Alkynyl Compounds Research Articles

Composite electroforming of precision Ni-P-PTFE mold inserts with low internal stress and self-lubricating properties

An electrolyte solution incorporating sodium saccharin and an alkynyl compound was provided to electroform Ni-P-PTFE mold inserts with both low internal stress and good self-lubricating properties. The results showed that with 5 g·L−1 sodium saccharin and 1 mL·L−1 alkynyl compound, the internal stress reached a minimum of −114 MPa, an 82 % reduction from the −646 MPa observed without additives. The presence of sodium saccharin and alkynyl compound in the electrolyte solution reduced the hydrogen evolution reaction current from 15.2 to 12.9 mA at the operating cathode potential of −1 V and decreased the RTC(111) from 100 % to 90 %. The reduction of internal stress in the electrodeposited Ni-P-PTFE composites was attributed to the decreased hydrogenation strain, diminished Ni (111) texture intensity, and the partial incorporation of alkynyl compound reaction products into the cathode surface, which weakened the connections between crystallites. Finally, 5 g·L−1 sodium saccharin and 1 mL·L−1 alkynyl compound was applied to electroform Ni-P-PTFE mold insert with micro features. Only slightly pile-up defects at the corner of grooves were observed on the polymer chips demolded from Ni-P-PTFE mold insert, demonstrating its good self-lubricating property.

Palladium(II)‐Catalyzed Markovnikov Hydroalkynylation of Unactivated Terminal Alkenes†

Comprehensive SummaryAlkynes are versatile synthons in organic synthesis, as well as important structural moieties in bioactive molecules. Recently, transition metal‐catalyzed hydroalkynylation of alkenes has been developed with reactive alkenes and alkenes bearing directing groups. However, the regioselective hydroalkynylation of simple alkenes is still challenging. Herein, we have developed a palladium‐catalyzed Markovnikov hydroalkynylation of unactivated terminal alkenes, which provides an efficient approach for the synthesis of branched alkynyl compounds under mild conditions. This reaction features excellent functional group tolerance, good reaction yields and excellent regioselectivity. Moreover, the asymmetric hydroalkynylation reaction has also been achieved with moderate enantioselectivity by introducing a sterically bulky chiral Pyox ligand.

Synthesis of α-Trifluoromethyl Alkynes through Fluoroalkynylation of gem-Difluoroalkenes.

A trifluoromethylalkynylation reaction of gem-difluoroalkenes with alkynyl sulfoxide by photoredox radical addition with good functional group tolerance in moderate to high yields, is developed for the synthesis of α-trifluoromethyl alkyne. This reaction features simple operation and inexpensive raw materials and provides an expeditious route to synthesize biologically relevant fluorine-containing alkynyl compounds with diverse structural skeletons.

Construction of an enzyme-free biosensor utilizing CuO nanoparticles enriched in DNA polymer to catalyze a click chemistry reaction for SERS detection of the p53 gene

The p53 gene is a known cancer marker. We report a novel protocol for the SERS tandem strategy to detect the p53 gene with high sensitivity. Herein, the click reaction between azide and alkyne was catalyzed by utilizing copper oxide nanoparticles (CuONPs), which were enriched by a T-DNA-triggered hybridization chain reaction (HCR). The T-DNA signal was amplified by establishing the correlation between the T-DNA signal and the concentration of CuONPs in a nonenzymatic isothermal environment. In contrast to other Raman reporters, we used alkynyl compounds as Raman reporters, which showed excellent characteristics in the Raman-silent region (1800–2800 cm−1). Therefore, the highly sensitive and highly selective SERS signals could be obtained in complex biological matrices. Due to utilizing multistep amplification strategies, including the nanoparticle-modified HCR polymer and “click” reaction, the limit of detection (LOD) and the limit of quantification (LOQ) of this sensor could be as low as 0.0174 pM and 0.0583 pM, respectively. The accuracy of the strategy expressed as the RSD was in the range of 3.14%–6.21%. The results indicated that the constructed sensor has excellent performance for the detection of the p53 gene in serum samples in a low concentration range, which suggests that the proposed enzyme-free SERS analytical sensor has good clinical application prospects.

