Carboxylation Of Alkynes Research Articles

Nickel-Catalyzed Atroposelective Carbo-Carboxylation of Alkynes with CO2: En Route to Axially Chiral Carboxylic Acids.

Precise synthesis of carboxylic acids via catalytic carboxylation with CO2 is highly appealing. Although considerable advancements have been achieved in difunctionalizing carboxylation of unsaturated hydrocarbons, the asymmetric variants are conspicuously underdeveloped, particularly in addressing axially chiral alkenes. Herein, we report the first catalytic atroposelective carboxylation of alkynes with CO2. A variety of valuable axially chiral carboxylic acids are obtained with good yields and high chemo-, regio-, E/Z and enantio-selectivities. Notably, an unexpected anti-selective carbo-carboxylation is observed in the sp2-hybrid carbo-electrophile-initiated reductive carboxylation of alkynes. Mechanistic studies including DFT calculation elucidate the origin of chiral induction and anti-selectivity in vinyl-carboxylation of alkynes.

Catalytic Behavior of NHC–Silver Complexes in the Carboxylation of Terminal Alkynes with CO2

A number of N-heterocyclic carbene–silver compounds (NHCs)AgX were tested in the direct carboxylation of terminal alkynes using carbon dioxide as the C1 carbon feedstock. The reactions proceed at a pressure of 1 atm of CO2 at room temperature, in the presence of Cs2CO3, and using silver–NHC complexes as catalysts. Thus, phenylacetylene and several alkynes are converted to the corresponding propiolic acids in good to high conversions. The activity of the catalysts is strongly influenced by the substituents on the NHC backbone and the nature of the counterion. Specifically, the most active compound exhibits iodide as the counterion and is stabilized by a benzimidazole derivative. After 24 h of reaction, a quantitative conversion is obtained utilizing DMF as the solvent and phenylacetylene as the substrate.

Unsupported Nanoporous Copper Catalyst for the Carboxylation of Terminal Alkynes with Carbon Dioxide

AbstractAn unsupported nanoporous copper catalyst (CuNPore) with highly bicontinuous nanostructure was prepared by a chemical dealloying method. Various characterization methods were used to investigate the structure and composition of CuNPore, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS). Active species of cuprous oxide were found on the surface of CuNPore catalyst. The nanoporous structure and the presence of Cu(I) enable CuNPore to catalyze the carboxylation reaction of terminal alkynes with CO2 under mild conditions. A wide range of terminal alkynes were tolerated to afford the alkynyl carboxylic acids in good to excellent yields. CuNPore catalyst can be easily recovered and recycled five times without any loss of activity.

Differential Activation of Alkynes between Capped and Naked Ag Nanoclusters Anchored by Highly-Open Mesoporous CeO2 for Two Coupling Reactions with CO2.

The cyclization of 3-hydroxy alkynes and the carboxylation of terminal alkynes both with CO2 are two attractive strategies to simultaneously reduce CO2 emission and produce value-added chemicals. Herein, the differential activation of alkynes over atomically precise Ag nanoclusters (NCs) supported on Metal-organic framework-derivedhighly-open mesoporous CeO2 (HM-CeO2) by reserving or removing their surface captopril ligands is reported. The ligand-capped Ag NCs possess electron-rich Ag atoms as efficient π-activation catalytic sites in cyclization reactions, while the naked Ag NCs possess partial positive-charged Ag atoms as perfect σ-activation catalytic sites in carboxylation reactions. Impressively, via coupling with HM-CeO2 featuring abundant basic sites and quick mass transfer, the ligand-capped Ag NCs afford 97.9% yield of 4,4-dimethyl-5-methylidene-1,3-dioxolan-2-one for the cyclization of 2-methyl-3-butyn-2-ol with CO2, which is 4.5 times that of the naked Ag NCs (21.7%), while the naked Ag NCs achieve 98.5% yield of n-butyl 2-alkynoate for the carboxylation of phenylacetylene with CO2, which is 15.6 times that of ligand-capped Ag NCs (6.3%). Density functional theory calculations reveal the ligand-capped Ag NCs can effectively activate alkynyl carbonate ions for the intramolecular ring closing in cyclization reaction, while the naked Ag NCs are highly affiliative in stabilizing terminal alkynyl anions for the insertion of CO2 in carboxylation reaction.

