Acetylenic Bond Research Articles

Supramolecular nanostructures constructed by rod-coil molecular isomers: effect of rod sequences on molecular assembly.

Coil-rod-coil molecules, composed of flexible oligoether chains and conjugated rod blocks, have a well-known ability to produce various nanostructures in bulk and in aqueous solution. Herein we report the synthesis and self-assembly of coil-rod-coil molecules based on the sequence of the rod building block and the type of oligoether coil chain. These molecules consist of conjugated rod segments, which are composed of biphenyl, terphenyl, and acetylenic bonds, with chiral oligoether chains as flexible coil segments. The experimental results imply that the sequence of the rod segments markedly influences the self-assembled nanostructures of coil-rod-coil molecules in the bulk state, and that the type of coil chain strongly affects the morphology of the supramolecular nanoassemblies of these molecules in aqueous solution. In the bulk state, molecules 1a and 1b, which contain biphenyl units connected to the end of the coil segments self-organize into a hexagonal perforated lamellar phase, and oblique columnar and body-centred tetragonal structures, respectively. However, molecules 2a and 2b bearing terphenyl units linked to the end of the coil segments self-assemble into lamellar, hexagonal perforated lamellar and hexagonal columnar structures. In aqueous solution, rod-coil molecular isomers with linear chiral oligoether chains self-assemble into helical nanofibres of various lengths. Meanwhile, isomers with chiral oligoether dendron chains self-organize into sheet-like nanoribbons of different sizes.

An aliphatic hexene-covalent triazine framework for selective acetylene/methane and ethylene/methane separation

Aliphatic hexene-covalent triazine framework for C2/C1 hydrocarbon separation – dependence on morphology.

General and selective syn-carboxylation-trifluoromethylation of terminal alkynes: application to the late-stage modification of dehydrocholic acid.

A general and selective method is developed that allows difunctionalization of terminal alkynes by a Cu(iii)-CF3 complex and a carboxylic acid regioselectively and with unusual syn-stereochemistry. This method is broadly applicable to various carboxylic acids and terminal alkynes, producing a range of biologically active trifluoromethyl enol carboxylic esters. The synthetic potential of this method is further demonstrated by the late-stage functionalization of a complex pharmaceutical compound dehydrocholic acid.

Quantitative Imaging of Lipid Synthesis and Lipolysis Dynamics in Caenorhabditis elegans by Stimulated Raman Scattering Microscopy.

Quantitative methods to precisely measure cellular states in vivo have become increasingly important and desirable in modern biology. Recently, stimulated Raman scattering (SRS) microscopy has emerged as a powerful tool to visualize small biological molecules tagged with alkyne (C≡C) or carbon-deuterium (C-D) bonds in the cell-silent region. In this study, we developed a technique based on SRS microscopy of vibrational tags for quantitative imaging of lipid synthesis and lipolysis in live animals. The technique aims to overcome the major limitations of conventional fluorescent staining and lipid extraction methods that do not provide the capability of in vivo quantitative analysis. Specifically, we used three bioorthogonal lipid molecules (the alkyne-tagged fatty acid 17-ODYA, deuterium-labeled saturated fatty acid PA-D31, and unsaturated fatty acid OA-D34) to investigate the metabolic dynamics of lipid droplets (LDs) in live Caenorhabditis elegans ( C. elegans). Using a hyperspectral SRS (hsSRS) microscope and subtraction method, the interfering non-Raman background was eliminated to improve the accuracy of lipid quantification. A linear relationship between SRS signals and fatty acid molar concentrations was accurately established. With this quantitative analysis tool, we imaged and determined the changes in concentration of the three fatty acids in LDs of fed or starved adult C. elegans. Using the hsSRS imaging mode, we also observed the desaturation of fatty acids in adult C. elegans via spectral analysis on the SRS signals from LDs. The results demonstrated the unique capability of hsSRS microscopy in quantitative analysis of lipid metabolism in vivo.

Fe,N-Codoped Graphdiyne Displaying Efficient Oxygen Reduction Reaction Activity.

