Molecular Structure of Co₂(<i>μ</i>-Alkyne) Complex Containing Ph₂PC₅F₆PPh₂Ligand

Oxidative-decarbonylation of Co2(CO) 6(μ-PhC≡CH) with Me3NO in the presence of an electron deficient ligand, Ph2PC5F6PPh2 (F6FOS), produces Co2 (CO) 4 (μ-PhC≡CH)(F6FOS), (1). The metrical values of 1 have been compared to those of the closely related cobalt carbonyl alkyne compound A containing (Z)-Ph2PCH=CHPPh2 (Z-dppe) ligand. Strikingly anomalous is an alkyne C≡C bond (1.34(1) ? in 1, which is somewhat elongated compared to A (1.31(1) ?). When taking a strong electron-withdrawing power of fluoride atom into account, F6FOS ligand appeared to reduce the π-back-donation ability of cobalt atom, making this bond shortened in comparison to the same bond in A. Bond lengthening in the alkyne C≡C bond in 1 is attributed to the enhanced electron donor ability of F6FOS compared to Z-dppe and can be understood by examining resonance structures of F6FOS ligand.

Catalytic nucleophilic addition of terminal alkynes to α,β-unsaturated-γ-lactams

A novel catalytic reaction has been developed for the nucleophilic addition of terminal alkynes toα,β‐unsaturated‐γ‐lactams via a cyclic N‐acyliminium ion intermediate. This simple reaction pro‐ceeds rapidly under mild conditions, and provided a practical approach for the synthesis of a wide range of 5‐alkynyl‐2‐pyrrolidinones in moderate to good yields （45%–76%）.

Visible light promoted difunctionalization reactions of alkynes

Visible light promoted difunctionalization of alkynes is reviewed. The difunctionalization reaction is achieved by different reagents. Radicals such as carbon(sp3), carbon(sp2), and other heteroatom(P, S, N, Se, O, and halide) radicals initiated by visible light can undergo radical addition to a carbon-carbon triple bond. Upon further transformation, the desired difunctionalized products are obtained. Some organometallic complexes can be activated by visible light;the difunctionalization of alkynes is catalyzed by these species. Other reagents like 1,3-dipole precursors could also react with alkynes to give difunctionalization products;here, the 1,3-dipole derivatives are obtained by visible light photocatalysis. So far, the strategy has been succeeded in the formation of C–C bonds and C–X bonds. Several valuable chemical skeletons have been constructed under mild conditions. However, high regio-and stereoselectivities in some direct difunctionalization methodologies are yet to be achieved.

Selectivity control in alkyne semihydrogenation:Recent experimental and theoretical progress

Researchers have been attempting to characterize heterogeneous catalysts in situ in addition to correlating their structures with their activity and selectivity in spite of many challenges.Here,we review recent experimental and theoretical advances regarding alkyne selective hydrogenation by Pd‐based catalysts,which are an important petrochemical reaction.The catalytic selectivity for the reaction of alkynes to alkenes is influenced by the composition and structure of the catalysts.Recent progress achieved through experimental studies and atomic simulations has provided useful insights into the origins of the selectivity.The important role of the subsurface species(H and C)was revealed by monitoring the catalyst surface and the related catalytic performance.The atomic structures of the Pd catalytic centers and their relationship with selectivity were established through atomic simulations.The combined knowledge gained from experimental and theoretical studies provides a fundamental understanding of catalytic mechanisms and reveals a path toward improved catalyst design.

Highly active binuclear Cu(Ⅱ) catalyst bearing an unsymmetrical bipyridine-pyrazole-amine ligand for the azide-alkyne cycloaddition reaction

Ligands containing NH groups often show special characteristics.In this paper,a well-defined dinuclear Cu（II） complex bearing an unsymmetrical bipyridine-pyrazole-amine ligand was synthesized by the condensation of N–H to release H2O.Using sodium L-ascorbate as a reductant,the binuclear complex showed excellent activity in 1,3-dipolar cycloaddition reactions between alkynes and azides to obtain 1,4-disubstituted triazoles in 95%–99% isolated yields.

Unveiling subsurface hydrogen inhibition for promoting electrochemical transfer semihydrogenation of alkynes with water

Highly selective electrocatalytic semihydrogenation of alkynes to alkenes with water as the hydrogen source over palladium-based electrocatalysts is significant but remains a great challenge because of the excessive hydrogenation capacity of palladium.Here,we propose that an ideal palladium catalyst should possess weak alkene adsorption and inhibit subsurface hydrogen formation to stimulate the high selectivity of alkyne semihydrogenation.Therefore,sulfur-modified Pd nanowires(Pd-S NWs)are designedly prepared by a solid-solution interface sulfuration method with KSCN as the sulfur source.The introduction of S weakens the alkene adsorption and prevents the diffusion of active hydrogen(H^(*))into the Pd lattice to form unfavorable subsurface H^(*).As a result,electrocatalytic alkyne semihydrogenation is achieved over a Pd-S NWs cathode with wide substrate scopes,potential-independent up to 99%alkene selectivity,good fragile groups compatibility,and easily synthesized deuterated alkenes.An adsorbed hydrogen addition mechanism of this semihydrogenation reaction is proposed.Importantly,an easy modification of commercial Pd/C by in situ addition of SCN–enabling the gram-scale synthesis of an alkene with 99%selectivity and 95%conversion highlights the promising potential of our method.

