Yield Of Carbamate Research Articles

Biomass-Derived, Target Specific, and Ecologically Safer Insecticide Active Ingredients.

With the continuous increase in food production to support the growing population, ensuring agricultural sustainability using crop-protecting agents, such as pesticides, is vital. Conventional pesticides pose significant environmental risks, prompting the need for eco-friendly alternatives. This study reports the synthesis of new amide-based insecticidal active ingredients from biomass-derived monomers, specifically furfural and vanillin. The process involves reductive amination followed by carbonylation. The synthesis of the furfural-based carbamate yield reaches a cumulative 88 %, with catalysts Rh/Al2O3 and La(OTf)3 being recyclable at each stage. Insecticidal activity assessments reveal that the furfural carbamate exhibits competitive performance, achieving an LC50 of 254.22 μg/cm2, compared to 251.25 μg/cm2 for carbofuran. Ecotoxicity predictions indicate significantly lower toxicity levels toward non-target aquatic and terrestrial species. The importance of the low octanol-water partition coefficient of the biobased carbamate, attributed to the oxygen heteroatom and electron density of the furan ring, is discussed in detail. Building on these promising results, the synthesis strategy was extended to six other biobased aldehydes, resulting in a diverse portfolio of biomass-derived carbamates. A techno-economic analysis reveals a minimum selling price of 11.1 $/kg, only half that of comparable carbamates, demonstrating the economic viability of these new biobased insecticides.

An efficient, selective, and solventless approach to carbamates in DBU-derived ionic liquids: Experimental and theoretical investigations

Herein, we report the synthesis of a diverse array of DBU (1,8-Diazabicyclo[5.4.0]undec-7-ene) based monocationic and dicationic ionic liquids with different inorganic and organic anions. All the synthesized ILs have been characterized by recording their 1H and 13C NMR spectra. The synthesized ILs have been utilized as catalysts in the carbamation of amines with dimethyl carbonate. A detailed study has been conducted to illuminate the possible mechanistic establishment by probing the role of catalysts played by the DBU and DBU-derived ionic liquids in the carbamation process. The attachment of the butyl group to the nitrogen of the DBU unit reversed the selectivity, which has been well established with the help of spectral techniques and theoretical (DFT) studies. The DBU-derived ionic liquids facilitated the N-methoxycarbonylation of amines over N-alkylation. Among all, the best carbamate yields were obtained in the presence of [BuDBU]Ala IL under optimized reaction conditions. The IL catalyst was efficiently reused five times without any significant catalytic loss. The current carbamation protocol possesses advantages like ease of setup, eco-friendly, catalytic reusability, and selectivity.

Mg/Al/Zr hydrotalcite like compounds as catalysts for green synthesis of carbamates

A series of Mg/Al/Zr hydrotalcite-like compounds catalysts were prepared using coprecipitation method with ranging from 0 to 0.62. The catalytic performance of prepared hydrotalcite was evaluated in the synthesis of carbamates from carbon dioxide, amines and alcohols. The effect of Zr incorporation on the structural and textural features was performed using a panel of techniques including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), elemental analysis (ICP-OES), physisorption at 77 K and temperature-programmed desorption of NH3 and CO2. It has demonstrated that the catalyst Mg/Al/Zr containing the lowest amount of Zr exhibited a well crystallized hydrotalcite like phase, a highest specific surface area with an average particle size of 20 nm. The results of catalytic performances were in good correlation with the specific surface area and the basic properties of the catalysts favoring the yield of carbamate. Catalyst HT0.20 showed the best performance in the phosgene-free-halogen-free synthesis of carbamates with a 46% of amine conversion at 473 K and a CO2 pressure of 90 bars and selectivity toward the carbamate of 63% in presence of DMP as a dehydrating agent. Supplemental data for this article can be accessed at the publisher’s website.

