Reaction Of Dimethyl Carbonate Research Articles

Sustainable methods for the carboxymethylation and methylation of ursolic acid with dimethyl carbonate under mild and acidic conditions.

Ursolic acid is a triterpene plant extract that exhibits significant potential as an anti-cancer, anti-tumour, and anti-inflammatory agent. Its direct use in the pharmaceutical industry is hampered by poor uptake of ursolic acid in the human body coupled with rapid metabolism causing a decrease in bioactivity. Modification of ursolic acid can overcome such issues, however, use of toxic reagents, unsustainable synthetic routes and poor reaction metrics have limited its potential. Herein, we demonstrate the first reported carboxymethylation and/or methylation of ursolic acid with dimethyl carbonate (DMC) as a green solvent and sustainable reagent under acidic conditions. The reaction of DMC with ursolic acid, in the presence of PTSA, ZnCl2, or H2SO4-SiO2 yielded the carboxymethylation product 3β-[[methoxy]carbonyl]oxyurs-12-en-28-oic acid, the methylation product 3β-methoxyurs-12-en-28-oic acid and the dehydration product urs-2,12-dien-28-oic acid. PTSA demonstrated high conversion and selectivity towards the previously unreported carboxymethylation of ursolic acid, while the application of formic acid in the system led to formylation of ursolic acid (3β-formylurs-12-en-28-oic acid) in quantitative yields via esterification, with DMC acting solely as a solvent. Meanwhile, the methylation product of ursolic acid, 3β-methoxyurs-12-en-28-oic acid, was successfully synthesised with FeCl3, demonstrating exceptional conversion and selectivity, >99% and 99%, respectively. Confirmed with the use of qualitative and quantitative green metrics, this result represents a significant improvement in conversion, selectivity, safety, and sustainability over previously reported methods of ursolic acid modification. It was demonstrated that these methods could be applied to other triterpenoids, including corosolic acid. The study also explored the potential pharmaceutical applications of ursolic acid, corosolic acid, and their derivatives, particularly in anti-inflammatory, anti-cancer, and anti-tumour treatments, using molecular ADMET and docking methods. The methods developed in this work have led to the synthesis of novel molecules, thus creating opportunities for the future investigation of biological activity and the modification of a wide range of triterpenoids applying acidic DMC systems to deliver novel active pharmaceutical intermediates.

Single-atom Au-modified CeO2 catalyst: Structure and its catalytic performance in 2,4-diaminotoluene methoxycarbonylation reaction

In the reaction of dimethyl carbonate (DMC) and 2,4-diaminotoluene (TDA), Au/CeO2 exhibits higher selectivity than CeO2 for dimethyl toluene-2,4-dicarbamate (TDC). However, its catalytic activity drops after H2 reduction (denoted as Au/CeO2-R). The characterization results illustrate that Au exists as a single atom with the primary species as Auδ+ in Au/CeO2, forming CexAu1−xO2 structure similar to solid solution. Whereas for Au/CeO2-R catalyst, Au mainly exists as Au0, forming the Au-O-Ce structure on CeO2 surface. Significantly, the strong interaction between Au and CeO2 increases Ce3+ and oxygen vacancies content, as well as modulates their acidic property. However, the catalytic activity of Au/CeO2-R is found to be lower than Au/CeO2 as the species formed by DMC dissociation on its surface are not easily desorbed. Other transition metals supported on CeO2 are also prepared, wherein Pt/CeO2 and Pd/CeO2 exhibit good TDC selectivity. In the end, the electronegativity and catalytic activity of metals are correlated.

