UV LASER INITIATED STEREOSELECTIVE HOMOGENEOUS CATALYSIS POLYMERIZATION OF PHENYLACETYLENE

In this paper, the stereoselective homogeneous catalysis polymerization of phenylacetylene by using two kinds of catalysts W(CO)_5CH_3I and W(CO)_4I_2 produced from UV laser photolysis of W (CO)_6 in CH_3I, I_2—C_6H_6 and CHI_3—C_6H_6 respectively was studied. The effects of laser energy, laser irradiation time and lifetime of catalyst on the polymerization of phenylacetylene were discussed. The photoproducts of W (CO)_6 in CH_3I, I2—C_6H_6 and CHI_3—C_6I_6 were determined by IR spectra. The structures of polyphenylacetylene obtained by W (CO)_5CH_3I and W (CO)_4I_2 catalysts were characterized by IR spectra and ~1H NMR spectra.

Asymmetric Transfer Hydrogenation of Naphthol and Phenol Derivatives with Cooperative Heterogeneous and Homogeneous Catalysis

Asymmetric hydrogenation of all-carbon aromatics is still a long-standing challenge in the area of asymmetric catalysis.To date,asymmetric(transfer)hydrogenation of naphthols and phenols remains unexplored.Here,we describe a new strategy for such asymmetric transformation via a bimetallic cooperative heterogeneous and homogeneous catalysis.By using HCOONa as the hydrogen source,various naphthols and phenols were partially hydrogenated in HFIP catalyzed by commercial Pd/C catalyst to give ketone intermediates.Further adding the second chiral Ru-tethered-TsDPEN catalyst and MeOH realized the asymmetric reduction of the resulting ketones in a one-pot manner,furnishing chiral alcohols with good to excellent enantioselectivity(up to 99%ee).The use of HFIP is crucial for suppressing ketone over-reduction via heterogeneous catalysis.More importantly,tandem asymmetric transfer hydrogenation of naphthols was also achieved by tuning the volume ratio of mixed HFIP/MeOH solvent,affording chiral 1,2,3,4-tetrahyronaphthols with excellent enantioselectivity but relatively low yield and limited substrate scope.

Recent Applications of Homogeneous Catalysis in Electrochemical Organic Synthesis

Although the combination of electrochemistry and homogeneous catalysis has proven to be a powerful strategy for achieving a diverse array of novel transformations,some challenges such as controlling the diffusion of catalyst-related species and the instability of catalysts at electrodes remain to be overcome.Herein,we review recent advances in electrochemical homogeneous catalysis,focusing on electrochemical noble-transition-metal catalysis,photoelectrochemical catalysis,and electrochemical enantioselective catalysis.The topics discussed include:(1)how the noblemetal catalystworks in the presence of cathodic hydrogen evolution,(2)how the photocatalyst gets enhanced redox property,and(3)how the enantioselectivity is regulated in a catalytic electrochemical reaction.

Dangling Ligand Enables an Iron Hexa-Coordinated Molecular Catalyst for Water Oxidation by Photocatalysis

Photocatalytic water oxidation reaction by transition metal complexes remains a challenge because of their poor stability under irradiation,especially for earth-abundant metal catalysts.In this regard,ironbased water oxidation catalysts are prone to hydrolysis and/or dissociate the ligands to form nanoparticles under a real catalytic condition.Herein,we describe a unique hexa-coordinated catalyst 1[Fe^(II)(Py_(3)tacn)Cl_(2)]and its reference 2[Fe^(II)(PhPy_(2)tacn)Cl_(2)]with a dangling pyridyl ligand and a phenyl group,respectively.We anticipated that the dynamically open and close coordination behaviors of the pyridyl ligand enabled balance of the reactivity and stability of catalyst 1.To our delight,the“open form”of catalyst 1 provided a free coordination site,and the“close form”guaranteed its molecular integrity,resulting in a water oxidation reaction with high efficiency and robustness.The turnover number and turnover frequency values of 2332 and 60 s^(−1)are the highest known to date among iron-based homogeneous water oxidation systems under visible light irradiation.

