Terminal Triple Bond Research Articles

Environmentally Friendly Synthesis and Self‐Catalytic Hydrolysis of Triazole‐Modified Organosilanes for Polysiloxane Production

AbstractOrganotrialkoxysilanes are unique compounds that play an important role in modern science and industry. Their structure determines their varied use both in production and academic research. The development of the synthesis of organotrialkoxysilanes and polymers based on them, taking into account environmental realities, is an important task. In our work, we present an original approach for the preparation of organotriethoxysilanes, starting from azidoalkyltriethoxysilanes and various types of substrates containing a terminal triple bond, by the azide‐alkyne cycloaddition (CuAAC) mechanism without the use of solvents, catalyst ligands, and amines. We also found the self‐catalyzing effect of the triazole fragment resulting from the azide‐alkyne cycloaddition in the reaction of hydrolysis and condensation of alkoxy groups, which made it possible to obtain a series of silsesquioxane products only by adding water, without the use of catalysts. As a result, a new, original scheme for the preparation of organosilicon organotrialkoxysilanes of a monomeric structure with their subsequent transformation into silsesquioxane polymers under “green” conditions is built.

Palladium Iodide Catalyzed Multicomponent Carbonylative Synthesis of 2-(4-Acylfuran-2-yl)acetamides.

2-Propargyl-1,3-dicarbonyl compounds have been carbonylated under oxidative conditions and with the catalysis of the PdI2/KI catalytic system to selectively afford previously unreported 2-(4-acylfuran-2-yl)acetamides in fair to good yields (54-81%) over 19 examples. The process takes place under relatively mild conditions and occurs via a mechanistic pathway involving Csp-H activation by oxidative monoamincarbonylation of the terminal triple bond of the substrates with formation of 2-ynamide intermediates, followed by 5-exo-dig O-cyclization (via intramolecular conjugate addition of the in situ formed enolate to the 2-ynamide moiety) and aromative isomerization.

Watson-Crick Base Pairs with Protecting Groups: The 2-Amino Groups of Purine- and 7-Deazapurine-2,6-Diamine as Target Sites for DNA Functionalization by Selective Nucleobase Acylation.

The recognition of Watson-Crick base pairs carrying nucleobase protecting groups is reported as a new approach for DNA functionalization. The 2-amino groups of purine- and 7-deazapurine-2,6-diamine 2'-deoxyribonucleosides served as molecular targets for this functionalization. The 2-amino group withstands oligonucleotide deprotection with ammonia, whereas all other protecting groups are released after chemical DNA synthesis. On this basis, a method was developed for the selective functionalization of oligonucleotides at the 2-position of purines and 7-deazapurines. Melting experiments and Tm values obtained from hybridization studies revealed that duplexes with protected (2-amino-dA) and (2-amino-7-deaza-dA)-dT base pairs are as stable as their nonprotected counterparts. Mismatch discrimination of protected purine- and 7-deazapurine-2,6-diamine DNA was superior to that of nonprotected DNA. Click functionalization in the minor groove of the DNA double helix became accessible via introduction of heptynoyl protecting groups bearing a terminal triple bond. Click reactions with pyrene azide validated the usability. DNA conjugates with bulky pyrene residues at the 2-position (minor groove) developed the same high stability as those functionalized at the 7-position (major groove). This demonstrates the potential of our new method using protected base pairs for DNA functionalization and paves the way for new DNA labeling strategies.

New calix[4]resorcinol rccc diastereoisomer with terminal triple bonds: Synthesis, structural features and reactions

One-pot acid-catalyzed cyclocondensation of 2-methyl-resorcinol with 4-(propargyloxy)benzaldehyde in CHCl3/CF3CO2H media affords all-cis (rccc) and/or cis-trans-trans (rctt) calix[4]resorcinol diastereomers bearing four terminal alkyne groups at aromatic substituents, the isomer ratio and yield being dependent on the CHCl3/CF3CO2H ratio. The rctt isomer (kinetic control product) can be converted to thermodynamically more stable rccc isomer at prolonged refluxing in CHCl3/CF3CO2H mixture. The rccc diastereomer was subjected to additional propargylation followed by the click reactions with benzylic azides to afford new highly triazolated calix[4]resorcinols.