Environmental-Friendly Synthesis of Alkyl Carbamates from Urea and Alcohols with Silica Gel Supported Catalysts

TiO2/SiO2, Cr2O3-NiO/SiO2, and TiO2-Cr2O3/SiO2 were prepared by the impregnation method for alkyl carbamate synthesis using urea as the carbonyl source. Up to 97.5% methyl carbamate yield, 97% ethyl carbamate yield, and 96% butyl carbamate yield could be achieved, respectively. The catalysts were characterized by ICP-AES, BET, XRD, XPS, NH3-TPD, and EPMA. Catalytic activity investigation revealed that TiO2/SiO2, Cr2O3-NiO/SiO2, and TiO2-Cr2O3/SiO2 were effective catalysts for methyl carbamate (MC), ethyl carbamate (EC), and butyl carbamate (BC), respectively. The recycling tests suggested that these silica gel supported catalyst system is active, stable, and reusable. A total of 96–97% alkyl carbamate (methyl, ethyl, and butyl) could be obtained in a 2 L autoclave, and these data suggested that our catalyst system is relatively easy to scale up.

Kinetic investigation on carbamate formation from the reaction of carbon dioxide with amino acids in homogeneous aqueous solution

The kinetics of carbamate formation from the reaction of carbon dioxide with α‐amino acids in D2O was first investigated by means of nuclear magnetic resonance spectroscopy. Potassium carbonate was used as the CO2 source. For each amino acid, the maximum carbamate yield, the apparent rate constant for the carbamate formation kapp, and the rate constants for the formation k1 and the breakdown k−1 of the carbamate were estimated. Plots of log k1 or log k−1 versus pKa of amino acids indicated that the formation rate k1 increased with the basicity (pKa) of amino acid, while the decomposition rate k−1 decreased. A Brϕnsted β value of 0.39 was obtained from the former plot, being in good agreement with the previously reported ones (0.26–0.43). The observed negative pKa dependence of log k−1 (Brϕnsted α = 0.34) is reasonable, because the carbamate decomposition is acid‐catalyzed and the steady‐state concentration of H+ should be higher for weaker basic amines. The charge (σ) and the lone‐pair energy (EN) at the nitrogen atom of the amino group were calculated. Although log k1 correlated with σ and EN, log k−1 was unrelated with both of these parameters. Considering that the carbamate formation (k1) is not only base‐catalyzed but should also be promoted by the nucleophilicity of the amino nitrogen, its correlation with σ and EN in addition to pKa is rational. The irrelevance of log k−1 to σ and EN is not surprising, because σ and EN are not a direct measure of [H+] of the solution. Copyright © 2011 John Wiley & Sons, Ltd.

The effect of the components of the PdCl2/Fe/I2/Py catalytic system on nitrobenzene carbonylation to ethyl N-phenylcarbamate

AbstractThe PdCl2/Fe/I2/Py catalytic system (Py-pyridine), reported to be highly active in the reaction of nitrobenzene carbonylation to ethyl phenylcarbamate was studied. The present paper describes the role of catalyst components and its effect on the activity and selectivity of the catalyst. The increase in the amount of PdCl2 in the system while retaining a constant level of the other catalyst components, results in the increase of both carbamate and aniline yields. The increase in the amount of iron while retaining the other components constant, initially causes an increase in the carbamate yield; however, at Fe: Pd ratios higher than 36, the carbamate yield remains constant. The change in the amount of iron has no effect on the amount of aniline formed in the system. An increase in the amount of iodine in the system while retaining the other components constant, results in a decrease in carbamate yield and a considerable increase in the aniline yield of the reaction products.

Carbomethoxylating reactivity of methyl phenyl carbonate toward aromatic amines in the presence of group 3 metal (Sc, La) triflate catalysts

Methyl phenyl carbonate (MPC) has been investigated as a carbomethoxylating agent of aromatic amines in the presence of group 3 metal (Sc or La) triflate catalysts. Under mild conditions (363 K), both Sc(OTf) 3 and La(OTf) 3 (OTf = O 3SCF 3) can promote the carbamation of aniline and a few industrially relevant aromatic diamines, such as 4,4′-methylenedianiline (MDA) and 2,4-diaminotoluene (TDA), with MPC. Carbamate yield and selectivity are markedly affected by the experimental conditions (temperature, reaction medium, nature of the metal center). Sc(OTf) 3 is a more effective and selective carbamation catalyst than La(OTf) 3. Ad hoc experiments have shown that, in the presence of the M(OTf) 3 (M = Sc, La) catalysts, MPC is not only more reactive but also a more selective carbomethoxylating agent than dimethyl carbonate (DMC).