On account of the high-cost of platinum, researchers are working to develop a new catalyst that is cheaper and has a catalytic effect equivalent to platinum. Herein, owing to the unique acetylenic bonds in graphdiyne, iron, nitrogen co-doped graphdiyne (Fe-N-GDY) is a promising nonprecious metal catalyst, which has been developed with just a small amount of iron precursor with the plan to substitute it for Pt-based catalysts. The as-synthesized Fe-N-GDY composited catalyst shows excellent catalytic performance with the onset potential of 0.94 V versus reversible hydrogen electrode and limited current density of 5.4 mA cm-2 . Moreover, it shows excellent resistance to methanol poisoning and stability in both acidic and alkaline electrolytes, which makes potentially applicable in the oxygen reduction reaction field.

Structural Elucidation and Cytotoxicity of a New 17-Membered Ring Lactone from Algerian Eryngium campestre.

The chemical composition of a hexanic extract of Eryngium campestre, obtained from its aerial parts, was investigated by GC-FID, GC/MS, HRMS, NMR and VCD analyses. The main compounds were germacrene D (23.6%), eudesma-4(15)-7-dien-1-β-ol (8.2%) and falcarindiol (9.4%), which are associated with a new uncommon and naturally found 17-membered ring lactone. This 17-membered ring features conjugated acetylenic bonds, named campestrolide (23.0%). The crude extract showed moderate antitrypanosomal (Trypanosoma brucei brucei), antileishmanial (Leishmania mexicana mexicana) and anticancer (cancerous macrophage-like murine cells) activities, and also displayed cytotoxicity, (human normal fibroblasts) in similar concentration ranges (IC50 = 3.0, 3.9, 4.0 and 4.4 µg/mL respectively). Likewise, campestrolide displayed low activity on all tested cells (IC50: 12.5–19.5 µM) except on Trypanosoma, on which it was very active and moderately selective (IC50 = 2.2 µM. SI= 8.9). In conclusion, the new compound that has been described, displaying a singular structure, possesses interesting antitrypanosomal activity that should be further investigated and improved.

Design, synthesis, ADME prediction and pharmacological evaluation of novel benzimidazole-1,2,3-triazole-sulfonamide hybrids as antimicrobial and antiproliferative agents

BackgroundNitrogen heterocyclic rings and sulfonamides have attracted attention of several researchers.ResultsA series of regioselective imidazole-based mono- and bis-1,4-disubstituted-1,2,3-triazole-sulfonamide conjugates 4a–f and 6a–f were designed and synthesized. The first step in the synthesis was a regioselective propargylation in the presence of the appropriate basic catalyst (Et3N and/or K2CO3) to afford the corresponding mono-2 and bis-propargylated imidazoles 5. Second, the ligation of the terminal C≡C bond of mono-2 and/or bis alkynes 5 to the azide building blocks of sulfa drugs 3a–f using optimized conditions for a Huisgen copper (I)-catalysed 1,3-dipolar cycloaddition reaction yielded targeted 1,2,3-triazole hybrids 4a–f and 6a–f. The newly synthesized compounds were screened for their in vitro antimicrobial and antiproliferative activities. Among the synthesized compounds, compound 6a emerged as the most potent antimicrobial agent with MIC values ranging between 32 and 64 µg/mL. All synthesized molecules were evaluated against three aggressive human cancer cell lines, PC-3, HepG2, and HEK293, and revealed sufficient antiproliferative activities with IC50 values in the micromolar range (55–106 μM). Furthermore, we conducted a receptor-based electrostatic analysis of their electronic, steric and hydrophobic properties, and the results were in good agreement with the experimental results. In silico ADMET prediction studies also supported the experimental biological results and indicated that all compounds are nonmutagenic and noncarcinogenic.ConclusionIn summary, we have successfully synthesized novel targeted benzimidazole-1,2,3-triazole-sulfonamide hybrids through 1,3-dipolar cycloaddition reactions between the mono- or bis-alkynes based on imidazole and the appropriate sulfonamide azide under the optimized Cu(I) click conditions. The structures of newly synthesized sulfonamide hybrids were confirmed by means of spectroscopic analysis. All newly synthesized compounds were evaluated for their antimicrobial and antiproliferative activities. Our results showed that the benzimidazole-1,2,3-triazole-sulfonamide hybrids inhibited microbial and fungal strains within MIC values from 32 to 64 μg/mL. The antiproliferative evaluation of the synthesized compounds showed sufficient antiproliferative activities with IC50 values in the micromolar range (55–106 μM). In conclusion, compound 6a has remarkable antimicrobial activity. Pharmacophore elucidation of the compounds was performed based on in silico ADMET evaluation of the tested compounds. Screening results of drug-likeness rules showed that all compounds follow the accepted rules, meet the criteria of drug-likeness and follow Lipinski’s rule of five. In addition, the toxicity results showed that all compounds are nonmutagenic and noncarcinogenic.

