Formate Salts Research Articles

Formate Salts: The Rediscovery of Their Radical Reaction under Light Irradiation Opens New Avenues in Organic Synthesis

AbstractFormates are abundantly available and inexpensive commodity chemical, widely used in laboratory and industrial organic synthesis. Formates are promising hydrogen carrier and green C1 source, and have also been a subject of research as SET reductants in recent years. Compared to the toxic and flammable gas carbon monoxide, which also serves as a C1 source, formates are easier to handle, store, and transport, and are more environmentally friendly. Therefore, in recent studies of radical reactions, formate is not only as an ideal source of green carbonyl, which is of great significance to synthesize carboxyl compounds with various structures, but also as a SET reductant for editing organic molecules either in scientific research or industrial production. The activation and conversion of formate, as a source of C1 or a SET reductant, is a very challenging and hot research field in organic synthesis.

Photoinduced Radical Approach for Desulfurative Alkylation of Cysteine Derivatives to Make Unnatural Amino Acids.

Unnatural amino acids (UAAs) are highly valuable molecules in organic synthesis, pharmaceutical sciences, and material science. Herein, we present a photocatalytic radical approach for desulfurative alkylation of cysteine derivatives with arenethiol as the hydrogen atom transfer catalyst for making UAAs and peptides. The formate salt, acting as the hydrogen atom donor, in situ generates the highly reductive CO2 radical anion species, which is the key to unlocking the C-S bond cleavage process with a simple benzoyl protecting group. No photocatalyst is required for the radical initiation and propagation, which makes such a visible-light-induced process mild, efficient, and sustainable.

Visible-Light-Promoted Reduction of Nitroarenes with Formate Salts as Reductants.

A visible-light-promoted reduction of nitrobenzenes using formate salts as the reductant was developed. A wide range of nitrobenzenes can be converted into aniline products in a transition metal free fashion. Mechanistic studies revealed that radical species (carbon dioxide radical anion and thiol radical) are key intermediates for the transformation. We anticipate that this method will provide a valuable and green strategy for the reduction of nitrobenzenes.

Light-Driven Formate-Salts-Induced Cleavage of Oxidized Lignin Model Compounds.

We report a light-induced cleavage of oxidized lignin model compounds utilizing formate salts. For compounds containing an aliphatic hydroxyl (γ-OH) group, the employment of a hydrogen atom transfer (HAT) catalyst was crucial to preserving the efficacy of the fragmentation reaction. Furthermore, we successfully converted a trimeric oxidized model compound into the desired products with moderate yields.

Formate Salt as a Bifunctional Reagent for Hydroxylation and Carbonylation Reactions Under Photochemically Driven Nickel Catalysis.

In this study, we disclose for the first time that formate salt can be used as a bifunctional reagent for the synthesis of phenol derivatives and as a CO source for carbonylative cross-coupling processes using the COware gas reactor under activation free conditions. Key to this success is the in-situ synthesis of aryl formate via an unprecedented nickel/organophotocatalyst system under blue LED irradiation. This developed system demonstrated high applicability to various aryl iodide substrates for synthesizing phenol derivatives. Moreover, the generated CO could be utilized in a range of carbonylative C-heteroatom and C-C processes. Notably, commercially available H13COONa salt can serve as a bifunctional reagent for both synthesizing phenols and generating 13CO.

Dietary Intervention of Benzoic Acid for Intestinal Health and Growth of Nursery Pigs.

