Palladium-catalyzed arylation of enynes and electron-deficient alkynes using diaryliodonium salts

A new single-pot procedure for the synthesis of aryl alkynes is described. Palladium catalyzes the coupling reaction of diaryliodonium compounds with enynes and electron-deficient alkynes to give aryl alkynes in good yields.     

The application of polymer-bound carbonylcobalt(0) species in linker chemistry and catalysis

Carbonylcobalt(0) species have been used as linkers between alkynes and a polymer support for the first time. The alkynes may be loaded indirectly onto a phosphine functionalised polymer via their hexacarbonyldicobalt(0) complex, or directly onto a cobalt coated polymer. The alkynes have been released either as alkynes, thus providing a traceless method of immobilising alkynes, or by reaction with an alkene to generate a cyclopentenone via the Pauson-Khand reaction. The cobalt coated polymers produced during this study were shown to catalyse the Pauson-Khand reaction.     

Anti-Markovnikov stereoselective hydroamination and hydrothiolation of (hetero)aromatic alkynes using a metal-free cyclic trimeric phosphazene base

Hydroamination and hydrothiolation are the most efficient and completely atom-economical process to construct important enamine and vinyl sulfide intermediates in pharmaceutical and organic chemistry. The cyclic trimeric phosphazene base (CTPB) showed great catalytic activity for the anti-Markovnikov stereoselective hydroamination and hydrothiolation of alkynes in good to excellent yields. A broad substrate scope of alkynes and nucleophiles was demonstrated, including aryl and heteroaryl alkynes, terminal and internal alkynes, different N-heterocycles, thiols and thiophenols. This versatile and cost-efficient approach with good stereoselectivity and excellent functional group tolerance provided new opportunity for the organocatalyzed hydrofunctionalization of alkynes.     

Bulky,spherical, and fluorinated anion BAr induces ‘on-water’ activity of silver salt for the hydration of terminal alkynes

AgBAr^F displays remarkable ‘on-water’ activity for catalytic hydration of terminal alkynes although it is ineffective in common organic solvents. Liquid alkynes do not require additive or co-solvent whereas a small amount of ethyl acetate triggers quantitative conversions for solid alkynes.     

Conformational analysis—CIX : Applications of molecular mechanics to the structures and energies of alkynes

An earlier described force-field has been extended to include alkynes. The structures and heats of formation of simple alkynes were calculated to approximately within experimental error for those for which data are available, and predictions are made for others. Rotational barriers and conformational equilibria were also adequately dealt with. Some macrocyclic alkynes were also examined.     

Highly selective hydrogenation of multiple carbon-carbon bonds promoted by nickel(0) nanoparticles

A new method for the highly stereoselective cis semihydrogenation of internal alkynes, semihydrogenation of terminal alkynes, reduction of dienes to alkenes, and reduction of alkynes and alkenes to alkanes is described based on in situ generated both Ni(0) nanoparticles and molecular hydrogen.     

On-surface construction of low-dimensional nanostructures with terminal alkynes: Linking strategies and controlling methodologies

Bottom-up approach to constructing low-dimensional nanostructures on surfaces with terminal alkynes has drawn great interest because of its potential applications in fabricating advanced functional nanomaterials. The diversity of the achieved products manifests rich chemistry of terminal alkynes and hence careful linking strategies and proper controlling methodologies are required for selective preparations of high-quality target nanoarchitectures. This review summarizes various on-surface linking strategies for terminal alkynes, including non-bonding interactions as well as organometallic and covalent bonds, and presents examples to show effective control of surface assemblies and reactions of terminal alkynes by variations of the precursor structures, substrates and activation modes. Systematic studies of the on-surface linkage of terminal alkynes may help efficient and predictable preparations of surface nanomaterials and further understanding of surface chemistry.     

Zirconium-promoted epoxide rearrangement-alkynylation sequence

Additions of terminal alkynes to electrophiles are important transformations in organic chemistry. Generally, activated terminal alkynes react with epoxides in an S(N)2 fashion to form homopropargylic alcohols. We have developed a new synthetic method to form propargylic alcohols from epoxides and terminal alkynes via 1,2-shifts. This method involves cationic zirconium acetylides as both the activator of epoxides and nucleophiles. Due to the mild conditions to pre-activate alkynes with silver nitrate, this synthetic method is useful for both electron-rich and electron-deficient alkynes with other acid- and base-sensitive functional groups.     

Visible light promoted copper-catalyzed Markovnikov hydration of alkynes at room temperature

A new and efficient method for the hydration of alkynes to the corresponding ketones was successfully developed. The hydration process proceeds smoothly at room temperature with 1% mol of CuCl as catalyst under visible light irradiation. This protocol is applicable to various alkynes, including aromatic alkynes, polycyclic aromatic and heterocyclic aromatic excellent regioselectivity in good to excellent yields.     

Palladium-catalyzed one-pot construction of difluorinated 1,3-enynes from α,α,α-iododifluoroacetones and alkynes

A palladium-catalyzed one-pot difunctionalization of alkynes with α,α,α-iododifluoroacetones is introduced for the synthesis of difluorinated 1,3-enynes. The reaction proceeds through the radical addition of RCOCF₂ radical to alkynes and subsequent Sonogashira coupling with the same alkynes to give the 1,3-enyne products with high regio and stereoselectivity.     

