Homocoupling Of Terminal Alkynes Research Articles

Engineering Cu2O/Cu/N-C interface to induce directional migration of charge for driving photocatalytic homo-coupling of terminal alkynes

Engineering Cu2O/Cu/N-C interface to induce directional migration of charge for driving photocatalytic homo-coupling of terminal alkynes

Rhodium-catalysed homo-coupling of terminal alkynes: divergent synthesis of bioactive 1,3-diynes and conjugated enediynes

C(sp)–C(sp) cross-coupling of terminal alkynes represents a robust tool for building biologically active 1,3-diynes although confronted with huge challenges regarding selectivity control.

Synergistic catalysis by Brønsted acid and Pd species on a mesoporous ZSM-5 zeolite for the oxidative homocoupling of terminal alkynes

The Brønsted acid and Pd species on Pd@MZSM-5 synergetically catalyzed the oxidative homocoupling of terminal alkynes, where the Brønsted acid promote the alkyne chemisorption and benefit the formation of the alkynyl-palladium(ii) complex.

Synthetic Access to 1,3-Butadiynes via Electro-redox Cuprous-Catalyzed Dehydrogenative Csp–Csp Homocoupling of Terminal Acetylenes

AbstractHerein, we disclose the oxidative homocoupling of terminal alkynes under electrochemically generated cuprous catalysis. The scope of this protocol was established by preparing an array of structurally and electronically different 1,3-butadiyne derivatives. Good synthetic yields, functional group tolerance, oxidant-free conditions, and no cross-selectivity are some of the intrinsic advantages of this methodology. The developed chemistry features the electro-redox formation of copper acetylide, an intermediate appropriate for the Csp–Csp coupling step. The chemical state of copper in the acetylide intermediate was found to be Cu(I), as confirmed by click trapping experiments, cyclic voltammetry, EPR spectroscopy, and XPS. A competition reaction to determine the reactivity of electronically dissimilar acetylenes revealed that the product ratio is rather dependent on the electronic nature of the alkynyl substituents. To highlight the synthetic value of the products, selected diynes were subjected to chemical diversification.

Oxidation coupling of terminal alkynes over CuPd bimetallic alloy enhanced by optimized charge transfer and alloy structure

Homocoupling of terminal alkynes is an effective approach for the synthesis of 1,3-diyne, which is an important building block for numerous fine chemicals and pharmaceuticals. However, this reaction frequently encounters difficulties in catalyst recovery, and requires the addition of base or organic ligands, limiting their practical applications. Herein, we developed an efficient and recyclable CuPd bimetallic nanoalloy catalyst, which exhibited superior activity and selectivity in the homocoupling of terminal alkynes under mild conditions without any additives. In contrast to the low activity of monometallic Cu or Pd catalysts, a full conversion with a 100% selectivity for 1,3-diyne was achieved on bimetallic Cu2Pd1-400 nanoalloy with an extremely high activity. The comprehensive characterizations clearly evidenced that the alloying Cu with Pd was found to perturb the Cu electronic structure, and the positively charged Cu on the step and edge sites of CuPd nanoalloy catalyzed the homocoupling reaction via Cu-acetylide intermediates, and the density functional theory calculations revealed that the desorption of 1,3-diyne on CuPd nanoalloy was the rate-determining step for the whole reaction. This work provides a viable strategy for the rational design and fabrication of other nanoalloy catalysts for the green synthesis related to terminal alkyne oxidation.

Structural and Synthetic Insights on Oxidative Homocouplings of Alkynes Mediated by Alkali-Metal Manganates.