钒取代的杂多酸催化一锅四组分Dakin-West反应合成β-乙酰氨基酮(英文)

The multicomponent condensation of an aryl aldehyde,acetyl chloride,acetonitrile,and enolizable ketone as one-pot synthesis of β-acetamido ketones in high yields was investigated using commercial,non-corrosive,and environmentally benign Keggin and Wells-Dawson heteropolyacid catalysts.The best catalyst was H5PW10V2O40.The methodology used simple experimental conditions,and the short reaction times and high yields indicate it is a useful strategy for the large scale synthesis of β-acetamido ketones.

Ethylene Oligomerization Promoted by Nickel Complexeswith 8-Iminoquinoline Derivatives

A series of 8-iminoquinoline derivatives nickel complexes were synthesized to proceed high activity in ethylene oligomerization.

Mono-lacunary PrIII-Polyoxotungstate: Epoxidation of Alkenes with Unusual Selectivity

The utilization of polyoxometalates （POMs） or their derivatives as homogeneous or heterogeneous catalysts in alkene epoxidation is a subject of considerable research activity[1]. The limitation to the use of POMs in these catalytic reactions is either their relatively low selectivity in epoxide formation or applicability for a rather limited type of alkenes. Therefore, it would be beneficial if the catalysts bear high selectivity for epoxidation and are applicable for a rather wide variety of alkenes, which is desirable in industrial processes and also vital for the selection of an ideal catalyst[2]. In search for an efficient and practical epoxidation method to utilize aqueous H2O2 as terminal oxidant, we focus on the rare-earth complexes with lacunary POM ligands.

Reductive Deoxygenative Functionalization of Alcohols by First-Row Transition Metal Catalysis

Alcohols are among the most accessible functionalities.Catalytic deoxygenative functionalization of alcohols is highly synthetically appealing.While significant progress has been made on the reactions with nucleophiles,the reactions with electrophilic coupling partners remain a real challenge.This manuscript highlights the advance in this direction,which is mainly achieved by the first-row transition metals.The low-valent titanium catalyst has shown the unique reactivity to homolytically cleave the C—OH bonds.The formed carbon radicals could either undergo reduction to give protonation products or couple with carbon fragments to form C—C bonds.This chemistry is initially realized using a stoichiometric amount of titanium reagents and later extended to catalytic variants.Nickel features a variety of oxidation states ranging from Ni0 to NiIV,and both two-electron oxidative addition and single-electron process are involved in their activation of an electrophile.These properties enable nickel to catalyze reductive C—C coupling of alcohols with R–X electrophiles.The reaction is first reported on the reactions of allylic alcohols,then extended to benzylic alcohols and,very recently non-activated alcohols.Recent effort has resulted in many invaluable methodologies that highly improve the reaction efficiency for the construction of aliphatic C—C bonds.The use of cobalt and copper catalysts not only expands the substrate scope of these reactions but also shows the new reactivity and selectivity issues.

Catalytic Arylalkylation of Alkenyl Amines at Remote Sites via Directed Nickel Catalysis

Directing group-assisted, transition metal-catalyzed three-component difunctionalization of alkenes has emerged as a powerful tool to drive molecular complexity. However, this strategy generally works with the substrates bearing directing groups in close proximity to the alkene moieties, due to the preference for formation of kinetically stable five-membered metallacycles. Herein, we have disclosed a complementary strategy to accomplish a nickel-catalyzed remote arylalkylation of alkenyl amines with excellent regioselectivity and diastereofidelity, involving rare six- or seven-membered metallacycles. This general protocol is compatible with a series of δ- and ε-alkenyl amines, providing corresponding valuable δ,ε- and ε,ζ-difunctionalized aliphatic amines that would be difficult to synthesize. The coordination of the bidentate picolinamide auxiliary and the facile oxidative addition of alkyl halides to Ni(I) species are the key to the success of the developed remote olefin dicarbofunctionalization.

