Acetylenic Chain Research Articles

The First Total Synthesis of the Proposed Structure of Montiporyne E

Montiporyne E, a novel diacetylenic lactam isolated from the stony coral Montipora sp., was shown to exhibit cytotoxicity against certain solid tumor cells. Construction of a suitably functionalized α,β-unsaturated lactam for palladium-catalyzed couplings was realized via a Beckmann rearrangement. Subsequent Sonagoshira coupling with a known alkyne chain efficiently afforded the alleged structure of the natural product.

γ‐Radiolysis of Polyynes in Heptane

The polyynes in heptane solution were γ‐radiolyzed at a total dose of 150, 300 and 600 kGy. After radiolysis the products were analyzed by electronic absorption spectroscopy, by HPLC (liquid chromatography) and by FT‐IR spectroscopy. Even at 150 kGy the polyynes disappear completely from the solution and the chromatographic analysis shows that the acetylenic chains undergo fragmentation, addition and crosslinking reactions with other chains and with solvent. The oxidative interference from air has been detected by FT‐IR.

Synthesis of Substituted Polyacetylenes Grafted with Polystyrene Chains by the Macromonomer Method and Their Characterization

Summary: A macromonomer (1) consisting of a polystyrene chain and an acetylenic chain end ( = 2 500, = 1.20) was prepared by atom transfer radical polymerization. Macromonomer 1 was copolymerized with phenylacetylene (2) and propargyl 2-bromopropionate (3) by using Rh catalysts at varying feed ratios from 10 to 50 wt.-% to produce graft copolymers 4 and 5, respectively. The synthesized copolymers 4 and 5 possessed a conjugated polyene main-chain and polystyrene grafts, and contained 11–34 and 16–77 wt.-% of polystyrene with of 61 400–144 000 and 19 300–22 500, respectively. Graft copolymer 4 was a yellow solid and thermally stable up to 225 °C, whereas 5 was a brown solid with weight loss beginning at 175 °C. Graft copolymers 4 and 5 exhibited UV-vis absorption edges at 525 and 425 nm, respectively, which are attributable to the conjugated main-chain structure. Copolymerization of the acetylene-terminated polystyrene-based macromonomer with monosubstituted acetylenes.

Effect of Acetylenic Chain Length on the Tuning of Functional Properties in Fluorene-Bridged Polymetallaynes and Their Molecular Model Compounds

We describe for the first time thermally stable and high-molecular-weight group 10 platinum(II) and group 12 mercury(II) polyyne polymers consisting of 2,7-bis(buta-1,3-diynyl)-9,9-dihexylfluorene linking units trans-[Pt(PBu3)2(C⋮C)2R(C⋮C)2]n and [Hg(C⋮C)2R(C⋮C)2]n (R = 9,9-dihexylfluorene-2,7-diyl). The optical absorption and photoluminescence spectra of these carbon-rich metallopolymers were examined and compared with their dinuclear model complexes trans-[Pt(Ph)(PEt3)2(C⋮C)2R(C⋮C)2Pt(Ph)(PEt3)2] and [MeHg(C⋮C)2R(C⋮C)2HgMe] as well as the group 11 gold(I) congener [(PPh3)Au(C⋮C)2R(C⋮C)2Au(PPh3)]. The regiochemical structures of the polymers were studied by NMR spectroscopy and ascertained by single-crystal X-ray structural analysis for the model platinum(II) compound. The heavy-atom effects of group 10−12 transition metals in triplet light energy harvesting and the influence of the C⋮C chain length on the spatial extent of singlet and triplet excitons in metalated systems of the form [M(C⋮C)mR(C⋮C)mM]n ...

Radical polymerization of methacrylates having acetylenic moiety activated by electron-withdrawing group as a reactive functional group

The synthesis of methacrylates having an acetylene moiety activated by an electron-withdrawing group and a radical polymerization of the methacrylates are described. The methacrylates were prepared from alkynoic acids via ω-hydroxyalkyl alkynoates in two steps. This was done by the radical polymerization of the synthesized methacrylates, polymthacrylates having the acetylene moieties activated by the electron-withdrawing group as the side-chain that were obtained in high yields. In the radical polymerization, the acetylene moiety slightly hindered the polymerization of the methacrylate moiety. The influences of the acetylene moiety decreased with the introduction of substituents at the acetylene moiety. The polymer reaction of the obtained polymer having the acetylenic side chain with thiols gave the corresponding polymers having the β-alkylmercaptoenoate moiety in high yields.