Exploiting bimetallic cooperation alkali-metal manganate (II) complexes can efficiently promote oxidative homocoupling of terminal alkynes furnishing an array of conjugated 1,3-diynes. The influence of the alkali-metal on these C-C bond forming processes has been studied by preparing and structurally characterizing the alkali-metal tetra(alkyl) manganates [(TMEDA)2 Na2 Mn(CH2 SiMe3 )4 ] and [(PMDETA)2 K2 Mn(CH2 SiMe3 )4 ]. Reactivity studies using phenylacetylene as a model substrate have revealed that for the homocoupling to take place initial metalation of the alkyne is required. In this regard, the lack of basicity of neutral Mn(CH2 SiMe3 )2 precludes the formation of the diyne. Contrastingly, the tetra(alkyl) alkali-metal manganates behave as polybasic reagents, being able to easily deprotonate phenylacetylene yielding [{(THF)4 Na2 Mn(C≡CPh)4 }∞ ] and [(THF)4 Li2 Mn(C≡CPh)4 ]. Controlled exposure of [{(THF)4 Na2 Mn(C≡CPh)4 }∞ ] and [(THF)4 Li2 Mn(C≡CPh)4 ] to dry air confirmed their intermediary in formation of 1,4-diphenyl-1,3-butadiyne in excellent yields. While the Na/Mn(II) partnership proved to be the most efficient in stoichiometric transformations, under catalytic regimes, the combination of MC≡CAr (M= Li, Na) and MnCl2 (6 mol %) only works for lithium, most likely due to the degradation of alkynylsodiums under the aerobic reaction conditions.

Deep Eutectic Solvent‐Mediated Oxidative Homocoupling of Terminal Alkynes to 1,3‐Diynes under Mild Green Conditions

AbstractWe prepared a commercially viable Deep Eutectic Solvent (DES) based on Choline Chloride‐Urea‐copper acetate for the first time. It mediates the homocoupling of terminal alkynes, using air as an oxidant. Water is the only by‐product of the entire process. The method avoids ligands, bases, oxidants, and costly palladium catalysts, which qualifies the process greener than ever. The DES can be reused at least three times without affecting the reaction yield significantly. The key features of the protocol that qualify the process as green include the ambient reaction temperatures, lesser use of conventional organic solvents in the reaction, higher yields, and easy product isolation qualify the protocol as a green process.

Green carbon-carbon homocoupling of terminal alkynes by a silica supported Cu(II)-hydrazone coordination compound.

A Cu(II) complex, [Cu(HL)(NO3)(CH3OH)]·CH3OH (1), was obtained by the reaction of Cu(NO3)2·3H2O and H2L in methanol solvent (H2L is (E)-4-amino-N'-(2-hydroxy-3-methoxybenzylidene)benzohydrazide). H2L and compound 1 were characterized by various spectroscopic analyses and the molecular structure of [Cu(HL)(NO3)(CH3OH)]·CH3OH was determined by single-crystal X-ray analysis. The results indicated the product is a mononuclear Cu(II) complex and contains a free NH2 functional group on the structure of the ligand. [Cu(HL)(NO3)(CH3OH)]·CH3OH was used for the preparation of a heterogeneous catalyst by supporting it on functionalized silica gel. The heterogeneous catalyst (Si-Cu) was prepared by an amidification reaction of [Cu(HL)(NO3)(CH3OH)]·CH3OH with functionalized silica gel. The resulting silica-supported catalyst (Si-Cu) was characterized by TGA, FT-IR, EPR, DRS, EDS, XRD, SEM and XPS analyses. Si-Cu was employed in a carbon-carbon coupling reaction and the effects of the amount of Si-Cu and temperature were investigated in the catalytic coupling. The structure of one of the products of the catalytic reactions (C16H22O2, CP1) was determined by single-crystal X-ray analysis, which proved the formation of a C-C bond and the production of di-acetylene by homocoupling of terminal alkyne. This catalytic system is stable and it can be reused for a coupling reaction without a significant change in its catalytic activity.

A synergistic {Cu2-W12O40} catalyst with high conversion for homo-coupling of terminal alkynes

The 2D {[Cu2(OAc)4]2(W12O40)}n network with unique Cu-POM synergistic cooperation to lead alkyne C–H activation is a super efficient catalyst with high conversion in homo-coupling of terminal alkynes.

