Alkynyl Carboxylic Acids Research Articles

Copper‐Mediated Decarboxylative Trifluoromethylselenolation of Alkynyl Carboxylic Acids with [Me4N][SeCF3

AbstractThe synthesis of alkynyl trifluoromethyl selenoethers from copper‐mediated aerobic decarboxylative trifluoromethylselenolation of alkynyl carboxylic acids with [Me4N][SeCF3] is reported. The reaction proceeded smoothly under mild conditions and enabled the facile conversion of both aryl and alkyl alkynyl carboxylic acids to the corresponding trifluoromethyl selenoethers in good yields, demonstrating that decarboxylative trifluoromethylselenolation of alkynyl carboxylic acids with the nucleophilic [Me4N][SeCF3] reagent is feasible at ambient temperature without irradiation. Advantages of the method include the use of bench‐stable and non‐volatile alkynyl carboxylic acids as starting materials, readily accessible SeCF3 reagent, excellent functional group tolerance, and the avoidance of harsh reaction conditions. This copper‐mediated reaction represents the first decarboxylative trifluoromethylselenolation of alkynyl carboxylic acids with a SeCF3 source.

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.

Silver‐Catalyzed Decarboxylative Radical Cyclizations: Developments and Insights

AbstractTransition‐metal‐catalyzed decarboxylative cross‐coupling reaction provides a powerful method for the construction C−C, C−N, C−O bonds, which have great impact on synthetic chemistry. The use of silver salts as catalyst in decarboxylative reaction gradually increases because of their easy availability, low toxicity, biocompatibility and adequate stability. In fact, various radical cyclization reactions have been accomplished by exploiting single electron transfer (SET) ability of silver salts. The present review highlights recent advances (2015‐mid 2023) in the silver‐catalyzed decarboxylative radical cyclizations for the construction of cyclic molecular scaffolds. The content of the review is organized on the basis of decarboxylative reagents, such as, α‐keto acids, aliphatic/aromatic carboxylic acids, α,α‐difluoroacetic acids, amino acids, alkynyl carboxylic acids, oxamic acids and miscellaneous acids. Additionally, mechanistic insights of most of the reactions are highlighted for well understanding of the reaction mode.

Pyrene-Based Nanoporous Covalent Organic Framework for Carboxylation of C-H Bonds with CO2 and Value-Added 2-Oxazolidinones Synthesis under Ambient Conditions.

The selective carbon capture and utilization (CCU) as a one-carbon (C1) feedstock offers dual advantages for mitigating the rising atmospheric CO2 content and producing fine chemicals/fuels. In this context, herein, we report the application of a porous bipyridine-functionalized, pyrene-based covalent organic framework (Pybpy-COF) for the stable anchoring of catalytic Ag(0) nanoparticles (NPs) and its catalytic investigation for fixation of CO2 to commodity chemicals at ambient conditions. Notably, Ag@Pybpy-COF showed excellent catalytic activity for the carboxylation of various terminal alkynes to corresponding alkynyl carboxylic acids/phenylpropiolic acids via C-H bond activation under atmospheric pressure conditions. Besides, carboxylative cyclization of various propargylic amines with CO2 to generate 2-oxazolidinones, an important class of antibiotics, has also been achieved under mild conditions. This significant catalytic activity of Ag@Pybpy-COF with wide functional group tolerance is rendered by the presence of highly exposed, alkynophilic Ag(0) catalytic sites decorated on the pore walls of high surface area (787 m2 g-1) Pybpy-COF. Further, density functional theory calculations unveiled the detailed mechanistic path of the Ag@Pybpy-COF-catalyzed transformation of CO2 to alkynyl carboxylic acids and 2-oxazolidinones. Moreover, the catalyst showed high recyclability for several cycles of reuse without significant loss in its catalytic activity and structural rigidity. This work demonstrates the promising application of Pybpy-COF for stable anchoring of Ag NPs for successful transformation of CO2 to valuable commodity chemicals at ambient conditions.

