N,N-Dimethylformamide: much more than a solvent

Mechanism of iron complexes catalyzed in the N-formylation of amines with CO2 and H2: the superior performance of N-H ligand methylated complexes

CO2 hydrogenation into value-added chemicals not only offer an economically beneficial outlet but also help reduce the emission of greenhouse gases. Herein, the density functional theory (DFT) studies have been carried out on CO2 hydrogenation reaction for formamide production catalyzed by two different N-H ligand types of PNP iron catalysts. The results suggest that the whole mechanistic pathway has three parts: (i) precatalyst activation, (ii) hydrogenation of CO2 to generate formic acid (HCOOH), and (iii) amine thermal condensation to formamide with HCOOH. The lower turnover number (TON) of a bifunctional catalyst system in hydrogenating CO2 may attribute to the facile side-reaction between CO2 and bifunctional catalyst, which inhibits the generation of active species. Regarding the bifunctional catalyst system addressed in this work, we proposed a ligand participated mechanism due to the low pKa of the ligand N-H functional in the associated stage in the catalytic cycle. Remarkably, catalysts without the N-H ligand exhibit the significant transfer hydrogenation through the metal centered mechanism. Due to the excellent catalytic nature of the N-H ligand methylated catalyst, the N-H bond was not necessary for stabilizing the intermediate. Therefore, we confirmed that N-H ligand methylated catalysts allow for an efficient CO2 hydrogenation reaction compared to the bifunctional catalysts. Furthermore, the influence of Lewis acid and strong base on catalytic N-formylation were considered. Both significantly impact the catalytic performance. Moreover, the catalytic activity of PNMeP-based Mn, Fe and Ru complexes for CO2 hydrogenation to formamides was explored as well. The energetic span of Fe and Mn catalysts are much closer to the precious metal Ru, which indicates that such non-precious metal catalysts have potentially valuable applications.

Photoassisted Charge Transfer Between DMF and Substrate: Facile and Selective N,N-Dimethylamination of Fluoroarenes

A reversible Van der Waals complex formation between the electron-deficient fluorinated aromatic ring and N,N-dimethylformamide (DMF) molecules followed by light irradiation resulted in charge transfer (CT) process. The complex was stabilized by ammonium formate and further decomposed to form the C-N bond. Control experiments revealed that the simultaneous S_N Ar pathway also contributes to product formation. This methodology is mild, metal-free, and effective for the amination of a variety of substrates. The reproducibility of this methodology was also verified on gram-scale reactions. The CT states were supported by control UV/Vis spectroscopy and computational studies.

Structural and Thermal Investigations of Co(II) and Ni(II) Coordination Polymers Based on biphenyl-4,4'-dioxydiacetate Linker

Two coordination polymers, [Co(µ₄-L)(H₂O)₂]_n (1) and [Ni(µ-L)(H₂O)₄]_n (2), were solvothermally assembled from the corresponding metal(II) chlorides and biphenyl-4,4-dioxydiacetic acid (H₂L) as a flexible dicarboxylate linker. The cobalt(II) compound 1 featured a layer-pillared 3D metal-organic network with a cds topology, while the nickel(II) derivative 2 represented a linear chain 1D coordination polymer with a 2C1 topology. The µ₄₋ and µ-L²⁻ linkers exhibited different denticity and coordination modes in the synthesized compounds, thus contributing to their structural diversity. The dimensionality of 1 and 2 had an influence on their thermal stability and decomposition processes, which were investigated in detail by TG-DSC and TG-FTIR methods. Thermal decomposition products of coordination polymers were also analyzed by PXRD, confirming the formation of Co₃O₄/CoO and NiO as final materials. The obtained compounds broaden a family of coordination polymers assembled from flexible dicarboxylate linkers.

Zinc salt-catalyzed reduction of α-aryl imino esters, diketones and phenylacetylenes with water as hydrogen source

The zinc salt-catalyzed reduction of α-aryl imino esters, diketones and phenylacetylenes with water as hydrogen source and zinc as reductant was successfully conducted. The presented method provides a low-cost, environmentally friendly and practical preparation of α-aryl amino esters, α-hydroxyketones and phenylethylenes. By using D2O as deuterium source, the corresponding products were obtained in high efficiency with excellent deuterium incorporation rate, which gives a cheap and safe tool for access to valuable deuterium-labelled compounds.