Modulation of metal species as control point for Ni-catalyzed stereodivergent semihydrogenation of alkynes with water

A base-assisted metal species modulation mechanism enables Ni-catalyzed stereodivergent transfer semihydrogenation of alkynes with water, delivering both olefinic isomers smoothly using cheap and nontoxic catalysts and additives. Different from most precedents, in which E-alkenes derive from the isomerization of Z-alkene products, the isomers were formed in orthogonal catalytic pathways. Mechanistic studies suggest base as a key early element in modulation of the reaction pathways: by adding different bases, nickel species with disparate valence states could be accessed to initiate two catalytic cycles toward different stereoisomers. The practicability of the method is showcased with nearly 70 examples, including internal and terminal triple bonds, enynes and diynes, affording semi-hydrogenated products in high yields and selectivity.

Functionalized 10-Membered Aza- and Oxaenediynes through the Nicholas Reaction.

The scope and limitations of the Nicholas-type cyclization for the synthesis of 10-membered benzothiophene-fused heterocyclic enediynes with different functionalities were investigated. Although the Nicholas cyclization through oxygen could be carried out in the presence of an ester group, the final oxaenediyne was unstable under storage. Among the N-type Nicholas reactions, cyclization via an arenesulfonamide functional group followed by mild Co-deprotection was found to be the most promising, yielding 10-membered azaendiynes in high overall yields. By contrast, the Nicholas cyclization through the acylated nitrogen atom did not give the desired 10-membered cycle. It resulted in the formation of a pyrroline ring, whereas cyclization via an alkylated amino group resulted in a poor yield of the target 10-membered enediyne. The acylated 4-aminobenzenesulfonamide nucleophilic group was found to be the most convenient for the synthesis of functionalized 10-membered enediynes bearing a clickable function, such as a terminal triple bond. All the synthesized cyclic enediynes exhibited moderate activity against lung carcinoma NCI-H460 cells and had a minimal effect on lung epithelial-like WI-26 VA4 cells and are therefore promising compounds in the search for novel antitumor agents that can be converted into conjugates with tumor-targeting ligands.

Hybrid Pd-Nanoparticles within Polymeric Network in Selective Hydrogenation of Alkynols: Influence of Support Porosity.

This work is addressing the selective hydrogenation of alkynols over hybrid catalysts containing Pd-nanoparticles, within newly synthesized hyper-cross-linked polystyrenes (HPS). Alkynols containing C5, C10, and C20 with a terminal triple bond, which are structural analogues or direct semi-products of fragrant substances and fat-soluble vitamins, have been studied. Selective hydrogenation was carried out in a batch mode (ambient hydrogen pressure, at 90 °C, in toluene solvent), using hybrid Pd catalysts with low metal content (less than 0.2 wt.%). The microporous and mesoporous HPS were both synthesized and used as supports in order to address the influence of porosity. Synthesized catalysts were shown to be active and selective: in the case of C5, hydrogenation selectivity to the target product was more than 95%, at close to complete alkynol conversion. Mesoporous catalysts have shown some advantages in hydrogenation of long-chain alkynols.

Regio- and Stereoselective Synthesis of (Z,Z)-Bis(3-amino-3-oxo-1-propenyl) Selenides and Diselenides Based on 2-propynamides: A Novel Family of Diselenides with High Glutathione Peroxidase-like Activity

The efficient regio- and stereoselective syntheses of (Z,Z)-bis(3-amino-3-oxo-1-propenyl) selenides and diselenides in high yields based on the nucleophilic addition of sodium selenide to 2-propynamides and sodium diselenide to 3-(trimethylsilyl)-2-propynamides have been developed. The first examples of the addition of a selenium-centered nucleophile to 2-propynamides with a terminal triple bond and diselenide anion to 3-(trimethylsilyl)-2-propynamides have been carried out. Bis(3-amino-3-oxo-1-propenyl) diselenides are a novel family of compounds, none of which has yet been described in the literature. The glutathione peroxidase-like activity of the obtained compounds has been evaluated and products with high activity have been found. It was established that diselenides are superior to selenides with the same substituents in glutathione peroxidase-like activity. The results of the structural studying of products by single-crystal X-ray diffraction analysis and 77Se-NMR data are discussed.

Isoguanine (2-Hydroxyadenine) and 2-Aminoadenine Nucleosides with an 8-Aza-7-deazapurine Skeleton: Synthesis, Functionalization with Fluorescent and Clickable Side Chains, and Impact of 7-Substituents on Physical Properties.

