Disubstituted Alkynes Research Articles

ChemInform Abstract: Experimental and Mechanistic Exploration of Zn‐Catalyzed Sonogashira‐Type Cross‐Coupling Reactions.

One of the most straightforward methods for the synthesis of disubstituted alkynes is the transition metal catalyzed Sonogashira-type cross-coupling reactions. Herein we report a detailed study of our recent research on the first Zn-catalyzed protocol for C(sp2)–C(sp) cross-coupling reaction of aryl iodides with terminal alkynes. A wide range of functional groups were tolerated in the reaction and both functionally and structurally diverse diaryl acetylenes were prepared efficiently using this protocol. The reaction mechanism for the Zn-catalyzed Sonogashira-type coupling reaction was investigated by means of density functional theory (DFT) methods on a model system. The calculations were performed using hybrid Becke Perdew Functional (BPV86) in conjugation with LANL-2DZ basis set and found that the reaction pathway involves oxidative addition and reductive elimination mechanism.

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.

ChemInform Abstract: Decarboxylative/Sonogashira‐Type Cross‐Coupling Using PdCl2(Cy*Phine)2.

AbstractThe PCYP‐catalyzed decarboxylative cross‐coupling of chlorides (I), (IV), and (VIII) with 3‐substituted propiolic acids (II) gives rise to unsymmetrically disubstituted alkynes (III), (V), and (IX) in high yields.

ChemInform Abstract: Metal‐Free, Visible Light‐Photocatalyzed Synthesis of Benzo[b]phosphole Oxides: Synthetic and Mechanistic Investigations.

AbstractStarting from various arylphosphine oxides and symmetrically or unsymmetrically disubstituted alkynes the title synthesis has a broad substrate scope

Secretory organs: Implications for lipoid taxonomy and kerogen formation (seed ferns, Pennsylvanian, Canada)

Secretory organs likely evolved with land plants in Silurian-Devonian time, but it is questionable if they were passed on to living cycadaleans upon the extinction of seed ferns (Triassic-Jurassic?). They are defined as ducts of schizo-, lysig- or rhexigenous origin that exuded a heterogeneous lipoid mixture that fossilized as secretory products (droplets). In this study we detailed (1) the physical properties and distributions based on the compression-preserved Neuropteris ovata var. simonii and Laveineopteris rarinervis frond sections (Late Pennsylvanian Sydney Coalfield, Canada). Examined were also 1300 cuticular slides representing a number of plant groups, complemented by published data to infer biomass accumulation as potential kerogen in the geological column. In addition, (2) from select pinnules of the two species mentioned, nine secretory products and four surrounding cuticles were analyzed by micro-FTIR to evaluate statistically (PCA) the chemotaxonomic potential, and the kerogen chemistry. Further studies in support of (1) or (2) included methods of NICI, SEM, TEM and AFM, and by EDS.Results indicate that the secretory organs occurred in the entire N. ovata frond, its associate petiole and trunk, and in great abundance on the pinnules of both species in a random fashion. Secretory products show layering effects, surfaces can be intact, convoluted, folded, or damaged. At 100,000 magnification, microstructures are not observable. The exact chemical composition is unknown because of insolubility. IR spectra show peaks of functional groups frequently found in isocyanates, disubstituted alkynes, nitriles, polyynes, thiocyanates, and allenes, in part underpinned by EDS results. These compounds were presumably derived from the diagenetic alteration of resin-like terpenoid- or phenolic-related structures. That is particularly the case for the polyynes (i.e. ‘polyacetylenes’), synthesized by living plants with a variety of biological functions, including pigments and flavorings, toxins, and chemical repellents.The chemical information of the lipoid exudate, together with their morphological information and distribution will contribute to (i) the progress of chemotaxonomy and systematics of plant fossils, and (ii) a better understanding of the genesis of kerogens from plant-derived materials, particularly resinous remains.

Synthesis of (Imido)niobium(V)–Alkylidene Complexes That Exhibit High Catalytic Activities for Metathesis Polymerization of Cyclic Olefins and Internal Alkynes

The (imido)niobium(V)–alkylidene complexes Nb(CHSiMe3)(NR)[OC(CF3)3](PMe3)2 (R = 2,6-Me2C6H3, 2,6-iPr2C6H3, 1-adamantyl), which could be isolated from the dialkyl analogues by α-hydrogen elimination in the presence of PMe3, exhibited remarkable catalytic activities for ring-opening metathesis polymerization (ROMP) of norbornene, and the polymerizations proceeded in a living manner. Metathesis polymerizations of (unstrained) disubstituted acetylenes also took place, affording polymers with uniform (narrow) molecular weight distributions.

