N-Aryl Carbamates Research Articles

Nickel(II)- and Silver(I)-Catalyzed C–H Bond Halogenation of Anilides and Carbamates

Abstract ortho-C–H bond halogenation of anilides and N-aryl carbamates using easily available N-halosuccinimides (NXS) as the active halogenation reagent in the presence of nickel or silver catalyst has been developed. This method provides a new approach to 2-haloanilides and carbamates, which may serve as starting materials for the synthesis of pharmaceutically and biologically active compounds.

One stone two birds: cobalt-catalyzed in situ generation of isocyanates and benzyl alcohols for the synthesis of N-aryl carbamates.

An efficient method for the synthesis of N-aryl carbamates from N-Boc-protected amines has been developed. The cobalt-catalyzed in situ generation of isocyanates from N-Boc-protected amines and benzyl alcohols from benzyl formates has been achieved for the first time, which in turn furnished the corresponding benzyl carbamates in moderate to high yields. The reaction was catalyzed by CoI2 with tris-(4-dimethylaminophenyl)-phosphine as the ligand and zinc powder as the reductant. The developed reaction conditions were found to be compatible for aromatic amines with both electron-donating and -withdrawing substituents.

An efficient one-pot synthesis of N,N′-disubstituted phenylureas and N-aryl carbamates using hydroxylamine-O-sulfonic acid

We have developed an efficient one-pot method for the microwave-assisted synthesis of ureas and carbamates via a proposed Lossen rearrangement. Herein we report the first examples of the direct conversion of benzoyl chlorides into N,N′-disubstituted ureas and N-aryl carbamates using hydroxylamine-O-sulfonic acid as reagent. Using our general method, we have produced 11 examples of N,N′-disubstituted phenylureas in yields up to 95% using various substituted anilines, and primary and secondary amines. Additionally, we were able to generate a series of N-aryl carbamates in moderate yields using primary, secondary and tertiary alcohols.

Palladium-Catalyzed Synthesis of N-Aryl Carbamates

Palladium-Catalyzed Synthesis of N-Aryl Carbamates

Towards a Phosgene-Free Synthesis of Aryl Isocyanates: Alcoholysis of N-phenylurea to N-phenyl-O-methyl Carbamate Promoted by Basic Metal Oxide Nanoparticles and Organocatalysts

There is an urgent need to develop new processes for the synthesis of polyurethanes and polycarbonates different from the current technology based on the use of phosgene. In the case of polyurethanes, the reaction of phosgene with aromatic amines renders N-aryl isocyanates that are the co-monomers for these polymers. In the search for a phosgene-free process for the synthesis of N-aryl isocyanates, N-aryl carbamates could play a key role of synthetic precursors. N-Aryl carbamates can be prepared in turn by alcoholysis of N-aryl ureas. Herein, we compare the catalytic activity of three homogeneous catalysts and four heterogeneous metal oxides for the methanolysis of N-phenylurea as a model probe for other aromatic ureas. In the present work we have carried out this reaction in the presence of KOH, 1,8-diaminonaphthalene (a protonic sponge), a dimeric phosphazene (strong, neutral soluble base) and nanometric ZnO, MgO, CaO and a mixed Mg/Al metal oxide derived from hydrotalcite calcination. Besides the target N-phenyl O-methyl carbamate, N-phenyl isocyanate and undesired aniline were also formed. It was observed that using KOH and diaminonaphthalene, aniline was formed preferentially with respect to the desired carbamate. In contrast, dimeric phosphazene forms the target N-phenyl O-methyl carbamate with 90% selectivity at 99% N-phenylurea conversion. In the case of the metal oxides, the best-performing solid catalyst was CaO that exhibits similar activity (99% N-phenylurea conversion) and carbamate selectivity (89%) as phosphazene. CaO performs as a truly heterogeneous catalyst and could be reused for a second run with only a 4 and 2% decrease in conversion and selectivity, respectively.

Interaction of O‐Allyl and O‐Propargyl Derivatives of N‐Aryl Carbamates with Acetaldoximes in the Presence of Chloramine B.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Substituent effects on the barrier to carbamate C–N rotation

Seven aryl-substituted t-butyl N-methyl- N-aryl carbamates were prepared, and in each case, the barrier to C–N bond rotation, ΔG ‡ , was determined in CDCl 3 solution using variable temperature NMR. A linear free energy relationship is observed between ΔG ‡ and the electronic stabilization effect of the substituent on the N-aryl ring. More specifically, electron donating groups increase ΔG ‡ , whereas withdrawing groups decrease ΔG ‡ . A plot against σ– was more linear ( r 2=0.96), than a plot against σ ( r 2=0.90) or σ+ ( r 2=0.88) and a value of ρ=1.76 was obtained at 243 K. Thus, rotation about the carbamate C–N bond in weakly polar chloroform involves a decrease in positive charge on the nitrogen.

The paradoxical toxic effect and antagonism to calcium ions of O-(N-arylcarbamoylated) acylhydroximoyl chlorides exhibiting anticholinesterase action

Carbamoylated oximes of the formula RR1NC(O)ON=C(Cl)R2, N-aryl-containing carbamates exhibit higher antiacetylcholinesterase activity and lower acute toxicity (with a paradoxical dose dependence of the lethal effect) than their N-alkyl analogs. In experiments on isolated guinea pig ilea. the N-aryl carbamates. unlike their N-alkyl-substituted derivatives, were shown to be calcium ion antagonists. The cause of the paradoxical toxic effect of the N-aryl-containing carbamates and their low toxicity in the high dose range is assumed to be a calcium-blocking action.

Hydrogenation of N-Aryl Carbamates to N-Alicyclic Carbamates

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHydrogenation of N-Aryl Carbamates to N-Alicyclic CarbamatesRussell E. Malz Jr. and Harold GreenfieldCite this: Ind. Eng. Chem. Prod. Res. Dev. 1978, 17, 4, 358–362Publication Date (Print):December 1, 1978Publication History Published online1 May 2002Published inissue 1 December 1978https://doi.org/10.1021/i360068a015RIGHTS & PERMISSIONSArticle Views167Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (659 KB) Get e-Alerts

Gas chromatography of N-methyl and N-aryl carbamates by flash-heater reaction with trimethylanilinium hydroxide

A simple derivatization procedure employing trimethylanilinium hydroxide (Methelute®) is described. This method may prove useful in the analysis of certain pesticidal carbamate residues. The flash-heater reaction product derived from N-aryl carbamates was identified as the N-methyl-N-aryl carbamate. For the N-methyl carbamates, however, a methyl substitution product (aryl methyl ether) was obtained rather than the anticipated N,N-dimethyl carbamate. Using propham and carbaryl as representative compounds for the two classes of carbamates, the degree of reaction for each with Methelute was estimated to be essentially quantiative. Chromatographic response was observed to be linear with increased concentration for the synthetic standards and the flash-heater products of propham and carbaryl. At the nanogram level, flash-heater reaction improved the sensitivity of detection of propham and carbaryl by approximately 30% and 400%, respectively.