Synthesis Of Carbamates Research Articles

Carbon Dioxide: Versatile, Cheap and Safe Alternative in the Syntheses of Organic Carbamates

Organic carbamates represent an important class of compounds showing various interesting properties. They find wide utility in various areas as pharmaceuticals, agrochemicals (pesticides, herbicides, insecticides, fungicides etc.), intermediates in organic synthesis, protection of amino group in synthetic organic chemistry, as linkers in combinatorial chemistry etc. Classical synthesis of carbamates involves use of harmful reagents such as phosgene, its derivatives and carbon monoxide. Recently, carbon dioxide has frequently been employed as a green reagent in its various conditions and forms for the synthesis of organic carbamates employing diversity of starting materials, reagents and catalytic systems. In the present review, we would like to highlight the recent developments on the synthesis of organic carbamates using various conditions and forms of carbon dioxide. Keywords: Amines, Carbon dioxide, Carbamation, Organic carbamates, tetra-ethyl ammonium bromide-superoxide/CO2, ethynyl alcohols, ruthenium, propargyl amines 41, regioselective, isopropenylacetylene 45

ChemInform Abstract: (Tosylimino)phenyl‐λ3‐iodane as a Reagent for the Synthesis of Methyl Carbamates via Hofmann Rearrangement of Aromatic and Aliphatic Carboxamides.

AbstractA new, mild, and efficient method to prepare various methyl carbamates as well as other alkyl carbamates is reported.

Efficient synthesis of methyl carbamate via Hofmann rearrangement in the presence of TsNBr2

An efficient method has been developed for the synthesis of carbamates from the corresponding amides via the Hofmann rearrangement using N,N-dibromo-p-toluenesulfonamide (TsNBr2) in the presence of DBU in methanol. The reaction goes into completion in 10–20min at 65°C to produce the corresponding carbamate in excellent yield.

ChemInform Abstract: Polyethylene Glycol Enhanced Chemoselective Synthesis of Organic Carbamates from Amines, CO2, and Alkyl Halides.

Abstract An efficient and environmentally benign method for the synthesis of organic carbamates was developed. Amines, CO2, and alkyl halides underwent a three-component reaction with the aid of K2CO3 and polyethylene glycol (PEG, MW = 400), affording the organic carbamates under ambient conditions. PEG could presumably act as a solvent and phase-transfer catalyst (PTC). Notably, the presence of PEG could also depress the alkylation of both the amine and the carbamate, thus resulting in enhanced selectivity toward the target carbamate. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.

ChemInform Abstract: Copper‐Catalyzed Oxidative C—O Coupling by Direct C—H Bond Activation of Formamides: Synthesis of Enol Carbamates and 2‐Carbonyl‐Substituted Phenol Carbamates.

AbstractA novel convenient copper‐catalyzed C—O bond coupling of formamides with β‐dicarbonyl compounds is presented, affording carbamates (III), (V) and (VIII) in moderate to good yields as single stereoisomers via a phosgene‐free pathway.

Design and synthesis of carbamate and thiocarbamate derivatives and their inhibitory activities of NO production in LPS activated macrophages

Series of carbamate and thiocarbamate derivatives were designed and synthesized and their inhibitory activities of NO production in lipopolysaccharide-activated macrophages were evaluated. Several thoicarbamate derivatives revealed promising inhibitory activity. The structure–activity relationship study of these compounds is also reported. Among these compounds, compound 12b was the most potent with 6.5μM of IC50. They inhibited NO production through the suppression of iNOS protein and mRNA expression and nuclear translocation of p65.

ChemInform Abstract: Perspectives on the Synthesis of Organic Carbamates

AbstractReview: ca. 350 refs.