Ni-Al mixed metal oxide with rich oxygen vacancies: CO methanation performance and density functional theory study

Ni-Al mixed metal oxides have been successfully prepared by high shear mixer(HSM)and coprecipitation(CP)methods for low temperature CO methanation.In this work,Ni-Al(HSM-CP)catalyst presented small Ni crystallite size and high surface area,which all contribute to the methanation reaction at low temperature conditions.The obtained Ni-Al(HSM-CP)sample exhibited a mass of defective oxygen,thereby accelerating the dissociation of CO and ultimately increasing the activity of the catalyst.Ni-Al(HSM-CP)catalyst offered the best activity with CO conversion=100%and CH_(4) selectivity=93%at 300℃,and the CH_(4) selectivity can reach 81.8%at 200℃.In situ Fourier transform infrared spectroscopy and density functional theory show that CHO and COH intermediates with lower activation energy barriers are produced during the reaction,and hydrogen-assisted carbon–oxygen bond scission is more favorable.

Practical N-alkylation via homogeneous iridium-catalyzed direct reductive amination

Direct reductive amination(DRA)is one of the most efficient methods for amine synthesis.Herein we report a practical homogeneous DRA procedure utilizing iridium catalysis.Applying simple,readily available and inexpensive PPh_(3)and alike ligands along with iridium at a low loading,aldehydes and ketones reductively coupled with primary and secondary amines to efficiently form structurally and functionally diverse amine products,including a set of drugs and compounds from late-stage manipulation.The reaction conditions were exceptionally mild and additive-free,in which oxygen,moisture,polar protic groups and multiple other functional groups were tolerated.For targeted products,this methodology is especially versatile for offering multiple possible synthetic options.The 10 gram-scale synthesis further demonstrated the potential and promise of this procedure in practical amine synthesis.DFT studies reveal an“outer-sphere”H-addition pathway,in whichπ-πinteractions and H-bonding play important roles.

Triethylamine-catalyzed Isomerization of Glucose to Fructose under Low Temperature Conditions in Aqueous Phase

Isomerization of glucose derived from lignocellulosic biomass is an important step in biorefinery.Fructose isomerized from glucose,is used as a highly attractive sweetener in the food and beverages industries.However,the prevalence of side reactions at high glucose concentrations is a serious issue,leading to a significant reduction in the fructose yield,especially in the aqueous phase.In this study,an efficient method for the conversion of highly concentrated glucose into fructose under low temperature conditions using triethylamine as the catalyst was developed.It was demonstrated that high fructose yield could be maintained at high glucose concentration.At 60℃,fructose yield of 38.7%and fructose selectivity of 80.6%were achieved in 1 mol/L(approximately 17 wt%)glucose.When glucose concentration was increased to 2 mol/L(approximately 31 wt%),the fructose yield and selectivity were maintained at 34.7%and 77.4%,respectively.13C nuclear magnetic resonance(NMR)spectrometer was used to examine the glucose isomerization reaction.Compared to the NaOH catalytic system,triethylamine acted as a buffer to provide a stable alkaline environment for the catalytic system,further maintaining a high level of catalytic efficiency for the isomerization of glucose to fructose.

Designed Bifunctional Ligands in Cooperative Homogeneous Gold Catalysis

Over the past two decades,homogeneous gold catalysis has experienced exponential development and contributed a plethora of highly valuable synthetic methods to the synthetic toolbox.Metal–ligand cooperative catalysis is a versatile strategy for achieving highly efficient and/or novel catalysis but has seldom been explored in gold chemistry.This minireview summarizes the progress we have made in developing remotely functionalized biaryl-2-ylphosphine ligands and employing them in cooperative gold catalysis that achieves excellent catalytic efficiency or realizes previously unknown reactivities.This approach also provides new venues for implementing asymmetric gold catalysis.