Plasmon Catalysis on Bimetallic Surface—Selective Hydrogenation of Alkynes to Alkanes or Alkenes

Utilization of plasmonics as a driving tool for chemical transformation triggering enables to achieve unprecedented results regarding photochemical conversion efficiency and chemical selectivity regulation. In this study, the bimetallic surface plasmon-polariton-supported grating is proposed as an effective background for plasmon-induced hydrogenation of alkynyl groups of absolute chemoselectivity. The periodical bimetallic structure consists of spatially modulated gold layers, covered with the nanometer-thick platinum layer. The alkyne bonds are covalently attached to the surface of the catalytic system through covalent grafting of the bimetallic surface with 4-ethynylbenzenediazonium tosylate, with triple bonds separated from the platinum layer by the benzene rings. The proposed bimetallic structure enables selective hydrogenation of alkyne bonds to alkenyl or alkyl moieties using cyclohexene as a hydrogen source. The selectivity of hydrogenation can be controlled by changing the structure parameters, for example, the thickness of the upper platinum layer.

Cyclohexenynone Precursors: Preparation via Oxidative Dearomatization Strategy and Reactivity

A unique approach toward the preparation of cyclohexenynone equivalents was successfully developed via oxidative dearomatization of aryne precursors, featuring multiple functionalities on the target rings. Upon activation, these in situ formed cyclohexenynone intermediates exhibit good to excellent reactivity with various trapping agents. Moreover, an unprecedented cascade was discovered with aryl allyl sulfoxides, revealing a deeper utilization of the alkyne bond by concomitantly introducing one nucleophile and two electrophiles.

Synthesis of a Dimeric Base-Stabilized Cobaltosilylene Complex for Catalytic C-H Bond Functionalization and C-C Bond Formation.

The synthesis of a dimeric base-stabilized cobaltosilylene complex and its catalytic reactions are described. Treatment of the amidinato silicon(I) dimer [LSi:]2 (1; L=PhC(NtBu)2 ) with CoBr2 in toluene for 10 days afforded the dimeric amidinato cobaltosilylene [(LSi)μ-{CoBr(LSiBr)}]2 (2), which is speculated to proceed via "LSiCoBr" and "LSiBr" intermediates in the reaction. Compound 2 is paramagnetic, with an effective magnetic moment of 2.8 μB. Its electronic structure was elucidated by single-crystal X-ray crystallography and DFT studies. It was capable of catalyzing C-H bond functionalization, in which a combination of 2, phosphine and MeMgI can regio- and stereoselectively promoted the addition of the C≡C triple bonds in alkynes to the ortho-C-H position in arylpyridines. In addition, compound 2 catalyzed Kumada-type coupling reactions between aryl chlorides and the Grignard reagent 2-mesitylmagnesium bromide.

Co(II)/Ag(I) Synergistically Catalyzed Monoinsertion Reaction of Isocyanide to Terminal Alkynes with H2O: Synthesis of Alkynamide Derivatives.

A Co(II)/Ag(I) synergistically catalyzed three-component reaction of isocyanide with terminal alkyne and water to afford alkynamide derivatives is reported. The insertion of monoisocyanide into the C-H bond of terminal alkynes is an efficient, straightforward, atom-economical route to alkynamides, which are useful synthons in organic synthesis. This synergistic process achieves the cleavage of a C-H bond and the construction of new C-C and C═O bonds under mild conditions through the reaction of Co(II)-activated isocyanides and a Ag(I)-complex-activated terminal alkyne. This reaction has broad substrate versatility and functional group tolerance.

Influence of Alkyne and Azide Substituents on the Choice of the Reaction Mechanism of the Cu+-Catalyzed Addition of Azides to Iodoalkynes.