Tellurium-induced cyclization of olefinic compounds

Abstract In this article, we discuss about the importance of Tellurium (Te) in organic synthesis. Tellurium-induced cyclization of alkenyl compounds, as well as alkynyl compounds, are considered for the study. The developments in this area are incorporated in great detail. The mechanism of the reactions does not follow any straightforward process. This study opens up the possibility of stereocontrolled synthesis of complex natural products.

NMR Indirect Spin–Spin Coupling Constants in a Modern Quasi-Relativistic Density Functional Framework

A quasi-relativistic implementation of NMR indirect spin-spin coupling constants is presented. The exact two-component (X2C) Hamiltonian and its diagonal local approximation to the unitary decoupling transformation (DLU) are utilized together with the (modified) screened nuclear spin-orbit approach. In a restricted kinetic balance, the finite nucleus model is available for both the scalar and vector potentials. The implementation supports density functionals up to the fourth rung of Jacob's ladder, i.e., (range-separated) hybrid and local hybrid functionals based on a seminumerical ansatz. We assess the quality of our quasi-relativistic X2C approach by comparison with "fully" relativistic four-component results for small main-group molecules and alkynyl compounds. The mean absolute error introduced by the DLU scheme is less than 0.05 × 1019 T J-2 of the reduced coupling constant for the small main-group molecules and 0.5 Hz for the alkynyl compounds. Thus, the error is significantly smaller than finite nucleus size effects for heavy elements. The basis set convergence and the impact of different density functional approximations are further studied. We propose a simple scheme to develop segmented-contracted relativistic all-electron basis sets for NMR spin-spin couplings. Our implementation allows us to perform calculations of extended molecules with reasonable computational effort, which is illustrated for the 1J(119Sn, 31P) coupling constant of a low-valent tin phosphinidenide complex. The corresponding results are in good agreement with the experimental findings.

Propargylimine in the laboratory and in space: millimetre-wave spectroscopy and its first detection in the ISM

Context. Small imines containing up to three carbon atoms are present in the interstellar medium (ISM). As alkynyl compounds are abundant in this medium, propargylimine (2-propyn-1-imine, HC ≡C−CH =NH) thus represents a promising candidate for a new interstellar detection. Aims. The goal of the present work is to perform a comprehensive laboratory investigation of the rotational spectrum of propargylimine in its ground vibrational state in order to obtain a highly precise set of rest frequencies and to search for it in space. Methods. The rotational spectra of E and Z geometrical isomers of propargylimine have been recorded in the laboratory in the 83–500 GHz frequency interval. The measurements have been performed using a source-modulation millimetre-wave spectrometer equipped with a pyrolysis system for the production of unstable species. High-level ab initio calculations were performed to assist the analysis and to obtain reliable estimates for an extended set of spectroscopic quantities. We searched for propargylimine at 3 mm and 2 mm in the spectral survey of the quiescent giant molecular cloud G+0.693-0.027 located in the central molecular zone, close to the Galactic centre. Results. About 1000 rotational transitions have been recorded for the E- and Z-propargylimine, in the laboratory. These new data have enabled the determination of a very accurate set of spectroscopic parameters including rotational, quartic, and sextic centrifugal distortion constants. The improved spectral data allowed us to perform a successful search for this new imine in the G+0.693-0.027 molecular cloud. Eighteen lines of Z-propargylimine were detected at level >2.5σ, resulting in a column-density estimate of N = (0.24 ± 0.02) × 1014 cm−2. An upper limit was retrieved for the higher energy E isomer, which was not detected in the data. The fractional abundance (with respect to H2) derived for Z-propargylimine is 1.8 × 10−10. We discuss the possible formation routes by comparing the derived abundance with those measured in the source for possible chemical precursors.