Organocatalyzed Kinetic Resolution of Racemic Carboxylic Acids

AbstractThe kinetic resolution of racemic compounds is a reliable method to prepare important chiral molecules in highly optically enriched forms. Although methods for the catalytic kinetic resolution of chiral alcohols, amines, and epoxides have been extensively investigated, the kinetic resolution of racemic carboxylic acids has remained under‐developed despite the importance of chiral carboxylic acids. Excellent catalytic approaches for the kinetic resolution of racemic carboxylic acids via esterification using chiral organocatalysts have been reported by several research groups. Furthermore, the organocatalyzed lactonization of alkenyl and alkynyl carboxylic acids has also been adapted to achieve kinetic resolution. Herein, the methods typically used to produce the organocatalyzed kinetic resolution of racemic carboxylic acids are reviewed to elucidate the current status of this research.

Samarium (III)–Modified MCM-41 Supported Ionic Liquids as Efficient Heterogeneous Catalysts toward the Fixation of CO2 into Alkynyl Carboxylic Acids

Samarium (III)–Modified MCM-41 Supported Ionic Liquids as Efficient Heterogeneous Catalysts toward the Fixation of CO2 into Alkynyl Carboxylic Acids

Supported gold nanoparticles prepared from NHC-Au complex precursors as reusable heterogeneous catalysts

Gold nanoparticles supported on SiO2, Al2O3, TiO2, and carbon (Maxsorb, Ketjen black and Shirasagi New Gold) were prepared by impregnation and solid grinding methods using N-heterocyclic carbene (NHC)-Au complexes as precursors. A total of nine NHC-Au complex precursors were tested by impregnation and solid grinding method, and [Au(OH)(IPr)] (IPr = 1,3-bis(2,6-diisopropylphenyl)1,3-dihydro-2H-imidazol-2-ylidene) complex led to (1–2 nm) particle sizes by both methods. The prepared catalysts were characterized by XRD (X-ray diffraction), HAADF-STEM (high-angle annular dark-field scanning transmission electron microscopy), in situ XAFS (X-ray absorption fine structure), etc. In addition, [Au(OH)(IPr)] and its impregnated [Au(OH)(IPr)]/SiO2 were subjected to TG-DTA (thermogravimetry analysis-differential thermal analysis) and in situ XAFS analysis under calcination conditions, respectively. Moreover, the obtained supported Au nanoparticles (NPs) were effective as catalysts for low-temperature CO oxidation, intramolecular cyclization of alkynyl carboxylic acids, and isomerization of allylic esters. Their results suggested that the reduction of [Au(OH)(IPr)] proceeds rapidly from around 300°C, and the residual ligands should be attached to the surface of the Au NPs and protect them from drastic agglutination. These results reveal that properly designed NHC-Au complexes can facilitate the preparation of supported Au NP catalysts with small particle sizes and high activities.

Supported Noble Metal Catalysts and Adsorbents with Soft Lewis Acid Functions.

Heterogeneous noble metal catalysts exhibit various functions. Although their redox functions have been extensively studied, we focused on their soft Lewis acid functions. Supported Au, Pt, and Pd catalysts electrophilically attack the π-electrons of soft bases such as alkynes, alkenes, and aromatic compounds to perform addition and substitution reactions. Hydroamination, intramolecular cyclization of alkynyl carboxylic acids, isomerization of allylic esters, vinyl exchange reactions, Wacker oxidation, and oxidative homocoupling of aromatics are introduced based on a discussion of the active species and reaction mechanisms. Furthermore, the adsorption of sulfur compounds, which are soft bases, onto the supported AuNPs is discussed. The adsorption and removal of 1,3-dimethyltrisulfane (DMTS), which is the compound responsible for the stale odor of "hine-ka" in alcoholic beverages, particularly Japanese sake, is described.

Cu-catalyzed carboxylation of organoboronic acid pinacol esters with CO2.

