C1 Building Block Research Articles

A Green Route to Methyl Formate from CO2-Derived Formamides over Solid Base Catalysts

The transformation of CO2 and CO2-derived chemicals into high value-added chemicals is an important method for reducing CO2 emissions and achieving carbon neutrality. Methyl formate (MF) is a critical C1 building block in synthesizing a wide range of important chemicals, such as formic acid, ethylene glycol, and formamide methyl propionate. Here, we report a green route for the sustainable synthesis of MF from CO2-derived formamides via the alcoholysis reaction catalyzed by supported CaO solid bases. The CaO/MgO catalyst with 13.5 wt.% CaO exhibited higher alcoholysis reaction efficiency and achieved 94.5% conversion of N-formylmorpholine and 100% selectivity of MF in methanol at 120 °C. Based on the kinetic studies, characterization results of structural and basic properties (XRD, and TEM, CO2-TPD, etc.), we found that the density of strong basic sites is linearly related to the activity of alcoholysis reaction, and the higher the base density on these catalysts, the greater the reaction rate. This study presents a sustainable route for the synthesis of MF by using CO2-derived formamides and green methanol, and a promising strategy for producing more efficient solid alcoholysis catalysts of amides.

Autocatalytic O-Formylation of Alcohols Using CO2

Global drive away from fossil feedstock requires the development of synthetic procedures to enhance the efficiency of CO2 capture and utilization processes using renewable starting materials and catalysts. Here, we report an alternative reaction pathway for the O-formylation of alcohols and bio-alcohols, which affords industrially relevant formate esters. Most products, reported herein, derive their carbon atoms exclusively from renewable sources. The reaction is catalyzed by formic acid, which can also be produced directly from CO2 captured in the reaction. The resulting in situ produced formic acid improves the reaction rate, with each catalyst recycling by simple filtration, product distillation, and reuse of the residual reaction mixture. Hence, CO2 is used as a C1 building block and simultaneously reduced to formic acid, which in turn autocatalytically promotes the reaction.

Continuous Flow Synthesis of Non‐Symmetrical Ureas from CO2

AbstractWe report on a continuous flow synthetic process of non‐symmetrical ureas, based on the implementation of a Staudinger/aza‐Wittig reaction sequence. This flow technology allows obtaining the key urea functional group directly from the fundamental C1 building block CO2. A library of 26 derivatives, including alkyl/alkyl, alkyl/aryl and aryl/aryl ureas could be synthesised. In addition, the method was also suitable for the synthesis of S‐thiocarbamates. The potential for large‐scale reaction implementation and a first application to continuous flow 13C‐isotope labeling are shown.

Copper-Catalyzed C(3+1) copolymerization of propargyl carbonates and aryldiazomethanes

Controlling the composition and sequence during diazo copolymerization with vinyl or acetylenic monomers is highly desired yet challenging. Here we report a new base-metal-catalysis strategy to address this problem via tandem coupling/polymerization. A selective Cu-catalyzed C(3+1) copolymerization reaction was developed using propargyl carbonates and aryldiazomethanes derived from N-tosylhydrazones as the C3 and C1 building blocks, respectively. This reaction rapidly produces alternating-like poly(1,4-diaryl-2-butyne-1,4-diyl)s (Mn up to 31.0 kg/mol) in a modular fashion, without detectable homopolymer segments. This work provides a new avenue for the synthesis of hydrocarbon polymers through diazo copolymerization.

Synthesis of vinyl-substituted alcohols using acetylene as a C2 building block.

Vinyl-substituted alcohols represent a highly useful class of molecular skeletons. The current method typically requires either stoichiometric metallic reagents or preformed precursors. Herein, we report a nickel catalysis-enabled synthesis of vinyl-substituted alcohols via a 5-membered oxa-metallacycle. In this protocol, acetylene, the simplest alkyne and abundant feedstock, is employed as an ideal C2 synthon. The reaction features mild conditions, good functional group tolerance and broad substrate scope. Mechanistic exploration implies that the oxa-metallacycle originated from the cyclometallation of aldehyde and acetylene is the key intermediate for this transformation, which is then terminated by a silane-mediated σ-bond metathesis and subsequent reductive elimination.

Regioselective hydroesterification of alkenes and alkenylphenols utilizing CO2 and hydrosilane.