Synthesis of cyclopropyl silyl ethers and their facile ring opening by photoinduced electron transfer as key step in radical/radical cationic cascade reactions

Various ring-fused cyclopropyl silyl ethers with an benzylic, olefinic or acetylenic side chain have been synthesized. Upon oxidative photoinduced electron transfer (PET) the cyclopropane ring opens and forms a reactive β-keto radical, which undergoes intramolecular cyclization. In some cases we observed only formation of ring opened non-cyclized products. With olefinic side chain 5- exo- trig mode of cyclization rather than 6- endo- trig mode of cyclization takes place whereas in case of acetylenic side chain we observed 6- endo cyclization.

Third-Order Nonlinear Optical Figure of Merits for Conjugated TTF−Quinone Molecules

We have revealed a substantial enhancement of third-order optical figure of merits by the synthesis of a compact molecule possessing the tetrathiafulvalene (TTF) group with two backside C=O groups. Addition of the saturated methylene chain substantially suppresses the third-order optical figure of merits and even local optical hyperpolarizabilities at lambda = 532 nm. Another TTF-derivative molecule possessing ethylenic and acetylenic chains demonstrates large hyperpolarizabilities; however, generally, the figure of merit factor decreases due to the increasing optical losses as a consequence of enhanced linear absorption. At the same time, both of the chromophores have a large nonlinear optical response. General approaches for search and design of the third-order optical materials with improved properties are given.

Regioselective Intramolecular Pauson–Khand Reactions of C60: An Electrochemical Study and Theoretical Underpinning

Suitably functionalized fulleropyrrolidines endowed with one or two propargyl groups at the C-2 position of the pyrrolidine ring (1,6-enynes) react efficiently and regioselectively with [Co2(CO)8] to afford the respective Pauson-Khand products with an unprecedented three (5 a-d, 7, and 24) or five (25) pentagonal rings, respectively, fused onto the fullerene sphere. Fulleropyrrolidines with 1,7-, 1,9-, 1,10-, or 1,11-enyne moieties do not undergo the PK reaction and, instead, the intermediate dicobalt complexes formed with the alkynyl group are isolated in quantitative yields. These differences in reactivity have been studied by DFT calculations with a generalized gradient approximation (GGA) functional and several important energy and structural differences were found for the intermediates formed by the interaction between the coordinatively unsaturated Co atom and the pi system of C60 in 1,6- and 1,7-enynes. The different lengths of the alkyne chains are responsible for the observed reactivities. Cyclic voltammetry reveals that the presence of the cyclopentenone's carbonyl group connected directly to the C60 core results in PK compounds with remarkable electron-accepting ability.

End‐Capped, Conjugated (Dimethylamino)naphthyl Nanostructures with Alternating (1‐Naphthylethynyl‐p‐phenylethynyl)x Branches on a 1,3,5‐Substituted Benzene Core

AbstractAlternating (1‐naphthylethynyl‐p‐phenylethynyl)x 1,3,5‐trisubstituted benzene dendrons were efficiently synthesised by the heterocoupling reaction between (1‐naphthylethynyl‐p‐phenyl)xacetylene (x = 1) and 1,3,5‐triiodobenzene in the presence of a palladium‐copper catalyst system. A longer terminal acetylene chain (x = 2) was obtained from the heterocoupling between 1,3,5‐tri(1‐ethynyl‐5‐naphthylethynyl)benzene and the appropriate iodoaryl derivative. The alternating chains, and their dendron structures, show fluorescence emission, with similar wavelengths and quantum yields. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Compression- and Shear-Induced Polymerization in Model Diacetylene-Containing Monolayers

Molecular dynamics simulations have been used to examine the response of monolayers composed of alkyne chains, which contain diacetylene moieties, to compression and shear. The simulations show that both compression and shear result in cross-linking, or polymerization, between chains. Irregular polymerization patterns appear among the carbon backbones. The vertical positioning of the diacetylene moieties within the alkyne chains (spacer length) and the sliding direction have an influence on the pattern of cross-linking and friction. In addition, chemical reactions between the chains of the monolayer and the amorphous carbon tip occur when diacetylene moieties are located at the ends of the chains closest to the tip. These adhesive interactions increase friction.