Copolymerization of azide-containing carbonate with lactide and post functionalization

The intention of this work was to study the polymerization of a cyclic carbonate monomer bearing one azido group, i.e. 2-(azidemethyl)-2-methyltrimethylene carbonate (AMTC), to disclose the characteristics of the resulted polymers and to explore the feasibility of their post-functionalization with alkynyl compounds via Click reaction. Homopolymerization of AMTC was first studied using stannous octoate (Sn(Oct)2) as the catalyst and dodecanol as the initiator, which had the characteristic of active polymerization. Copolymerization of AMTC with L-lactide (L-LA) was then investigated under the same reaction condition, in which L-LA exhibited higher reactivity than AMTC. The reactivity of AMTC was low not only in its homopolymerization but also in its copolymerization with L-LA, while the conversion of AMTC increased by extending the reaction time. The copolymer P(AMTC-co-LLA) (PLAC) had the semicrystalline characteristic due to the relative long block-like segments of PLLA ( $$ {\overline{L}}_{\mathrm{L}}=35.5 $$ ). Based on these results, copolymerization of AMTC with L-LA using PEG4K as macroinitiator was further studied to afford PLAC-PEG-PLAC copolymers. The copolymerization could be well controlled at low ratio of [M]0/[I]0 (from 10 to 50) and molar fraction of AMTC in feed (fAMTC = 0.1, 0.2). The pendent azido groups of PLAC-PEG-PLAC could undergo post-functionalization through azide-alkyne click reaction easily and efficiently.

An Optical Power Limiting and Ultrafast Photophysics Investigation of a Series of Multi-Branched Heavy Atom Substituted Fluorene Molecules

A common molecular design paradigm for optical power limiting (OPL) applications is to introduce heavy atoms that promote intersystem crossing and triplet excited states. In order to investigate this effect, three multi-branched fluorene molecules were prepared where the central moiety was either an organic benzene unit, para-dibromobenzene, or a platinum(II)–alkynyl unit. All three molecules showed good nanosecond OPL performance in solution. However, only the dibromobenzene and Pt–alkynyl compounds showed strong microsecond triplet excited state absorption (ESA). To investigate the photophysical cause of the OPL, especially for the fully organic molecule, photokinetic measurements including ultrafast pump–probe spectroscopy were performed. At nanosecond timescales, the ESA of the organic molecule was larger than the two with intersystem crossing (ISC) promoters, explaining its good OPL performance. This points to a design strategy where the singlet-state ESA is balanced with the ISC rate to increase OPL performance at the beginning of a nanosecond pulse.

Syntheses and Structures of 1,8,13,16‐Substituted Triptycenes

New triptycene derivatives have been synthesised based on the cycloaddition between 1,8‐bis[(trifluoromethanesulfonyl)‐oxy]anthracene as well as 1,8‐bis[(trimethylsilyl)ethynyl]anthracene and p‐benzoquinone. The resulting triptycenequinones were the key compounds for further functionalisation of the triptycene backbone, which were completely characterised by multinuclear NMR spectroscopy, mass spectrometry and X‐ray diffraction experiments. The aim was to substitute the triptycene backbone in positions 1, 8, 13 and 16 to avoid the formation of mixtures of syn‐ and anti‐isomers of trisubstituted triptycenes. Based on the ditriflate‐substituted triptycenequinone triptycene 1,8,13,16‐tetratriflate was synthesised and reacted with alkynyl compounds in cross‐coupling reactions. In further experiments the alkynyl‐substituted triptycene to quinone was directly reacted with lithiated trimethylsilylacetylene or was initially reduced, consequently functionalised with triflate groups and reacted in Sonogashira cross‐coupling reactions. It was found that both reaction pathways generate the anti‐substituted product in position 16 as main product.

