Selective photosynthesis of Z-olefins through crystalline metal-organic cage-initiated expeditious cascade reactions

The semi-hydrogenation of alkyne to form Z-olefins with high conversion and high selectivity is still a huge challenge in the chemical industry.Moreover,flammable and explosive hydrogen as the common hydrogen source of this reaction increases the cost and danger of industrial production.Herein,we connect the photocatalytic hydrogen evolution reaction and the semihydrogenation reaction of alkynes in series and successfully realize the high selective production of Z-alkenes using low-cost,safe,and green water as the proton source.Before the cascade reaction,a series of isomorphic metal–organic cage catalysts(Co_(x)Zn_(8−x)L_(6),x=0,3,4,5,and 8)are designed and synthesized to improve the yield of the photocatalytic hydrogen production.Among them,Co_(5)Zn_(3)L_(6) shows the highest photocatalytic activity,with a H_(2) generation rate of 8.81 mmol g^(−1) h^(−1).Then,Co_(5)Zn_(3)L_(6) is further applied in the above tandem reaction to efficiently reduce alkynes to Z-alkenes under ambient conditions,which can reach high conversion of>98%and high selectivity of>99%,and maintain original catalytic activity after multiple cycles.This“one-pot”tandem reaction can achieve a highly selective and safe stepwise conversion from water into hydrogen into Z-olefins under mild reaction conditions.

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.

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 (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.

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.

Synthesis and Crystal Structure of μ4—alkyne Cluster Complex（μ4—η^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.

Palladium-Catalyzed Sonogashira Coupling Reaction of 2-Amino-3-Bromopyridines with Terminal Alkynes

Palladium-catalyzed the Sonogashira coupling reaction of 3-halogen-2-aminopyridines 1 with terminal alkynes 2 afforded the corresponding 21 target products 3a-3u in the presence of palladium catalyst. The structure of target products 3a-3u was confirmed and characterized by 1H NMR, 13C NMR, and HRMS. The influences of different kinds of catalyst loading, bases, substrates and temperature were also investigated. Under the optimized conditions, including 2.5 mol% Pd?(CF3COO)2, 5 mol% PPh3 and 5 mol% CuI as additive, 1 mL Et3N, substrate 1 with terminal alkynes 2 for the cross-coupling reactions at 100°C for 3 h in DMF afforded the corresponding products of 2-amino-3-alkynylpyridines 3 in moderate to excellent yields (72%?-?96%). The present methodology has provided an effective synthetic method including operational convenience, high efficiency and wide-application.

Reactivity of Fe3(CO)(12) with Alkynes R-C≡C-R＇： Syntheses and Crystal Structures of Substituted Cyclic Ketones and Carbonyl Iron Complexes

The reactivity of carbonyl iron cluster with alkynes has been studied by the thermal reaction of Fe_3（CO）_（12） with R-C≡C-R＇（R = Fc（Ferrocenyl）; R′ = Ph（Phenyl）, Fc, H）. The hexacarbonyldiiron cluster with ferracyclopentadiene ring（μ_2, η~4-C_4Ph_4）Fe_2（CO）_6（1） and one tetraphenyl substituted cyclopentadienone（Ph_4C_4CO）（2） were simultaneously obtained by the reaction of Fe_3（CO）_（12） with alkyne（Ph-C≡C-Ph）. Only one ferrole cluster（μ_2, η~4-C_4Fc_2H_2）Fe_2（CO）_6（3） was separated by using Fc-C≡C-H as alkyne. One tri-carbonyl iron complex（η~4-C_4Fc_4CO）Fe（CO）_3（4） and an unexpected new cyclic ketone compound 2,2,4,5-tetraferrocenylcyclopenta-4-en-1,3-di-one [Fc_4C_3（CO）_2]（5） were obtained by using Fc-C≡C-Fc as alkyne. A new complex（η4-2,4-diphenyl-3,5-diferrocenylcyclopenta-2,4-dien-1-one）-tricarbonyl iron（η~4-C_4Ph_2Fc_2CO）Fe（CO）_3（6） was synthesized by the reaction of Fe_3（CO）_（12） with Fc-C≡C-Ph. The structures of compounds 1~6 were determined by X-ray single-crystal diffraction and spectroscopic characterization. The crystal structures of two new compounds 5 and 6 were analyzed. Our experimental results reveal the structural models of the reaction products are affected by the kinds of substituents from alkynes R-C≡C-R′.

