Disubstituted Alkynes Research Articles

Rhodium(III)‐Catalyzed (5+2) Annulation Reaction for the Synthesis of Nitro and Cyano Substituted Benzo[b]Oxepines

AbstractA Rh(III)‐catalyzed annulation reaction of 2‐(2‐nitrovinyl)phenols and disubstituted alkynes is developed to complete the first synthesis of biologically important 4‐nitro substituted benzo[b]oxepines. The same reaction conditions are also applied for the efficient synthesis of 4‐cyano substituted benzo[b]oxepines which have high biological significance. Some of the synthesized 4‐nitrobenzo[b]oxepines are easily transformed to triazole fused dibenzo[b]oxepines.

SELECTIVE HYDROGENATION OF ISOPRENE, PIPERYLENE AND THEIR MIXTURES ON SKELETAL NICKEL CATALYSTS

Results of the hydrogenation process of isoprene and piperylene mixtures, as well as their mixtures on multicomponent skeletal nickel catalysts are reported in this article. Hydrogenation of piperylene and isoprene proceeds at a higher rate (W=215-220 cm3/min·g Ni) on Ni-Mo-Cu alloy catalyst than on skeletal nickel (W=112-115 cm3/min·g Ni). The results of chromatographic analysis indicate that the hydrogenation of piperylene proceeds with high selectivity. The selectivity coefficient Кs is 0.95 and 0.98 on skeletal nickel and Ni-Mo-Cu catalyst, respectively. At hydrogenation of the piperylene-isoprene mixture the piperylene conversion rate (P > J) is prevailed. At piperylene conversion degree P=50 % the isoprene J conversion is 35-37 % on Renea Nickel. 34 % on Ni-Mo-Cu catalyst. The selectivity degree of hydrogenation of this mixture is Sp-i = 0.34-0.36 on Renea Nickel, Sp-i = 0.40 on Ni-Mo-Cu. It was found that during hydrogenation of piperylene and isoprene mixtures on Ni-Al-Mo-Cu (42-50-3-5 %) catalysts the mono- and disubstituted acetylenes are saturated with a high degree of conversion compared with isoprene.

Palladium-Catalyzed Cross-Coupling of Aryl Bromides and Chlorides with Trimethylsilylalkynes under Mild Conditions.

Herein, we disclose a palladium-catalyzed cross-coupling of aryl bromides and chlorides with trimethylsilylalkynes under mild reaction conditions. This method utilizes commercially available and air stable palladium precatalysts and avoids the use of copper cocatalysts. Moreover, it allows for the synthesis of a wide range of disubstituted alkynes in high yields with excellent functional group tolerance. The utility of the developed method was further demonstrated via the late-stage alkynylation of pharmaceuticals and natural bioactive compounds.

Nickel-catalyzed regiodivergent syn-hydrosilylation of disubstituted alkynes

Nickel-catalyzed regiodivergent syn-hydrosilylation of disubstituted alkynes

Broad-Scope (3 + 2) Cycloaddition of Cyclopropanes and Alkynes Enabled by Boronyl Radical Catalysis.

Cyclopentene skeletons are ubiquitous in natural products and small molecule drugs. The (3 + 2) cycloaddition of cyclopropanes and alkynes represents an efficient and atom-economic strategy for synthesizing these structures. However, the types of substituents on cyclopropane and alkyne used in previous works show evident limitations, restricting the application of this type of reaction to some extent. Herein, we report a broad-scope (3 + 2) cycloaddition of cyclopropanes and alkynes catalyzed by boronyl radicals. In this method, various substrates, such as mono-, di-, tri-, and tetrasubstituted cyclopropanes, as well as mono- and disubstituted alkynes, were compatible with up to 98% isolated yield.

Influence of Phosphorus Modifier and Nature of the Support on the Properties of Palladium Catalysts in the Chemoselective Hydrogenation of Acetylenic Compounds

Efficient heterogeneous catalysts for the chemoselective hydrogenation of terminal and disubstituted alkynes and alkynols to monoenes based on Pd–P particles have been proposed. The influence of a zeolite support (Na-ZSM-5, MCM-41) and a phosphorus modifier on the properties of palladium catalysts in the semihydrogenation of acetylenic compounds is considered. It has been shown that promotion with phosphorus increases the activity of palladium catalysts in the hydrogenation of various acetylenic compounds from 2.5 to 30 times without reducing the selectivity for monoenes. High selectivity for monoenes is determined by both thermodynamic and kinetic factors. Using the example of the acetylenic alcohol hydrogenation the possibility of changing the ratio of hydrogenation rates of triple and double bonds as a result of varying the solvent nature and the structural order of the catalyst particles was demonstrated.

Cyclic polymers from alkynes: a review.