Cu(I)/Diamine-catalyzed Aryl-alkyne Coupling Reactions

CuI/ethylene diamine/K2CO3/dioxane is shown to be a useful system for the cross coupling reactions of various aryl iodides and bromides with aryl and alkyl alkynes. Compared to the conventional Sonogashira reactions, the new procedure is free of palladium and phosphines.

On the comparable activity in plasmonic photocatalytic and thermocatalytic oxidative homocoupling of alkynes over prereduced copper ferrite

Despite of extensive attention on the copper-based heterogeneous oxidative homocoupling of alkynes(OHA)to 1,3-diynes,the photocatalytic OHA is scarcely investigated.By screening copper-containing spinel catalysts,we discovered that a prereduced copper ferrite(CuFe2O4)not only can catalyze the thermocatalytic OHA but also is efficient for the photocatalytic OHA under visible light irradiation.It is found that the sol-gel combustion(SG)method and the partial reduction at 250 ℃ can result in the optimal CuFe2O4-SG-250 catalyst showing high activity and stability.Surface oxidized Cu2O is evidenced to be the active species for the thermocatalytic OHA,whereas metallic copper nanopaticles(CuNPs)are identified as the active sites for the photocatalytic OHA.The efficiency of photocatalytic OHA at ambient temperature is comparable to that of thermocatalytic OHA at 120 ℃,and the CuFe2O4-SG-250 catalyst can be magnetically separated and reused at least five times.The localized surface plasmon resonance effect of CuNPs contributes to visible light-induced photocatalytic OHA.

Tri(t-butyl)phosphine-assisted selective hydrosilylation of terminal alkynes

A highly efficient and regio-/stereoselective method of hydrosilylating terminal alkynes was developed using Pt(DVDS)-tri(t-butyl) phosphine catalyst system at room temperature.Trans-products or alpha-products were obtained almost exclusively depending on the alkynes and silanes employed.

Efficient visible light initiated hydrothiolations of alkenes/alkynes over Ir_(2)S_(3)/ZnIn2S4:Role of Ir_(2)S_(3)

The hydrothiolations of alkynes/alkenes with thiols is an atom-economic and thus attractive method for the constructions of C‒S bonds.Here Ir_(2)S_(3)/ZnIn_(2)S_(4)nanocomposites with varied Ir_(2)S_(3)loadings were obtained by one-pot solvothermal method from ZnCl_(2),InCl_(3)and thioacetamide with IrCl_(3).The loading of Ir_(2)S_(3)on the surface of ZnIn_(2)S_(4)promoted the hydrothiolations of alkenes and alkynes,with an optimum performance observed over 0.5 mol%Ir_(2)S_(3)/ZnIn_(2)S_(4)nanocomposite.Based on the studies on the performance of several other cocatalysts(MoS2,NiS and Pd)loaded ZnIn_(2)S_(4)and the EIS analyses,it was proposed that the superior performance over Ir_(2)S_(3)/ZnIn_(2)S_(4)nanocomposite can be ascribed to an improved efficiency on the photogeneration of the thiyl radicals by loading Ir_(2)S_(3)as well as its inactivity for photocatalytic hydrogen evolution,a side reaction in the light initiated hydrothiolation reaction over ZnIn_(2)S_(4).This study not only demonstrates an efficient and green strategy to synthesize thiolated products under visible light based on semiconductor photocatalysis,but also provides some guidances for the design and development of photocatalytic systems for light induced organic syntheses.

Higher Order Cuprate Species( Ⅱ )——Stereospecific Carbocupration of Terminal Alkynes and Its Synthetic Utility for ( ± )-Ipsenol and (E)-β-Farnesene

The stereospecific carbocupration of terminal alkynes via higher order cuprates to give 1,1'-disubstituted olefins with 99% configuration purity is described. Its synthetic utility as a general method for the preparation of substituted olefins is further illustrated by the direct synthesis of (±)-ipsenol and (E)-β-farnesene with highly geometric purity of the carbon-carbon double bond.

