Monosubstituted Acetylenes Research Articles

高分子末端の構造を自由に設計できる一置換アセチレン類の精密重合法の開発

Substituted polyacetylene derivatives are promising π-conjugated materials, which can be synthesized by polymerization of the corresponding substituted acetylenes by transition metal catalysis. Rhodium(I) complexes have been widely used for the polymerization of monosubstituted acetylenes such as phenylacetylene derivatives because they are functional group tolerant and provide cis-stereoregular polymers. There are some examples of well-controlled polymerization of phenylacetylene derivatives using well-defined rhodium(I) complexes as initiators. However, versatile design of polymer end structures is difficult in such known methods because initiators having various functional groups are not easily available. To overcome such a problem, we have developed a new method for well-controlled polymerization of phenylacetylene derivatives using a multicomponent catalytic system composed of bicyclo[2.2.1]hepta-2,5-diene-rhodium(I) chloride dimer [Rh(nbd)Cl]2, arylboronic acids, diphenylacetylene and 50% aqueous solution of KOH. This polymerization method showed a typical living nature, and structures derived from aryl boronic acids and diphenylacetylene were introduced to the initiating end of the obtained polymers. Moreover, functionalization of the polymer terminal end could be achieved by reactions of the living polymer terminus with α,β-unsaturated carbonyl compounds such as acrylates, and various telechelic poly(phenylacetylene)s were obtained. Novel 1,3,5-hexatrienylrhodium(I) complexes were isolated from the present multicomponent catalytic system, and their structures were identified. When [Rh(nbd)Cl]2 was replaced with hydroxy(1,5-cyclooctadiene) rhodium(I) dimer ([Rh(cod)OH]2) in the present catalytic system, cyclobutenylrhodium(I) complexes were exclusively obtained. These complexes provided insights into the initiation mechanism in the living polymerization. The present catalytic system was applied to the living polymerization of water-soluble phenylacetylene derivatives and non-conjugated monosubstituted acetylenes such as N-propargylamides.

Straightforward and Efficient Deuteration of Terminal Alkynes with Copper Catalysis

The mild and effective preparation of deuterated organic molecules is an active area of research due to their important applications. Herein, we report an air-stable and easy to access copper(I) complex as catalyst for the deuteration of mono-substituted alkynes. Reactions were carried out in technical solvents and in the presence of air, to obtain excellent deuterium incorporation in a range of functionalised alkynes.

Synthesis of Pentaarylcyclobutenylrhodium(I) Complexes and Their Reactivity and Initiation Mechanism in Polymerization of Monosubstituted Acetylenes

Synthesis of Pentaarylcyclobutenylrhodium(I) Complexes and Their Reactivity and Initiation Mechanism in Polymerization of Monosubstituted Acetylenes

Platinum-catalyzed reactions of 2,3-bis(dimethylsilyl)pyridine with mono- and di-substituted alkynes

The synthesis and platinum-catalyzed reactions of 2,3-bis(dimethylsilyl)pyridine (1) are described. The reaction of 1 with diphenylacetylene in the presence of a platinum catalyst gave the corresponding six-membered ring compound arising from dehydrogenative double silylation of the alkyne. Similar reactions of 1 with mono-substituted acetylenes such as tert-butylacetylene, 1-hexyne, and phenylacetylene proceeded to give regioisomers of cyclic products.

Zwitterionic π-coordination compounds of copper(I) with monosubstituted alkynes: synthesis, crystal and electronic structure of two copper(I) halide π-complexes with 4-amino-1-propargylpyridinium

Crystals of two mononuclear π-coordination compounds of copper(I) halide with 4-amino-1-propargylpyridinium cation – [(HC≡CCH2NC5H4NH2)CuBr2] (1) and [(HC≡CCH2NC5H4NH2)CuCl1.61 Br0.39] (2) – were obtained in the CuX–H2O–(HC≡CCH2NC5H4 NH2)Br system (HC≡CCH2N+C5H4NH2 is 4-amino-1-propargylpyridinium cation (app +), X=Cl or Br). The purity and identity of the synthesized compounds were verified by elemental analysis and IR spectroscopy. The compounds were structurally characterized using X-ray single crystal method and are isostructural. Both crystals are built of zwitterionic appCuX 2 units, in which triple C≡C bond is coordinated to only one copper(I) ion. The Cu–m distance (m is the middle of the C≡C bond) is 1.933(5) and 1.917(3) Å for 1 and 2, respectively. The predisposition of copper(I) halides to coordination polymer self-assembly through Cu–X···Cu bridge formation is not realized in 1 and 2. However, the ≡C–H···Х and N–H···Х hydrogen bonds along with π–π stacking of 4-aminopyridinium groups compensate an absence of the structure-forming interaction Cu–X···Cu. DFT calculations of an electron structure of [(app)CuCl2] were carried out (the restricted Hartree–Fock (RHF) method with a 6–31 G* orbital basis set). Calculated values of the charge density distribution on atoms as well as the constructed molecular orbitals (MOs) are in agreement with stereochemical parameters of the (Cu(I)–(C≡C))-core of both coordination compounds.