Cross-dehydrogenative Coupling Reactions Between Formamidic C(sp2)-H and X-H (X = C, O, N) Bonds

In the last decade, the scientific community has witnessed explosive growth in research on the direct carbamoylation of C-H and X-H (X = N, O) bonds with formamides via cross-dehydrogenative coupling reactions. This novel approach is an effective means of preparing a variety of carboxamide, carbamate as well as urea derivatives, which are prevalent in medicinal chemistry and natural product synthesis. This review elaborates the most important advances and developments in the field, with an emphasis on the reaction patterns and mechanisms.

Synthesis of 3,3'-methylenebis(4-hydroxyquinolin-2(1H)-ones) of prospective anti-COVID-19 drugs

During formylation of 2-quinolones by DMF/Et₃N mixture, the unexpected 3,3'-methylenebis(4-hydroxyquinolin-2(1H)-ones) were formed. The discussed mechanism was proved as due to the formation of 4-formyl-2-quinolone as intermediate. Reaction of the latter compound with the parent quinolone under the same reaction condition gave also the same product. The structure of the obtained products was elucidated via NMR, IR and mass spectra. X-ray structure analysis proved the anti-form of the obtained compounds, which were stabilized by the formation hydrogen bond. Molecular docking calculations showed that most of the synthesized compounds possessed good binding affinity to the SARS-CoV-2 main protease (M^pro) in comparable to Darunavir.

Growth of Crystalline Bimetallic Metal-Organic Framework Films via Transmetalation

Crystalline films of the Cu₃(BTC)₂ (BTC^3- = 1,3,5-benzenetricarboxylate) metal-organic framework (MOF) have been grown by dip-coating an alumina/Si(111) substrate in solutions of Cu(II) acetate and the organic linker H₃BTC. Atomic force microscopy (AFM) experiments demonstrate that the substrate is completely covered by the MOF film, while grazing incidence wide-angle X-ray scattering (GIWAXS) establishes the crystallinity of the films. Forty cycles of dip-coating results in a film that is ∼70 nm thick with a root mean squared roughness of 25 nm and crystallites ranging from 50-160 nm in height. Co²⁺ ions were exchanged into the MOF framework by immersing the Cu₃(BTC)₂ films in solutions of CoCl₂. By varying the temperature and exchange times, different concentrations of Co were incorporated into the films, as determined by X-ray photoelectron spectroscopy experiments. AFM studies showed that morphologies of the bimetallic films were largely unchanged after transmetalation, and GIWAXS indicated that the bimetallic films retained their crystallinity.

Synthesis of tertiary amines by direct Brønsted acid catalyzed reductive amination

Tertiary amines are ubiquitous and valuable compounds in synthetic chemistry, with a wide range of applications in organocatalysis, organometallic complexes, biological processes and pharmaceutical chemistry. One of the most frequently used pathways to synthesize tertiary amines is the reductive amination reaction of carbonyl compounds. Despite developments of numerous new reductive amination methods in the past few decades, this reaction generally requires non-atom-economic processes with harsh conditions and toxic transition-metal catalysts. Herein, we report simple yet practical protocols using triflic acid as a catalyst to efficiently promote the direct reductive amination reactions of carbonyl compounds on a broad range of substrates. Applications of this new method to generate valuable heterocyclic frameworks and polyamines are also included.

Copper-catalyzed synthesis of aminoquinolines from β-(2-aminophenyl)-α,β-ynones using DMF as dual synthon

A new and efficient method has been developed for the synthesis of 4-aminoquinoline through aerobic Cu(i)-catalyzed cyclization of β-(2-aminophenyl)-α,β-ynones. Under the optimized conditions, DMF could serve as a methine source to introduce C2 carbon and a nitrogen source to incorporate amino functionality in the 4th position. Mechanistic studies using 13C- and DMF-d7 revealed that the methine group was derived from a methyl substituent.