Thiol Treatment Creates Selective Palladium Catalysts for Semihydrogenation of Internal Alkynes

Summary Surface and interfacial engineering of heterogeneous metal catalysts is effective and critical for optimizing selective hydrogenation for fine chemicals. By using thiol-treated ultrathin Pd nanosheets as a model catalyst, we demonstrate the development of stable, efficient, and selective Pd catalysts for semihydrogenation of internal alkynes. In the hydrogenation of 1-phenyl-1-propyne, the thiol-treated Pd nanosheets exhibited excellent catalytic selectivity (>97%) toward the semihydrogenation product (1-phenyl-1-propene). The catalyst was highly stable and showed no obvious decay in either activity or selectivity for over ten cycles. Systematic studies demonstrated that a unique Pd-sulfide/thiolate interface created by the thiol treatment was crucial to the semihydrogenation. The high catalytic selectivity and activity benefited from the combined steric and electronic effects that inhibited the deeper hydrogenation of C=C bonds. More importantly, this thiol treatment strategy is applicable to creating highly active and selective practical catalysts from commercial Pd/C catalysts for semihydrogenation of internal alkynes.

Relativistic effects on the NMR parameters of Si, Ge, Sn, and Pb alkynyl compounds: Scalar versus spin-orbit effects.

The NMR chemical shifts and indirect spin-spin coupling constants of 12 molecules containing 29Si, 73Ge, 119Sn, and 207Pb [X(CCMe)4, Me2X(CCMe)2, and Me3XCCH] are presented. The results are obtained from non-relativistic as well as two- and four-component relativistic density functional theory (DFT) calculations. The scalar and spin-orbit relativistic contributions as well as the total relativistic corrections are determined. The main relativistic effect in these molecules is not due to spin-orbit coupling but rather to the scalar relativistic contraction of the s-shells. The correlation between the calculated and experimental indirect spin-spin coupling constants showed that the four-component relativistic density functional theory (DFT) approach using the Perdew's hybrid scheme exchange-correlation functional (PBE0; using the Perdew-Burke-Ernzerhof exchange and correlation functionals) gives results in good agreement with experimental values. The indirect spin-spin coupling constants calculated using the spin-orbit zeroth order regular approximation together with the hybrid PBE0 functional and the specially designed J-coupling (JCPL) basis sets are in good agreement with the results obtained from the four-component relativistic calculations. For the coupling constants involving the heavy atoms, the relativistic corrections are of the same order of magnitude compared to the non-relativistically calculated results. Based on the comparisons of the calculated results with available experimental values, the best results for all the chemical shifts and non-existing indirect spin-spin coupling constants for all the molecules are reported, hoping that these accurate results will be used to benchmark future DFT calculations. The present study also demonstrates that the four-component relativistic DFT method has reached a level of maturity that makes it a convenient and accurate tool to calculate indirect spin-spin coupling constants of "large" molecular systems involving heavy atoms.

Synthesis, structure and redox chemistry of the aminoallenylidene complex [Mo{C[dbnd]C[dbnd]C(Me)NEt2}(dppe)(η-C7H7)][BPh4

The reaction of [MoBr(dppe)(η-C7H7)] (dppe = Ph2PCH2CH2PPh2) with HCCCCSiMe3 and Na[BPh4] in 1:1 NHEt2/THF as solvent yields the aminoallenylidene complex [Mo{CCC(Me)NEt2}(dppe)(η-C7H7)][BPh4], [1][BPh4]. The reaction likely proceeds via nucleophilic addition of NHEt2 at Cγ of a butatrienylidene intermediate. Structural and spectroscopic characterisation of [1][BPh4] indicate a significant contribution of an iminium alkynyl resonance form to the overall structure of the heteroatom stabilised allenylidene ligand. The X-ray structural study of [1][BPh4] determines a MoCα bond length of 2.077(3) Å, intermediate between that of the cumulenic diphenylallenylidene analogue [Mo(CCCPh2)(dppe)(η-C7H7)][PF6] (1.994(3) Å) and the alkynyl compound [Mo(CCPh)(dppe)(η-C7H7)] (2.138(5) Å). Complex [1][BPh4] undergoes a reversible one-electron oxidation with E½ = −0.19 V with respect to the FeCp2/FeCp2+ couple and the stable 17-electron radical dication [1]2+ is readily observed by spectroelectrochemical methods. IR spectroelectrochemistry in CH2Cl2 demonstrates that the ν(CCC) stretch, characteristic of the allenylidene ligand, shifts to higher wavenumber (from 1959 to 2032 cm−1) as a result of oxidation of [1]+ to [1]2+, consistent with a strongly metal-centred redox process and an enhancement in the alkynyl character of the allenylidene ligand following one-electron oxidation.

