-fused dihydro-pyrrole motif,which is a kind of important unit in natural products and bio-active molecules,could be constructed and installed with a boric ester group.Furthermore,the utilities of products have been illustrated by the study of further transformations.Importantly,by using chiral ligand,the enantioselectivity of this borylative cyclization reaction could be controlled.Moreover,the borylative mechanism,which should proceed through a Pd(II)/Pd(IV)catalytic cycle,has been proposed based on the DFT calculations.

Rapid Access to Polysubstituted Tetrahydrocarbazol-4-ones via Sequential Selective C—H Functionalization from N-Nitrosoanilines

Comprehensive Summary Herein,we have developed a strategy of Rh(III)-catalyzed C—H activation of N-nitrosoanilines and iodonium ylides to construct novel tetralydrocarbzol-4-one scaffolds,which provided valuable templates for sequential C—H functionalization such as alkylation,alkenylation,amidation and(hetero)arylation at C^(5)-position of tetralydrocarbzol-4-one with different coupling partners.Gram-scale synthesis and further transformations of tetralydrocarbzol-4-one derivatives to Ondansetron and its analogues demonstrated the utility of this protocol,which enabled the concise and diverse construction of biologically active molecules.

Reoxidation of Transition-metal Catalysts with O2

Transition-metal catalyzed oxidation reactions are central components of organic chemistry. On behalf of green and sustainable chemistry, molecular oxygen （02） has been considered as an ideal oxidant due to its natural, inexpensive, and environmentally friendly characters,