Preparation and UV curing properties of oxazolidinone-based acrylate derivatives

The oxazolidinone-based acrylate derivatives were prepared by the oxa-Michael addition reaction of neopentyl glycol diacrylate (NPGDA), trimethylolpropane triacrylate (TMPTA) and ethylene glycol dimethacrylate (EGDMA) with 3-(2-hydroxyethyl)-2-oxazolidinone (Z1), which was prepared by the reaction of dimethyl carbonate (DMC) with diethanolamine (DEA). The molecular structures of the products were characterized by FT-IR, 1H NMR and electrospray ionization high resolution mass spectrometry (ESI-HRMS). Under initiated by 1 wt% 2-isopropyl-9H-thioxanthen-9-one (ITX) and 1 wt% 2-hydroxy-2-methyl-1-phenylpropan-1-one (Da-1173), the oxazolidinone- based acrylates were cured in 30 s with double bond conversion of 92% and 98%, respectively. The photopolymerization activity is in the order of oxazolidinone-based acrylate > conventional acrylate with 3 wt% EDB > conventional acrylate. The first-order kinetics for oxazolidinone part indicates that the oxazolidinone group is a hydrogen donor, which can terminate the polymeric radicals, forming an active radical to re-initiate the polymerization. HRMS analysis of oligomers extracted from the UV-cured film of butyl acrylate confirms further the role of oxazolidinone part, and the plausible UV polymerization mechanism was proposed. The composition of addition product of TMPTA with Z1 (named as TMPTA-Z1) with epoxy acrylate can be 3D printed forming various models with the hardness of 5H.

Study on MoO3/SBA-16 catalyzed transesterification to synthesize diphenyl carbonate.

In this paper, the mesoporous molecular sieve SBA-16 with good dispersion was prepared by hydrothermal method. Under the condition of Si/Mo= 1.0, MoO3/SBA-16 catalysts were prepared by iso-dipping method at 550 °C, 650 °C and 750 °C calcination temperature, which for the synthesis of diphenyl carbonate (DPC) from dimethyl carbonate (DMC) and phenyl acetate (PA) was used, and the uncalcined MoO3/SBA-16 was used as a reference. XRD, TG-DTA, XPS, ICP-MS, FT-IR, BET, SEM and TEM characterization. The effects of calcination temperature and reaction conditions on the catalytic performance of MoO3/SBA-16 in transesterification of DMC and PA were investigated. The results show that the MoO3/SBA-16 catalyst prepared at 550 °C has the best catalytic performance in the reaction of DMC and PA ester exchange, and the catalyst has the best catalytic performance in the appropriate reaction strip (n(PA) = 1.0 mol; n (PA)/n (DMC) = 2.0; m (MoO3/SBA-16) = 6.0g; t = 5.0 h; T = 180 °C), the DMC conversion is 78.5%, and the selectivity of methyl phenyl carbonate (MPC) and DPC is 51.1% and 46.5%, respectively. After five cycles, the catalyst activity decreased and the conversion of DMC decreased from 78.5% to 15.8%. However, its crystal structure remained unchanged. The used catalyst can be easily regenerated by calcination in air at 550 °C for 5 h. The catalytic performance of the regenerated catalyst was almost as high as that of the fresh one.

Study on oxidation and pyrolysis of carbonate esters using a micro flow reactor with a controlled temperature profile. Part II: Chemical kinetic modeling of ethyl methyl carbonate

Little is known on reactivity of ethyl methyl carbonate (EMC), which is widely used as an electrolyte solvent in lithium-ion batteries (LIB). A better understanding on the reactivity of EMC and its chemical kinetics are required to assess the fire risks of LIB. The reactivity of a stoichiometric EMC/air mixture was investigated with a weak flame in a micro flow reactor with a controlled temperature profile (MFR) at atmospheric pressure and a maximum wall temperature (Tw,max) of 1300 K. To investigate species evolution formed in EMC oxidation (equivalence ratios of 0.5, 1.0 and 1.5) and pyrolysis, species measurements were performed in MFR at atmospheric pressure and Tw,max range of 700–1300 K. These experimental insights were used for modeling and validation of a chemical kinetic mechanism for EMC. The first chemical kinetic mechanism of EMC was developed based on reactions of dimethyl carbonate (DMC) and diethyl carbonate (DEC), and literature data.The present EMC mechanism reproduced measured species profiles well. Both experiments and computations showed two-stage increases in CO2 mole fraction: initial fuel decomposition producing CO2 at Tw,max = 850 K and subsequent CO oxidation to CO2 at Tw,max = 1050 K. In the first CO2 increase region, a series of decomposition reaction of EMC produced CO2, C2H4 and CH3OH via methyl formic acid. The oxidation of CH3OH and C2H4 proceeded in the region corresponding to second CO2 increase. The present EMC mechanism also reproduced experimental weak flame position of EMC well. Computational weak flame structure of EMC indicated a three-stage reaction: EMC decomposition, oxidation of decomposition products to CO and oxidation of CO to CO2. The three-stage reaction initiated by fuel decomposition reaction is distinct from the one initiated by low-temperature oxidation of ordinary hydrocarbons. This novel three-stage reaction was also observed for DEC, which has two ethyl groups.