Carbamate synthesis via transfunctionalization of substituted ureas and carbonates

Synthesis of carbamates from substituted ureas and organic carbonates has been demonstrated using di-n-butyltin oxide (DBTO) as a catalyst. Reactivity pattern of ureas indicated that substituents on ureas have no significant effect on the carbamate yields. While, the carbonate reactivity pattern seems to be following the rule that is expected based on the leaving group ability of alkoxides and phenoxide to form carbamate observed in aminolysis of carbonates, it has been shown that basicity of reacting urea plays a vital role in the catalytic activity of this reaction. The effect of reaction parameters such as temperature, catalyst loading, solvent, concentration of reactants, etc. were investigated for synthesis of methyl methyl carbamate (MMC). The Arrhenius activation energy for the reaction between dimethyl urea (DMU) and dimethyl carbonate (DMC) was found to be 7.57 kcal/mol. A reaction mechanism has been postulated explaining the role of DBTO in the synthesis of carbamate from urea and carbonate.

Cleavage of O‐Acylates of Isatin 3‐Oximes in the Presence of Alcohols.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Semi‐continuous Process for the Synthesis of Methyl Carbamate from Urea and Methanol

AbstractA semicontinuous process for the synthesis of methyl carbamate from urea and methanol was investigated in the autoclave without the catalyst. Some significant parameters were determined in terms of the methyl carbamate yield. The optimal reaction conditions were found at an initial molar ratio of methanol/urea of 6:1, a reaction temperature of 423 K, a flow rate of fresh methanol at 4 mL/min, a stirring speed of 800 rpm and a reaction time of 6 hours, respectively. A MC yield of 98.7 % was obtained at the optimal reaction conditions. Furthermore, the kinetics of this reaction were researched and the reaction activation energy was obtained as 110.498 kJ/mol. It was demonstrated that removing methanol containing ammonia from the autoclave and replacing it with continuously feeding fresh methanol resulted in a higher reaction rate and a high MC yield.

Cleavage of O-Acylates of Isatin 3-Oximes in the Presence of Alcohols

In continuing our study of the reaction of O-acyl derivatives of isatin 3-oximes with nucleophilic agents, we have established that no structural changes occur when oximes 1a-d are heated with alcohols. However, when fairly small amounts of triethylamine are added to hot alcoholic solutions of O-acylates of isatin 3-oximes 1a,c, an exothermic reaction occurs and in most cases, we were able to isolate the corresponding N-(2-cyanoaryl)carbamates 2a-c in good yields; but in the case of tert-butyl alcohol, the yields were only up to 11%. The cleavage of heterocyclic nucleus is catalyzed by pyridine, too, but the yields are by half lower. The nature of the acyl group almost exerts no influence on the yield of carbamate.

CuCl2 and PdCl2 catalysts for oxidative carbonylation of aniline with methanol

Synthesis of methyl-N-phenyl carbamate from the oxidative carbonylation of aniline with methanol has been studied over CuCl2-NaI, PdCl2-NaI, PdCl2-CuCl2-NaI, and PdCl2-CuCl2-HCl in an autoclave at 373/438 K and 0.13/3.79 MPa. Carbamate yields decreased in the order: CuCl2-NaI>PdCl2-NaI>PdCl2-CuCl2-NaI>PdCl2-CuCl2-HCl at 438 K and 3.79 MPa. Product distribution profiles showed that carbamate yield increased with reaction time and leveled off at 43.5% over CuCl2-NaI after 1 h of batch reaction at 438 K and 3.79 MPa. The low cost and high activity of CuCl2-NaI could provide a novel and cost-effective process for carbamate synthesis.