The objectives of this review are to investigate how benzoic acid can mitigate the negative effects of weaning stress, improve the intestinal microbiota, intestinal health, and growth of nursery pigs, determine the optimal dose level of benzoic acid for the growth rate in nursery pigs, and compare the efficacy of benzoic acid and other acids in pig feeds. After weaning, pigs are exposed to less lactose and solid feed with high acid-binding capacity at infrequent intervals, causing an increase in digesta pH, reducing protein digestion, and increasing ammonia-producing bacteria in the stomach. Benzoic acid supplementation has improved the intestinal health and growth of nursery pigs through its antimicrobial properties and pH reduction in the digesta. The positive modulation of luminal microbiota in the small intestine of pigs by benzoic acid improves intestinal morphology and enhances nutrient utilization, especially nitrogen, of nursery pigs. Benzoic acid supplementation of up to 1% in feeds also increases hippuric acid contents in the urine of nursery pigs, decreasing urinary pH, which is related to ammonia emission and barn conditions in intensive pig production. Supported by the beneficial impacts of benzoic acid, the growth performance of nursery pigs was also improved. However, excessive benzoic acid (over 2.5% up to 5%) in feeds reduces the growth performance of nursery pigs. Thus, this review conducted a meta-analysis of the results from 16 papers to determine the optimal dose level of benzoic acid for body weight gain of nursery pigs, which was found to be 0.60%. The efficacy of benzoic acid was similar to that of other organic acids, including citric acid, fumaric acid, formic acid, and formate salts. Collectively, benzoic acid supplementation can positively modulate the luminal and mucosal microbiota in the small intestine, increase nutrient utilization and intestinal health, decrease urinary pH, and improve the growth performance of nursery pigs.

Formate and CO2 Enable Reductive Carboxylation of Imines: Synthesis of Unnatural α-Amino Acids.

Herein, a photocatalytic umpolung strategy for reductive carboxylation of imines for the synthesis of α-amino acids was disclosed. Carbon dioxide radical anion (CO2•-) generated from formate is the key single electron reductant in the reactions. An unprecedentedly broad substrate scope of imines with excellent reaction yields was obtained with carbon dioxide (CO2) and formate salt as carbon sources.

A zero-liquid discharge process to recover all critical metals from spent NCM111 cathode material of end-of-life lithium-ion batteries: statistically optimized leaching with formic acid and in-situ crystallization

A green chemistry process has been developed to recycle cathode material from end-of-life lithium ion batteries. NCM111 (LiNi1/3Co1/3Mn1/3O2) was completely leached with 13 M formic acid to produce two groups of salts with different solubilities: sparingly soluble cobalt, manganese, and nickel (CMN) formates and highly soluble lithium formate. During leaching, CMN formate salts exceeded their solubility limit in the pregnant leach solution (PLS) and crystallized. Mixed CMN formate salts were recovered by filtering the PLS. Lithium was completely recovered by evaporating the filtered PLS then thermally decomposing the lithium formate obtained in air to lithium carbonate. The purity of the lithium carbonate was 98.1 wt%.The leaching process was optimized through response surface methodology experiments. The minimum time required to completely leach NCM111 with 13 M formic acid was 30.8 h. Optimum leaching conditions were L/S = 2.81 mL/g (equivalent to S/L = 356 g/L) and T = 95 °C. During leaching, 98% of CMN formate salts exceeded their solubility limit and crystallized from the PLS.The recycling process is simple and generates no liquid or solid waste products. The only reagent is 13 M formic acid. The only by-products are water vapour, which can be condensed and reused, and carbon dioxide gas.

Molar-scale formate production via enzymatic hydration of industrial off-gases

Decarbonizing the steel industry, a major CO2 emitter, is crucial for achieving carbon neutrality. Escaping the grip of CO combustion methods, a key contributor to CO2 discharge, is a seemingly simple yet formidable challenge on the path to industry-wide net-zero carbon emissions. Here we suggest enzymatic CO hydration (enCOH) inspired by the biological Wood‒Ljungdahl pathway, enabling efficient CO2 fixation. By employing the highly efficient, inhibitor-robust CO dehydrogenase (ChCODH2) and formate dehydrogenase (MeFDH1), we achieved spontaneous enCOH to convert industrial off-gases into formate with 100% selectivity. This process operates seamlessly under mild conditions (room temperature, neutral pH), regardless of the CO/CO2 ratio. Notably, the direct utilization of flue gas without pretreatment yielded various formate salts, including ammonium formate, at concentrations nearing two molar. Operating a 10-liter-scale immobilized enzyme reactor feeding live off-gas at a steel mill resulted in the production of high-purity formate powder after facile purification, thus demonstrating the potential for decarbonizing the steel industry.