Unveiling the mechanism of N-methylation of indole with dimethylcarbonate using either DABCO or DBU as catalyst.

Depending on the catalyst used, N-methylation of indole with dimethylcarbonate (DMC)-an environmentally friendly alkylation agent-yields different products. With 1,4-diazabicyclo[2.2.2]octane (DABCO), the reaction forms only N-methylated indole, but with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), both N-methylated and N-methoxycarbonylated indole are formed. Using direct ESI(+)-MS monitoring to collect actual snapshots of the changing ionic composition of the reaction solution, we report on the interception and characterization of key intermediates for such reactions. Although a mechanism has been proposed with methoxycarbonylated base as the key intermediate for both DBU and DABCO, the ESI(+)-MS data and B3LYP-D3/6-311+G** calculations suggest that the reaction of DMC with indole under either DABCO or DBU catalysis follows contrasting mechanisms.

Mechanism and kinetics of the oxidation of dimethyl carbonate by hydroxyl radical in the atmosphere.

The mechanism and kinetics for the reaction of dimethyl carbonate (DMC) with OH radical have been studied by using quantum chemical methods. Four reaction pathways were identified for the initial reaction. In the first two pathways, hydrogen atom abstraction is taking place and alkyl radical intermediate is formed with the energy barrier of 6.4 and 7.9kcal/mol. In the third pathway, OH addition reaction to the carbonyl carbon (C2) atom of DMC and intermediate, I2, is formed with an energy barrier of 11.9kcal/mol. In the fourth pathway, along with CH3O●, methyl hydrogen carbonate is formed. For this C-O bond breaking and O-H addition reaction, the energy barrier is 27kcal/mol. The calculated enthalpy and Gibbs energy values show that the studied initial reactions are exothermic and exoergic except the OH addition reaction. For the initial reactions, the rate constants were calculated by using canonical variational transition state theory (CVT) with small curvature tunneling (SCT) correction over the temperature range of 278-1200K. At 298K, the calculated rate coefficient for the in-plane and out-of-plane hydrogen atom abstraction reaction pathway is 2.30 × 10-13 and 0.02 × 10-13cm3molecule-1s-1. Further, the reaction between alkyl radical intermediate formed from the first pathway and O2 is studied. The reaction of alkyl peroxy radical intermediate with atmospheric oxidants, HO2, NO, and NO2 is also studied. It was found that the formic (methyl carbonic) anhydride is the end product formed from the atmospheric oxidation and secondary reactions of DMC.

Quantum Chemical Study of Addition–Elimination Reactions of Dimethyl Carbonate with Methylamine

The mechanisms of noncatalytic and autocatalytic addition–elimination reactions of dimethyl carbonate with methylamine have been studied in terms of wB97XD/6-311++G(df,p), M06/6-311++G(df,p), and PBE0/6-311++G(df,p) quantum chemical methods, and thermodynamic and activation parameters of these reactions have been calculated. The rate-determining stage is the formation of tetrahedral carbon intermediate. The addition–elimination mechanism is preferred over the autocatalytic SN2 mechanism determined by enhanced donor–acceptor and acid–base properties of amine complexes with alcohol associates in comparison to amines.

A solvent-free route to non-isocyanate poly(carbonate urethane) with high molecular weight and competitive mechanical properties