7-Functionalized 8-aza-7-deaza-2'-deoxyisoguanine and 8-aza-7-deaza-2-aminoadenine 2'-deoxyribonucleosides decorated with fluorescent pyrene or benzofuran sensor tags or clickable side chains with terminal triple bonds were synthesized. 8-Aza-7-deaza-7-iodo-2-amino-2'-deoxyadenosine was used as the central intermediate and was accessible by an improved two-step glycosylation/amination protocol. Functionalization of position-7 was performed either on 8-aza-7-deaza-7-iodo-2-amino-2'-deoxyadenosine followed by selective deamination of the 2-amino group or on 7-iodinated 8-aza-7-deaza-2'-deoxyisoguanosine. Sonogashira and Suzuki-Miyaura cross-coupling reactions were employed for this purpose. Octadiynyl side chains were selected as linkers for click reactions with azido pyrenes. KTaut values calculated from H2O/dioxane mixtures revealed that side chains have a significant influence on the tautomeric equilibrium. Photophysical properties (fluorescence, solvatochromism, and quantum yields) of the new 8-aza-7-deazapurine nucleosides with fluorescent side chains were determined. Remarkably, a strong excimer fluorescence in H2O was observed for pyrene dye conjugates of 8-aza-7-deazaisoguanine and 2-aminoadenine nucleosides with a long linker. In other solvents including methanol, excimer fluorescence was negligible. The 2-aminoadenine and isoguanine nucleosides with the 8-aza-7-deazapurine skeleton expand the class of nucleosides applicable to fluorescence detection with respect to diagnostic and therapeutic purposes.

Cyclobenzoin Esters as Hosts for Thin Guests.

Cyclotetrabenzoin esters can host terminal triple bonds of alkynes and nitriles in their cavities, as revealed by cocrystal structures of four such complexes. Within cyclotetrabenzoin cavities, π-clouds of triple bonds establish favorable and virtually equidistant interactions with the four aromatic walls of the cyclotetrabenzoin skeleton. Binding is selective for aliphatic nitriles and terminal alkynes, with their aromatic counterparts residing outside of the cyclotetrabenzoin cavity.

One-Pot Synthesis of 2,5-Dihydrosiloles and Their Silole-Annulated Analogs Starting from Alkynylsilanes with a Terminal Alkynyl Group.

In contrast to the reaction of vinyl(alkynyl)silanes with 9-BBN-H, leading to the quantitative formation of 5-R-4-(9-BBN)-2,3-dihydro-1H-siloles, treatment of bis(alkynyl)silanes bearing one terminal alkynyl group with 2 equiv of 9-BBN-H followed by methanolysis afforded 5-R-4-(9-BBN)-2,5-dihydro-1H-siloles with yields of 85-90% (by NMR integration). The reaction proceeds via a double 1,2-hydroboration of the terminal triple bond with the formation of the geminal diborane followed by ring closure via intramolecular 1,1-carboboration of the remaining alkynyl fragment. Depending on the nature of the substituent R in position 5, the allylic BBN group locates in position 3 (R = Ph) or position 5 (R = SiHMe2, SiMe3) to give 2,3- or 2,5-dihydrosiloles, respectively. The protodeborylation of the allylic BBN group with MeOH of both 3,4-(9-BBN)2-2,3-dihydro- and 4,5-(9-BBN)2-2,5-dihydrosiloles results in the exclusive formation of 4-(9-BBN)-2,5-dihydrosiloles. In all cases, the formation of 10-12% of 2-R-2,4-(9-BBN)2-2,3-dihydrosilole minor isomers has been observed, which occurs from vicinal diboranes formed as side products by a second hydroboration of the terminal triple bond. Similarly, treatment of the tri- and tetraalkynes containing a terminal triple bond with 2 equiv of 9-BBN-H followed by treatment with methanol resulted in the high-yield formation of 1,2,6,6a-tetrahydro-1,6-disilapentalenes and 2,6,7,7a-tetrahydro-1,6,7-trisila-1H-cyclopenta[a]pentalenes, respectively.

Structure-activity relationship of avocadyne.

Avocado consumption is associated with numerous health benefits. Avocadyne is a terminally unsaturated, 17-carbon long acetogenin found almost exclusively in avocados with noted anti-leukemia and anti-viral properties. In this study, specific structural features such as the terminal triple bond, odd number of carbons, and stereochemistry are shown to be critical to its ability to suppress mitochondrial fatty acid oxidation and impart selective activity in vitro and in vivo. Together, this is the first study to conduct a structure-activity analysis on avocadyne and outline the chemical moieties critical to fatty acid oxidation suppression.

Copper-Catalyzed Anti-Markovnikov Hydrosilylation of Terminal Alkynes.