Rhodium Catalyzed [2π + 2π + 2π]-Cycloaddition of Alkynyl-Ynamides and Carbon Disulfide to Indolo-Thiopyrane Thiones

The synthesis of new indoloannulated thiopyranethiones is reported. The key-step is a rhodium-catalyzed [2 + 2 + 2]-cycloaddition of alkynyl-ynamides with carbon disulfide to close the pyrrole and the thiopyranethione rings simultaneously. A violet idolothiopyrane thione or a mixture of the violet and a red isomer result from [RhCl(C8H14)2]2/3BINAP catalyzed cycloadditions, the regiochemistry is controlled by the substitution pattern on the alkynyl-ynamide.

Enhancing alkyne semi-hydrogenation through engineering metal-support interactions of Pd on oxides

Supported Pd catalysts show superior activities for olefin productions from alkynes through semi-hydrogenation reactions,but over-hydrogenation into alkanes highly decreases olefin selectivity.Using phenylacetylene semi-hydrogenation as a model reaction,here we explore the optimization approaches toward better Pd catalysts for alkyne semi-hydrogenation through investigating support effect and metal-support interactions.The results show that the states of Pd with supports can be tuned by varying oxide reducibility,loading ratios,and post-treatments.In our system,0.06 wt.%Pd on rutile-TiO_(2) nanorods shows the highest activity owing to the synergistic effects of single-atoms and clusters.Support reducibility can change the filling degrees of Pd 4d orbitals through varying interfacial bonding strengths,which further affect catalytic activity and selectivity.

Ni-Catalyzed Enantioselective Difunctionalization of Alkynes to Azepine Derivatives Bearing a Quaternary Center and an Unprotected Imine

Comprehensive Summary,The azepine ring is a prominent structural scaffold in biologically significant molecules. In this study, we present a Ni(II)-catalyzed asymmetric difunctionalization of alkynes, involving intermolecular regioselective arylation and intramolecular nitrile addition, enabling the synthesis of enantioenriched azepine derivatives. This reaction simultaneously installs an all-carbon quaternary stereocenter and introduces an unprotected imine functionality, showing great promise for subsequent transformations. The reaction exhibits good tolerance toward various functional groups, resulting in high yields and enantioselectivities. The synthetic utility of this methodology is further demonstrated through gram-scale synthesis and product derivatization. This research offers an efficient approach to the synthesis of seven-membered nitrogen heterocycles.

Recent Advances in Cobalt-Catalyzed Regio-or Stereoselective Hydrofunctionalization of Alkenes and Alkynes

Hydrofunctionalization of alkenes and alkynes is increasingly important in preparing and modifying carbon-centered organic molecules such as pharmaceuticals,agrochemicals,andmaterial precursors.The development of transition-metal-catalysts has revolutionized the hydrofunctionalization of unsaturated hydrocarbons,greatly improving the synthetic efficiency and selectivity of these reactions.In recent years,notable progress has been achieved in low-cost metal-catalyzed alkene and alkyne hydrofunctionalization reactions following the utilization of traditional precious metal catalysts,including palladium,platinum,and rhodium.Earth-abundant cobalt catalysts,which are low in toxicity and exhibit unique reactivity and selectivity,are widely implemented in academic and industrial research.In this review,we highlight recent examples of cobalt-catalyzed hydrofunctionalization of alkenes and alkynes to provide an overview of hydrofunctionalization methods,particularly hydroalkylation reactions.Hydroalkylation reactions greatly expand the scope and utility of cobalt-catalyzed couplings of carbon—carbon bonds.We also highlight the mechanistic considerations and selective determinants involved.We hope our discussion will be informative for future developments in cobalt catalysis and hydrofunctionalization reactions.