Structural investigation of solid biopolymer electrolytes: 2-hydroxyethyl cellulose doped ammonium formate as a promising proton conductor

Fabrication of solid biopolymer electrolytes (SBEs) was mainly to cater the drawbacks of lithium-ion electrolytes in terms of leakage, high cost, and toxic material. In this present work, solid biopolymer electrolytes system comprises of 2-Hydroxyethyl Cellulose (2-HEC) as polymer host, and various weight percentage (wt.%) of Ammonium Formate (AF) as ionic doping salt are produced by using solution casting technique. The relation between structural and ionic conductivity of 2-HEC/AF was analyzed and investigated by using X-Ray Diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), and Electrical Impedance Spectroscopy (EIS). Through the analysis of XRD, it can be observed that the amorphous region of SBEs increases as the concentration of AF salt increases. The amorphous region of SBEs can be confirmed due to the interaction of salt concentration and polymer. However, in this present work, the broadest peak in XRD of the sample does not necessarily correlate with the highest conductivity among the samples. The interaction between polymer-salt complexes is proved through FTIR spectrum at the range of 700 cm−1 to 1300 cm−1. The highest ionic conductivity of 2-HEC/AF achieved is 2.40 × 10−3 S/cm at room temperature for SBEs containing 40 wt.% of AF. The findings from this study made it clear that the concentration of Ammonium Formate salt affects the increase in ionic conductivity.

A Mild and Modular Approach to the Total Synthesis of Desferrioxamine B.

A mild and modular approach to the total synthesis of the WHO-listed essential medicine desferrioxamine B is described. Hydroxamic acid fragments were installed under mild conditions, a generalized divergent acylation procedure used to access two monomer precursors, and a transfer hydrogenation reaction used to unmask the hydroxamic acid moieties. Desferrioxamine B was generated over ten linear steps as the formate salt in 17% overall yield using standard amide coupling conditions or in 13% overall yield using microwave-assisted amide coupling conditions.

Photoredox-Catalyzed Defluorinative Carboxylation of gem-Difluorostyrenes with Formate Salt.

Herein, we present a transition-metal-free, easy handling protocol for regioselective carboxylation of gem-difluorostyrenes with sodium formate as the C1 source. 30 examples of α-fluoracrylates were obtained in yields of 30 to 80% under these conditions. A defluorinative monofluorovinyl intermediate and consecutive photoinduced electron transfer mechanism were proposed after mechanism investigation.

Visible-light-driven alkene dicarboxylation with formate and CO2 under mild conditions.

Low-cost formate salt was used as the reductant and part of the carboxyl source in a visible-light-driven dicarboxylation of diverse alkenes, including simple styrenes. The highly competing hydrocarboxylation side reaction was successfully overridden. Good yields of products were obtained under mild reaction conditions at ambient temperature and pressure of CO2. The dual role of formate salt may stimulate the discovery of a range of new transformations under mild and friendly conditions.

Ruthenium polyhydrides supported by rigid PCP pincer ligands: dynamic behaviour and reactions with CO2.

Two rigid β-elimination immune PCcarbeneP pincer ligands, differing in their electron donor properties by variation of the substitution pattern on the aromatic linker arms, were complexed to ruthenium to form the dichlorides LRRuCl2 (R = H or NMe2). These compounds were converted to hydrido chlorides by treatment with dihydrogen (H2) and a base. By converting to tert-butoxide derivatives in situ under an atmosphere of H2, the poly hydride PCalkylP complexes LHRRu(H)3 compounds were generated. In these complexes, H2 has added across the RuC bond in the PCcarbeneP starting materials. The polyhydrides are dynamic in solution and extensive NMR studies helped to elucidate the speciation and fluxional processes operative in this dynamic system. The polyhydride complexes react rapidly with CO2 to give the PCcarbeneP formato hydride complexes LRRu(H)-κ2-O2CH. For R = H, the 1,2-hydride shift from the anchoring alkyl of the PCalkylP carbon to the metal is reversible, but for R = NMe2 it is irreversible. The CO2 incorporated into the formato ligand of these compounds exchanges with free CO2via a bimolecular mechanism that is more rapid for R = NMe2 than for R = H; plausible explanations for this observation are proffered. Experiments designed to evaluate the efficacy of the R = NMe2 formato hydride complex as a catalyst precursor for CO2 hydrogenation to formate salts reveal poor performance in comparison to state-of-the-art ruthenium-based catalysts. This is due primarily to the precipitation of a dimeric μ-κ2-κ1-CO3 carbonate complex that is not an active catalyst for the reaction.