Facile Synthesis of the Shape‐Persistent 4‐Hydroxybenzaldehyde Based Macrocycles and Exploration of their Key Electronic Properties: An Experimental and DFT Approach

AbstractIn the current study, a series of stabilized bis‐acetylene incorporated 4‐hydroxybenzaldehyde based macrocycles using the alkyne‐homocoupling approach were synthesized in moderate yields. A total of six newly stiff macrocycles were synthesized in a stepwise manner starting from 4‐hydroxybenzaldehyde. In the first step, base mediated propargylation was performed followed by copper mediated terminal alkyne homocoupling. The alkyne homocoupled substrate having carbonyl at both the terminals is cyclized in the final step via double imine formation reactions using substituted diamines as linker. All the newly synthesized rigid framework of the macrocycles were optimized at B3LYP/6‐31G (d,p) level of theory. Nonlinear optical behaviors of the synthesized macrocycles were explored by the DFT calculations where high values of first‐order hyperpolarizability and dipole moment were examined. In the reported study, a good agreement between experimental and theoretical parameters was observed that may play a significant contribution for the NLO applications.

Cobalt-Catalyzed Glaser-type Homocoupling Reaction

AbstractA highly efficient cobalt-catalyzed homocoupling of terminal alkynes with di-tert-butyldiaziridinone as the oxidant has been developed. The protocol tolerates a wide array of terminal alkynes, both activated and unactivated alkynes, to afford the corresponding conjugated 1,3-diynes. The mild reaction conditions further allow late-stage homocoupling of alkynes derived from complex natural products.

Homocoupling of terminal alkynes catalyzed by CuCl under solvent-free conditions

A series of symmetrical 1,4-disubstituted buta-1,3-diynes is prepared with excellent yields (up to 95%) through homocoupling of terminal alkynes catalyzed by a copper salt under solvent-free conditions. This method provides an environmentally friendly process to prepare 1,3-diynes in short reaction times under mild conditions. Furthermore, the method is suitable for a wide substrate scope and has excellent functional group compatibility. The reaction can also be scaled up to gram level.

Cu Catalyst Supported on Nitrogen and Phosphorus Co-Doped Carbon Nanosheets for Homocoupling of Terminal Alkynes Using CO2 as a Soft Oxidant

A bifunctional role of carbon dioxide (CO2) was developed in this research as a medium for catalyst preparation and as a soft oxidant for the subsequent coupling reaction. A highly dispersed and lo...

Supporting a Cu@In2O3 core–shell structure on N-doped graphitic carbon cuboctahedral cages for efficient photocatalytic homo-coupling of terminal alkynes

N-doped carbon cuboctahedral cage-supported core–shell Cu@In2O3 nanocomposites exhibit highly enhanced photocatalytic performances towards the home-coupling of terminal alkynes.

Tribromoisocyanuric acid as a useful oxidant for the synthesis of 1,3-diynes via Glaser coupling

A simple method has been developed for homocoupling of terminal alkynes bearing different functional groups by reaction with CuI/tribromoisocyanuric acid/piperidine in acetonitrile at room temperature. A telescoped approach based on Hunsdiecker/Cadiot–Chodkiewicz reactions for C(sp)-C(sp) cross-coupling was also presented.

Collision-Induced Reductive Elimination of 1,3-Diynes from [MAu24(C≡CR)18]2– (M = Pd, Pt) Yielding Clusters of Superatoms

We studied collision-induced dissociation (CID) processes of alkynyl-protected alloy clusters [MAu24(C≡CR)18]2– (M = Pd, Pt; R = 3,5-(CF3)2C6H3) having an icosahedral M@Au12(8e) superatomic core using mass spectrometry and density functional theory (DFT) calculations. [MAu24(C≡CR)18]2– underwent CID into [MAu24(C≡CR)18–2n]2– (n = 1–6) by sequential desorption of 1,3-diynes (RC≡C–C≡CR). Notably, the number of the valence electrons of the fragments increased by 2 upon every reductive elimination of a single 1,3-diyne. DFT calculations on the [MAu24(C≡CR)16]2– fragment revealed that the increased two electrons are not accommodated into a 1D superatomic orbital, but are localized at the Au2(C≡CR)1 site newly formed on the M@Au12(8e) core from the original Au2(C≡CR)3 unit by the desorption of 1,3-diyne. This desorption step continued to n = 6, leading to the formation of M@Au12[Au2(C≡CR)1]6. Thus, the [MAu24(C≡CR)18–2n]2– fragments can be viewed as clusters of the M@Au12(8e) superatomic core and n units of Au(2e) in terms of the electronic structure. The average number of 1,3-diynes eliminated from the precursor with M = Pd was larger than that from M = Pt, suggesting that Pd doping may facilitate the reductive elimination step of the homocoupling of terminal alkynes by Au cluster catalysts. These results illustrate that the CID is not only a useful probe for elementary steps for catalysis but also a tool for synthesizing novel superatomic compounds.