The cycloaddition of azides to iodoalkynes is strongly enhanced by some Cu+-complexes. We have studied computationally six reaction pathways for the cycloaddition of 24 combinations of azide and iodoalkyne to identify the dominant pathways and the influence of reactant structure on the evolution of the reaction. Two pathways were found to be operating for distinct sets of reactants. In the first pathway, initial complexation of iodoalkyne by Cu+ is followed by the binding of the azide to the metal through its substituted nitrogen atom, followed by attack of the nonhalogenated alkyne carbon by the terminal nitrogen atom. This pathway is generally followed by aromatic or electron-deficient azides, unless the iodoalkyne bears an electron-withdrawing group. The second pathway is a single-step mechanism similar (apart from the alkyne bond weakening caused by complexation) to that observed in the absence of catalyst. Electron-deficient iodoalkynes and methyl azides strongly prefer this mechanism, regardless of the identity of the reaction partners. The catalytic gain obtained through the use of Cu+ depends only partially on its direct effect on the energy of the transition state (relative to that of the infinitely separated reactants) and may be lost if the iodoalkyne itself strongly interacts with the catalyst through the formation of too strong a π-complex.

Nonplanar Macrocycle Consisting of Four Pyridine and Phenol Units Connected with Acetylene Bonds Displaying Preferential Binding to Maltoside over Monosaccharides.

A nonplanar macrocycle consisting of four pyridine-acetylene-phenol units was developed as a host for saccharide guest molecules. The macrocycle was found to strongly associate with a lipophilic maltose derivative, with an association constant of 107 M-1, over monosaccharide derivatives, for which much smaller association constants were determined, ranging from 103 M-1 to 104 M-1. The macrocycle was found to adopt a boat-like conformation, encapsulating β-d-maltoside in a twisted manner through approximately seven intermolecular hydrogen bonds.

Organic transformations catalyzed by palladium nanoparticles on carbon nanomaterials

An efficient C–C bond coupling reactions (Suzuki–Miyaura and Glaser) catalyzed by PdO/GO nano-catalyst is presented. In addition, PdO/MWCNT nano-catalyst-mediated domino one-pot synthesis of 2-alkyl/2-aryl benzofurans has been accomplished from 2-iodophenols and terminal alkynes. The formation of benzofurans proceeds through intermolecular Sonogashira reaction followed by intramolecular nucleophilic addition of internal hydroxyl group onto the acetylenic bond. The catalyst PdO/GO has been reused successfully, with nearly no loss of activity up to 5 cycles. Synopsis: An efficient PdO/GO and PdO/MWCNT nanocatalysts have been developed for C–C coupling reactions like Suzuki and Glaser coupling reactions, multi-catalytic one-pot synthesis of 2-aryl, 2-alkyl benzofurans staring from 2-iodophenols and terminal alkynes. The protocol involves formation of benzofuran derivatives, i.e., Sonogashira reaction followed by 2-ethynyl phenol cyclization..

Difunctionalization of Cyclopropylanilines and Cyclobutylanilines

We have previously developed photoredox conditions for ring opening of cyclopropylanilines and cyclobutylanilines. Distonic radical cations are presumably the intermediates. Although commonly producing in gas phase such as in the ionization chamber of a mass spectrometer, in solution phase, the methods for generating them are quite limited. Bearing a spatially separated radical and cation within the same molecule, these species possess bimodal reactivities that are distinct from those of radicals, ions, or classical radical ions (the radical and the ion reside at the same atom). In the [3+2] annulation of cyclopropylanilines and the [4+2] annulation of cyclobutylanilines developed by us, only one pi bond of alkenes, alkynes, dienes, enynes, or diynes reacts with the radical and the cation moiety of the distonic radical cations sequentially to form a five-membered and six-membered carbocycle respectively. Therefore, the two reactions don’t maximize the distonic radical cations’ bimodal reactivity. We have recently focused on identifying a suitable nucleophile and a radical acceptor to orthogonally intercept the cation and the radical moiety, which allows us to capitalize the distonic radical cations’ bimodal reactivity fully. Herein, we report our efforts in harvesting the distonic radical cations' bimodal reactivity, which results in 1,3-difunctionalization of cyclopropylanilines and 1,4-difunctionalization of cyclobutylanilines.