Directly Knitted Hierarchical Porous Organometallic Polymer-Based Self-Supported Single-Site Catalyst for CO2 Hydrogenation in Water.

In recent times, heterogenization of homogeneous molecular catalysts onto various porous solid support structures has attracted significant research focus as a method for combining the advantages of both homogeneous as well as heterogeneous catalysis. The design of highly efficient, structurally robust and reusable heterogenized single-site catalysts for the CO2 hydrogenation reaction is a critical challenge that needs to be accomplished to implement a sustainable and practical CO2 -looped renewable energy cycle. This study demonstrated a heterogenized catalyst [Ir-HCP-(B/TPM)] containing a molecular Ir-abnormal N-heterocyclic carbene (Ir-aNHC) catalyst self-supported by hierarchical porous hyper-crosslinked polymer (HCP), in catalytic hydrogenation of CO2 to inorganic formate (HCO2 - ) salt that is a prospective candidate for direct formate fuel cells (DFFC). By employing this unique and first approach of utilizing a directly knitted HCP-based organometallic single-site catalyst for CO2 -to-HCO2 - in aqueous medium, extremely high activity with a single-run turnover number (TON) up to 50816 was achieved which is the highest so far considering all the heterogeneous catalysts for this reaction in water. Additionally, the catalyst featured excellent reusability furnishing a cumulative TON of 285400 in 10 cycles with just 1.6 % loss in activity per cycle. Overall, the new catalyst displayed attributes that are important for developing tangible catalysts for practical applications.

Directly Knitted Hierarchical Porous Organometallic Polymer‐Based Self‐Supported Single‐Site Catalyst for CO2 Hydrogenation in Water

AbstractIn recent times, heterogenization of homogeneous molecular catalysts onto various porous solid support structures has attracted significant research focus as a method for combining the advantages of both homogeneous as well as heterogeneous catalysis. The design of highly efficient, structurally robust and reusable heterogenized single‐site catalysts for the CO2 hydrogenation reaction is a critical challenge that needs to be accomplished to implement a sustainable and practical CO2‐looped renewable energy cycle. This study demonstrated a heterogenized catalyst [Ir‐HCP‐(B/TPM)] containing a molecular Ir‐abnormal N‐heterocyclic carbene (Ir‐aNHC) catalyst self‐supported by hierarchical porous hyper‐crosslinked polymer (HCP), in catalytic hydrogenation of CO2 to inorganic formate (HCO2−) salt that is a prospective candidate for direct formate fuel cells (DFFC). By employing this unique and first approach of utilizing a directly knitted HCP‐based organometallic single‐site catalyst for CO2‐to‐HCO2− in aqueous medium, extremely high activity with a single‐run turnover number (TON) up to 50816 was achieved which is the highest so far considering all the heterogeneous catalysts for this reaction in water. Additionally, the catalyst featured excellent reusability furnishing a cumulative TON of 285400 in 10 cycles with just 1.6 % loss in activity per cycle. Overall, the new catalyst displayed attributes that are important for developing tangible catalysts for practical applications.

Stronger Together! Mechanistic Investigation into Synergistic Effects during Homogeneous Carbon Dioxide Hydrogenation Using a Heterobimetallic Catalyst.