Dynamic Kinetic Resolution of 1,3-Dihydro-2H-isoindole-1-carboxylic Acid Methyl Ester: Asymmetric Transformations toward Isoindoline Carbamates

Asymmetric syntheses of isoindoline carbamates have been successfully achieved through enzyme-mediated dynamic kinetic resolution processes and without requirement of metal or acid-base catalyst for the substrate racemization. Optically active carbamates were obtained in good yields and an excellent degree of stereoselectivity when Pseudomonas cepacia lipase (PSL) was used as biocatalyst, with diallyl or dibenzyl carbonates being both adequate reagents in alkoxycarbonylation reactions.

ChemInform Abstract: Copper‐Catalyzed Coupling of Arylboronic Acids with Potassium Cyanate: A New Approach to the Synthesis of Aryl Carbamates.

The copper-catalyzed coupling of aromatic boronic acids with potassium cyanate in the presence of an alcohol has been employed for the synthesis of arylcarbamates. This simple and highly efficient approach can be carried out in air at room temperature and, importantly, no base, ligand, or additive is required.

Highly Efficient Synthesis of Ureas and Carbamates from Amides by Iodosylbenzene‐Induced Hofmann Rearrangement

AbstractA simple and efficient method for the synthesis of 1,3‐disubstituted ureas and carbamates from amides by using iodosylbenzene as the oxidant is described. Symmetric and asymmetric ureas and carbamates can be prepared by this procedure in up to 98 % yield. Ureidopeptides can also be prepared in good yield by this method.

(Tosylimino)phenyl-λ3-iodane as a Reagent for the Synthesis of Methyl Carbamates via Hofmann Rearrangement of Aromatic and Aliphatic Carboxamides

A new, mild procedure for the Hofmann rearrangement of aromatic and aliphatic carboxamides using (tosylimino)phenyl-λ(3)-iodane, PhINTs, as a reagent is reported. Because of the mild reaction conditions, this method is particularly useful for the Hofmann rearrangement of substituted benzamides, which usually afford complex reaction mixtures with other hypervalent iodine oxidants. The mild reaction conditions and high selectivity in the reaction of carboxamides with PhINTs allow the isolation of the initially formed labile isocyanates or their subsequent conversion to stable carbamates by treatment with alcohols.

Phosgene-free synthesis of 1,3-diphenylurea via catalyzed reductive carbonylation of nitrobenzene

1,3-Diphenylurea (DPU) has been proposed as a synthetic intermediate for phosgene-free synthesis of methyl N-phenylcarbamate and phenyl isocyanate, which are easily obtained from the urea by reaction with methanol. Such an alternative route to synthesis of carbamates and isocyanates necessitates an improved phosgene-free synthesis of the corresponding urea. In this work, it is reported that Pd(II)-diphosphine catalyzed reductive carbonylation of nitrobenzene in acetic acid (AcOH)-methanol proceeds in high yield and selectivity as a one-step synthesis of DPU. We have found that the catalytic activity and selectivity of this process depends on solvent composition and on the bite angle of the diphosphine ligands. Under optimum reaction conditions, yields in excess of 90 molar % and near-quantitative selectivity can be achieved.

A new route of CO2 catalytic activation: syntheses of N-substituted carbamates from dialkyl carbonates and polyureas

This paper reports an effective route for the syntheses of N-substituted dicarbamates from dialkyl carbonates and polyurea derivatives, in which polyurea derivatives could be successfully synthesized from aliphatic diamines and CO2 in the absence of any catalyst. Under the optimized reaction conditions, various N-substituted carbamates were successfully synthesized with 93–98% isolated yields over a MgO–ZnO catalyst. The catalyst could be reused for several runs without deactivation. The catalysts were characterized with X-ray photoelectron spectroscopy, X-ray diffraction and temperature-programmed desorption.

Versatile approach to α-alkoxy carbamate synthesis and stimulus-responsive alcohol release

A series of α-alkoxy carbamates that cleave under mild conditions to release alcohols has been synthesized through a multicomponent process. The relationship between structural features in these compounds and the rate of alcohol release in the presence of basic hydrogen peroxide has been studied. The preparation of carbamates that cleave under other conditions has been demonstrated.