Gold(I)-Organic Frameworks as Catalysts for Carboxylation of Alkynes with CO2.

Construction of gold-based metal-organic frameworks (Au-MOFs) would bring the merits of gold chemistry into MOFs. However, it still remains challenging because gold cations are easily reduced to metallic gold under solvothermal conditions. Herein, we present the first example of Au-MOFs prepared from the networking of cyclic trinuclear gold(I) complexes by formal transimination reaction in a rapid (<15 min) and scalable (up to 1 g) fashion under ambient condition. The Au-MOFs feature uniform porosity, high crystallinity, and superior chemical stability toward base (i.e., 20 M NaOH). With open Au(I) sites in the skeleton, the Au-MOFs as heterogeneous catalysts delivered good performance and substrate tolerance for the carboxylation reactions of alkynes with CO2. This work demonstrates a facile approach to reticularly synthesize Au-MOFs by combining the coordination and dynamic covalent chemistry.

Catalytic Carboxylation of Terminal Alkynes with Copper(I) Azothioformamide Complexes

Redox-active azothioformamide (ATF) ligands produce coordination complexes with Cu(I) salts. A series of monosubstituted ligands were used to synthesize Cu(I) complexes and investigated for the catalytic insertion of carbon dioxide into terminal alkynes. The optimal catalytic conditions were found using phenylacetylene with 4 mol % of a halogen-bridged (μ-I)-para-substituted [(p-MeOATF-Cu(I)I)]2 dimer with 3 equiv of Cs2CO3 as the base in dimethyl sulfoxide under 1 atm of CO2 at 40 °C for 24 h, followed by treatment with HCl. A variety of aryl and alkyl substrates were evaluated giving yields from 47 to 99%. The reaction was computationally deconstructed, and a series of likely intermediates and associated energies are provided along with a proposed mechanism. Additionally, it was found that the conditions were suitable for one-pot esterification.

Photocatalytic reductive carboxylation of terminal alkynes with CO2 using heterostructured ZIF-7/BiOBr under visible-light illumination

Carboxylation of the organic compounds utilizing CO2 is a challenging task because of the higher thermodynamic stability and chemical inertness of the CO2 molecule. In the present study a straight protocol for the reductive carboxylation of terminal alkynes with CO2 has been developed, providing regioselective synthesis of α, β-unsaturated carboxylic acids using a heterostructured photocatalyst composed of Zn-benzimidazolate framework (ZIF-7) and BiOBr without any additional reducing agent at room temperature and atmospheric pressure conditions. The electron rich derivatives of phenyl acetylene substrates afforded α-acids; whereas, electron deficient substrates provided terminal acids. The DFT calculations indicated the type-II band alignment nature of ZIF-7/BiOBr in which electrons migrated from the ZIF to BiOBr and interacted with CO2 to generate CO2 radical anion at the conduction band of BiOBr.

Green carboxylation of CO2 triggered by well-dispersed silver nanoparticles immobilized by melamine-based porous organic polymers

CO2 fixation via directly formation of C-C bonds to obtain carboxylation compound is an essential reaction in industry. Creating efficient, inexpensive and industrially valuable key catalysts have always been a desire, but also an urgent challenge. Here, we synthesized a kind of melamine-based porous organic polymers (POPs) evenly loaded Ag Nanoparticles (Ag NPs/Melamine-based POPs) by the gas bubbling-assisted membrane reduction (GBMR) approach. The melamine-based POPs were used as good nitrogen-rich supports for loading and dispersing Ag nanoparticles. Ag NPs/ melamine-based POPs exhibited good CO2 absorption capacity (2.1 mmol/g, 273 K and 0.1 MPa) and the excellent activity was up to 93% towards the carboxylation of terminal alkynes with CO2 under mild reaction conditions (323 K, 0.1 MPa). And the TOF is 2.23 h−1. Specially, this is very few report of heterogeneously catalyzed directly formation of carboxylation compound only applying terminal alkynes with CO2 under low temperature and atmospheric pressure. The mechanistic study revealed that the well-dispersed Ag active species promoted highly efficient and green conversion of CO2. Moreover, the catalyst was easily recovered and could be reused at least six times with retention of high catalytic activity.

Novel and sustainable carboxylation of terminal alkynes and CO2 to alkynyl carboxylic acids using triazolium ionic liquid-modified PMO-supported transition metal acetylacetonate as effective cooperative catalysts.