Recent Advances in Catalytic Carbonylation Reactions in Alternative Reaction Media

Since the discovery of the hydroformylation(oxo-synthesis or Roelen reaction)and the Reppe-reaction,the transition metal-catalyzed carbonylation reactions,providing versatile,facile,and even atom-economic methods for the selective incorporation of C=O functionality to various skeletons,have gained tremendous importance in synthetic organic chemistry from laboratories to industrial applications.The carbonylation of carbon-carbon multiple bonds,aromatic halides,triflates,etc.,in the presence of various nucleophiles has led the way to produce aldehydes,carboxylic acids,esters,amides,etc.,in the fine chemical industry.However,these protocols usually proceed in conventional,fossil-based,and usually toxic reaction environments.Thus,several attempts have been directed to developing efficient carbonylation methods in alternative,less harmful,non-fossil-based and even in renewable reaction media.In this review,we overview the recent applications of alternative solvents such as water,biomass-based alcohols,γ-valerolactone(GVL),2-methyltetrahydrofuran(2-MeTHF),ionic liquids(ILs),deep eutectic solvents(DES),alkyl levulinates,limonene,α-pinene,and dimethyl carbonate as well as fluorous media to improve efficiency,safety and environmentally benign nature of carbonylation protocols.

Palladium Complexes with N,O-Bidentate Ligands Based on N-Oxide Units from Cyclic Secondary Amines:Synthesis and Catalytic Application in Mizoroki-Heck Reaction

Palladium-catalyzed Mizoroki-Heck reaction is a powerful and efficient method for construction of Csp2–Csp2 bonds.Herein,four palladium complexes(I—IV)with N,O-bidentate ligands(L1—L4)based on N-oxide units from cyclic secondary amines were easily synthesized and successfully applied in Mizoroki-Heck reaction of aryl bromides with electron-deficient olefins.X-ray diffraction analyses indicated the palladium(II)atom of II took the distorted square planar geometry and was four-coordinated by nitrogen and oxygen atoms from two ligands(L2).Two free chloride ions were presented as counter anions in complex II.But the palladium(II)center of IV was coordinated by nitrogen and oxygen atoms from one ligand(L4)as well as two chlorine atoms,which exhibited the nearly square-planar geometry.The study on catalytic properties of palladium complexes revealed that complex II exhibited high activity superior to the other complexes.The coupling reactions of a series of aryl bromides and olefin derivatives proceeded in the presence of 2—5 mol%palladium complex II,giving the desired products in good to excellent yields.The advantages of this method such as good compatibility of functional groups,high yields,and short reaction times made it more attractive for constructing Csp2–Csp2 bonds in the synthesis of functional molecules and materials.

Combinations of electron and proton donors in transition-metal complex mediated nitrogen reduction reactions

Nitrogen fixation is a complex process involving the transfer of six electrons and protons.Diverging from the conventional Haber-Bosch process,which relies on hydrogen(H_(2))to provide both electrons and protons to reduce nitrogen(N_(2)),homogeneous transition metal complex-catalyzed N_(2)reduction reactions(NRR)employ an array of electron and proton donors or even electron donors combined with silanes.As the synthesis of diverse catalytic progress,the categories of donors have seen rapid expansion.However,existing literature only provides summaries regarding the metal,ligands,and mechanism.Despite the significance of electron and proton donor combinations in nitrogen reduction reactions,no literature has thoroughly reviewed this aspect.Therefore,we hereby compiled a comprehensive list of commonly used reagents in N_(2)reduction and classified them according to their specific donor combinations.This review presents clear and organized information about these combinations,along with a summary of their general performance trend in NRR with related catalysts.Finally,we conclude the discussion by highlighting key points for researchers to consider when selecting catalysts and donor combinations,with the ultimate goal of advancing the field of nitrogen fixation.

