Carboxylic acids and ureas

Amide formation, from a carboxylic acid and urea, 37, 50 from 2-amino-5-nitroanisole and ethyl benzoylacetate, 37, 4 from aniline and ethyl benzoylacetate, 37, 3... 

As we have previously discussed in Section I, the use of carbon dioxide as an industrial source of chemical carbon has been limited mainly to the production of organic carbonates, carboxylic acids, and ureas. In contrast, carbon dioxide has been utilized more extensively in the laboratory for the... 

Carboxylic acid amides from carboxylic acids and ureas... 

In 1872, Griess fused urea and 2-aminobenzoic acid and, although unaware of the nature of his product, had made quinazoline-2,4-dione. Since that time, the reaction has been frequently used for converting C-substituted 2-aminobenzoic acids to their corresponding quinazoline-2,4-diones in excellent yields, usually at 190°-200°C maintained for 1-5 hr.307,308 In addition, 2-aminopyridine-3-carboxylic acid and urea, slowly heated to 210°C, gave a good yield of pyrido[2,3-rf]pyrimidine-2,4-dione.286 Pyrido-[3,4-d]pyrimidine-2,4-dione was formed similarly (yield not given).288... 

Furthermore, a mixed catalyst, 3,5-(CFj)2QHjB(OH)2-HOReOj is effective for a one-pot synthesis of nitriles from the corresponding carboxylic acids and urea (Equation 13) [13]. Thus, 4-phenylbutyronitrile is obtained in gocxi yield. This means that urea can be used as a synthetic equivalent of ammonia. 

Other persalts are known but have not heen cortmiercialized in fabric washing detergents. These include perphosphates, persulfates, persilicates, peroxide complexes with carboxylic acids, and urea peroxyhydrate. 

A, A -Bistrimethylsilylurea, CH2Cl2. The reagent readily silylates carboxylic acids and alcohols. The byproduct urea is easily removed by filtration. 

In the course of this study, the authors determined /Lvalues for dibenzyl, methyl phenyl, methyl p-nitrophenyl, di-p-tolyl, di-isopropyl and tetramethylene sulphoxides and for diethyl, dipropyl and dibutyl sulphites. The /Lscales are applied to the various reactions or the spectral measurements. The /Lscales have been divided into either family-dependent (FD) types, which means two or more compounds can share the same /Lscale, family-independent (FI) types. Consequently, a variety of /Lscales are now available for various families of the bases, including 29 aldehydes and ketones, 17 carboxylic amides and ureas, 14 carboxylic acids esters, 4 acyl halides, 5 nitriles, 10 ethers, 16 phosphine oxides, 12 sulphinyl compounds, 15 pyridines and pyrimidines, 16 sp3 hybridized amines and 10 alcohols. The enthalpies of formation of the hydrogen bond of 4-fluorophenol with both sulphoxides and phosphine oxides and related derivatives fit the empirical equation 18, where the standard deviation is y = 0.983. Several averaged scales are shown in Table 1588. 

Nitrosation of primary amides results in deamination to produce carboxylic acid and nitrogen as products. Secondary amides, when nitrosated, give the corresponding nitrosamides in a reversible process [51]. In order to obtain good yields of the nitrosamides, it is best to add a base to remove the acid formed (Scheme 3.2). This reaction also occurs with ureas and carbamates. 

Isocyanates are quite reactive and they react with compounds which contain active hydrogen such as hydroxy, amine, carboxylic acids, amide, urea, etc. They can also undergo addition reaction ... 

In contrast to the other large cats, the urine of the cheetah, A. jubatus, is practically odorless to the human nose. An analysis of the organic material from cheetah urine showed that diglycerides, triglycerides, and free sterols are possibly present in the urine and that it contains some of the C2-C8 fatty acids [95], while aldehydes and ketones that are prominent in tiger and leopard urine [96] are absent from cheetah urine. A recent study [97] of the chemical composition of the urine of cheetah in their natural habitat and in captivity has shown that volatile hydrocarbons, aldehydes, saturated and unsaturated cyclic and acyclic ketones, carboxylic acids and short-chain ethers are compound classes represented in minute quantities by more than one member in the urine of this animal. Traces of 2-acetylfuran, acetaldehyde diethyl acetal, ethyl acetate, dimethyl sulfone, formanilide, and larger quantities of urea and elemental sulfur were also present in the urine of this animal. Sulfur was found in all the urine samples collected from male cheetah in captivity in South Africa and from wild cheetah in Namibia. Only one organosulfur compound, dimethyl disulfide, is present in the urine at such a low concentration that it is not detectable by humans [97]. 

C02 as a feedstock for organic substances will continue to be in the production of urea, carboxylic acids, and organic carbonates. On the other hand, many laboratory syntheses of organic substances derived from C02 have been published, ranging from hydrocarbons to cyclic lactones. These have recently been surveyed by Denise and Sneeden (S). 

Abou-Basha and Aboul-Enein [22] presented an isocratic and simple HPLC method for the direct resolution of the clenbuterol enantiomers. The method involved the use of a urea-type CSP made of hS )-indoline-2-carboxylic acid and (R)-1 -(naphthyl) ethylamine known as the Chirex 3022 column. The separation factor (a) obtained was 1.27 and the resolution factor (Rs) was 4.2 when using a mobile phase composed of hexane-1,2-dichloroethane-ethanol (80 10 10, v/v/v). The (+)-enantiomer eluted first with a capacity factor (k) of 2.67 followed by a (—)-enantiomer with a k of 3.38. Biesel et al. [23] resolved 1-benzylcyclohexane-1,2-diamine hydrochloride on a Chirex D-penicillamine column. Gasparrini et al. [24] synthesized a series of the chiral selectors based on /ra s -1,2 - d i a m i n o eye I o hexane. The developed CSPs were used for the chiral resolution of arylacetic acids, alcohols, sulfoxides, selenoxides, phosphinates, tertiary phosphine oxides, and benzodiazepines. In another study, the same authors [25] described the chiral resolution of /i-aminocstcrs enantiomers on synthetic CSPs based on a re-acidic derivatives of trans- 1,2-diaminocyclohexane... 

A Curtius rearrangement was reported as the key step in the synthesis of protected anilines and aromatic ureas.84 The reaction is a single step from the corresponding carboxylic acid and produces urea or aniline, depending on the conditions. 

An extension of the above method for the preparation of cyclic ureas (imidazolidin-2-ones) was developed by the same group [63], by employing carbon dioxide/methanol in place of a carboxylic acid, and the UDC strategy. Additionally, treatment of the Ugi-5CR products with base afforded hydantoins in good yield. 

Ketones Aldehydes Acetals, Ketals Quinones Carboxylic acids and derivs. Thioureas Ureas, Carbonates Oximes Imines con iu9 on If - III itec sor iug ate( ... 

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