As an important and attractive C1 building block, the diversified exploitation of CO2 in chemical transformations possesses significant research and application value. Herein, an effective palladium-catalyzed intermolecular hydroesterification of a wide range of alkenes with CO2 and PMHS is described, successfully generating diverse esters with up to 98% yield and up to 100% linear-selectivity. In addition, the palladium-catalyzed intramolecular hydroesterification of alkenylphenols with CO2 and PMHS is also developed to construct a variety of 3-substituted-benzofuran-2(3H)-ones with up to 89% yield under mild conditions. In both systems, CO2 functions as an ideal CO source with the assistance of PMHS, thus smoothly participating in a series of alkoxycarbonylation processes.

Synthesis of cyclic carbonates from CO2 cycloaddition to bio-based epoxides and glycerol: an overview of recent development.

Anthropogenic carbon dioxide (CO2) emissions contribute significantly to global warming and deplete fossil carbon resources, prompting a shift to bio-based raw materials. The two main technologies for reducing CO2 emissions are capturing and either storing or utilizing it. However, while capture and storage have high reduction potential, they lack economic feasibility. Conversely, by utilizing the CO2 captured from streams and air to produce valuable products, it can become an asset and curb greenhouse gas effects. CO2 is a challenging C1-building block due to its high kinetic inertness and thermodynamic stability, requiring high temperature and pressure conditions and a reactive catalytic system. Nonetheless, cyclic carbonate production by reacting epoxides and CO2 is a promising green and sustainable chemistry reaction, with enormous potential applications as an electrolyte in lithium-ion batteries, a green solvent, and a monomer in polycarbonate production. This review focuses on the most recent developments in the synthesis of cyclic carbonates from glycerol and bio-based epoxides, as well as efficient methods for chemically transforming CO2 using flow chemistry and novel reactor designs.

Continuous synthesis and transformation of diazomethane

Diazomethane is the simplest diazo compound with high reactivity and is an exceptionally versatile C1-building block. However, diazomethane’s application is greatly limited due to its special properties such as highly toxic, carcinogenic, inflammable and explosive. The application of the one-pot reaction and emerging continuous flow technology in the field of hazardous chemicals enable the generated diazomethane to be directly consumed and transformed, effectively ensuring the safety of the reaction process and providing the possibility for its mass production and use. According to the different precursors of diazomethane, the applications of diazomethane in continuous synthesis and in situ transformation in laboratory and industry are systematically summarized.

A unified strategy for the synthesis of aldohexoses by boronate assisted assembly of CH2X2 derived C1-building blocks.

A synthetic strategy for all aldohexoses with individually addressable protecting groups from dihalomethane C1-units is reported. The underlying synthesis of C6-sugar alcohols relies on three consecutive Matteson sequences, vinylation and bishydroxylation. Erythro and threo isomers have been realized for every glycol motif by strategic variation of the sequence.

Transition metal–free ketene formation from carbon monoxide through isolable ketenyl anions

The capacity of transition metals to bind and transform carbon monoxide (CO) is critical to its use in many chemical processes as a sustainable, inexpensive C1 building block. By contrast, only few s- and p-block element compounds bind and activate CO, and conversion of CO into useful carbonyl-containing organic compounds in such cases remains elusive. We report that metalated phosphorus ylides provide facile access to ketenyl anions ([RC=C=O]-) by phosphine displacement with CO. These anions are very stable and storable reagents with a distinctive electronic structure between that of the prototypical ketene (H2C=C=O) and that of ethynol (HC≡C-OH). Nonetheless, the ketenyl anions selectively react with a range of electrophiles at the carbon atom, thus offering high-yielding and versatile access to ketenes and related compounds.