A copper-catalyzed anti-Markovnikov hydrosilylation of alkynes with PhSiH3 was reported. This reaction represents a notable and efficient example on copper-catalyzed hydrosilylatioin of alkynes, which shows excellent recognition between the terminal and internal triple bonds. Various (hetero)aromatic and aliphatic substituted terminal alkynes underwent this reaction to afford the (E)-vinylsilanes in high yields and with excellent regioselectivity.

Improvement of viscoelastic, elastic and plastic properties of Poly(L-lactide)/Graphene Oxide-Graft-Poly(L-lactide) nanocomposites by modulation of grafted chain length

The full potential of poly(L-lactide) (PLLA) reinforced with graphene oxide, GO, nanocomposites tends to be hindered by aggregation of the nanofillers. In order to promote a good dispersion of GO in the PLLA matrix, polymer grafting techniques have been explored to anchor PLLA onto functionalized GO surface to produce GO-PLLA hybrids. For this purpose, PLLA with a terminal triple bond was synthesized by ring-opening polymerization. By controlling the concentration of monomer to initiator, PLLA samples with three different chain lengths have been prepared and later coupled to azide-functionalized GO using click chemistry. These hybrids were then mixed with commercial PLLA and cast films have been prepared. The ensuing nanocomposite films were studied using Depth Sensing Indentation and the results have shown that PLLA matrix-filler interaction can be modulated by controlling the chain length of PLLA graft. This is a critical point because the enhancement of these interactions provides a stronger matrix-filler interphase which improves the stress transfer between both phases and increases the contribution of the interphase to the stiffening of the nanocomposites. Therefore, it has been proven that judicious functionalization of GO is an effective procedure for improving the strength, the stiffness and the creep resistance of the PLLA composites.

A multicomponent palladium-catalyzed carbonylative approach to imidazopyridinyl-N,N-dialkylacetamides

A novel, multicomponent approach to 2-(imidazo[1,2-a]pyridin-3-yl)-N,N-dialkylacetamides (very important class of fused heterocyclic derivatives, known to act on central nervous system by enhancing the activity of the GABA) is reported. It is based on the carbonylation reaction of N-Boc-(prop-2-yn-1-yl)pyridin-2-amines carried out in the presence of secondary amines (2–3 equiv) under oxidative conditions, using oxygen (from air) as oxidant (4:1 CO-air, total pressure 20 atm) and PdI2/KI as the catalytic system (0.33–1 mol% of PdI2 and 0.5 equiv of KI) in MeCN as the solvent at 100 °C. The process leads to the target compounds in good to high yields (67–90%) through an ordered sequence of steps, occurring in situ under the reaction conditions: Boc-deprotection of the substrate is followed by PdI2/KI-catalyzed oxidative monoaminocarbonylation of the terminal triple bond (or vice versa) to give a 2-ynamide intermediate, which then undergoes intramolecular aza-Michael reaction and isomerization.

Synthesis of One New Sugar Imine Molecule

In this research, the molecule Nand#39;-((E)-5-methoxy-2-((1-((2R,3R,4S,5S,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-2-yl)-4,5-dihydro-1H-1,2,3-triazol-4-yl)methoxy) benzylidene)-4-methyl-1,2,3-thiadiazole-5-carbohydrazide were synthesized and characterized by several conventional analysis methods. Its physical properties and thermal stability was studied. The synthesis was conducted based on D-glucose using concept of click chemistry reaction mechanism. Some of the reaction was conducted using microwave irradiation. The synthesis steps initiated by adding propargyl bromide to 2- hydroxy-5-methoxy benzaldehyde under vigorous measure of moister isolated environment to produce propargyl ether(5-methoxy-2-(prop-2-yn-1-yloxy)benzaldehyde) 3 in which has terminal triple bond. In parallel a glycocyl azide was prepared by applying glycocyl acetate (acetate for protection) via bromination and then substituted by treatment with sodium azide to produce glycocyl azide in which actively reacted with terminated triple bond by click reaction in the present of Cu(II) catalyst. The coupling reaction of terminal alkyle group in compound 3 with azide group of (2R,3R,4S,5R,6R)-2-(acetoxymethyl)-6-azidotetrahydro-2H-pyran-3,4,5-triyl triacetate) has given high yield of triazole. The produced triazole molecule is triazole(2R,3R,4S,5R,6R)-2-(acetoxymethyl)-6-(4-((2-formyl-4-methoxy)methyl)-1H-1,2,3-triazole-1-yl)tetrahydro-2H-pyran-3,4,5,-triyacetate) 7 undergoes further reaction to substitute carbonyl of the aromatic with hydrazide by applying 4-methyl-1,2,3-thiadiazole-5-carbohydrazide reagent. The glycocyl acetate was de-esterifide by sodium methoxide to remove the acetate protection. The structure of all these synthesized molecules was confirmed by FTIR, H1NMR, C13 NMR.