Reaction of aromatic diamines with diphenylcarbonate catalyzed by phosphorous acids: a new clean synthetic route to mono- and dicarbamates

In the presence of organophosphorus acids [Ph 2P(O)OH, (PhO) 2P(O)OH, (BuO) 2P(O)OH, (BuO)P(O)(OH) 2], aromatic diamines, such as 4,4′-methylendianiline (MDA) or 2,4-diaminotoluene (TDA), react with diphenylcarbonate (DPC) to afford in a very selective way mono- and dicarbamate phenyl esters. The carbamation process is strongly influenced by the temperature and solvent. The influence of both these factors on carbamate yield and selectivity has been investigated and we present in this study the kinetics of formation of both mono- and dicarbamate esters.

ChemInform Abstract: Phase‐Transfer Alkoxycarbonylation of Secondary Alkyl Amines. Application of a Factorial Design.

AbstractTo establish optimum operating conditions for obtaining the best yield of carbamate (III) in the solid‐liquid phase‐transfer reaction of model dialkylamine (I) with model alkyl halide (II), a 24 factorial design at two levels is applied by varying the following four factors by which the competitive formation of carbamate (IV) and trialkylamine (V) is governed: a) ratio of base K2CO3 (III) to amine(I), b) solvent (MeCN or heptane), c) halide anion X(Cl vs.

A study of the phase-transfer alkoxycarbonylation of secondary alkyl amines. Application of a factorial design

A 24 factorial design has been applied to the study of the competitive alkylation versus alkoxycarbonylation of secondary alkyl amines under phase-transfer conditions. The relative influence of the experimental variables and their interactions in the course of the reaction have been rationalized. The optimal conditions to obtain high carbamate yields have been established and experimentally corroborated.

ChemInform Abstract: THE REACTION OF ISOCYANIDES WITH HALOGENS OR N‐HALOSUCCINIMIDES AND ALCOHOLS

AbstractDie Reaktion von Isocyaniden des Typs (I) mit C12 bzw. Br2 in Gegenwart von Alkoholen (II) ergibt über die Zwischenstufen (IV) und (V) neben Aminen die Carbamate (III), wobei die Ausb. bei Br, höher sind.

The Reaction of Isocyanides with Halogens or N-Halosuccinimides and Alcohols

Abstract The reaction of aliphatic isocyanides with bromine or chlorine in primary alcohols, followed by hydrolysis, afforded the corresponding carbamates in moderate yields, together with various amounts of amines. Bromine was superior to chlorine as a halogen source for the formation of carbamates. unexpectedly, the addition of HgCl2 resulted in a decrease in the carbamate yield. When N-halosuccinimides were used in the place of halogens, an additional formation of the succinimide-incorporated product was observed to some extent.

ChemInform Abstract: A THREE‐COMPONENT REACTION OF ISOCYANIDES WITH HALOGENS AND CYCLIC ETHERS

In the presence of a Lewis-acid catalyst, such as HgCl2 or ZnCl2, cyclohexyl isocyanide reacted with chlorine and tetrahydrofuran to give, after hydrolysis, 4-chlorobutyl cyclohexylcarbamate in a fair yield. When one of the reactants was replaced by another isocyanide, bromine, or another cyclic ether, the reactions proceeded similarly, but the corresponding carbamate yields were rather poor.

A Three-Component Reaction of Isocyanides with Halogens and Cyclic Ethers

Abstract In the presence of a Lewis-acid catalyst, such as HgCl2 or ZnCl2, cyclohexyl isocyanide reacted with chlorine and tetrahydrofuran to give, after hydrolysis, 4-chlorobutyl cyclohexylcarbamate in a fair yield. When one of the reactants was replaced by another isocyanide, bromine, or another cyclic ether, the reactions proceeded similarly, but the corresponding carbamate yields were rather poor.