Chemical fixation of CO2 has received much attention. In particular, catalytic C-C bond formation with CO2 giving carboxylic acids is of great significance. Among the CO2 fixation methods, multiple carboxylation is one of the challenging subjects. Here we investigated the Cu-catalyzed carboxylation of a variety of boronic acid pinacol esters (C(sp2)-, C(sp3)-, and C(sp)-B compounds) with CO2, which efficiently provided the corresponding products, including aryl, alkenyl, alkyl, and alkynyl carboxylic acids. This carboxylation was also applicable to multiple CO2 fixation giving di- and tri-carboxylic acids under robust reaction conditions (totally 29 examples).

Palladium-catalyzed regioselective decarboxylative hydroarylation of alkynyl carboxylic acids with arylboronic acids.

The synthesis of (deuterated) 1,1-disubstituted alkenes via Pd-catalyzed decarboxylative hydroarylation of alkynyl carboxylic acids with arylboronic acids has been developed. The reaction features excellent regioselectivity, a broad substrate scope and gram-scale synthetic ability and offers a general synthetic method to synthesize 1,1-dideuterio olefins. Preliminary mechanism investigations indicate that 1,1-disubstituted alkenes are formed by hydroarylation of terminal alkynes generated by in situ decarboxylation of alkynyl carboxylic acids.

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.

Cobalt‐Mediated Decarboxylative/Desilylative C−H Activation/Annulation Reaction: An Efficient Approach to Natural Alkaloids and New Structural Analogues

AbstractA Co(II)‐mediated decarboxylative/desilylative C−H activation/annulation reaction for the efficient synthesis of 3‐arylisoquinolines has been developed. Using alkynyl carboxylic acid and alkynyl silane as terminal alkyne precursors, providing straightforward routes for the synthesis of natural alkaloids and novel structural analogues.

Cu(i)- and Pd(ii)-catalyzed decarboxylative cross-couplings of alkynyl carboxylic acids with N-tosylhydrazones: access to trisubstituted allenes and conjugated enynes

This paper reports the copper- and palladium-catalyzed decarboxylative cross-coupling reactions of alkynyl carboxylic acids and N-tosylhydrazones, affording trisubstituted allenes and conjugated enynes, respectively.

Development of Axially Chiral Styrene-Type Carboxylic Acid Ligands via Palladium-Catalyzed Asymmetric C-H Alkynylation.

A weakly coordinated carboxylate-directed palladium-catalyzed atroposelective C-H alkynylation method for the development of novel axially chiral styrene-type carboxylic acids is disclosed. This transformation exhibits good yields (up to 85%), excellent enantiocontrol (up to 99% ee), and mild conditions. Notably, the synthetic utility of the resulting alkynyl carboxylic acid derivatives was demonstrated by various derivatizations as well as their potential as chiral ligands in asymmetric C-H activations.

Copper‐Catalyzed Decarboxylative Cycloaddition of Alkynyl Carboxylic Acids and Sodium Azide with Epoxides and Ethers

AbstractCopper‐catalyzed decarboxylative cycloaddition of alkynyl carboxylic acids and sodium azide with structurally different epoxides and ethers has been reported for the regioselective synthesis of 1,4‐disubstituted‐1,2,3‐triazoles. These one‐pot transformations are likely to proceed through a mechanism that involves an in situ generated organic azide intermediate, a decarboxylative formation of copper‐alkyne component, and a ring closure to form triazole product. The present three‐component protocols offer several advantages including using economic, bench stable and safe azide source, simple and convenient experimental procedures, high product yields, excellent regioselectivity, wide substrate scope and good functional group tolerance, which could promote their potential synthetic applications in many related areas.

Synthesis of Tetracyclic Indolines through Palladium‐Catalyzed Asymmetric Dearomative reaction of Aryl Iodides

AbstractA palladium‐catalyzed asymmetric intramolecular Heck reaction of aryl iodides with alkynyl carboxylic acids has been developed, delivering various indoline frameworks in moderate to excellent yields (up to 95 %) with excellent enantioselectivities (up to 96 % ee) and diastereoselectivities (>20 : 1) using BINOL‐based phosphoramidite as chiral ligand. This cascade annulation protocol, which tolerates a broad variety of functional groups and is conducted under an argon atmosphere, provides efficient and atom‐economical access to structurally diverse 2,3‐disubstituted indolines bearing vicinal tertiary and quaternary stereocenters. Additionally, the synthetic products could be converted to useful unique indoline derivatives without loss of enantiomeric excess.