Two 8-hydroxyquinoline-based fluorescent chemosensors for ultra-fast and sensitive detection of water content in strong polar organic solvents with large Stokes shifts

It is of great significance to detect the moisture in organic solvents before used in water-sensitive reactions. Herein, two Schiff base quinoline derivatives, 8-hydroxyquinoline-2-carboxaldehyde thiosemicarbazone (HQCT) and 8-hydroxyquinoline-2-carboxaldehyde (pyridine-2-carbonyl)-hydrazine (HQPH), were designed and synthesized by a simple one-step reaction, and used as fluorescent chemosensors for ultra-fast and sensitive detection of water content in strong polar organic solvents. Based on excited-state intramolecular proton transfer (ESIPT) process, HQCT and HQPH exhibited strong fluorescence emissions with large Stokes shifts in dimethyl sulfoxide (DMSO) and N, N-dimethylformamide (DMF) solvents compared to other various organic solvents, and their fluorescence quenching and fluorescent color changes were obviously observed with increasing water content. The experimental results revealed that the hydroxyl groups substituted at the 8-position of HQCT and HQPH played a key role in the fluorescence emission processes. Dynamic light scattering (DLS) and ¹H NMR titration indicated that the sensing mechanism for the detection of water was based on inhibition of the ESIPT by H₂O via forming hydrogen bonds. In the range of 0.0-1.8 wt%, the fluorescence intensity of chemosensors changed as a linear function of water content. The detection limits of water in DMSO by HQCT and HQPH were as low as 0.0220 wt% and 0.0274 wt%, respectively. Moreover, HQCT and HQPH are successfully applied for the detection of moisture content in real commercial organic solvents.

Crystal structure of dimethylammonium 5-fluorouracil-1-acetate, C8H12N3O4F

C8H12N3O4F, monoclinic, P21/c (no. 14), a = 4.8090(3) Å, b = 9.9340(6) Å, c = 22.2437(13) Å, β = 90.138(8)°, V = 1062.64(11) Å3, Z = 4, R gt(F) = 0.0452, wR ref(F 2) = 0.1227, T = 293(2) K.

N,N-Dimethylformamide-Protected Single-Sized Metal Nanoparticles and Their Use as Catalysts for Organic Transformations

In this mini-review, we summarize the solution syntheses of N,N-dimethylformamide (DMF)-protected metal nanoparticles (NPs) and nanoclusters (NCs) and their use in catalytic reactions. Representative examples are given of external-stabilizer/protectant-free metal NP and NC syntheses by reduction with DMF. In this method, DMF has three roles, i.e., a solvent, reductant, and protectant. Recent applications of DMF-stabilized metal NPs are summarized. These applications have enabled a versatile organic transformation such as cross-coupling reactions, hydrosilylation, and methylation to be achieved. These reactions proceed under low catalyst loadings and ligandless conditions.

The Reims Journey Towards Discovery and Understanding of Pd-Catalyzed Oxidations

This review recounts the development by the authors of the Pd-catalyzed procedures devoted to various kinds of oxidation. Starting with reactions assisted with UV light, the research has explored reactions under light-free conditions: allylic oxidation, alcohol oxidation, etherification, Wacker oxidation and dehydrogenations with, always, accompanying efforts towards mechanism determination.

Selective N-monomethylation of primary anilines with the controllable installation of N-CH2D, N-CHD2, and N-CD3 units

The selective N-monomethylation of primary anilines with the controllable installation of N-CH₂D, N-CHD₂, and N-CD₃ units was realized by using the amine-borane/N,N-dimethylformamide (DMF) system as the methyl precursor.

Copper- and DMF-mediated switchable oxidative C–H cyanation and formylation of imidazo[1,2-a]pyridines using ammonium iodide

The cyanation and formylation of imidazo[1,2-a]pyridines were developed under copper-mediated oxidative conditions using ammonium iodide and DMF as a nontoxic combined cyano-group source and DMF as a formylation reagent.