The Polymerization of Acetylene, Hydrogen Cyanide, and Carbon Chains in the Neutral Layers of Carbon-rich Proto-planetary Nebulae

I present chemical evolution models for the neutral layers of proto-planetary nebulae in order to explain the high abundance of polyynes, cyanopolyynes, methyl-polyynes, benzene, and other C-bearing species found in CRL 618 by Cernicharo et al. In the neutral regions behind the H II region, the radiation field produces a rich photochemistry on timescales shorter than the dynamical evolution of the central H II region, leading to the formation of large carbon-rich molecules CnH2, HC(2n+1)N, and Cn. Reactions between radicals H and H2 play a crucial role in maintaining a high abundance for these species in spite of the strong radiation field emerging from the central star. The models predict that proto-planetary nebulae in the early stages of evolution will have high abundances for species such as HC(2n+1)N, CnH4, and CnH3N. The role of reactions between neutrals and radicals in the growth of aromatic molecules is discussed. The large abundance derived for small cumulenes suggests that the growth of small carbon grains with C/H ≫ 1 could be dominated by reactions between polyynes and cumulenes. The models also explain the observed abundances of H2CO, OH, H2O, CO2, and [O I] in the region where CO is photodissociated.

Synthetic applications in radical/radical cationic cascade reactions.

Oxidative photoinduced electron transfer (PET) reactions have been performed with various cyclic cyclopropyl(vinyl) silyl ethers bearing an olefinic or acetylenic side chain. The reactions result in bi- to tetracyclic ring systems via a fragmentation-radical/radical cationic addition reaction pathway with well defined ring juncture. The mode of cyclisation (endo/exo) can be partially controlled by addition of nucleophiles due to the suppression of radical cationic reaction pathways. Quantum chemical calculation of the cyclisation transition states underline the experimentally found selectivities. Additional mechanistic studies concerning the saturation step reveal that the final radical is saturated mostly by the solvent and traces of water in the solvent.

Electron affinity versus Coulomb repulsion—when dialkoxides become stable gas phase species

The possible existence of α,ω-dialkoxide species (deprotonated terminal diols) in the gas phase is investigated by density functional and ab initio quantum methods. The calculations reveal that terminal aliphatic dialkoxides − O–( CH 2) n– O − are unstable with respect to electron loss up to a very high chain length ( n>22). Contrary to what one expects from a classical Coulomb distribution of point charges, charge conjugation through an alkene or alkyne chain stabilizes the two negative charges and − O–( C 2 H 2) m– O − ( m≥10) and − O–( C C) k– O − ( k≥6) are predicted to be stable with respect to electron loss in the gas phase.

Excess molar volumes of tetrahydrofuran or tetrahydrothiophene + an alkyne at [formula omitted] K

Excess molar volumes V M E were measured as a function of mole fraction at T=(293.15,298.15 and 303 .15) K and atmospheric pressure for {(tetrahydrofuran or tetrahydrothiophene) + (hex-1-yne, or hept-1-yne, or oct-1-yne)}. The results of the hydrogen-bonded mixtures are discussed in terms of: alkyne chain length; molecular size and temperature dependence.

Polyacetylenes and Cumulenes, Potential Elements for Molecular Machines and Precursors of Carbon Clusters: A Theoretical Study

AbstractA recently described very simple procedure for estimating Hartree–Fock (H. F.) energy and accurate nonrelativistic energy has been used with simple hydrocarbons possessing CC or CC bonds and for the acetylene dimer. Experimental characteristics (heats of formation, ionization potentials, electron affinities), structural features, and reactivity have been discussed in terms of quantum‐chemistry characteristics at the H. F. level and also at a level including a part of electron correlation. Deviations from linearity with derivatives of long polyacetylenes and cumulenes are ascribed to the lowest‐energy deformation vibrations, which decrease rapidly when passing from short to long acetylenic and cumulenic chains. The role of derivatives and heteroanalogues of hydrocarbons under study in atmospheric and interstellar chemistry is briefly mentioned. Derivatives with enhanced stability represent potentially promising construction materials for molecular devices and also resources for the preparation of defined clusters of C‐atoms.

Lipase-catalyzed hydrolysis of TG containing acetylenic FA.