Mining industrial materials as heterogeneous catalyst for high value‐added cyclic carbonates production from CO2

AbstractChemical fixation of CO2 and its utilization as C1 building block into fine chemicals are among key areas of research to mitigate greenhouse gas effect. The catalysts requirement to form cyclic organic carbonates by coupling reaction between CO2 and epoxides is a well‐stablished strategy for CO2 fixation. In this work, this coupling reaction has been investigated using a catalytic system comprised by a selected industrial mining raw material, with potential valorization interest, and a commercial cocatalyst. Herein, industrial mining raw materials are explored as a renewable, recyclable, nontoxic, cheap, and ready‐available catalysts for the transformation of CO2 into highly valuable products such as cyclic carbonates. Initial experiments with the mining materials and alternative by‐products of industrial valorization interest were carried out using propylene oxide (OP) as an initial selected oxirane. The most active raw materials were fully characterized to study their morphology, composition, and surface hydroxyl groups to determine active basic sites as novel heterogeneous base catalysts. The achieved yield of cyclic carbonate in these preliminary experiments was observed in the range of 37–85% for the different tested catalysts. In the case of the most active by‐product used as catalyst (Sulfamag), propylene carbonate reached the yield of 85% as a higher result obtained under mild conditions. Sulfamag was selected to optimize reaction conditions, including the study of different cocatalysts. Moreover, coupling reactions between CO2 and other aliphatic and aromatic epoxides were also performed efficiently for Sulfamag, showing yields between 71 and 91% and selectivity of 99% under mild conditions, demonstrating their potential as a renewable raw material solid‐based heterogeneous catalyst in the synthesis of different cyclic carbonates from CO2 and epoxides. Furthermore, Sulfamag showed high recycling efficiency in a test of four cycles and the deactivation of catalyst was compared with commercially available MgO. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.

Electrochemical Cross‐Electrophile‐Coupling for Transition‐Metal‐Free Allylic Carboxylation with Ambient CO2

AbstractThe use of CO2as a C1 building block to access carboxylic acids is one of the key aspects in the context of carbon capture and utilization (CCU). Herein we report on an electrochemical carboxylation of allyl esters with CO2at atmospheric pressure. This strategy enabled to the synthesis of diverse carboxylic acids without the need for a transition metal catalyst. Furthermore, the mechanism was studied through ICP‐MS analysis and cyclic voltammetry studies for the cross‐electrophile CO2coupling.

Challenges and Prospects in the Catalytic Conversion of Carbon Dioxide to Formaldehyde

AbstractFormaldehyde (HCHO) is a crucial C1 building block for daily‐life commodities in a wide range of industrial processes. Industrial production of HCHO today is based on energy‐ and cost‐intensive gas‐phase catalytic oxidation of methanol, which calls for exploring other and more sustainable ways of carrying out this process. Utilization of carbon dioxide (CO2) as precursor presents a promising strategy to simultaneously mitigate the carbon footprint and alleviate environmental issues. This Minireview summarizes recent progress in CO2‐to‐HCHO conversion using hydrogenation, hydroboration/hydrosilylation as well as photochemical, electrochemical, photoelectrochemical, and enzymatic approaches. The active species, reaction intermediates, and mechanistic pathways are discussed to deepen the understanding of HCHO selectivity issues. Finally, shortcomings and prospects of the various strategies for sustainable reduction of CO2 to HCHO are discussed.

Challenges and Prospects in the Catalytic Conversion of Carbon Dioxide to Formaldehyde.

Formaldehyde (HCHO) is a crucial C1 building block for daily-life commodities in a wide range of industrial processes. Industrial production of HCHO today is based on energy- and cost-intensive gas-phase catalytic oxidation of methanol, which calls for exploring other and more sustainable ways of carrying out this process. Utilization of carbon dioxide (CO2 ) as precursor presents a promising strategy to simultaneously mitigate the carbon footprint and alleviate environmental issues. This Minireview summarizes recent progress in CO2 -to-HCHO conversion using hydrogenation, hydroboration/hydrosilylation as well as photochemical, electrochemical, photoelectrochemical, and enzymatic approaches. The active species, reaction intermediates, and mechanistic pathways are discussed to deepen the understanding of HCHO selectivity issues. Finally, shortcomings and prospects of the various strategies for sustainable reduction of CO2 to HCHO are discussed.

Glycolaldehyde as a Bio-Based C1 Building Block for Selective N-Formylation of Secondary Amines.

Biomass derived glycolaldehyde was employed as C1 building block for the N-formylation of secondary amines using air as oxidant. The reaction is atom economic, highly selective and proceeds under catalyst free conditions. This strategy can be used for the synthesis of cyclic and acyclic formylamines, including DMF. Mechanistic studies suggest a radical oxidation pathway.

