CO2 as a C1-organic building block: Enantioselective electrocarboxylation of aromatic ketones with CO2catalyzed by cinchona alkaloids under mild conditions

The fate of nanoparticle surface chemistry during reductive electrosynthesis in aprotic media

Reductive electrochemical coupling of carbon dioxide with organic molecules (electrocarboxylation, EC) represents a green route towards value-added carboxylic acids and serves as a promising strategy for carbon footprint mitigation. Despite the industrial prospects of this synthetic process, little has been done towards the optimization of cathode materials at the nanoscale. Herein, we pave the way towards the use of metal nanoparticles (NPs) as electrocatalysts in EC by demonstrating the effects of NP surface chemistry on electroorganic transformations and the evolution of surface functionalization in the course of reductive electrosynthesis in aprotic media. Using spherical Au NPs capped with citrate or cetylpyridinium chloride (CPC) as our study subjects, we examined the effect of Au NP surface chemistry on the selectivity of EC of benzyl bromide in acetonitrile and determined the fate of the surface adsorbates of Au NPs in the course of the reaction using Raman spectroscopy and X-ray photoelectron spectroscopy. We show that the CPC-stabilized Au NPs outperform the citrate-stabilized NPs at a low applied potential of -1.5 V vs. Ag/Ag+ with the former showing an almost two-fold increase in the faradaic efficiency towards phenylacetic acid. This higher selectivity is attributed to the reaction on the liberated Au surface stemming from the stripping of CPC molecules. In contrast to the CPC-functionalized NPs, the citrate-stabilized Au NPs retain their adsorbates during the reaction, which undergo electrochemical transformations during EC.

Catalytic Regio- and Enantioselective Remote Hydrocarboxylation of Unactivated Alkenes with CO2

The catalytic regio- and enantioselective hydrocarboxylation of alkenes with carbon dioxide is a straightforward strategy to construct enantioenriched α-chiral carboxylic acids but remains a big challenge. Herein we report the first example of catalytic highly enantio- and site-selective remote hydrocarboxylation of a wide range of readily available unactivated alkenes with abundant and renewable CO2 under mild conditions enabled by the SaBOX/Ni catalyst. The key to this success is utilizing the chiral SaBOX ligand, which combines with nickel to simultaneously control both chain-walking and the enantioselectivity of carboxylation. This process directly furnishes a range of different alkyl-chain-substituted or benzo-fused α-chiral carboxylic acids bearing various functional groups in high yields and regio- and enantioselectivities. Furthermore, the synthetic utility of this methodology was demonstrated by the concise synthesis of the antiplatelet aggregation drug (R)-indobufen from commercial starting materials.

Electrochemical ring-opening carboxylation of cyclic carbonate with carbon dioxide

Electroreductive ring-opening carboxylation of styrene carbonates with CO2 to achieve dicarboxylic acids and/or β-hydroxy acids has been developed via the selective cleavage of the C(sp3)-O bond in cyclic carbonates. The product selectivity is probably determined by the stability and reactivity of the key benzylic radical and carbanion intermediate.

Asymmetric electrocarboxylation of 4′-methylacetophenone over PrCoO3 perovskites

Asymmetric electrocarboxylation of aromatic ketones has been achieved over PrCoO3 perovskites with the help of chiral auxiliary t-Bu(R,R)salen(Co[ii]) under CO2 atmosphere.

Electrochemical asymmetric synthesis of biologically active substances

Electrically driven oxidation and reduction reactions are well-established methods for synthesis even in the chemical industry, but asymmetric versions are still few. The mild conditions used, atom efficiency and low cost make these reactions a very attractive alternative to other methods of synthesis. Very fine tuning can be achieved based on minute changes in potentials, allowing only one functional group in a molecule to react in the presence of several others, which is ideal for applications in total synthesis. In this review, the literature in the field of asymmetric synthesis of biologically active substances over the last 10 years is surveyed.

Recent Advances in Asymmetric Catalytic Electrosynthesis

The renewed interest in electrosynthesis demonstrated by organic chemists in the last years has allowed for rapid development of new methodologies. In this review, advances in enantioselective electrosynthesis that rely on catalytic amounts of organic or metal-based chiral mediators are highlighted with focus on the most recent developments up to July 2020. Examples of C-H functionalization, alkene functionalization, carboxylation and cross-electrophile couplings are discussed, along with their related mechanistic aspects.