Synthesis of α,β-alkynyl ketones via the nickel catalysed carbonylative Sonogashira reaction using oxalic acid as a sustainable C1 source

An efficient and economic nickel-dppb catalyzed, carbonylative Sonogashira cross-coupling reaction was demonstrated to provide rapid access to various α,β-alkynyl ketones from aryl iodides and terminal alkynes using oxalic acid as the ex situ C1 source in a double vial (DV) system. Notably, the role of the ligand in combination with the Ni catalyst for the selective formation of carbonylative Sonogashira products was investigated and supported with control experiments. Yet, no reports are available for carbonylative Sonogashira coupling by using a CO-surrogate under Ni-catalyzed conditions. In this process, for the first time, oxalic acid is used as an ex situ solid, bench stable, easy to handle and efficient CO surrogate in a DV-system for the carbonylative Sonogashira coupling reaction with vast substrate scope.

Comparision on the Low-Temperature NH3-SCR Performance of γ-Fe2O3 Catalysts Prepared by Two Different Methods

Maghemite (γ-Fe2O3) catalysts were prepared by two different methods, and their activities and selectivities for selective catalytic reduction of NO with NH3 were investigated. The methods of X-ray powder diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR), ammonia temperature-programmed desorption (NH3-TPD), transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDS), and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) were used to characterize the catalysts. The resulted demonstrated that the γ-Fe2O3 nanoparticles prepared by the facile method (γ-Fe2O3–FM) not only exhibited better NH3-SCR activity and selectivity than the catalyst prepared by the coprecipitation method but also showed improved SO2 tolerance. This superior NH3-SCR performance was credited to the existence of the larger surface area, better pore structure, a high concentration of lattice oxygen and surface-adsorbed oxygen, good reducibility, a lot of acid sites, lower activation energy, adsorption of the reactants, and the existence of unstable nitrates on the surface of the γ-Fe2O3–FM.

Stereoselective three-component cascade synthesis of α-substituted 2,4-dienamides from gem-difluorochloro ethanes

Herein, we describe a new transition metal-free Claisen rearrangement for the synthesis of α-substituted 2,4-dienamides. The one-pot, stereoselective three-component cascade reaction between a series of propargyl alcohols, amines, and gem-difluorochloro ethane derivatives afforded various polysubstituted 2,4-dienamides in good yields. This synthetic method for 1,1-captodative dienes, α-substituted 2,4-dienamides, can be utilized for preparing pharmaceutical analogues containing an indolin-2-one or lactone moiety.

Direct Csp3-H methylenation of 2-arylacetamides using DMF/Me2NH-BH3 as the methylene source

A direct Csp3-H methylenation of 2-arylacetamides using DMF/Me2NH-BH3 as the methylene source was developed. The formyl group of DMF delivered the carbon and one hydrogen atoms, and the Me2NH-BH3 donated the remaining one hydrogen atom. This protocol offers a new alternative to make useful 2-arylacrylamides from simple starting materials.

Active catalyst construction for CO2 recycling via catalytic synthesis of N-doped carbon on supported Cu

Bridging homogeneous and heterogeneous catalysis is a long-term pursuit in the field of catalysis. Herein, we report our results in integration of nano- and molecular catalysis via catalytic synthesis of nitrogen doped carbon layers on AlOx supported nano-Cu which can finely tune the catalytic performance of the supported copper catalyst. This synthetic catalytic material, which can be generated in situ by the reaction of CuAlOx and 1,10-Phen in the presence of hydrogen, could be used for controllable synthesis of N,N-dimethylformamide (DMF) from dimethylamine and CO₂/H₂ via blocking reaction pathways of further catalytic hydrogenation of DMF to N(CH₃)₃. Detailed characterizations and DFT calculations reveal that the presence of N-doped layered carbon on the surface of the nano-Cu particles results in higher activation energy barriers during the conversion of DMF to N(CH₃)₃. Our primary results could promote merging of homogeneous catalysis and heterogeneous catalysis and CO₂ recycling.