Recent advances in chemical fixation of CO2 based on flow chemistry

Carbon dioxide (CO2) is an attractive C1 building block in chemical synthesis due to its abundance, availability and sustainability. However, the low reactivity and high stability generally limits its transformations under mild conditions to value added chemicals. Recent advances in flow chemistry provide effective means for the chemical transformation of CO2, and many new methods and techniques that fully utilized the advantages of continuous flow platforms for the chemical fixation of CO2 have been realized. In view of the rapid development and the urgent need for continuous transformation of CO2, herein we wish to present an update of the recent advances in this research area.

Fluoroiodomethane: A CH2F‐Moiety‐Delivering Agent Suitable for Nucleophilic‐, Electrophilic‐, and Radical‐Harnessed Operations

AbstractThe recent renewed interest in mono‐fluoromethylation chemistry – somehow less developed than the analogous well‐established trifluoro‐ and difluoro‐methylation tactics – identified the simple C1 building block fluoroiodomethane as an effective and versatile CH2F‐delivering agent. The convenient physical state – liquid with a boiling point of 53 °C – and the nowadays commercial availability, boosted in the last years the flourishing of protocols where it is used for generating the fluoromethyl group under conceptually distinct logics: electrophilic, nucleophilic, and radical. Depending on the reaction conditions adopted, the reagent serves as a pluripotent precursor of variously functionalized CHF fragments, thus considerably simplifying the installation of the motif into organic skeletons. A critical analysis of the applications found by the reagent in the literature (mainly) published in the last 5 years is provided with vistas to its employment in the preparation of drug molecules (and precursors thereof).magnified image

Oxidative C-H/N-H Carbonylation of Benzamide by Nickel Catalysis with CO as the Carbonyl Source.

An efficient and direct carbonylation of aminoquinoline benzamides has been developed using abundant and inexpensive Ni(OAc)2·4H2O as the catalyst and carbon monoxide as a cost-efficient C1 building block. This process features good functional-group tolerance and can be conducted on gram scale. The directing group can be easily removed under mild conditions.

(Digital Presentation) Synthesis of Ureas and Carbamates from Carbon Tetrahalides By B12-TiO2 Catalyst Modified with Magnesium Ion

Organometallic B12 compounds are unique metal complexes having a cobalt-carbon s-bond present in biological systems. Cleavage of the metal-organic σ-bond initiates many B12 dependent enzymatic reactions. Based on unique properties of B12 enzymes, many B12-inspired reactions were developed.1-3 Here we report the visible light-driven B12inspired reaction for the synthesis of base chemicals from carbon tetrahalides as C1 building block. The hybrid catalyst, B12-Mg2+-TiO2, composed of the B12 derivative and titanium oxide modified with magnesium ion (Mg2+-TiO2) was synthesized for the visible light-driven catalytic reaction (Figure 1). Carbon tetrachloride (CCl4) was converted to N,N-diethylurea by the B12-Mg2+-TiO2 catalyst under the visible light irradiation (l>420 nm) with diethylamine (Et2NH) in air at room temperature. Valuable ureas are synthesized from CCl4 under mild condition. This photochemical catalytic reaction was applied to the synthesis of asymmetric ureas, carbamates, and carbonate ester via carbamoyl chloride in the presence of corresponding nucleophiles, RNH2, R2NH, ROH. Furthermore, the reactions were applied to carbon tetrabromide (CBr4) as substrate. Carbon tetrabromide is a commercially available solid compound which is stable at room temperature and can be easily handled. Scope of substrate and detailed reaction mechanism will be reported in this presentation.

Recyclable polymerized Lewis acid poly-BPh(C6F5)2 catalyzed selective N-formylation and N-methylation of amines with carbon dioxide and phenylsilanes

A new boron-centered polymer, which is named poly-BPh(C6F5)2 (polymerized-bis(perfluorophenyl)-(phenyl)borane) was designed and synthesized, which is found to be an efficient catalyst for selective N-formylation and N-methylation of amines using CO2 as C1 building block in the presence of hydrosilanes. Milder reaction conditions (even at room temperature and 1 bar of CO2), remarkable recyclability, tolerance against a variety of functional groups and excellent yields reveal the excellent stability and catalytic activity of poly-BPh(C6F5)2. The process herein represents a simple, ecologically friendly and efficient route for CO2 chemical fixation into value-added chemicals.