ChemInform Abstract: Sustainable Metal Alkynyl Chemistry: 3d Metals and Polyaza Macrocyclic Ligands

AbstractReview: 91 refs.

ChemInform Abstract: Catalytic σ‐Activation of Carbon—Carbon Triple Bonds: Reactions of Propargylic Alcohols and Alkynes

AbstractReview: [76 refs.

Assembly of silver alkynyl compounds with various nuclearities.

A convenient method for the synthesis of silver alkynyl compounds containing different nuclearities has been developed. The reaction of AgC[triple bond, length as m-dash]CBu(t) and AgX (X = CF3CO2(-), C2F5CO2(-)) in the presence of auxiliary ligands L (L = bipyridine, bipy; 1,10-phenanthroline, phen; 2-(diphenylphosphino)pyridine, dppy) under different conditions afforded a family of new silver alkynyl compounds, namely, [Ag3(bipy)(C[triple bond, length as m-dash]CBu(t))(CF3CO2)2]n (), [Ag4(bipy)2(C[triple bond, length as m-dash]CBu(t))(CF3CO2)3]n (), [Ag6(phen)3(C[triple bond, length as m-dash]CBu(t))2(C2F5CO2)4(MeOH)(EtOH)] (), [Ag8L4(C[triple bond, length as m-dash]CBu(t))2(C2F5CO2)6] (L = bipy, ; L = phen, ), [Ag10(dppy)2(C[triple bond, length as m-dash]CBu(t))6X4] (X = CF3CO2(-), ; X = C2F5CO2(-), ), [Ag12(bipy)2(C[triple bond, length as m-dash]CBu(t))8(C2F5CO2)4] () and [Ag12(phen)4(C[triple bond, length as m-dash]CBu(t))6(CF3CO2)6]·2EtOH (). Single-crystal X-ray analysis revealed that compounds and display infinite-chain structures, while the other seven compounds are discrete molecules containing silver nuclearities varying from 6 to 12. The formation of various structural motifs depends on the reactant ratios and the ligands/anions with different nature.

Azide-functionalized hollow silica nanospheres for removal of antibiotics

Antibiotics, which are hardly removed from polluted water by conventional water-treatment technologies, adsorption has been deemed as one of the efficient and promising method to resolve the problems of antibiotics pollution. Herein, we reported a synthesis of filtration separable hollow nanostructured silicas (HNSs) with efficient click functionalization property for antibiotics adsorption. The clickable HNSs were synthesized by the co-condensation and assembling of tetramethoxysilane (TMOS) and 3-azidopropyltrimethoxysilane (AzPTMS) around F127 single micelle template. Alkynyl compounds such as phenylacetylene (Ph), propargyl alcohol (PA), 1-heptyne (Hep), and 2-butyne-1,4-diol (BD) have been linked to the materials through click reaction with high efficiency. Antibiotic adsorption results reveal that functional groups play an important role in adsorption properties of adsorbents and phenyl was found to be the optimal functional group due to the π–π stacking effect. Excellent adsorption capacity and recyclability indicate that the clickable hollow nanostructured silicas exhibit potential application for antibiotics removal.