Transition-Metal-Free Cleavage of C–C Triple Bonds in Aromatic Alkynes with S8 and Amides Leading to Aryl Thioamides

A novel transition-metal-free cleavage reaction of C-C triple bonds in aromatic alkynes with S8 and amides furnishes aryl thioamides in moderate to excellent yields. The remarkable features of this thioamidation include the metal-free cleavage of C-C triple bond, mild reaction conditions, as well as wide substrate scope that is particularly compatible with some internal aromatic alkynes and acetamides.

Carbon Atom Hybridization Matters: Ultrafast Humidity Response of Graphdiyne Oxides.

Graphdiyne oxide (GDO), the oxidized form of graphdiyne (GDY), exhibits an ultrafast humidity response with an unprecedented response speed (ca. 7 ms), which is three times faster than that of graphene oxide (GO) with the same thickness and O/C ratio. The ultrafast humidity response of GDO is considered to benefit from the unique carbon hybridization of GDO, which contains acetylenic bonds that are more electron-withdrawing than ethylenic bonds in GO, consequently giving rise to a faster binding rate with water. This distinctive structure-based property enables the fabrication of a novel GDO-based humidity sensor with an ultrafast response speed and good selectivity against other kinds of gas molecules as well as high sensitivity. These properties allow the sensor to accurately monitor the respiration rate change of human and hypoxic rats.

Carbon Atom Hybridization Matters: Ultrafast Humidity Response of Graphdiyne Oxides

AbstractGraphdiyne oxide (GDO), the oxidized form of graphdiyne (GDY), exhibits an ultrafast humidity response with an unprecedented response speed (ca. 7 ms), which is three times faster than that of graphene oxide (GO) with the same thickness and O/C ratio. The ultrafast humidity response of GDO is considered to benefit from the unique carbon hybridization of GDO, which contains acetylenic bonds that are more electron‐withdrawing than ethylenic bonds in GO, consequently giving rise to a faster binding rate with water. This distinctive structure‐based property enables the fabrication of a novel GDO‐based humidity sensor with an ultrafast response speed and good selectivity against other kinds of gas molecules as well as high sensitivity. These properties allow the sensor to accurately monitor the respiration rate change of human and hypoxic rats.

Silver-Catalyzed Stereoselective Cyclization to Polysubstituted ( Z)-1,2-Dihydrobenzo[ cd]indoles.

Silver-catalyzed stereoselective synthesis of polysubstituted ( Z)-1,2-dihydrobenzo[ cd]indoles from 8-ethynylnaphthalen-1-amines is reported. In this protocol, a series of nitrogen-containing heterocyclic compounds were synthesized by silver-catalyzed α-addition of an alkyne bond with high selectivity and high yields. The synthesized polysubstituted 1,2-dihydrobenzo[ cd]indoles could be easily converted to benzo[ cd]indol-2(1 H)-ones, and both 1,2-dihydrobenzo[ cd]indoles and benzo[ cd]indol- 2(1 H)-ones are biological and pharmaceutical cores.

Transformations of 5-(2-arylethynyl)-2-methyl-2H-tetrazoles under superelectrophilic activation

Reaction of 5-arylethynyl-2-methyl-2H-tetrazoles (acetylene tetrazoles) with arenes under the action of Brønsted superacid CF3SO3H or acidic zeolite HUSY CBV-720 gives rise to E-/Z-5-(2,2-diarylethenyl)-2-methyl-2H-tetrazoles, as products of hydroarylation of acetylene bond, in yields up to 98% with predominant formation of E-isomers. Cationic intermediates of these reactions have been studied theoretically by DFT calculations. Addition of CF3SO3H to the triple bond of acetylene tetrazoles leads to the corresponding E-/Z-vinyl triflates in high yields. Hydration of triple bond in these tetrazoles in H2SO4 results in the formation of 5-(2-aryl-2-oxoethyl)-2-methyl-2H-tetrazoles. Tandem hydroarylation-ionic hydrogenation of acetylene tetrazoles in the systems acid(CF3SO3H or AlCl3)-arene-cyclohexane affords 5-(2,2-diarylethyl)-2-methyl-2H-tetrazoles.