Experimental and Mechanistic Exploration of Zn‐Catalyzed Sonogashira–type Cross‐Coupling Reactions

AbstractOne of the most straightforward methods for the synthesis of disubstituted alkynes is the transition metal catalyzed Sonogashira‐type cross‐coupling reactions. Herein we report a detailed study of our recent research on the first Zn‐catalyzed protocol for C(sp2)–C(sp) cross‐coupling reaction of aryl iodides with terminal alkynes. A wide range of functional groups were tolerated in the reaction and both functionally and structurally diverse diaryl acetylenes were prepared efficiently using this protocol. The reaction mechanism for the Zn‐catalyzed Sonogashira‐type coupling reaction was investigated by means of density functional theory (DFT) methods on a model system. The calculations were performed using hybrid Becke Perdew Functional (BPV86) in conjugation with LANL‐2DZ basis set and found that the reaction pathway involves oxidative addition and reductive elimination mechanism.

Zirconium-mediated selective synthesis of 1,4-dialkyl(aryl)-hexa-substituted benzenes from two silyl-substituted alkynes and one internal alkyne

Based on the formation of 2,5-bis(trimethylsilyl)-zirconacyclopentadienes from two silylalkynes with Cp2ZrBu2 and the Cu-mediated formation of 1,4-disilylbenzene via the cycloaddition of zirconacyclopentadienes to disubstituted alkynes, a selective synthesis of 1,4-dialkyl(aryl)-hexa-substituted benzenes was achieved followed by iodination and coupling reaction. The coupling reactions were carried out with either organolithium reagent or organozinc reagent(Negishi coupling), depending on the electrophilic species.

ChemInform Abstract: Synthesis of Substituted Benzo[ij]imidazo[2,1,5‐de]quinolizine by Rhodium(III)‐Catalyzed Multiple C—H Activation and Annulations.

AbstractA novel method is elaborated for the preparation of benzo[ij]imidazo[2,1,5‐de]quinolizines (III) and (VII) by a Rh‐catalyzed cascade oxidative annulation of N‐arylimidazoles with two molecules of disubstituted alkynes.

ChemInform Abstract: Controlled Rh‐Catalyzed Mono‐ and Double‐Decarbonylation of Alkynyl α‐Diones to Form Conjugated Ynones and Disubstituted Alkynes.

A Rh-catalyzed controlled decarbonylation of alkynyl α-diones is described. By using different ligand and solvent combinations, mono- and double-decarbonylation can be selectively achieved to give conjugated ynones and disubstituted alkynes, respectively. A fundamental study on catalytic activation of unstrained C–C bonds under nonoxidative conditions is presented.

Application of Pd Nanoparticles Supported on Mesoporous Hollow Silica Nanospheres for the Efficient and Selective Semihydrogenation of Alkynes

AbstractHerein, the preparation of a heterogeneous catalyst consisting of 1–2 nm sized Pd nanoparticles supported on amino‐functionalized mesoporous hollow silica nanospheres and its use for the semihydrogenation of mono‐ and disubstituted alkynes is reported. By utilizing this Pd nanocatalyst together with the green poisoning agent DMSO, high yields of the desired alkenes could be achieved, while suppressing the degree of over‐reduction to alkanes. To our delight, the Pd nanocatalyst displayed remarkable chemoselectivity towards the alkyne moiety, allowing the transformation to be carried out in the presence of other reducible functionalities, such as halogens, carbonyl, and nitro groups.

ChemInform Abstract: A Sequential One‐Pot Approach to 1,2,4,5‐Tetrasubstituted‐2H‐imidazole Synthesis from Disubstituted Alkynes.

A sequential one-pot approach to the tetrasubstituted 2H-imidazole scaffolds has been developed from disubstituted alkynes and structurally diverse ketones. The reaction proceeds via a diketo intermediate generated from internal alkynes followed by the addition of ammonium acetate and a suitable ketone, affording a diverse range of 2H-imidazoles. Using air-moisture stable reaction conditions and inexpensive reagents, the transformation demonstrates a broad substrate scope and good functional group compatibility.