Cyclic polymers have applications across various fields, including material science, biomedicine, and inorganic chemistry. Cyclic polymers derived from alkyne monomers have expanded the application scope to include electronic materials and polyolefins. This review highlights recent advancements in the synthesis of cyclic polymers from both mono- and disubstituted alkynes. The aim is to provide a comprehensive overview of the synthetic methodologies and the application of cyclic polymers derived from alkynes. Additionally, this review will facilitate a comparative analysis of the advantages and limitations of various synthetic methods and describe opportunities for future development of novel catalytic systems to synthesize cyclic polymers from alkynes.

Tuning catalyst performance in asymmetric carbene transfer toward CF3-cyclopropenes

In this issue of Chem Catalysis, Zhang, Ma, Marek, et al. report a highly enantioselective carbene-transfer reaction of 2,2,2-trifluorodiazoethane (CF3CHN2) and challenging disubstituted alkynes. Key to the success of this approach is the fine-tuning of chiral dirhodium(II) carboxylate paddlewheel complexes featuring a molecule of dioxane as achiral axial ligand.

Dirhodium(II)-catalyzed enantioselective cyclopropenation of internal alkynes with trifluoromethyl carbene

Catalytic enantioselective reactions of trifluoromethyl carbene represent a powerful method for the construction of chiral trifluoromethyl-functionalized molecules, but the utilization of less reactive internal alkynes remains a persistent challenge in this domain. Herein, we report a chiral dirhodium(II) complex-catalyzed enantioselective cyclopropenation reaction of disubstituted alkynes by using 2,2,2-trifluorodiazoethane (CF3CHN2) as the trifluoromethyl carbene precursor. Achiral axial ligation by solvent molecules proves to be a key to improve the reactivity and control the stereoselectivity of metallocarbene species. This transformation provides efficient access to a wide range of enantioenriched trifluoromethyl group-substituted cyclopropenes, cyclopropanes, fused cyclopropane derivatives, and cyclopropyl boronate. The presented methodology constitutes a practical solution to a long-standing hurdle in catalytic enantioselective cyclopropenation of trifluoromethyl carbene with internal alkynes.

Reduction of disubstituted acetylenes under conditions of organotantalum and organoniobium synthesis

Reduction of disubstituted acetylenes under conditions of organotantalum and organoniobium synthesis

Development of Silicon Carbide-Supported Palladium Catalysts and Their Application as Semihydrogenation Catalysts for Alkynes under Batch- and Continuous-Flow Conditions

Silicon carbide (SiC)-supported palladium (Pd) catalysts [3% Pd/SiC and a 3% Pd-diethylenetriamine (DETA)/SiC complex] for chemoselective hydrogenation under batch- and continuous-flow conditions were developed. The alkyne, alkene, azide, nitro, and benzyloxycarbonyl-protected aromatic amine (N-Cbz) functionalities were chemoselectively reduced in the presence of 3% Pd/SiC. By contrast, benzyl ether, alkyl N-Cbz, epoxide, aromatic chloride, aromatic ketone, and tert-butyldimethylsilyl ether were tolerant to the 3% Pd/SiC-catalyzed hydrogenation. The combined use of 3% Pd/SiC and DETA demonstrated excellent chemoselectivity toward the semihydrogenation of various mono- and disubstituted alkynes under batch- and continuous-flow conditions. Furthermore, compared with the separate use of 3% Pd/SiC and DETA, the newly developed 3% Pd(DETA)/SiC-packed in a cartridge showed higher chemoselectivity toward the continuous-flow semihydrogenation of alkyne over 24 h.

Tantalum-catalyzed reaction of disubstituted acetylenes with EtAlCl2

Tantalum-catalyzed reaction of disubstituted acetylenes with EtAlCl2

Metal–Organic Framework Derived Cobalt Oxide Supported Bimetallic Pd/Cu Nanoparticles for Efficient Catalysis of the Sonogashira Reaction under Aerobic Conditions

AbstractA bimetallic Pd/Cu catalyst supported on a metal-organic-framework-derived cobalt oxide was prepared and characterized by SEM, EDS, XRD, XPS, and ICP-OES analyses. The catalyst promoted the Sonogashira reaction of aryl iodides with terminal alkynes at a low loading of the palladium (0.032 mol%) and copper species (0.012 mol%) to give the corresponding disubstituted alkynes in moderate to good yields. When the catalyst was recovered by using an external magnetic field, its catalytic activity decreased slightly in a second cycle.

Zinc (II) complex immobilized on the surface of magnetic nanoparticles modified with phenanthroline: A novel and efficient nanomagnetic reusable catalyst for cross-coupling reaction of aryl iodides with terminal aromatic alkynes

A novel and green nanomagnetic zinc catalyst were fabricated via the immobilization of zinc (II) complex on the surface of magnetic nanoparticles modified with phenanthroline (MNPs-Phen-Zn(II)). The structure of MNPs-Phen-Zn(II) nanomaterial was characterized by a series of spectroscopic techniques including FT-IR spectroscopy, SEM, TEM, EDX, XRD, VSM, and ICP-OES. The resulting zinc nanomagnetic catalyst was shown high catalytic activity for the synthesis of disubstituted alkynes via C(sp2)–C(sp) cross-coupling reactions of alkynes with aryl iodides under eco-friendly conditions. To the best of our knowledge, it is the first report on the utilization of zinc nanomagnetic catalyst for the Sonogashira type cross-coupling reaction of alkynes with aryl iodides in the absence of added Pd and Cu sources. The simple preparation of the catalyst from commercially available materials, excellent chemoselectivity, easy separation of products, and straightforward recovery and reusability of the catalyst with unaltered activity make our procedure a green and practical method.