Homogeneous Light-Driven Catalytic Direct Carboxylation with CO2

Carbon dioxide is a ubiquitous and inexpensive one-carbon source for chemical synthesis, and the efficient incorporation of CO2 into organic molecules is of widespread research interest both for economic and ecological reasons. The methodologies to employ carbon dioxide as a single-carbon unit to construct molecules relevant for agrochemical and pharmaceutical research include many elegant approaches, including asymmetric transformations. Even though remarkable achievements have been made in the field of light-driven catalysis, especially photoredox catalysis, homogeneous light-driven catalytic carboxylation by employing CO2 as the key reagent has only become a subject of increasing attention in recent years. Therefore, this concise review will discuss the latest advances in this research area.

Recent Advances in Homogeneous Carbonylation Using CO_2 as CO Surrogate

Carbon dioxide is a sufficient and important carbon resource, which has been widely used as a C1 building block in synthetic chemistry. Car- bonylations with CO are important processes in industry. However, due to the toxicity of CO, its storage and transport are problematic. Attentions are gradually focused on using other safe reagents to be the CO surrogates in carbonylation reactions. This review focuses on the summary of recent devel- opments in using CO_2 as a CO surrogate in homogeneous catalysis. Reductive processes by using H2, Si-H, alcohols, etc and redox-neutral processes are separately summarized.

Effective Homogeneous Hydrolysis of Phosphodiester and DNA Cleavage by Chitosan-copper Complex

We aimed to explore the role of chitosan-based metal complexes in catalyzing the hydrolysis of phosphodiesters To this end, we performed detailed studies on the kinetics of the chitosan copper complex （CSCu）-catalyzed hydrolysis of bis（4-nitrophenol） phosphate （BNPP） in Tris-H＋ buffer and in an organic solvent. A significant enhancement in the rate of reaction （up to 3 X 105-fold acceleration） was observed at pH 8.0 （25 ℃）. The pH depend- ence of BNPP hydrolysis at pH 5.5-9.5 and the UV spectra revealed that the copper-bounded water molecules un- derwent deprotonation to form the active catalytic species CSCu-OH. The kinetic behavior of BNPP catalytic hydrolysis in the Tris-H＋ buffer was consistent with that predicted by the Michaelis-Menten kinetics model. An in-ramolecular nucleophilic attack by the copper-bonded hydroxide group on the same activated phosphodiester substrate was proposed as the catalytic mechanism for CSCu-catalyzed reaction system. The results of DNA binding and cleavage experiments indicated electrostatic binding mode of CSCu to DNA as well as the strong capability of CSCu to disturb the supercoiled strand of DNA and cleave it to nicked circular form.

Heavy-Atom-Free Photosensitizers for High-Yield CO_(2)-to-CO Conversion

Heavy-Atom-Free photosensitizers(HAFPs)with abundant resources showgreat potential to construct noble metal-free and high-yield CO_(2)photoreduction systems,but have rarely been achieved due to their poor intersystem crossing(ISC)efficiency.Herein,a library of HAFPs(B-1-B-8)were rationally designed by coupling various anthracene donors and boron dipyrromethene acceptors to break the short-lived excited state limitation of pure organic chromophores.The special orthogonal geometry between electron donor and acceptor contributes totriggering spin-orbit charge transfer-induced ISCs to achieve long-lived triplet and reduced states,which can facilitate consecutive intermolecular electron transfers to further boost CO_(2)reduction.Impressively,the reduced HAFP B-8 can efficiently sensitize iron catalysts to construct noble metal-free photocatalytic systems for highly efficient and selective CO_(2)-to-CO conversion with 1311μmol yield.Experimental and theoretical investigations clearly illustrate the structure-activity relationship,highlighting a new avenue to develop highly efficient organic photosensitizers to boost CO_(2)photoreduction.