Photochemical and Electrochemical Carbon Dioxide Utilization with Organic Compounds

In the last few years, photochemical and electrochemical CO₂ transformations have attracted increasing attention in response to topical interest in renewable energy and green chemistry. The present minireview offers an overview about the current approaches for the photochemical and electrochemical carbon dioxide fixation with organic compounds. Valuable products, including carboxylic acids and heterocyclic compounds, are accessible through carboxylation and carboxylative cyclization, respectively. In photochemical and electrochemical processes, photo‐ or electro‐induced radical ions or other high‐energy organic compounds are considered as key intermediates to react with CO₂. Besides, activation of CO₂ to produce radical anion has also been reported.     

Synthesis of 2-arylpropionic acids by electrocarboxylation of benzylchlorides catalysed by PdCl2(PPh3)2

Electrochemical carboxylation of benzylchlorides catalysed by Pd(II) complex afforded 2-arylpropionic acids in good yields under atmospheric pressure of carbon dioxide at constant current of 10 mA cm⁻². Mechanistic and electrochemical studies revealed the cooperative role of reduced palladium species in the activation of carbon dioxide.     

Electrochemical carboxylation of bicyclo[n.1.0]alkylidene derivatives

Electrochemical carboxylation of bicyclo[n.1.0]alkylidene derivatives (ring-fused alkylidenecyclopropanes) in a suitable aprotic solvent using a one-compartment electrochemical cell equipped with a platinum plate cathode and a zinc plate anode under an atmospheric pressure of carbon dioxide afforded either mono- or dicarboxylic acid in moderate to good yields.     

Synthesis of 2-aryl-3,3,3-trifluoropropanoic acids using electrochemical carboxylation of (1-bromo-2,2,2-trifluoroethyl)arenes and its application to the synthesis of β,β,β-trifluorinated non-steroidal anti-inflammatory drugs

Electrochemical carboxylation of (1-bromo-2,2,2-trifluoroethyl)arenes resulted in an efficient fixation of carbon dioxide to give the corresponding 2-aryl-3,3,3-trifluoropropanoic acids in good yields, and the present reactions were successfully applied to the synthesis of β,β,β-trifluorinated non-steroidal anti-inflammatory drugs (NSAIDs).     

二氧化碳作为羧化试剂用于羧酸及其衍生物的合成(英文)

二氧化碳是储量丰富、廉价易得且可再生的C1资源,将其催化转化成高附加值精细化学品的研究已经引起了人们的广泛关注.目前,虽然二氧化碳用作初始原料的反应已经工业化的很少,但过去几十年中仍有二十多个具有实际应用前景的二氧化碳参与的新反应被发现,其中以二氧化碳作为羧化试剂合成各种羧酸及其衍生物的反应为突出代表.本文综述了过渡金属催化合成羧酸及其衍生物的二氧化碳与多种碳亲核试剂、碳氢键以及碳碳多重键化合物的反应,并总结了无过渡金属参与或有机小分子催化条件下将二氧化碳转化成羧酸及其衍生物的反应.     

过渡金属催化不饱和烃与二氧化碳的羧化反应研究与进展

CO₂是一种无毒、廉价易得、储量丰富的可再生资源,通过化学方法将其转化为具有高附加值的化学品已成为实现可持续发展的战略性课题。其中,以CO₂作为羧化试剂合成羧酸及其衍生物的研究已成为CO₂催化活化领域的研究热点。本文按照不同过渡金属催化的不饱和烃与CO₂的羧化反应,分类归纳了近些年来的羧化反应研究进展。     

Stereoselective electrochemical carboxylation of α,β-unsaturated sulfones

As an attractive C1 synthon, carbon dioxide (CO₂) has been extensively used in organic synthesis to produce carboxylic acids. In this research, stereoselective electrochemical carboxylation of α,β-unsaturated sulfones has been developed under transition-metal-free conditions. All the cinnamic acids and the derivatives are obtained selectively in the E-configuration. Besides, arylpropiolates also can be produced from alkynyl sulfones.     