Green synthesis of silver nanoparticles using Citrus limon peels and evaluation of their antibacterial and cytotoxic properties.

The present work aimed to synthesis silver nanoparticles (AgNPs) using biological waste products Citrus limon peels, its characterization, antimicrobial activities and the cytotoxic effect of the synthesized green AgNPs. Characterization of the prepared AgNPs showed the formation of spherical, and few agglomerated AgNPs forms as measured by UV–visible spectrophotometer. The average size of the prepared AgNPs was 59.74 nm as measured by DLS technique. The spectrum of the synthesized AgNPs was observed at 3 KeV using the EDX. On the other hand, FTIR analysis of the green synthesized AgNPs showed the presence of alcohols, phenolics, mono-substituted alkynes, aliphatic primary amines, sodium salt, amino acid, or SiOH alcohol groups. The antimicrobial studies of the formed AgNPs showed positive activity against most of the studied human pathogenic bacteria with varying degrees. Finally, the evaluation of the cytotoxic effect of the green synthesized AgNPs were done using two types of cell lines, human breast cancer cell line (MCF-7) and human colon carcinoma cell line (HCT-116). The results revealed the concentration has a direct correlation with cell viability. The 50% inhibitory concentration (IC50) of MCF-7 cell line was in of 23.5 ± 0.97 µL/100 µL, whereas the HCT-116 cell line was in 37.48 ± 5.93 µL/100 µL.

Conductive Metal-Organic Framework Thin Film Hybrids by Electropolymerization of Monosubstituted Acetylenes.

1-Hexyne monomers were potentiostatically electropolymerized upon confinement in 1D channels of a surface-mounted metal-organic framework Cu(BDC) (SURMOF-2). A layer-by-layer deposition method allowed for SURMOF depostition on substrates with prepatterned electrodes, making it possible to characterize electrical conductivity in situ, i.e., without having to delaminate the conductive polymer thin film. Successful polymerization was evidenced by mass spectroscopy, and the electrical measurements demonstrated an increase of the electrical conductivity of the MOF material by 8 orders of magnitude. Extensive DFT calculations revealed that the final conductivity is limited by electron hopping between the conductive oligomers.

Photochemically Driven Tandem Process in the Construction of a Biscyclopropylcage from 2,5-Dimethoxy-p-benzoquinone and Terminal Acetylenes.

A photochemical two-step one-pot synthesis of novel biscyclopropyl-box-shaped compounds via the reaction of 2,5-dimethoxy-para-benzoquinone and monosubstituted alkynes is reported. The reaction mechanism for a process in which six new C-C bonds are formed is explored by means of experimental and computational techniques. The whole process occurs with complete selectivity, and only one densely decorated diastereomer is obtained; such a degree of control and substitution makes for a rather powerful and complexity-building process.

Copper-catalyzed enantioselective arylalkynylation of alkenes.

A copper-catalyzed enantioselective arylalkynylation of alkenes with diaryliodonium salt and a monosubstituted alkyne is reported. The three-component coupling reactions proceed under mild reaction conditions with a broad substrate scope, leading to synthetically valuable 1,2-diaryl-3-butynes. The key to the success of this chemistry is the employment of the chiral bisoxazoline-phenylaniline (BOPA) ligand. A novel reaction pathway involving the phenyl radical generation under thermal copper catalysis is proposed according to mechanistic studies.

Copper-Hydride-Catalyzed Enantioselective Processes with Allenyl Boronates. Mechanistic Nuances, Scope, and Utility in Target-Oriented Synthesis.

Synthesis of complex bioactive molecules is substantially facilitated by transformations that efficiently and stereoselectively generate polyfunctional compounds. Designing such processes is hardly straightforward, however, especially when the desired route runs counter to the inherently favored reactivity profiles. Furthermore, in addition to being efficient and stereoselective, it is crucial that the products generated can be easily and stereodivergently modified. Here, we introduce a catalytic process that delivers versatile and otherwise difficult-to-access organoboron entities by combining an allenylboronate, a hydride, and an allylic phosphate. Two unique selectivity problems had to be solved: avoiding rapid side reaction of a Cu-H complex with an allylic phosphate, while promoting its addition to an allenylboronate as opposed to the commonly utilized boron-copper exchange. The utility of the approach is demonstrated by applications to concise preparation of the linear fragment of pumiliotoxin B (myotonic, cardiotonic) and enantioselective synthesis and structure confirmation of netamine C, a member of a family of anti-tumor and anti-malarial natural products. Completion of the latter routes required the following noteworthy developments: (1) a two-step all-catalytic sequence for conversion of a terminal alkene to a monosubstituted alkyne; (2) a catalytic SN2'- and enantioselective allylic substitution method involving a mild alkylzinc halide reagent; and (3) a diastereoselective [3+2]-cycloaddition to assemble the polycyclic structure of a guanidyl polycyclic natural product.