A series of non-isocyanate linear poly(carbonate urethanes) (PCUs) were prepared through an environmentally-friendly route based on dimethyl carbonate, 1,6-hexanediol and 1,6-hexanediamine. Bis-1,6-hexamethylencarbamate (BHC) was first synthesized from diamine and excess dimethyl carbonate. To prevent the detrimental crosslinking problem, a new “hard segment first” route was developed. In this route, the polyurethane diol was first prepared by the reaction between BHC and 1,6-hexanediol. Polycarbonate diol was obtained by the reaction of dimethyl carbonate and 1,6-hexanediol. The subsequent polycondensation of polyurethane diol and polycarbonate diol led to linear PCUs. The polymers were characterized by GPC, FT-IR, 1H NMR, 13C NMR, DSC, WAXD, TGA and tensile testing. The results indicated that the PCUs possessed a linear structure and high molecular weight with a number-average molecular weight of up to 60,000 g/mol. It should be noted that the PCUs exhibited good thermal properties with a composition-dependent melting point ranging from 60 °C to 137 °C, and a good mechanical strength, with tensile strength values lying between 17 MPa and 29 MPa and elongation at break varying from 665% to 26%. Considering the green procedure and raw materials as well as the good processability and mechanical properties of the resultant PCUs, this kind of aliphatic thermoplastic PCU offers great potential to be industrialized and applied in the biomedical field such as tissue scaffolds and cardiovascular implants.

The reactions of dimethyl carbonate and its derivatives

The worldwide urge to embrace a sustainable and bio-compatible chemistry has led industry and academia to develop chlorine-free methodologies focused on the use of CO2-based compounds, such as dimethyl carbonate, as feedstocks, promoters and reaction media.

ChemInform Abstract: Reactions of Dimethyl Carbonate with Aliphatic Amines under High Pressure.

AbstractA catalyst‐free and solvent‐free high‐pressure synthesis of carbamates is described.

Reactions of Dimethyl Carbonate with Aliphatic Amines Under High Pressure

A facile synthesis of methyl carbamates from primary amines and dimethyl carbonate has been achieved at room temperature using high pressure. High-pressure synthesis of methyl carbamates described herein provides access to the target molecules in an efficient and environmentally friendly way without solvent or catalyst. Better conversion and selectivity than previously published procedures were obtained.

Explosives Based on Diaminourea

AbstractDiaminourea (DAU, 1) is synthesized by the reaction of dimethylcarbonate with hydrazine hydrate. DAU was protonated using nitric as well as perchloric acid yielding diaminouronium nitrate (2), diaminouronium dinitrate monohydrate (3) and diaminouronium perchlorate (4). The bis‐perchlorate salt could not be isolated due to its high hygroscopicity. Explosives 2–4 were fully characterized using X‐ray diffraction, NMR and vibrational spectroscopy, mass spectrometry and elemental analysis. The thermal properties were determined by differential scanning calorimetry (DSC). The sensitivities towards impact (2: 9 J, 3: >40 J, 4: 2 J), friction (2: 288 N, 3: >360 N, 4: 5 N) and electrical discharge (2: 0.60 J, 3: 0.50 J, 4: 0.30 J) were investigated using Bundesanstalt für Materialforschung (BAM) methods and a small scale electrostatic discharge device. The detonation parameters of 2 and 3 were computed using the EXPLO5.04 code with the X‐ray densities as well as calculated (CBS‐4 M) energies of formation as input values.

Pseudo-Homogenous Kinetics Model for the Synthesis of Dimethyl Carbonate from Urea and Methanol with Heterogeneous Catalyst

The synthesis of dimethyl carbonate (DMC) from urea and methanol includes two main reactions: one amino of urea is substituted by methoxy to produce the intermediate methyl carbamate (MC) which further converts to DMC via reaction with methanol again. In a stainless steel autoclave, the kinetics of these reactions was separately investigated without catalyst and with Zn-containing catalyst. Without catalyst, for the first reaction, the reaction kinetics can be described as first order with respect to the concentrations of methanol and methyl carbamate (MC), respectively. For the second reaction, the results exhibit characteristics of zero-order reaction. Over Zn-containing catalyst, the first reaction is neglected in the kinetics model since its rate is much faster than second reaction. After the optimization of reaction condition, the macro-kinetic parameters of the second reaction are obtained by fitting the experimental data to a pseudo-homogenous model, in which a side reaction of DMC synthesis is incorporated since it decreases the yield of DMC drastically at high temperature. The activation energy of the reaction from MC to DMC is 104 KJ/mol while that of the side reaction of DMC is 135 KJ/mol.