Hyperbaric laser chemical vapor deposition of carbon fibers from the 1-alkenes, 1-alkynes, and benzene

The growth of long carbon fibers was investigated using hyperbaric-pressure laser chemical vapor deposition (HP-LCVD). Precursors included the unbranched alkenes with linear structure 1-C(x)H(2x) (where x = 2,4,5,6,7,8), the unbranched alkynes, i.e., 1-C(x)H(2)(x-2) (where x = 3,4,5,6,8), and benzene. Rate constants, reaction orders, and apparent activation energies were derived for each precursor over a range of experimental conditions. Axial growth rates from the alkenes were 1-2 orders of magnitude greater than for the alkynes, while growth rates for benzene exceeded 10 mm s(-1). Generalized expressions for the growth rate vs molecular weight were determined. For the alkenes, the growth rate was directly proportional to the square root of the precursor molecular weight, while the alkynes exhibited an inverse relationship. Two regions of differing reaction order were identified for the alkynes; at pressures less than 2.0-2.5 bar, the average reaction order was 3.07, while above 2.0-2.5 bar, reaction orders diverged. Expressions were derived for the fraction of carbon atoms deposited per alkyne molecule transported; the deposition efficiency decreased with molecular weight for the alkynes, due in part to the Soret effect. In contrast, the reaction order for the alkenes was 1.65, and for benzene was 2.25. A phase change in the deposit was observed for both the alkenes and alkynes, with the exceptions of pentene and pentyne. Complete axial rate equations for the alkenes and alkynes were derived, as well as volumetric growth equations for the alkynes. It was shown that the volumetric rate increases nonlinearly with laser power at sufficiently high pressures.     

Copper‐Catalyzed Aerobic Oxidative Transformation of Ketone‐Derived N‐Tosyl Hydrazones: An Entry to Alkynes

A novel strategy involving Cu‐catalyzed oxidative transformation of ketone‐derived hydrazone moiety to various synthetic valuable internal alkynes and diynes has been developed. This method features inexpensive metal catalyst, green oxidant, good functional group tolerance, high regioselectivity and readily available starting materials. Oxidative deprotonation reactions were carried out to form internal alkynes and symmetrical diynes. Cross‐coupling reactions of hydrazones with halides and terminal alkynes were performed to afford functionalized alkynes and unsymmetrical conjugated diynes. A mechanism proceeding through a Cu‐carbene intermediate is proposed for the C? C triple bond formation.     

Enantioselective synthesis of indolizidines bearing quaternary substituted stereocenters via rhodium-catalyzed [2+2+2] cycloaddition of alkenyl isocyanates and terminal alkynes

An enantioselective synthesis of indolizidines bearing quaternary substituted stereocenters by way of a rhodium-catalyzed [2+2+2] cycloaddition of substituted alkenyl isocyanates and terminal alkynes is described. The reaction provides lactam products using aliphatic alkynes, whereas aryl alkynes give rise to vinylogous amide products. Through modification of the phosphoramidite ligand, high levels of enantioselectivity, regioselectivity, and product selectivity are obtained for both products.     

Palladium-catalyzed cross-coupling reaction of aryl trimethoxysilanes with terminal alkynes

A palladium-catalyzed cross-coupling reaction of aryl trimethoxysilanes with terminal alkynes was described. Thus, di-substituted alkynes were prepared in moderate to good yields. The electron-deficient terminal alkynes also worked well in the procedure.     

Silicon-tethered cyclocarbonylation of alkynes

[reaction: see text] Temporary union of alkynes in the Fe(CO)5-promoted cyclocarbonylation provides a method for carbonylative cross-coupling of alkynes to construct unsymmetrically substituted cyclopentadienones.     

Zr-Mediated hydroboration: stereoselective synthesis of vinyl boronic esters

An improved process for the preparation of (E)-vinylboronic esters via a Zr-mediated hydroboration of alkynes, especially oxygen-containing alkynes, is described.     

Chromium-mediated synthesis of polycyclic aromatic compounds from halobiaryls

[reaction: see text] Reaction of 2,2'-dihalobiphenyl with butyllithium followed by the addition of chromium(III) chloride and alkynes afforded the corresponding phenanthrene derivatives via formal [4 + 2] cycloaddition. A variety of alkynes could be used for this reaction, such as alkyl, aryl, silyl, and alkoxycarbonyl alkynes. Repetitive process of the reaction gave more extended polycyclic compounds such as benzo[g]chrysene and azacyclopentaphenalene derivatives.     

Indium triflate-catalysed double addition of heterocyclic arenes to alkynes

Indium triflate was found to be a prominent catalyst for addition of heterocyclic arenes to alkynes to afford 2:1 adducts, where two heterocyclic arenes regioselectively attacked the same carbon atom of alkynes.     

Sequential catalytic process: synthesis of quinoline derivatives by AuCl3/CuBr-catalyzed three-component reaction of aldehydes, amines, and alkynes

A sequential catalytic process has been developed based on gold-catalyzed nucleophilic addition of terminal alkynes to imines, and gold-catalyzed intramolecular reaction of aromatic ring to alkynes. This one-pot reaction of aldehydes, amines, and alkynes gives quinoline derivatives in good yields.     

Au(Ⅰ)配合物催化剂室温高效催化炔烃水合反应

合成了一系列(1,1'-联苯)-2-二(1-金刚烷基)磷配体, 并制备出8种相应的Au(Ⅰ)配合物. 以甲醇为溶剂, 在6-十二炔水合反应中考察了8种Au(Ⅰ)配合物的催化性能, 结果表明, 以含有3'-(吡咯-1-羰基)官能团的Au(Ⅰ)配合物为催化剂时, 其用量仅需炔烃用量的0.1%~0.3%(摩尔分数), 室温下即可高效地催化炔烃进行水合反应.