Commercially available palladium salts as practical and green single-component catalysts in the coordination polymerization of 1-chloro-2-phenylacetylenes in air

Commercially available Pd salts serve as single-component catalysts for coordination polymerization of 1-chloro-2-phenylacetylenes, which affords a new design concept of metal catalysts for coordination polymerization of disubstituted alkynes.

Preparation of vincinal hetero 1,2-dihalo-olefins by using aqueous hydrohalic acid

An efficient simple method was developed to prepare hetero E-1,2-dihaloolefins from mono- or disubstituted alkynes, in which, NXS (X = Br, I) was utilized as the electrophilic reagents and aqueous hydrohalic acid as the nucleophile. Moreover, Z-type dihalogenation olefins could be obtained from the terminal silylacetylene.

Platinum-catalyzed reactions of 2,3-bis(dimethylsilyl)pyridine with mono- and di-substituted alkynes

The synthesis and platinum-catalyzed reactions of 2,3-bis(dimethylsilyl)pyridine (1) are described. The reaction of 1 with diphenylacetylene in the presence of a platinum catalyst gave the corresponding six-membered ring compound arising from dehydrogenative double silylation of the alkyne. Similar reactions of 1 with mono-substituted acetylenes such as tert-butylacetylene, 1-hexyne, and phenylacetylene proceeded to give regioisomers of cyclic products.

Bimetallic Ni/Cu mesoporous silica nanoparticles as an efficient and reusable catalyst for the Sonogashira cross-coupling reactions

A bimetallic mesoporous system (Ni/Cu-MCM-41) has been developed and evaluated as an efficient catalyst for the Sonogashira cross-coupling reaction, under palladium-free conditions. In this new methodology, a wide range of aryl halides react with phenylacetylene to give the corresponding disubstituted alkynes in good yields. Moreover, the present catalytic system is desired because of its high efficiency, easy preparation, low cost, high activity, and good recyclability.

Ruthenium-Catalyzed [2 + 2] versus Homo Diels-Alder [2 + 2 + 2] Cycloadditions of Norbornadiene and Disubstituted Alkynes: A DFT Study.

The ruthenium-catalyzed [2 + 2] and homo Diels–Alder [2 + 2 + 2] cycloadditions of norbornadiene with disubstituted alkynes are investigated using density functional theory (DFT). These DFT calculations provide a mechanistic explanation for observed reactivity trends with different functional groups. Alkynyl phosphonates and norbornadiene form the [2 + 2 + 2] cycloadduct, while other functionalized alkynes afford the respective [2 + 2] cycloadduct, in excellent agreement with experimental results. The computational studies on the potential energy profiles of the cycloadditions show that the rate-determining step for the [2 + 2] cycloaddition is the final reductive elimination step, but the overall rate for the [2 + 2 + 2] cycloaddition is controlled by the initial oxidative cyclization. Two distinct mechanistic pathways for the [2 + 2 + 2] cycloaddition, cationic and neutral, are characterized and reveal that Cp*RuCl(COD) energetically prefers the cationic pathway.

A molecular electron density theory study for [3 + 2] cycloaddition reactions of1‐pyrroline‐1‐oxide with disubstituted acetylenes leading to bicyclic 4‐isoxazolines

AbstractThe [3 + 2] cycloaddition (32CA) reactions of 1‐pyrroline‐1‐oxide with acetylene and with a series of four symmetrically disubstituted acetylenes (XC ≡ CX, X = CH3, NH2, OH, F), leading to 4,5‐disubstituted bicyclic 4‐isoxazolines, have been studied within molecular electron density theory at the B3LYP‐D3/6‐311++G(d,p) computational level. These 32CA reactions take place through aone‐stepmechanism, with activation enthalpies in toluene between 24.4 (X = NH2) and 12.9 (X = F) kcal mol−1. Due to the strong exergonic character of these 32CA reactions, between −12.0 and −47.6 kcal mol−1, they are irreversible. The 32CA reaction of difluoroacetylene, involving fluorine as the most electronegative atom of this series attached to the acetylene carbons, presents the lowest activation enthalpy due to the increase of the polar character of this 32CA reaction, evidenced by the analysis of the global electron density transfer at the corresponding transition state structure. The topological analysis of the electron localization function along the reaction paths of these 32CA reactions allows us to characterize them as the zwitterionic‐type ones. The formation of the new CC and CO single bonds takes place at the end of the reactions through the coupling ofpseudoradicalcenters.