Hydrolysis of symmetrical acetylenic TG of type AAA [viz., glycerol tri-(4-decynoate), glycerol tri-(6-octadecynoate), glycerol tri-(9-octadecynoate), glycerol tri-(10-undecynoate), and glycerol tri-(13-docosynoate)] in the presence of eight microbial lipases was studied. Novozyme 435 (Candida antarctica), an efficient enzyme for esterification, showed a significant resistance in the hydrolysis of glycerol tri-(9-octadecynoate) and glycerol tri-(13-docosynoate). Hydrolysis of acetylenic TG with Lipolase 100T (Humicola lanuginosa) was rapidly accomplished. Lipase PS-D (Pseudomonas cepacia) showed a fair resistance toward the hydrolysis of glycerol tri-(6-octadecynoate) only, which reflected its ability to recognize the delta6 positional isomer of 18:1. Lipase CCL (Candida cylindracea, syn. C. rugosa) and AY-30 (C. rugosa) were able to catalyze the release of 10-undecynoic acid and 9-octadecynoic acid from the corresponding TG, but less readily the 13-docosynoic acid in the case of glycerol tri-(13-docosynoate). The two lipases CCL and AY-30 were able to distinguish the small difference in structure of fatty acyl moieties in the TG substrate. To confirm this trend, three regioisomers of mixed acetylenic TG of type ABC (containing one each of delta6, delta9, and delta13 acetylenic FA in various positions) were prepared and hydrolyzed with CCL and AY-40. The results reconfirmed the observation that AY-30 and CCL were able to distinguish the slight differences in the molecular structure (position of the acetylenic bond and chain length) of the acyl groups in the TG during the hydrolysis of such TG substrates.

Linear and Nonlinear Polarizabilities of Fragmental Molecules for the Phenylacetylene Dendrimers

Abstract Linear and nonlinear polarizabilities of small fragmental molecules for the phenylacetylene dendrimers have been calculated with the frequency-dependent moment schemes based on the sum-over-states expressions of the polarizabilities, including all of the singly-excited configurations in the semiempirical CNDO/S approximation. The smallest system, consisting of two benzene rings connected by an acetylene chain, corresponds to a molecular unit that is usually adopted in the exciton model for a theoretical analysis of the phenylacetylene dendrimers. The dependences of the polarizabilities upon the molecular size were examined. It has been shown that the linear polarizability in the static-field condition increases linearly with the number of acetylene chains (N). MO calculations of the nonlinear polarizabilities of these molecules have been carried out for the first time. The third-order polarizability in the static-field condition is shown to depend quadratically upon N, which suggests that two chromophores at a time participate in the optical process of the third-order polarization.

Reduction of short chain alkynes by a nitrogenase α-70Ala-substituted MoFe proteinBased on the presentation given at Dalton Discussion No. 4, 10–13th January 2002, Kloster Banz, Germany. Research supported by National Institutes of Health Grant R01-GM59087.

The Mo-dependent nitrogenase comprises two component proteins, called the Fe protein and MoFe protein, which together catalyze the nucleotide-dependent reduction of N2 to NH3. Nitrogenase also catalyzes the reduction of a variety of other multiply bonded substrates including the short chain alkyne acetylene. Substrate reduction is known to occur at an Fe7S9Mo : homocitrate cluster, designated FeMo-cofactor. Despite 40 years of intensive research and knowledge of the macromolecular structures of the nitrogenase component proteins from several different sources, the mechanism for the binding, activation and reduction of N2 is still unclear. Based on amino acid substitution studies for those residues that provide the first shell of non-covalent interactions with FeMo-cofactor we previously targeted a specific 4Fe-4S face of FeMo-cofactor approached by the MoFe protein α-subunit residues α-70Val and α-96Arg as providing the substrate binding and reduction site. In the present work, support for this hypothesis was obtained by showing that substitution of the α-70Val residue by α-70Ala relaxes constraints within the substrate-binding pocket so that effective reduction of the short chain alkynes, propargyl alcohol and propyne, which are not effectively reduced by the wild type enzyme, is now permitted.

Synthesis and Evaluation of Efavirenz (Sustiva TM) Analogues as HIV-1 Reverse Transcriptase Inhibitors: Replacement of the Cyclopropylacetylene Side Chain

Two series of efavirenz analogues have been developed: one in which the cyclopropane ring has been replaced by small heterocycles and another in which the entire acetylenic side chain has been replaced by alkyloxy groups. Several members of both series show equivalent potency to efavirenz against both wild-type virus and the key K103N mutant.

Synchronous electron-nuclear vibrations in a π-conjugated nanopoly(acetylene) chain

An unusual behavior was observed for the spontaneous Raman spectra in the range of the passband of trans-poly(acetylene) nanoparticles. The following phenomena are observed for the stretching carbon-carbon vibrations: large scattering cross section; high anti-Stokes-to-Stokes ratio; no correlation between the absorption spectra of trans-nanopoly(acetylene) and the Raman excitation spectrum. A qualitative model is proposed for synchronous weakly damping electron-nuclear vibrations in the ordered poly(acetylene) chain.