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.

고압반응 하에서 요소와 메탄올을 사용한 메틸카바메이트와 디메틸카보네이트 제조에 관한 금속산화물 촉매 및 이온성액체의 영향

고압 반응시스템에서 요소와 메탄올로부터 메틸카바메이트(MC) 및 디메틸카보네이트(DMC)의 제조에 관한 금속산화물촉매와 이온성액체의 영향을 고찰하였다. 고립계에서 요소와 메탄올로부터 MC 수율은 촉매를 사용하지 않고도 <TEX>$150^{\circ}C$</TEX> 이상의 반응온도에서 거의 100%를 나타내었으나, DMC 수율은 반응온도와 무관하게 1.5% 이하로 매우 낮은값을 나타내었다. 또한 MC와 메탄올로부터 DMC 수율은 <TEX>$ZnCl_{2}$</TEX> 촉매를 사용한 경우에 가장 우수하였으며, 최적조건에서 16.3% 정도를 나타내었다. DMC 수율은 반연속식 실험에서 나노 크기의 촉매와 이온성액체를 함께 적용한 경우에 좀 더 향상되었다. Effect of metal oxide catalysts and ionic liquids on the synthesis of methyl carbamate(MC) and dimethyl carbonate (DMC) from urea and methanol was investigated in a high pressure reaction system. In closed system, MC yield from urea and methanol reached almost 100% at reaction temperature over <TEX>$150^{\circ}C$</TEX> without catalyst, whereas DMC yield of 1.5% under was obtained irrespective of catalysts used. In DMC synthesis from MC and methanol, <TEX>$ZnCl_{2}$</TEX> showed the highest catalytic activity and led to the DMC yield of 16.3% under optimal conditions. Furthermore, DMC yield can be enhanced by the simultaneous application of ionic liquids with nano-sized catalysts in semi-continuous reaction system.

ChemInform Abstract: Recent Developments on the Carbamation of Amines

AbstractReview: 300 refs.

Copper‐Catalyzed Oxidative CO Coupling by Direct CH Bond Activation of Formamides: Synthesis of Enol Carbamates and 2‐Carbonyl‐Substituted Phenol Carbamates

Die Aktivierung von Formamid-C-H-Bindungen gelang unter oxidativen Bedingungen mit einem Kupferkatalysator und tert-Butylhydroperoxid (TBHP) als externem Oxidationsmittel (siehe Schema). Diese mit hohen Ausbeuten verlaufende oxidative Kupplung einer Vielzahl an Dialkylformamiden bietet einen einfachen, phosgenfreien Zugang zu Z-Enolcarbamaten und 2-carbonylsubstituierten Phenolcarbamaten.

Copper‐Catalyzed Oxidative CO Coupling by Direct CH Bond Activation of Formamides: Synthesis of Enol Carbamates and 2‐Carbonyl‐Substituted Phenol Carbamates

A novel convenient copper-catalyzed C—O bond coupling of formamides with β-dicarbonyl compounds is presented, affording carbamates (III), (V) and (VIII) in moderate to good yields as single stereoisomers via a phosgene-free pathway.

ChemInform Abstract: Synthetic Access to New Carbamate and Thiocarbamate Derivatives from Pyridinecarbaldehyde Oximes and Hydroxypyridines.

The synthesis of pyridine carbamate and thiocarbamate derivates is described. A series of oxime carbamate and thiocarbamate derivatives were synthesized by the addition of 2-, 3-, and 4-pyridinecarbaldehyde oximes to isocyanates and isothiocyanates. Furthermore, carbamate and thiocarbamate derivatives of pyridine were synthesized by the addition of 2-, 3-, and 4-hydroxy pyridine to isocyanates and isothiocyanates. Their structures were confirmed by both analytical and spectral data.