Bridging homogeneous and heterogeneous catalysis is a long-term pursuit in the field of catalysis. Here, the authors present results on integration of nano- and molecular catalysis via catalytic synthesis of nitrogen doped carbon layers on AlO_x supported nano-Cu which can finely tune the catalytic performance of the supported copper catalyst.

Direct synthesis of 2-oxo-acetamidines from methyl ketones, aromatic amines and DMF via copper-catalyzed C(sp3)-H amidination

A convenient method for the synthesis of 2-oxo-acetamidines from methyl ketones using aromatic amines and DMF as nitrogen sources is reported via copper-catalyzed C(sp3)-H amidination. Various methyl ketones react readily with aromatic amines and DMF, producing 2-oxo-acetamidines in yields of 47 to 92%. This protocol features the simultaneous formation of C-N and C[double bond, length as m-dash]N bonds using DMF and aromatic amines as two different nitrogen sources. It thus provides an efficient approach to construct acyclic amidines via three C(sp3)-H bond amidination. Based on the preliminary experiments, a plausible mechanism of this transformation is disclosed.

Metal- and solvent-free synthesis of amides using substitute formamides as an amino source under mild conditions

This study described an efficient and practical approach for amide synthesis. The reaction was conducted under metal- and solvent-free conditions at a mild temperature (40 °C) in air, and readily available formamides were used as an amino source. This reaction can be easily upgraded to the gram level with an excellent yield.

A Comprehensive Study on the Dye Adsorption Behavior of Polyoxometalate-Complex Nano-Hybrids Containing Classic β-Octamolybdate and Biimidazole Units

Six new hybrids based on β-[Mo₈O26]4- polyoxometalates, [Ni(H₂biim)₃]₂[β-Mo₈O26]•8DMF(1); (DMA)₂[M(H₂biim)₂(H₂O)₂][β-Mo₈O26]•4DMF (M = Ni (2), Co (3)), DMA = dimethyl-ammonium, H₂biim=2,2'-biimidazole); [M(H₂biim)(DMF)₃]₂[β-Mo₈O26]•2DMF (M = Zn (4), Cu (5)); [(DMA)₂[Cu(DMF)₄][β-Mo₈O26]•2DMF]n (6), have been successfully synthesized and characterized. Compounds 2⁻5 show favorable capacity to adsorb methylene blue (MB) at room temperature, and they can selectively capture MB molecules from binary-mixture solutions of MB/MO (MO = Methyl Orange), or MB/RhB (RhB = Rhodamine B). Compound 3 can uptake up to 521.7 mg g-1 MB cationic dyes rapidly, which perform the maximum adsorption in an hour among the reported materials as far as we know. The compounds are stable and still work very efficiently after three cycles. For compound 3, the preliminary adsorption mechanism studies indicated that the adsorption is an ion exchange process and the adsorption behavior of polyoxometalate-complex can be benefited from additional exchangeable protons in the complex cations.

MoS2-Catalyzed transamidation reaction

The MoS2-catalyzed transamidation reaction with high yields using N,N-dimethylformamide and other amides as carbonyl sources is developed here. The protocol is simple, does not require any additive such as acid, base, ligand, etc., and encompasses a broad substrate scope for primary, secondary and heterocyclic amines. Moreover, the acetylation and propanylation of amines also can be achieved with good to excellent yield by this strategy.

Eco-Friendly Syntheses of 2-Substituted Benzoxazoles and 2-Substituted Benzothiazoles from 2-Aminophenols, 2-Aminothiophenols and DMF Derivatives in the Presence of Imidazolium Chloride

A simple, economical and metal-free approach to the synthesis of 2-substituted benzoxazoles and 2-substituted benzothiazoles from 2-aminophenols, 2-aminothiophenols and DMF derivatives, only using imidazolium chloride (50% mmol) as promoter without any other additive, was reported. Various 2-substituted benzoxazoles and 2-substituted benzothiazoles were thus prepared in moderate to excellent yields.

DMF/NaOH/H2O: a metal-free system for efficient and chemoselective reduction of α-ketoamides

A metal-free method for efficient and chemoselective reduction of α-ketoamides using DMF/NaOH/H₂O system has been developed.