Development in the green synthesis of cyclic carbonate from carbon dioxide using ionic liquids

This brief review presents the recent development in the synthesis of cyclic carbonate from carbon dioxide (CO₂) using ionic liquids as catalyst and/or reaction medium. The synthesis of cyclic carbonate includes three aspects: catalytic reaction of CO₂ and epoxide, electrochemical reaction of CO₂ and epoxide, and oxidative carboxylation of olefin. Some ionic liquids are suitable catalysts and/or solvents to the CO₂ fixation to produce cyclic carbonate. The activity of ionic liquid is greatly enhanced by the addition of Lewis acidic compounds of metal halides or metal complexes that have no or low activity by themselves. Using ionic liquids for the electrochemical synthesis of the cyclic carbonate can avoid harmful organic solvents, supporting electrolytes and catalysts, which are necessary for conventional electrochemical reaction systems. Although the ionic liquid is better for the oxidative carboxylation of olefin than the ordinary catalysts reported previously, this reaction system is at a preliminary stage. Using the ionic liquids, the synthesis process will become greener and simpler because of easy product separation and catalyst recycling and unnecessary use of volatile and harmful organic solvents.     

Transformation of Carbon Dioxide with Homogeneous Transition‐Metal Catalysts: A Molecular Solution to a Global Challenge?

A plethora of methods have been developed over the years so that carbon dioxide can be used as a reactant in organic synthesis. Given the abundance of this compound, its utilization in synthetic chemistry, particularly on an industrial scale, is still at a rather low level. In the last 35 years, considerable research has been performed to find catalytic routes to transform CO(2) into carboxylic acids, esters, lactones, and polymers in an economic way. This Review presents an overview of the available homogeneous catalytic routes that use carbon dioxide as a C(1) carbon source for the synthesis of industrial products as well as fine chemicals.     

Umpolung Reactivity of Aldehydes toward Carbon Dioxide

Carbon dioxide is an intrinsically stable molecule. Therefore, its activation requires extra energy input in the form of reactive reagents and/or activated catalysts and, often, harsh reaction conditions. Reported here is a direct carboxylation reaction of aromatic aldehydes with carbon dioxide to afford α‐keto acids as added‐value products. In situ generation of a reactive cyanohydrin was the key to the successful carboxylation reaction under operationally mild reaction conditions (25–40 °C, 1 atm CO₂). The resulting α‐keto acids served as a platform for α‐amino acid synthesis by reductive amination reactions, illustrating the chemical synthesis of essential bioactive molecules from carbon dioxide.     

Electrochemical carboxylation with carbon dioxide

Studies carried out in the past two years on electrochemical fixation of carbon dioxide with carbon-carbon bond formation, so-called electrochemical carboxylation or electrocarboxylation, are reviewed. Among about twenty papers on electrochemical carboxylation published from 2014 to the present, recent advances in electrochemical carboxylation regarding asymmetric carboxylation, sacrificial anode-free carboxylation, and carboxylation following aryl radical cyclization are focused on and discussed.     

Carboxylation Reactions with Carbon Dioxide Using N‐Heterocyclic Carbene‐Copper Catalysts

The development of versatile catalyst systems and new transformations for the utilization of carbon dioxide (CO₂) is of great interest and significance. This Personal Account reviews our studies on the exploration of the reactions of CO₂ with various substrates by the use of N‐heterocyclic carbene (NHC)‐copper catalysts. The carboxylation of organoboron compounds gave access to a wide range of carboxylic acids with excellent functional group tolerance. The C?H bond carboxylation with CO₂ emerged as a straightforward protocol for the preparation of a series of aromatic carboxylic esters and butenoates from simple substrates. The hydrosilylation of CO₂ with hydrosilanes provided an efficient method for the synthesis of silyl formate on gram scale. The hydrogenative or alkylative carboxylation of alkynes, ynamides and allenamides yielded useful α,β‐unsaturated carboxylic acids and α,β‐dehydro amino acid esters. The boracarboxylation of alkynes or aldehydes afforded the novel lithium cyclic boralactone or boracarbonate products, respectively. The NHC‐copper catalysts generally featured excellent functional group compatibility, broad substrate scope, high efficiency, and high regio‐ and stereoselectivity. The unique electronic and steric properties of the NHC‐copper units also enabled the isolation and structural characterization of some key intermediates for better understanding of the catalytic reaction mechanisms.     