A series of group 6 heterobimetallic complexes [M0;IrIII] (M = Cr, Mo, W) were synthesized and fully characterized, and the catalytic behavior was studied. The heterobimetallic complex [Mo0;IrIII] (C1) was by far the most active and has shown a considerable synergistic effect, with both metals actively participating in homogeneous carbon dioxide hydrogenation, leading to formate salts. Based on theoretical calculations, the synergistic interaction is due to Pauli repulsion, lowering the transition state and thus enabling higher catalytic activity. The mechanism of both the hydrogenation itself and the synergistic interaction was studied by NMR spectroscopy, kinetic measurements, and theoretical calculations. The homogeneous nature of the reaction was proven using in situ high-pressure (HP) NMR experiments. The same experiments also showed that the octahedral Mo(CO)3P3 moiety of the complex is stable under the reaction conditions. The hydride complex is the resting state because the hydride transfer is the rate-determining step. This is supported by kinetic measurements, in situ HP NMR experiments, and theoretical calculations and is in contrast to the monometallic IrIII counterpart of C1.

Carbon Dioxide Radical Anion by Photoinduced Equilibration between Formate Salts and [11C, 13C, 14C]CO2: Application to Carbon Isotope Radiolabeling.

The need for carbon-labeled radiotracers is increasingly higher in drug discovery and development (carbon-14, β-, t1/2 = 5730 years) as well as in positron emission tomography (PET) for in vivo molecular imaging applications (carbon-11, β+, t1/2 = 20.4 min). However, the structural diversity of radiotracers is still systematically driven by the narrow available labeled sources and methodologies. In this context, the emergence of carbon dioxide radical anion chemistry might set forth potential unexplored opportunities. Based on a dynamic isotopic equilibration between formate salts and [13C, 14C, 11C]CO2, C-labeled radical anion CO2•- could be accessed under extremely mild conditions within seconds. This methodology was successfully applied to hydrocarboxylation and dicarboxylation reactions in late-stage carbon isotope labeling of pharmaceutically relevant compounds. The relevance of the method in applied radiochemistry was showcased by the whole-body PET biodistribution profile of [11C]oxaprozin in mice.

CO2 Radical Anion in Photochemical Dicarboxylation of Alkenes

AbstractCO2 radical anion (CO2⋅−) is a highly reductive species (Ered=−2.2 V vs SCE), which can undergo Giese radical addition to an unsaturated C−C bond and install a carbonyl group to synthesize acids. Normally, it has been generated through the direct reduction of CO2 gas or from formate salts via HAT (hydrogen atom transfer) as the BDE (bond dissociation energy) of the C−H bond in formate is only around 86 kcal/mol. This concept highlights the recent developments on alkenes dicarboxylation reaction with CO2 and/or formate as the carbonyl sources. In these reactions, CO2 radical anion species played significant roles in the carboxylation step.

Enhancing the efficiency and scalability of perovskite solar cells through pseudo-halide salt addition

Organic–inorganic halide perovskites have significant potential for application in next-generation solar cells. However, their applications are limited by challenges associated with large-area processability and long-term stability owing to the presence of pinholes and defect sites. Here, we incorporated cesium formate in a perovskite active layer using a sequential perovskite fabrication process to eliminate the defect sites of perovskites and improve the film processability via roll-to-roll (R2R) processing. The addition of cesium formate salt to the PbI2 layer influences the perovskite crystal formation behavior as well as increases the perovskite crystallinity and decreases the defect density. Furthermore, cesium formate addition eliminated small PbI2 grains and smoothed the perovskite surface, resulting in a large crystal grain size. The formate ions interact with the PbI2 component and passivate halide vacancy defects, reducing nonradiative recombination and improving charge transfer. Additionally, the treated perovskite films were highly stable in air, exhibiting improved efficiency retention over time and achieving a power conversion efficiency (PCE) of > 22% compared to the control. Furthermore, the additive-treated perovskite film was processed using the R2R method, achieving a high PCE of >14% with minimal hysteresis.