Platinum-catalyzed reactions of 2,3-bis(dimethylsilyl)furan with alkynes

The synthesis and platinum-catalyzed reactions of 2,3-bis(dimethylsilyl)furan (1) have been reported. The reactions of 1 with diphenylacetylene and phenyl(trimethylsilyl)acetylene in the presence of a platinum catalyst gave the corresponding six-membered ring compounds produced from dehydrogenative double silylation of alkynes. The similar reactions of 1 with mono-substituted acetylenes such as phenylacetylene and trimethylsilylacetylene proceeded to give the regioisomers of cyclic products. DFT calculations for the reaction mechanism of the platinum-catalyzed reaction of 1 with phenyl(trimethylsilyl)acetylene are also reported.

Catalytic Dinuclear Nickel Spin Crossover Mechanism and Selectivity for Alkyne Cyclotrimerization

Homodinuclear transition-metal catalysts with a direct metal–metal bond have the potential to induce novel reaction mechanisms and selectivity compared with mononuclear catalysts. The dinuclear (i-PrNDI)Ni2(C6H6) (NDI = naphthyridine-diimine) complex catalyzes selective cyclotrimerization of monosubstituted alkynes, whereas mononuclear Ni catalysts generally give cyclotetramerization of alkynes. Density functional theory calculations reveal that the homodinuclear Ni–Ni catalyst induces a spin crossover mechanism that involves metallacyclopentadiene and nonclassical bridging metallacycloheptatriene intermediates. The cis configuration of the nonclassical bridging metallacycloheptatriene Ni–vinyl bonds results in alkyne cyclotrimerization by fast reductive elimination. This dinuclear mechanism differs from previously reported mononuclear Ni mechanisms and provides an explanation for cyclotrimerization versus cyclotetramerization selectivity and arene regioselectivity.

Alkyne Addition and Insertion Reactions of [(Me3 Si)3 Si]2 Ge⋅PMe3.

Silylated germylene-PMe3 adducts exchange their phosphane moiety smoothly for an N-heterocyclic carbene or isocyanide species to form their respective base adducts. Reaction of the silylated germylene-PMe3 adducts with monosubstituted alkynes produce germylene adducts with the alkyne inserted into a Ge-Si bond. A computational study of this process provides evidence for the initial formation of a germirene, which rearranges to a vinylgermylene species. The thermodynamic driving force for this reaction is provided by subsequent adduct formation with PMe3 . Reaction of the PMe3 adduct of bis[(trimethylsilyl)silyl]germylene with disubstituted alkynes leads to the formation of stable germirenes, which can be isomerized further to silagermetes.

Silver(I) oxide nanoparticles as a catalyst in the azide–alkyne cycloaddition

1,3-Dipolar cycloadditions between a number of azides and monosubstituted acetylenes have been carried out in the presence of catalytic amounts of silver(I) oxide nanoparticles. 4-Substituted 1,2,3-triazoles were usually the only products, while the presence of electron-withdrawing groups onto the azide moiety caused a loss of regioselectivity giving mixtures of 4- and 5-substituted 1,2,3-triazoles. A novel catalytic cycle has been proposed to rationalize this latter ‘non-click’ behaviour.

Silylated Group 14 Ylenes: An Emerging Class of Reactive Compounds

AbstractSilyl‐substituted heavy‐element tetrylenes are very reactive entities and therefore prefer variously to dimerize to heavy olefin analogues, to oligomerize to cyclic products, or to undergo some type of rearrangement reaction. Our work on the synthesis of oligosilanyl‐substituted plumbylenes, stannylenes, and germylenes has shown that trapping such tetrylenes as phosphine adducts is a good method for preventing dimerization or rearrangement and allows the chemistry of the free tetrylene to be studied either through phosphane abstraction or even through thermally induced dissociation. In addition to a number of typical reactions with these tetrylenes, which occur in such a way that the divalent element becomes tetravalent, it was found in the case of germylenes that addition of monosubstituted alkynes proceeds by insertion into a Ge–Si bond with preservation of the divalent state of the germylene. The obtained tetrylene phosphane adducts could also be used as precursors for the generation of transition‐metal complexes with tetrylene ligands.

Dimerization of two alkyne units: model studies, intermediate trapping experiments, and kinetic studies.