Palladium(II)-catalyzed carboxylation of benzene and other aromatic compounds with carbon monoxide under very mild conditions

Aromatic compounds such as benzene, toluene, chlorobenzene, anisole, and naphthalene were carboxylated by palladium(II) acetate catalyst with carbon monoxide in the presence of potassium peroxodisulfate in trifluoroacetic acid (TFA) at room temperature under atmospheric pressure. The aromatic carboxylic acids were formed in good yields; for example, the carboxylation of benzene with carbon monoxide proceeds quantitatively under the optimal conditions.     

Syntheses of α‐Amino Acids by Using CO2 as a C1 Source

The incorporation of CO₂ into organic compounds is currently one of the most active research topics in organic chemistry, because CO₂ is an abundant, inexpensive, nontoxic, and renewable C1 source. However, CO₂ is also a thermodynamically stable and kinetically inert gaseous compound, and as such, special strategies are required to activate CO₂ and incorporate it into organic compounds. In particular, because the carbon atom adjacent to the nitrogen atom of amine derivatives is positively charged, umpolung carboxylation, which is a difficult chemical process, should be considered for the production of α‐amino acids by using CO₂. In this Minireview, we summarize recent synthetic methods for α‐amino acids that use CO₂ as a carboxylic acid unit.     

Electrochemical carboxylation of acyl chlorides, freons, and halogen-containing polymers

Processes of the carbon dioxide fixation are studied. The fixation is done by an electrochemical carboxylation of chlorides of aliphatic and aromatic carboxylic acids (acetyl chloride, benzoyl chloride and its derivatives), halogen-containing polymers (polyvinyl chloride, polyvinyl bromide), polybutadiene, and polyfluoroalkyl halides (CF₃Br, CF₃I, C₃F₇I). Major effects of some factors (reagent electronic structure, electrode materials, supporting electrolyte) on the occurrence of such processes and the yield of target products are studied.     

可见光促进二氧化碳参与的羧基化反应

二氧化碳是众所周知的温室气体, 也是重要的C1资源, 利用二氧化碳合成高附加值化合物具有重要意义. 其中, 羧酸类化合物广泛存在于天然产物、 药物、 日化品及工业原料中, 是一类非常重要的化合物. 因此, 利用二氧化碳合成羧酸类化合物是一个重要的研究方向; 另一方面, 由于二氧化碳反应活性低, 其转化通常需要高温等苛刻条件. 为解决该问题, 人们利用可见光作为能量来源, 可以在温和条件下实现二氧化碳的高效转化. 鉴于该方向近年来的蓬勃发展, 本文主要对可见光促进二氧化碳参与的羧基化反应进行介绍和总结, 按烯烃、 炔烃、 醛酮、 亚胺和(类)卤代物等重要的化工原料分类阐述, 并将各个反应的特点和机理将作为阐述的重点. 本文也对该领域的未来发展方向进行了展望, 希望为该领域的进一步发展提供参考.     

Electrochemical Carboxylation of 2‐Iodoaromatic Compounds

Abstract

The electrochemical reduction of a series of 2‐iodoaromatic substituted compounds in acetonitrile under an atmospheric pressure of carbon dioxide leads to ortho‐substitued aromatic carboxylic acid. The maximum yield of acid obtained by electrolysis performed in a diaphragm‐less cell at low temperature (5°C) with a sacrificial magnesium anode and by the use of a low current density was slightly higher than 70%.     