Chemoselective On-surface Homocoupling of Terminal Alkynes Catalyzed by Exogenous Cupric Ions.

The on-surface coupling reactions of terminal alkynes catalyzed by exogenous cupric ions on chemically inert highly oriented pyrolytic graphite (HOPG) surface have been investigated by scanning tunnelling microscopy. In the presence of exogenous cupric ions, diyne-linked nanostructures generated via homocoupling of terminal alkynes are the exclusive products, whereas no coupling reaction occurs for the terminal alkynes on the surface in the absence of the cupric ions, suggesting that exogenous cupric ions are efficient to catalyze the highly chemoselective on-surface reaction of terminal alkynes. The HOPG surface displays a template effect to the growth and alignment of the products on the surface. As a result, 2D arrays of diyne-linked zigzag polymers and 2D diyne-linked porous polymers are fabricated from ditopic monomer 3,6-diethynylcarbazole and tritopic monomer 1,3,5-tris-(4-ethynylphenyl) benzene, respectively. This synthetic strategy combining the high selectivity of cupric ion catalyst as well as the template effect of on-surface synthesis approach could be a general strategy to fabricate diyne-linked nanostructures and nanomaterials on solid surfaces.

Copper-catalyzed enantioselective Sonogashira-type oxidative cross-coupling of unactivated C(sp3)\u2212H bonds with alkynes

Transition metal-catalyzed enantioselective Sonogashira-type oxidative C(sp3)—C(sp) coupling of unactivated C(sp3)−H bonds with terminal alkynes has remained a prominent challenge. The difficulties mainly stem from the regiocontrol in unactivated C(sp3)—H bond functionalization and the inhibition of readily occurring Glaser homocoupling of terminal alkynes. Here, we report a copper/chiral cinchona alkaloid-based N,N,P-ligand catalyst for asymmetric oxidative cross-coupling of unactivated C(sp3)—H bonds with terminal alkynes in a highly regio-, chemo-, and enantioselective manner. The use of N-fluoroamide as a mild oxidant is essential to site-selectively generate alkyl radical species while efficiently avoiding Glaser homocoupling. This reaction accommodates a range of (hetero)aryl and alkyl alkynes; (hetero)benzylic and propargylic C(sp3)−H bonds are all applicable. This process allows expedient access to chiral alkynyl amides/aldehydes. More importantly, it also provides a versatile tool for the construction of chiral C(sp3)—C(sp), C(sp3)—C(sp2), and C(sp3)—C(sp3) bonds when allied with follow-up transformations.

CuI/AgI‐Promoted Decarboxylative Alkynylation of ortho‐Nitro Benzoic Acids

AbstractWe report herein, a novel copper‐silver‐promoted alkynylation of ortho‐nitrobenzoic acids with arylacetylenic acids through a double decarboxylation. The present cross‐coupling is extremely challanging due to sluggish decarboxylation of arene carboxylates and deleterious oxidative Glaser‐Hay type homocoupling of terminal alkynes. Mechanistically, this sp2‐sp cross‐coupling may proceed through a silver‐assisted decarboxylation of 2‐nitrobenzoic acids followed by transmetalation with copper‐acetylide and reductive elimination. The ortho‐nitroacetylenic product is an important precursor for the synthesis of functionalized indoles.

Synergistic effect of bimetallic PdAu nanocrystals on oxidative alkyne homocoupling

Bimetallic PdAu nanocrystals with different component ratios were obtained to investigate alkyne homocoupling. We found that the synergistic effect of Pd and Au plays an important role in the reaction. Alkynes with a variety of substituent groups could efficiently be converted into the corresponding 1,3-diynes through oxidative coupling.