Heterogeneous CeO2 catalyst for the one-pot synthesis of organic carbamates from amines, CO2 and alcohols

Heterogeneous CeO2 catalyst can catalyze the one-pot synthesis of methyl benzylcarbamate from benzylamine, CO2 and methanol. The yield of methyl benzylcarbamate reached 92% at >99% benzylamine conversion and 92% benzylamine-based selectivity even in the absence of the dehydrating agents. The catalyst is reusable after the calcination at 873 K for 3 h. Various carbamates can be synthesized with good yield and high selectivity by the reaction of amines + CO2 + alcohols over CeO2. The main formation route of methyl benzylcarbamate is suggested to be the reaction of dimethyl carbonate or the precursor of dimethyl carbonate formation with benzylamine.

Non-phosgene synthesis of isocyanates based on CO 2: Synthesis of methyl N-phenyl carbamate through coupling route with lead compound catalysts

The synthesis of methyl N-phenyl carbamate (MPC), the key intermediate for the non-phosgene synthesis of isocyanates based on CO 2, was studied from the reaction of dimethyl carbonate and N, N′-diphenyl urea under pressure. A variety of solid catalysts were screened, which showed lead compounds such as PbO, PbO 2, PbCO 3, and 2PbCO 3·Pb(OH) 2 had excellent catalytic activity. The characterization of XRD showed that the screened lead compound catalysts after reaction were changed into the same lead compound with the group –PbOH. With the increase of recycling times of the used lead compound catalysts, the selectivity of MPC and conversion of DPU were still about 99%. And the characterization of XRD and FTIR showed that new lead compound, which was produced with the increase of recycling times of the used lead compound catalysts, was also a lead compound with –PbOH. So the above results indicated that the real lead catalyst was the compound containing –PbOH. A possible reaction mechanism was discussed with the lead compound catalysts.

ChemInform Abstract: Green Approaches to Highly Selective Processes: Reactions of Dimethyl Carbonate over Both Zeolites and Base Catalysts

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The methylation of benzyl-type alcohols with dimethyl carbonate in the presence of Y- and X-faujasites: selective synthesis of methyl ethers

At 165–200 °C, in the presence of sodium-exchanged faujasites (NaX or NaY) as catalysts, the reaction of dimethyl carbonate with benzyl-, o- and p-methoxybenzyl-, p-hydroxybenzyl-, diphenylmethyl-, and triphenylmethyl-alcohols (1a, 2a,b, 3a, 4a, and 4c, respectively), produces the corresponding methyl ethers in up to 98% yields. A peculiar chemoselectivity is observed for hydroxybenzyl alcohols (compounds 3a and 3b, para- and ortho-isomers) whose etherification takes place without affecting the OH aromatic groups. Acid–base interactions of alcohols and DMC over the faujasite surface offer a plausible explanation for the catalytic effect of zeolites NaY and NaX, as well as for the trend of reactivity shown by the different alcohols (primary > secondary > tertiary). However, in the case of substrates with mobile protons in the β-position (i.e.1-phenylethanol and 1,1-diphenylethanol), the dehydration reaction to olefins is the major, if not the exclusive, process.

Green Synthetic Method for 1,5‐Disubstituted Carbohydrazones.

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Green approaches to highly selective processes: Reactions of dimethyl carbonate over both zeolites and base catalysts

Abstract Nowadays available by clean industrial processes, dimethyl carbonate (DMC) possesses properties of nontoxicity and biodegradability which make it a true green reagent/solvent to devise syntheses that prevent pollution at the source. In particular, the versatile reactivity of DMC allows both methylation and carboxymethylation protocols that can replace conventional and highly noxious reagents such as methyl halides (and dimethyl sulfate, DMS) and phosgene. In the field of DMC-mediated methylations, representative examples are the reactions of DMC with CH2-active compounds and primary aromatic amines. In the presence of organic/inorganic bases or zeolites (faujasites) catalysts, these processes proceed with unprecedented selectivity (up to 99 %, at complete conversion) toward the corresponding mono-C- and mono-N-methyl derivatives, a result hitherto not possible with conventional alkylation reagents. In the case of ambident amines (e.g., aminophenols, aminobenzyl alcohols, aminobenzoic acids, and aminobenzamides), the unique combination of DMC and zeolites allows not only a very high mono-N-methyl selectivity, but also a complete chemoselectivity toward the amino group. The other nucleophilic functionalities (OH, CO2H, CH2OH, CONH2) are fully preserved from alkylation and/or transesterification reactions, usually observed over basic catalysts.