非金属催化剂在催化环氧化物和CO2合成环状碳酸酯中的研究进展

随着科学技术的进步和工业化的发展,大量化石燃料被消耗,大气中二氧化碳浓度急剧增加,导致温室效应加剧,严重威胁到人类的生存和发展。基于可持续发展的思想,利用储量丰富且廉价的二氧化碳作为 C1资源替代有毒的气体(如一氧化碳和光气等)制备具有广泛应用的环状碳酸酯,不仅满足“绿色化学”的要求,而且符合“原子经济性”的原则。迄今为止,大量用于催化二氧化碳和环氧化物环加成反应合成环状碳酸酯的催化剂,包括均相催化剂(如金属卤化物、有机碱、离子液体和金属配合物),多相催化剂(如金属氧化物、负载型催化剂、有机聚合物、金属有机框架材料和碳材料等)被报道。其中金属催化剂占主导地位,大多表现出优异的催化活性。然而,目前可供开采的金属矿越来越少,大多数金属的回收再利用率较低,重金属污染日趋严重。因此,开发新型、廉价、绿色、高效、循环性和稳定性好的非金属催化剂具有重要意义。
　　本文主要介绍了近3年以来用于催化二氧化碳和环氧化物环加成反应合成环状碳酸酯的非金属催化剂,主要包括有机碱、离子液体、固载型催化剂、有机聚合物和碳材料等。概括了不同种类催化剂的设计思想及其催化反应机理,重点阐述了分子内以及分子间各种功能基团的协同作用对环加成反应的影响。通过比较发现,具有“C–N=C”结构的有机碱活性相对较高,氢键给体和亲核物质都能与有机碱协同作用提高其催化活性;传统离子液体的活性一般不理想,氢键给体如羟基和羧基的引入有利于促进环加成反应,且多阳离子和多氢键给体功能化的离子液体表现出更高的催化活性;负载型催化剂中,载体和活性组分之间的协同作用有利于加速环加成反应的进行,多种功能基团负载和以共价键方式多层固载能更好地提高催化剂稳定性和催化活性;利用非烯烃化合物制得的活性组分位于主链的多孔有机聚合物,催化活性和稳定性大多高于活性组分位于侧链的烯烃聚合物;碳材料催化剂中,引入不饱和的 N物种(如伯胺和吡啶氮),有利于 CO2的吸附和活化,能促进环加成反应。此外,利用密度泛函的方法,计算模拟催化反应过程,能更好地揭示反应机理,并为设计和制备高效的催化剂提供理论指导。
　　该领域目前面临的重要挑战是研发可以同时实现二氧化碳捕获和转化的新型、环保和高效非金属催化剂,终极目标是利用多孔催化材料在常温和常压下直接捕获工业废气中的二氧化碳,并利用捕获的二氧化碳实现环状碳酸酯的连续生产。基于协同催化的设计思想,利用多种基团功能化的策略合成高效吸附和活化二氧化碳以及开环活化环氧化物的非金属催化剂,有望实现上述目标。     

CO2电化学还原研究进展

综述了利用电化学方法研究CO2在水溶剂，非水溶剂中的转化情况和机理，以及将CO2固定在有机络合物中或用光电化学，光催化还原CO2及仿光合作用转移CO2的最新研究情况，旨在寻求一种合理，高效的CO2转化方法以缓解温室效应。     

超临界二氧化碳中含氟聚合物的合成

超临界二氧化碳是廉价、低毒、不易燃、易回收、环境友好的惰性聚合介质,是传统有机溶剂的替代品。尤其是有望成为含氟单体的聚合溶剂,以替代目前使用的氟氯烃。本文详细地介绍了近年来以超临界二氧化碳为介质的氟烷基丙烯酸酯类单体和氟烯烃类单体的聚合反应研究,其中涉及氟烷基丙烯酸酯类单体的均聚和共聚,可熔融加工的四氟乙烯聚合物,离子交换树脂,偏氟乙烯的均聚和共聚合等。研究表明在超临界二氧化碳中的含氟单体的聚合反应有其它溶剂体系无法比拟的优点。