Facile assembly of 1D multinuclear Agn(n = 11, 11, 12) alkynyl chains with CF3COO−/CH3COO−as the auxiliary ligand

Three 1D multinuclear silver(I) alkynyl compounds, [Ag11(CCtBu)6(CF3COO)5(CH3OH)]n (1), [Ag11(CCtBu)7(CH3COO)4]n (2) and [Ag12(CCtBu)7(CF3COO)5·H2O]n (3), constructed from AgCCtBu ligand and CF3COO−/CH3COO− auxiliary ligand, have been obtained by changing the type and source of the auxiliary ligand as well as adjusting the pH value in different solvents. The synthesis of 1–3 indicates that this kind of 1D multinuclear Agn (n = 11, 11, 12) alkynyl chain can be isolated through a facile one-pot process. Among these, an infinitely extended 2D supramolecular network is fabricated from 1D chains of 1 via hydrogen bonds, while 3 crystallizes in the chiral space group P21. In addition, the solid state optical diffuse reflection spectra and luminescence spectra of 1–3 have been obtained. Compound 2 is taken as an example to study the electrochemical behaviour of this kind of compound, and the results indicate that 2-CPE possesses good electrocatalytic activity toward the reduction of nitrite.

Rational synthesis, structural characterization and theoretical exploration on third-order nonlinear optical properties of isolated Agn (n = 5, 8, 12) alkynyl clusters

Three silver(Ι) alkynyl compounds, [Ag5(CCtBu)(CF3COO)7(nBu4N)3·H2O] (1), [Ag8(CCtBu)2(CF3COO)10(Et3N)4] (2), and [Ag12(CCtBu)6(CF3COO)8(nBu4N)2(Et3N)2(CF3COO)2] (3), have been obtained. Concomitantly, isolated [Ag5(CCtBu)(CF3COO)7]3–, [Ag8(CCtBu)2(CF3COO)10]4– and [Ag12(CCtBu)6(CF3COO)8]2– clusters (Ag5, Ag8 and Ag12 for short) appear in 1–3, respectively. The synthesis of 1–3 demonstrates silver(I) alkynyls are better systems for the study of the template effect. ESI-MS analysis indicates compounds 1–3 can stably exist in methanol, and they have been proved to be potential wide gap semiconductor materials by the reflectance spectra. Notably, the second hyperpolarizabilities (γ values) of Ag5, Ag8 and Ag12 have been studied by using time-dependent density functional theory (TDDFT) calculations and the finite filed (FF) approach combining CAM-B3LYP. The calculated results show that they can be applied as potential third-order nonlinear optical (NLO) materials owing to their second hyperpolarizabilities rising from 39.1 × 10−36, 60.3 × 10−36 to 97.7 × 10−36 esu with the growth of the number of Ag atoms and CC groups.

Alkynyl Compounds of the Rare‐earth Metals

AbstractConversion of the rare‐earth tetramethylaluminates [Ln(AlMe4)3] with phenylacetylene afforded the homoleptic alkynylaluminates [Ln{(μ‐C≡CPh)2AlMe2}3] [Ln = Ce (1), Er(2)]. The reaction of five equivalents of phenylacetylene with the yttrium aluminate [Y(AlMe4)3] afforded [Y{(μ‐C≡CPh)AlMe3}{(μ‐C≡CPh)2AlMe2}2] (3). The cationic yttrium complex [(TMTAC)2YMe2][AlMe4] (4) (TMTAC = 1, 3,5‐trimethyl‐1, 3,5triazacyclohexane) was reacted with phenylacetylene to give the product [(TMTAC)2Y(C≡CPh)2][Me2Al(C≡CPh)2] (5), in which two methyl groups of each, the cation and the anion, were substituted by phenylacetylide groups. Under the same conditions as for the synthesis of compound 5, the holmium analogue reveals different reactivity in forming a neutral alkynyl complex [(TMTAC)2Ho(C≡CPh)3] (6). The introduction of 1, 8‐diethynylanthracene to 4 leads to a structural very similar complex [(TMTAC)2Ho(μ‐1, 8‐diethynylanthracene)3] (7) and offers the same reactivity as observed for the synthesis of 6. All compounds were characterized by X‐ray diffraction experiments. Compounds 1–3 and 5 were also characterized by NMR and elemental analyses.