Synthesis of One New Sugar Imine Molecule

In this research, the molecule Nand#39;-((E)-5-methoxy-2-((1-((2R,3R,4S,5S,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-2-yl)-4,5-dihydro-1H-1,2,3-triazol-4-yl)methoxy) benzylidene)-4-methyl-1,2,3-thiadiazole-5-carbohydrazide were synthesized and characterized by several conventional analysis methods. Its physical properties and thermal stability was studied. The synthesis was conducted based on D-glucose using concept of click chemistry reaction mechanism. Some of the reaction was conducted using microwave irradiation. The synthesis steps initiated by adding propargyl bromide to 2- hydroxy-5-methoxy benzaldehyde under vigorous measure of moister isolated environment to produce propargyl ether(5-methoxy-2-(prop-2-yn-1-yloxy)benzaldehyde) 3 in which has terminal triple bond. In parallel a glycocyl azide was prepared by applying glycocyl acetate (acetate for protection) via bromination and then substituted by treatment with sodium azide to produce glycocyl azide in which actively reacted with terminated triple bond by click reaction in the present of Cu(II) catalyst. The coupling reaction of terminal alkyle group in compound 3 with azide group of (2R,3R,4S,5R,6R)-2-(acetoxymethyl)-6-azidotetrahydro-2H-pyran-3,4,5-triyl triacetate) has given high yield of triazole. The produced triazole molecule is triazole(2R,3R,4S,5R,6R)-2-(acetoxymethyl)-6-(4-((2-formyl-4-methoxy)methyl)-1H-1,2,3-triazole-1-yl)tetrahydro-2H-pyran-3,4,5,-triyacetate) 7 undergoes further reaction to substitute carbonyl of the aromatic with hydrazide by applying 4-methyl-1,2,3-thiadiazole-5-carbohydrazide reagent. The glycocyl acetate was de-esterifide by sodium methoxide to remove the acetate protection. The structure of all these synthesized molecules was confirmed by FTIR, H1NMR, C13 NMR.

Reactive molecular dynamics simulation of the amorphous carbon growth: Effect of the carbon triple bonds

The growth behavior of amorphous carbon (a-C) film was studied by reactive molecular dynamics simulation using the atom-by-atom deposition approach. Various reactive force field (ReaxFF) models were compared in terms of the structural properties of the resulting a-C films. By linking the structural properties of the film with the difference in the parameter sets of the ReaxFF models, we reveal that the carbon triple bond stabilization energy in the ReaxFF model, vtrip, significantly affects the growth dynamics and structural evolution of the simulated a-C films. When the negative vtrip value is too high, the generation of a large number of CC dimers and triple bond-terminated chain structures induces an etching-like process. In contrast, too small negative value results in an overestimation of both the formation energy for CC dimers and the bonding energy for terminal triple bonds. By ab initio calculation of the triple bond and comparing it with the molecular static calculation using the ReaxFF models, we tailored the vtrip value to −13.34 kcal/mole, and the simulated a-C film has an atomic structure comparable with the existing experimental and theoretical results.

Palladium-Catalyzed Cyclocarbonylation Approach to Thiadiazafluorenones: A Correction.

The palladium-catalyzed carbonylation of 2-(propynylthio)benzimidazoles bearing a terminal triple bond leads to 2-methyl-1-thia-4a,9-diazafluoren-4-ones instead of the previously reported 3-methyl isomers, as unequivocally established by XRD analysis of a representative product. A correction is therefore provided here in order to rectify the previous erroneous assignment of the position of the methyl group. Moreover, the process has been generalized to substrates bearing an internal triple bond, which lead to 3-alkyl-2-methyl-1-thia-4a,9-diazafluoren-4-ones, whose structure was confirmed by XRD analysis of two representative derivatives.

Mercuration of a Terminal Triple Bond of Substituted Azoles

Mercuration of a terminal triple bond in pirazoles and triazoles derivatives in the presence of acetylacetone followed by demercuration of intermediates by NaBH4 afforded heterocyclic oxoenol derivatives.