Ordered Mesoporous Carbon Embedded with Cu Nanoparticle Materials for Electrocatalytic Synthesis of Benzyl Methyl Carbonate from Benzyl Alcohol and Carbon Dioxide

We prepared a series of ordered mesoporous carbons embedded with different contents of Cu nanoparticles (Cu/OMC-X) and applied them to electrocatalytic synthesis of benzyl methyl carbonate. The materials were characterized by many measurements, which showed that Cu/OMC-X materials maintain highly ordered mesoporous structures with high surface area and highly dispersed Cu nanoparticles. As expected, the materials exhibit good electrocatalytic performance. The optimal yield of benzyl methyl carbonate reaches 69.7% on Cu/OMC-3.

Catalytic enantioselective synthesis using carbon dioxide as a C1 synthon

This review summarizes the advances in catalytic enantioselective reactions using CO₂ as a C1 synthon, introduces strategies and discusses advantages and limitations, highlights the application, and outlines the synthetic opportunities.

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

The direct exploitation of ‘electrons’ as reagents in synthetic organic transformations is on the verge of a renaissance by virtue of its greenness, sustainability, atom economy, step economy and inherent safety. Achieving stereocontrol in such organic electrochemical reactions remains a major synthetic challenge and hence demands great expertise. This review provides a comprehensive discussion of the details of stereoselective organic electrochemical reactions along with the synthetic accomplishments achieved with these methods.

Transition Metal-Free CO2 Fixation into New Carbon-Carbon Bonds

CO₂ is the ultimate renewable carbon source on Earth and the essential C₁ building block for carbohydrate biosynthesis in photosynthetic organisms. Modern synthetic chemistry is facing the key challenge of developing fundamental transformations, such as C-C bond formation, in a sustainable and efficient manner from renewable sources. In this Minireview, the most significant methods recently reported for CO₂ fixation under transition metal-free conditions are summarized, organized into three different chapters according to the nature of the chemical transformation that forges the new C-C bond. The focus is on the mechanistic aspects of the different CO₂ activation modes, with specific attention to those systems that operate under catalytic conditions.

Fixation of CO2 along with bromopyridines on a silver electrode

Resulting from the drastic increase of atmospheric CO₂ concentration day by day, global warming has become a serious environmental issue nowadays. The fixation of CO₂ to obtain desirable, economically competitive chemicals has recently received considerable attention. This work investigates the fixation of CO₂ along with three bromopyridines via a facile electrochemical method using a silver cathode to synthesize picolinic acids, which are important industrial and fine chemicals. Cyclic voltammetry is employed to investigate the cyclic voltammetric behaviour of bromopyridines. In addition, systematic study is conducted to study the relationships between the picolinic acids' yield and the electrolysis conditions and intrinsic parameters. The results show that the target picolinic acids' yields are strongly dependent on various conditions such as solvent, supporting electrolyte, current density, cathode material, charge passed, temperature and the nature of the substrates. Moreover, in the studied electrode materials such as Ag, Ni, Ti, Pt and GC, electrolysis and cyclic voltammetry show that Ag has a good electrocatalytic effect on the reduction and carboxylation of bromopyridine. This facile electrochemical route for fixation of CO₂ provides an indispensable reference for the conversion and utilization of CO₂ under mild conditions.

Synthetic Organic Electrochemical Methods Since 2000: On the Verge of a Renaissance

Electrochemistry represents one of the most intimate ways of interacting with molecules. This review discusses advances in synthetic organic electrochemistry since 2000. Enabling methods and synthetic applications are analyzed alongside innate advantages as well as future challenges of electroorganic chemistry.

Alkaloid-induced asymmetric hydrogenation on bimetallic Pt@Cu cathodes under electrochemical conditions

Pt@Cu NPs were coated on carbon paper and used as a cathode for asymmetric electrohydrogenation of pro-chiral aromatic ketones catalyzed by cinchonidine (CD) alkaloids.

Ionic liquids as an electrolyte for the electro synthesis of organic compounds

The use of ionic liquids (ILs) as a solvent and an electrolyte for electro organic synthesis has been reviewed.

Electrocarboxylation: towards sustainable and efficient synthesis of valuable carboxylic acids

The near-unlimited availability of CO₂ has stimulated a growing research effort in creating value-added products from this greenhouse gas. This paper presents the trends on the most important methods used in the electrochemical synthesis of carboxylic acids from carbon dioxide. An overview is given of different substrate groups which form carboxylic acids upon CO₂ fixation, including mechanistic considerations. While most work focuses on the electrocarboxylation of substrates with sacrificial anodes, this review considers the possibilities and challenges of implementing other synthetic methodologies. In view of potential industrial application, the choice of reactor setup, electrode type and reaction pathway has a large influence on the sustainability and efficiency of the process.