Efficient and sustainable chemical fixation of CO2 into value-added chemicals is one of the most promising objectives in environmental chemistry. In this work, transition metal acetylacetonate immobilized onto triazolium ionic liquid-modified periodic mesoporous organosilica PMO-IL-M(x) was successfully prepared and investigated as an effective and heterogeneous catalyst in the direct carboxylation of terminal alkynes and CO2 to the desired alkynyl carboxylic acids. It was found that the catalyst PMO-IL-Sn(0.3) exhibited extraordinary catalytic performance in terms of excellent activity, stability, productivity, and excellent yields under mild reaction conditions. Moreover, the catalyst PMO-IL-Sn(0.3) could be easily recovered and reused at least six times without considerable loss in catalytic activity. This work provides a sustainable and efficient synergistic strategy for the chemical fixation of carbon dioxide into valuable alkynyl carboxylic acids.

Heterogeneous catalytic carboxylation of terminal alkynes with CO2 over a copper(II)-based metal-organic framework catalyst

Developing efficient, inexpensive and robust heterogeneous catalysts for CO2 conversion is greatly important. In this study, a new stable copper(II)-based metal-organic framework [Cu(Fbtx)2Br2]n (denoted as CZU-7, CCDC-2165700, Fbtx = 1,4-bis(1,2,4-triazole-1-ylmethyl)-2,3,5,6-tetrafluorobenzene) was synthesized via a facile and fast microwave heating method. CZU-7 exhibits a two-dimensional layer structure with the 44-sql topology. This material was demonstrated to be an efficient heterogeneous catalyst for the direct carboxylation of 1-ethynylbenzene with CO2, and various propiolic acids were synthesized in moderate to good yields under optimized reaction conditions. Moreover, the catalyst could be easily recovered and reused five times without significant loss of catalytic activity.

Carboxylation of terminal alkynes with CO2 catalyzed by imidazolium-bridged bis(phenolato) rare-earth metal complexes

An imidazolium-bridged bis(phenolato) yttrium complex shows excellent catalytic reactivity in the direct carboxylation of terminal alkynes and further one-pot three-component esterification.

Carboxylation of Alkenes and Alkynes Using CO2 as a Reagent: An Overview

: CO2 fixation reactions are of paramount interest both from economical and environmental perspectives. As an abundant, non-toxic, and renewable C1 feedstock, CO2 can be utilized for the synthesis of fuels and commodity chemicals under elevated reaction conditions. The major challenge in the CO2 utilization reactions is its chemical inertness due to high thermodynamic stability and kinetic barrier. The carboxylation of unsaturated hydrocarbons with CO2 is an important transformation as it forms high-value reaction products having industrial as well as medicinal importance. This mini-review is mainly focused on the recent developments in the homogeneously and heterogeneously catalyzed carboxylation of alkenes and alkynes by using carbon dioxide as a reagent. We have highlighted various types of carboxylation reactions of alkenes and alkynes involving different catalytic systems, which comprise mainly C-H bond activation, hydrocarboxylation, carbocarboxylation, heterocarboxylation, and ring-closing carboxylation, including visible-light assisted synthesis processes. The mechanistic pathways of these carboxylation reactions have been described. Moreover, challenges and future perspectives of these carboxylation reactions are discussed.

Photocatalytic Reductive Carboxylation of Terminal Alkynes with Co2 Using Heterostructured Zif-7/Biobr Under Visible-Light Illumination

Photocatalytic Reductive Carboxylation of Terminal Alkynes with Co2 Using Heterostructured Zif-7/Biobr Under Visible-Light Illumination

Covalent Organic Framework Catalysts for Carboxylation of Terminal Alkynes

Covalent Organic Framework Catalysts for Carboxylation of Terminal Alkynes

SiO2-Coated Ag Nanoparticles for Conversion of Terminal Alkynes to Propolic Acids via CO2 Insertion

Integration of adequate activity, stability, and productivity in a catalyst is of strategical importance to achieve high performance, particularly for inactive reactants, e.g., CO2. Here, using a reversed microemulsion method, ultrafine metallic Ag nanoparticles coated with porous SiO2 can be facilely obtained using micelles as separated nanoreactors for the preparation. Such architectures allowed the rigid SiO2 matrices to act as physical spacers, so that aggregation of the Ag particles could be avoided. Meanwhile, due to the templating effect from the surfactant, large mesopores could be induced in the SiO2 shell, and thus the diffusion barrier of reactants could be minimized. When used as a heterogeneous catalyst for carboxylation of terminal alkynes by CO2 under mild conditions, the prepared x[email protected]2 catalysts showed extraordinary performance in terms of excellent activity, stability, productivity, and wide substrate scope. The knowledge developed here may also enrich the toolbox for performance promotion of metal catalysts via specially fabricated structures.