A Facile Stereospecific Synthesis of 1, 3-Enynylsulfides via Sonogashira Coupling of （E）-a-Iodovinyl Sulfides with 1-Alkynes

（E）-α-Iodovinyl sulfides 1 underwent the Sonogashira coupling reactions with terminal alkynes 2 in piperidine at room temperature in the presence of 5 mol % of Pd（PPh3）4 and 10 mol % of CuI to afford the corresponding 1, 3-enynylsulfides 3 stereospecifically in high yields.

A facile stereospecific synthesis of (Z)-2-sulfonyl-substituted 1,3-enynes via Sonogashira coupling of (E)-α-iodovinyl sulfones with 1-alkynes

（E）-α-Iodovinyl sulfones 1 underwent the Sonogashira coupling reactions with terminal alkynes 2 in piperidine at room temperature in the presence of 5 mol% of Pd（PPh3）4 and 10 mol% of CuI to stereospecifically afford the corresponding （Z）-2-sulfonyl-substituted 1,3-enynes 3 in high yields.

A DFT Study of Alkenes and Alkynes Reacting with H-GaN (0001) Surface

The addition reactions of alkenes and alkynes to the H-terminated GaN （0001） surface with a Ga dangling-bond have been studied employing periodic density functional theory （PDFT） calculations. Detailed information on the reaction pathways of these alkenes and alkynes with H-GaN （0001） surface is provided, which indicates that the reactions contain two steps separated by the metastable intermediates： elementary addition reaction and H-abstraction process. From the energy curves, the reactions are clearly viable in the cases of ethene, styrene and phenylacetylene; while for ethyne, the H-abstraction barrier is higher than the desorption barrier of the intermediate, so the adsorbed C2H2 in intermediate is more likely to be desorbed back into the gas phase than to form a stable adsorbed species. Furthermore, it is obvious that for either alkenes or alkynes, the systems substituted by phenyl have more stable intermediates because π conjugation could improve their stabilities.

Organic Polyvalent Iodinc Reagents-Promoted Coupling Reaction of 1-Alkynes

Teminal alkynes couple smoothly in the presence of PhI(OAc)2 or PhI(OH)OTs.catalytie Cul and base. affording conjugated diynes.

Poly{[4-(hydroxyl)(tosyloxyl)iodo]styrene} Promoted Halotosyloxylation Reaction of Alkynes

Halotosyloxylation reaction of alkynes with iodine or NBS or NCS was efficiently promoted by the poly{[4-(hydroxyl)(tosoyloxyl)iodo]styrene}.

Synthesis and Crystal Structure of μ_4-alkyne Cluster Complex (μ_4-η^(2)-C_2Ph_2) Co_4 (CO)_8 (μ-CO)_2

The cluster complex (μ4-η2-C2Ph2) Co4 (CO)8 (μ-CO)2 was synthesized by 'one pot' method starting from Co2(CO)8 and PhCCPh in toluene and characterized by single-crystal structure analysis. It crystallizes in the monoclinic space group P21/c with a=9. 149(3). b=11. 732(2), c=23.551 (6) A, β=92. 62(2)°, V=2525 (1), Z=4, Dc= 1. 83 g/cm3,Mr = 694. 07.μ=26.33cm-1,F(000)=1368. The final R= 0. 039, Rω= 0. 047 for 2812 observed independent reflections(I≥3σ(I)). In the molecule, four cobalt atoms form a butterflyshaped metal skeleton and the ligand C2Ph2 is coordinated to cobalt atoms through two σ bonds and a delocalized four- center π-bonding system.

(Z)-ETHYL 3-BROMO-4,4,4-TRIFLUORO-2-BUTENOATE AS A NOVEL CF_3-CONTAINING BUILDING BLOCK: Its Preparation and Pd-Catalysed Reaction with Alkynes and Organozinc Reagents

A novel CF_3-containing building block, (Z)-ethyl 3-bromo-4,4,4-trifluoro-2-butenoate, was easily prepared from CF_3CBr_3, the former reacted with alkynes Or organozinc reagents in the presence of Pd complexes to afford useful CF_3-containing intermediates in good yield.

STUDY ON Cp_2TiCl_2/Fe-INITIATED ADDITION OF 2-HALOTETRAFLUOROETHYL IODIDES TO ALKYNES AND ALKENES

Initiated by CP_2TiCl_2/Fe redox system,2-halotetrafluoroethyl iodides readily reacted with alkynes or alkenes to give 1:1 adducts in good to excellent yields.

BrCo (dmgh)_2Py/Zn Promoted Addition of BrCF_2CF_2CH=CHCH_2X to Alkynes: Direct Synthesis of 4,4,5,5-Tetrafluorocyclopentene Derivatives

BrCF2CF2CH=CHCH2X(x=Cl, OAc, OH) reacted smoothly with alkynes in the presence of BrCo(dmgh)2Py/Zn, giving 4,4,5,5-tetrafluorocyclopentene derivatives in moderate yields.