By means of high level quantum chemical calculations (B2PLYPD and CCSD(T)), the dimerization of alkynes substituted with different groups such as F, Cl, OH, SH, NH2, and CN to the corresponding diradicals and dicarbenes was investigated. We found that in case of monosubstituted alkynes the formation of a bond at the nonsubstituted carbon centers is favored in general. Furthermore, substituents attached to the reacting centers reduce the activation energies and the reaction energies with increasing electronegativity of the substituent (F > OH > NH2, Cl > SH, H, CN). This effect was explained by a stabilizing hyperconjugative interaction between the σ* orbitals of the carbon-substituent bond and the occupied antibonding linear combination of the radical centers. The formation of dicarbenes is only found if strong π donors like NH2 and OH as substituents are attached to the carbene centers. The extension of the model calculations to substituted phenylacetylenes (Ph-C≡C-Y) predicts a similar reactivity of the phenylacetylenes: F > OCH3 > Cl > H. Trapping experiments of the proposed cyclobutadiene intermediates using maleic anhydride as dienophile as well as kinetic studies confirm the calculations. In the case of phenylmethoxyacetylene (Ph-C≡C-OCH3) the good yield of the corresponding cycloaddition product makes this cyclization reaction attractive for a synthetic route to cyclohexadiene derivatives from alkynes.

Synthesis, helical conformation, and infrared emissivity property study of optically active substituted polyacetylenes derived from serine

ABSTRACTSerine‐based monosubstituted acetylene monomers were synthesized and polymerized with rhodium zwitterion catalyst in THF to afford optically active polyacetylene derivatives (LPA and DPA) and corresponding racemic polyacetylenes (RPA) with moderate molecular weights in good yields. All of the substituted polyacetylenes (SPA) were characterized by FT‐IR, NMR, GPC, UV‐Vis spectroscopy, circular dichroism (CD) spectroscopy, and TGA. LPA and DPA were soluble in common organic solvents and possessed single‐handed helical conformation according to their intense Cotton effect and large specific rotations, while RPA presented random coiled polymer chain. The characterization results showed that helical structure of these SPAs was stabilized by intra‐ and intermolecular hydrogen bonding between the substituents which played a significant role in creating and maintaining the helix. Further, the infrared emissivity properties of them at wavelength of 8 to 14 μm were investigated at room temperature. Consequently, the LPA and DPA exhibited lower infrared emissivity values than RPA, which came down to 0.632 and 0.616. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41210.

Optically active amino acid-based polyacetylenes: Effect of tunable helical conformation on infrared emissivity property

Chiral amino acid-based monosubstituted acetylene monomers [N-tert-butoxy-carbonyl-l-phenylalanine-N′-propargylamide (LP), and N-tert-butoxycarbonyl-l-serine-N′-propargylamide (LS)] were (co)polymerized with rhodium zwitterion catalyst in THF to afford helical polyacetylenes (PAs) with moderate molecular weights (4400–14,800) in good yields. The optically active PA copolymers were soluble in common organic solvents and proven to adopt predominately single-handed helical conformations according to their intense Cotton effect and large specific rotations. Various contents of amino acid units in side chains facilitated controllable helical secondary structure while the helix was primarily stabilized by hydrogen bonding and steric repulsion between the substituents. Intramolecular hydrogen bonds constructed between hydroxyl and amide groups, in particular, played a significant role in adjusting the helicity and orderliness of the helix. The infrared emissivity values of the PAs at wavelength of 8–14μm were measured and the correlation between helical conformations and their effect on infrared emission were systematically investigated. The results showed that more well-ordered and compact screw-sense could enhance the performance of organic polymers in lowering their infrared emissivity. Among all the as-prepared PAs, poly(LP50-co-LS50) exhibited the lowest infrared emissivity value (ε25=0.632) and possessed excellent resistance against heat.

ChemInform Abstract: Stereoselective Rhodium‐Catalyzed [(3 + 2) + 2] Carbocyclization Reaction of Trialkoxysilyl‐Substituted Alkenylidenecyclopropanes with Monosubstituted Alkynes.

AbstractAll compounds are isolated in high diastereopurity of at least 96% d.e.

A Rhodium‐Catalyzed Tandem Alkyne Dimerization/ 1,4‐Addition Reaction

AbstractA convenient three‐component coupling reaction for the construction of conjugated enynes using rhodium catalysis is reported. Dimerization of a monosubstituted alkyne followed by trapping of the vinyl metal intermediate with an electron‐deficient alkene, such as methyl vinyl ketone, provided moderate to good yields of these enynes. The use of the hindered electron‐rich tris(ortho‐tolyl)phosphine as a ligand for the rhodium catalyst provided the best conversions to these complex products.magnified image