Deoxyfluorination of Carboxylic Acids with CpFluor: Access to Acyl Fluorides and Amides.

3,3-Difluoro-1,2-diphenylcyclopropene (CpFluor), a bench-stable fluorination reagent, has been developed in the deoxyfluorination of carboxylic acids to afford various acyl fluorides. This all-carbon-based fluorination reagent enabled the efficient transformation of (hetero)aryl, alkyl, alkenyl, and alkynyl carboxylic acids to the corresponding acyl fluorides under the neutral conditions. This deoxyfluorination method was featured by the synthesis of acyl fluorides with in-situ formed CpFluor, as well as the one-pot amidation reaction of carboxylic acids via in-situ formed acyl fluorides.

Decarboxylative A3‐coupling reactions: An overview

AbstractThe propargylamine motif is not only prevalent in a wide variety of pharmaceuticals and other biologically active compounds but also utilized as a versatile building block in organic synthesis. Among the various methods for the synthesis of propargylamine derivatives, A3‐coupling represents one of the most general and attractive routes, since it offers the possibility for the construction of complex molecules from simple starting materials (amines, aldehydes, and alkynes) in one‐step with high atom economy. However, the use of volatile alkynes is the main disadvantage of this reaction. Recently, alkynyl carboxylic acids were successfully used as easily accessible and high stable surrogates for alkynes (via in situ decarboxylation) in A3‐coupling reactions. This Focus‐Review aims to give an overview of the decarboxylative A3‐coupling reactions by hoping that it will be beneficial to elicit further research in this appealing research arena. A special emphasis is placed on mechanistic aspect of reactions which may allow possible new insights into catalyst improvement.

Corrigendum: Cobalt(III)−Catalyzed C−H Activation: A Secondary Amide Directed Decarboxylative Functionalization of Alkynyl Carboxylic Acids Wherein Amide NH‐group Remains Unreactive

In the communication by Nachimuthu Muniraj and Kandikere Ramaiah Prabhu, in Volume 360, Issue 7, 2018, pp 1370–1375 (DOI: 10.1002/adsc.201701406), the structural formula of compound 4 an in Scheme 3 on page 1372 is incorrect. The correct Scheme is given here. Scheme 3. Scope for alkynylcarboxylic acids.[a] In the Supporting Information, there were errors in the data in the spectrum of 4 an (chemical shift value of 164.9 ppm was missing in the characterization data as well as 13C NMR spectra) and drawing for the compound 4 an. A corrected Supporting Information is provided. The authors apologize for these mistakes. The authors thank Prof. S. Gharpure (IIT, Mumbai) for pointing out these corrections.

Ce(OTf)3-Catalyzed Multicomponent Reaction of Alkynyl Carboxylic Acids, tert-Butyl Isocyanide, and Azides for the Assembly of Triazole-Oxazole Derivatives.

Cerium(III) triflate-catalyzed multicomponent reactions between alkynyl carboxylic acids, tert-butyl isocyanide, and organic azides have been developed. In the presence of Ce(OTf)3 (10 mol %), the cascade reaction of one molecule of alkynyl carboxylic acid with three molecules of tert-butyl isocyanides proceeds chemoselectively and regioselectively via a triple and ordered isocyanide insertion process at room temperature, and then the cesium-catalyzed [3 + 2] cycloaddtion reaction between the resulted alkynyl oxazole and organic azides was further initiated by the temperature elevation (100 °C), thereby leading to multisubstituted triazole-oxazole derivatives in practical, time-saving, one-pot operations. Furthermore, some of the synthesized target compounds showed potential anticancer activities against MGC803 (human gastric cancer cell) with IC50 values below 20 μmol L-1.