Ru(ii)-Catalyzed C-H activation and annulation of salicylaldehydes with monosubstituted and disubstituted alkynes.

The Ru(ii)-catalyzed C-H activation and annulation reaction of salicylaldehydes and disubstituted alkynes affords chromones in high yields. This reaction also works with terminal alkynes and tolerates a wide range of sensitive functional groups. The selectivity pattern of this Ru(ii)-catalyzed annulation reaction is different from the known Au(i), Rh(iii)-catalyzed annulation reactions of salicylaldehydes and terminal alkynes.

ChemInform Abstract: Rhodium(III)‐Catalyzed Oxidative Bicyclization of 4‐Arylbut‐3‐yn‐1‐amines with Internal Alkynes Through C—H Functionalization.

AbstractA new Rh‐catalyzed reaction of 4‐arylbut‐3‐yn‐1‐amines (I) with symmetrically 1,2‐disubstituted acetylenes (II) gives rise to cross‐bicyclization products (III), whilst the use of unsymmetrically disubstituted alkynes (IV) leads to a mixture of regioisomers (V) and (VI).

Synthesis of functionalized alkynes via palladium-catalyzed Sonogashira reactions

A highly efficient protocol for the copper and phosphine free Sonogashira cross-coupling reactions of aryl iodides with terminal alkynes under aerobic conditions has been developed. Using 1mol% of the palladium-bis(oxazoline) complex, Pd-BOX A, in the presence of KOH, and a CH3CN–H2O solvent system allowed for the cross-coupling reactions to proceed at room temperature or 60°C. This new catalytic system was found to be highly active for the cross-coupling reaction of aryl diiodo substrates with unactivated alkyl alkynes to produce various symmetrical dialkynes, as well as for the cross-coupling of terminal dialkynes with aryl iodides to generate symmetrical disubstituted internal alkynes.

Controlled Rh-Catalyzed Mono- and Double-decarbonylation of Alkynyl α-Diones To Form Conjugated Ynones and Disubstituted Alkynes.

A Rh-catalyzed controlled decarbonylation of alkynyl α-diones is described. By using different ligand and solvent combinations, mono- and double-decarbonylation can be selectively achieved to give conjugated ynones and disubstituted alkynes, respectively. A fundamental study on catalytic activation of unstrained C-C bonds under nonoxidative conditions is presented.

ChemInform Abstract: Ga(DS)3‐Catalyzed Double Hydroarylation of Acetylenic Esters with Indoles for the Synthesis of Bisindolyl Propanoates.

AbstractUsing disubstituted alkynes instead of terminal alkynes, the formation of the title bisindole derivatives is not observed.

Second hyperpolarizability of delta shaped disubstituted acetylene complexes of beryllium, magnesium, and calcium.

Present theoretical study involves the delta shape complexes of beryllium, magnesium, and calcium where the metal atom interacts perpendicularly with disubstituted acetylene. Most of the complexes are found to be fairly stable. The dependence of second-hyperpolarizability on the basis set with increasing polarization and diffuse functions has been examined which showed the importance of 'f-type' type polarization function for heavy metal (Mg, Ca) and 'd-type' polarization function for beryllium. Larger second hyperpolarizability has been predicted for complexes having significant ground state polarization and low lying excited states favoring strong electronic coupling. Transition energy plays the most significant role in modulating the second hyperpolarizability.

An efficient zinc-catalyzed cross-coupling reaction of aryl iodides with terminal aromatic alkynes

The first Zn-catalyzed protocol for C(sp2)–C(sp) cross-coupling reactions for the synthesis of disubstituted alkynes is described. A broad spectrum of functional groups is tolerated during the catalysis and successfully afforded a variety of diaryl substituted acetylenes.

Polymerization of a Disubstituted Acetylene Using Palladium Catalysts

Abstract Novel palladium complexes bearing a di-tert-butyl(4-substituted phenyl)phosphine ligand were synthesized and employed as catalysts for the polymerization of 1-chloro-2-(4-tert-butylphenyl)acetylene. Polymers were obtained as THF-soluble (weight-average molecular weights: 5100–59800) and insoluble parts, which were considered to be lower and higher molecular weight polyacetylenes. The catalytic activity increased as increasing the electron-withdrawing character of the substituent on the phosphine ligand.