Microwave‐assisted fabrication of a mixed‐ligand [Cu4(μ3‐OH)2]‐cluster‐based metal–organic framework with coordinatively unsaturated metal sites for carboxylation of terminal alkynes with carbon dioxide

The development of efficient and stable metal–organic framework (MOF) catalysts with coordinatively unsaturated metal sites for modern organic synthesis is greatly important. Herein, a robust [Cu4(μ3‐OH)2]‐cluster‐based MOF (Cu‐MOF) with a mixed‐ligand system was successfully fabricated by a microwave‐assisted method under mild conditions. The as‐prepared Cu‐MOF catalyst possessing unsaturated Cu (II) sites exhibited excellent catalytic activity toward the direct carboxylation of 1‐ethynylbenzene with CO2, and various propiolic acid derivatives were synthesized in moderate to good yields under optimized reaction conditions. Furthermore, the catalyst remained stable and could be easily recycled for five sequential runs without incredible decrease in catalytic efficiency.

An efficient Ag/MIL-100(Fe) catalyst for photothermal conversion of CO2 at ambient temperature

The conversion of CO2 under mild condition is of great importance because these reactions involving CO2 can not only produce value-added chemicals from abundant and inexpensive CO2 feedstock but also close the carbon cycle. However, the chemical inertness of CO2 requires the development of high-performance catalysts. Herein, Ag nanoparticles/MIL-100(Fe) composites were synthesized by simple impregnation-reduction method and employed as catalysts for the photothermal carboxylation of terminal alkynes with CO2. MIL-100(Fe) could stabilize Ag nanoparticles and prevent them from aggregation during catalytic process. Taking the advantages of photothermal effects and catalytic activities of both Ag nanoparticles and MIL-100(Fe), various aromatic alkynes could be converted to corresponding carboxylic acid products (86%–92% yields) with 1 atm CO2 at room temperature under visible light irradiation when using Ag nanoparticles/MIL-100(Fe) as photothermal catalysts. The catalysts also showed good recyclability with almost no loss of catalytic activity for three consecutive runs. More importantly, the catalytic performance of Ag nanoparticles/MIL-100(Fe) under visible light irradiation at room temperature was comparable to that upon heating, showing that the light source could replace conventional heating method to drive the reaction. This work provided a promising strategy of utilizing solar energy for achieving efficient CO2 conversion to value-added chemicals under mild condition.

Carbon-11 carboxylation of terminal alkynes with [11 C]CO2.

A copper-catalysed radiosynthesis of carbon-11 radiolabelled carboxylic acids was developed by reacting terminal alkynes and cyclotron-produced carbon-11 carbon dioxide ([11 C]CO2 ) in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). A small library of 11 C-labelled propiolic acid derivatives were obtained with a total synthesis time of 15 min from end of bombardment (EOB) with a (non-isolated) radiochemical yield ranging from 7% to 28%.

Schiff-base molecules and COFs as metal-free catalysts or silver supports for carboxylation of alkynes with CO2

Triformylphloroglucinol-derived imine molecules and COFs act as transition-metal-free catalysts for the title reaction, and COFs are also composited with Ag nanoparticles to afford higher activity.

Organocatalytic Strategy for the Fixation of CO2 via Carboxylation of Terminal Alkynes.

An organocatalytic strategy for the direct carboxylation of terminal alkynes with CO2 has been developed. The combined use of a bifunctional organocatalyst and Cs2CO3 resulted in a robust catalytic system for the preparation of a range of propiolic acid derivatives in high yields with broad substrate scope using CO2 at atmospheric pressure under mild temperatures (60 °C). This work has demonstrated that this organocatalytic method offers a competitive alternative to metal catalysis for the carboxylation of terminal alkynes and CO2. In addition, this protocol was suitable for the three-component carboxylation of terminal alkynes, alkyl halides, and CO2.