Urea and carbamate derivatives

The reactions of phosgene with ammonia lead, depending upon the conditions, to the formation of the useful materials urea, biuret (NH CONHCONH j), cyanuric acid (1,3,5-triazine-2,4,6-triol), and successive products of ammonolysis up to melamine HjNCN(NHj)NC(NHj)N (see Section 9.10.2.1) [718a]. Urea is usually manufactured from ammonia and carbon dioxide, but a useful fertilizer mixture can be produced by injecting ammonia into gaseous phosgene in the ratio of 4 1 respectively [1439]. Urea and ammonium 

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B. A. Rasmussen, Y. Lin, T.S. Mansour, Phenyl thaizolyl urea and carbamate derivatives as new inhibitors of bacterial cell-wall biosynthesis, Bioorg. Med. Chem. Lett. 

The urea and carbamate derivatives can often be produced by alternative routes avoiding the manufacture and handling of isocyanates. The Du Pont process of methylamine carboxylation with carbon monoxide to give N-methylformamide, followed by oxidation to methyl isocyanate and further in situ conversion of the isocyanate to the less volatile derivatives, is only one example of a safer route to pesticides. 

Derivatives (Table I) formed by the reaction of the chosen polysaccharide with an isocyanate or acid chloride are carbamates and esters respectively. However, chitin or poly[(1+4)(N-acetyl-2-amino-2-deoxy-f3-glucopyranose)] actually used in this experiment contains approximately 16% free amine groups which can form urea and amide derivatives with the above reagents. 

C. Morisseau, G. Du, J. W. Newman, B. D. Hammock, Mechanism of Mammalian Soluble Epoxide Hydrolase by Chalcone Oxide Derivatives , Arch. Biochem. Biophys. 1998, 356, 214 - 228 C. Morisseau, M. H. Goodrow, D. Dowdy, J. Zheng, J. F. Greene, J. R. Sanborn, B. D. Hammock, Potent Urea and Carbamate Inhibitors of Soluble Epoxide Hydrolases , Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 8849 - 8854. 

The IR carbonyl stretch frequencies for a number of simple A,A-dialkoxyamides, -ureas and -carbamates are presented in Table 11 and reflect an increase of between 20 and 30 cm relative to the hydroxamic esters from which they were derived. In confirmation of theoretical studies, N—C(0) double-bond character is considerably less than in the hydroxamic esters, although the carbonyl stretch frequencies are not as... 

Cohen and Wheals [185] used a gas chromatograph equipped with an electron capture detector to determine 10 substituted urea and carbamate herbicides in river water, soil and plant materials in amounts down to 0.001-0.05ppm. The methods are applicable to those urea and carbamate herbicides that can be hydrolysed to yield an aromatic amine. A solution of the herbicide is first spotted on to a silica gel G plate together with herbicide standards (5-10pg) and developed with chloroform or hexane-acetone (5 1). The plate containing the separated herbicide or the free amines is sprayed with 1-fluoro-1,4-dinitrobenzene (4% in acetone) and heated at 190°C for 40min to produce the 2,4-dinitrophenyl derivative of the herbicide amine moiety. Acetone extracts of the areas of interest are subjected to gas chromatography on a column of 1% of XE-60 and 0.1% of Epikote 1001 on Chromosorb C (AE-DCMS) (60-80 mesh) at 215°C. 

Acid-induced reactions of silicon-containing unsaturated compounds with A -acyliminium intermediates have proven particularly useful. Allylsilanes lead to the corresponding allyl-substituted products. This reaction proceeds well even for -lactams (equation 49). 5.86 j, g penicillin-derived 4-acetoxyazet-idinone (91) reacts with excess allylsilane in refluxing dichloroethane, catalyzed by TMSOTf, to produce as the sole product trans compound (92). A -Acyliminium ions generated from cyclic ureas and carbamates (93) likewise yield allylated products with virtually complete trans stereoselectivity (equation SO). Allylstannanes react under somewhat milder conditions than allylsilanes, requiring only a catalytic amount of BFsZ EtjO at room temperature for a 3-lactam system (equation 51). This allylstannane procedure was applied to cyclic carbamate systems for the stereoselective synthesis of several isomers of statine. Thus, ethoxycarbamate (94) reacts with methallyltributylstannane in excellent yield and dia-stereoselectivity (equation 52). ... 

Similarly, carbamic acid, the amide derivative of carbonic acid, is also unstable, and loses carbon dioxide to give amines (Fig. 17.56). The diamide, urea, and carbamates, which cannot lose carbon dioxide, are stable. 

The twofold diversity of the desired target bound to the resin was then increased by various reactions such as amidation using BOP-Cl and DIPEA in DCM at rt, or the formation of urea or carbamate derivatives (Scheme 8.16) by the reaction of a suitable isocyanate or chloroformate. The hnal cleavage of the desired 1,2,5-trisubstituted imidazolidin -ones was effected in TFA/water/iPrOH (3 20 80) at 50°C (Scheme 8.16). 

Forsyth M., MacFarlane D.R., Meakin P.,.Smith M.E Bastow T.J. (1995) An nmr investigation of ionic structure and mobility in plasticized solid polymer electrolytes, Electrochimica Acta, International symposium on polymer electrolytes, vol.40, n°13-14, pp. 2343-2347, (October 1995), ISSN 0013-4686 Fort Y., Gottardi C. Caubere P. (1993). New selective syntheses of (meth)acrylic monomers Isocyanates, carbamates, ureas and isocyanurates derivatives. Tetrahedron. Letters, vol.34, n°24, pp.3857-3860, (June 1993), ISSN 0040-4039 Fredlake C.P., Crosthwaite J.M., Hert D.G., Aki S.N.V.K. Brennecke J.F.J. (2004). 

This group of substances includes chemically very different compounds, such as ureas and carbamates, organic phosphorus and sulfur compounds, chlorinated hydrocarbons, and heterocyclic compounds. Depending on the type of functional groups in the molecule, common derivatives of these groups are applied. For the analysis of antibiotics TMS derivatives are generally prepared. Vitamins include compounds that differ considerably in their chemistry and therefore the range of possible derivatives is fairly wide. 

The Finnish viscose producer Kemira Oy Saeteri collaborated with Neste Oy on the development of a carbamate derivative route. This system is based on work (89) that showed that the reaction between cellulose and urea gives a derivative easily dissolved in dilute sodium hydroxide ... 

Miscellaneous Resins. Much less important than the melamine—formaldehyde and urea—formaldehyde resins are the methylo1 carbamates. They are urea derivatives since they are made from urea and an alcohol (R can vary from methyl to a monoalkyl ether of ethylene glycol). 

Various halogenated and nitrated aniline derivatives are used in the manufacture of dyestuffs and carbamate and urea based pesticides. Many of these compounds are suspected to be carcinogenic. 

Amides, carbamates, and ureas can be generated by nucleophilic cleavage of resin-bound esters, carbonates, and carbamates, respectively, with amines (Figure 3.20). These reactions only proceed well if sufficiently reactive resin-bound derivatives are used. 

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