Alkyl, amines ureas

IV-Alkyl substituted ureas usually eliminate the IV-substituted amine (80JHC235), but IV-arylthioureas may give ring IV-aryl derivatives 66UC447). 

Aresta and Quaranta studied the reactivity of alkylammonium N-alkylcarbamates (RNH3)02CNHR towards a different acylating substrate, such as dimethyl carbonate (DMC) [62a, b]. Carbamate salts (RNH3)02CNHR (R = benzyl, allyl, cyclohexyl), prepared in situ from aliphatic primary amines and C02, reacted with DMC to afford N-alkyl methylcarbamates (Equation 6.6). The reaction requires mild conditions (343-363 K 0.1 MPa C02 pressure) and can be carried out in DMC used as solvent and reagent. At 363 K, carbamate esters were obtained in satisfactory yield (45-92%) with high selectivity, as side products such as ureas, N,N-dialkylcarbamate esters, and alkylated amines were formed in very small amounts. 

Second-order reactions of type II are probably among the most common of all reactions studied. A few typical examples are the gas-phase formation of hydrogen iodide, II2 + I2 2HIthe reactions of free radicals with molecules, for example, H + Br2 HBr + H the famous synthesis of urea from NH4 and CNO ions the hydrolysis of organic esters in non-aqueous media and the reaction of tertiary alkyl amines with alkyl halides to produce quaternary ammonium salts, R3N + R X — R RsN+ +... 

Alkyl Ureas.—By substituting alkyl amines for ammonia in the reaction for the synthesis of urea from carbonyl chloride, or by using alkyl derivatives of ammonium cyanate (cyanic acid salts of alkyl amines), in the Wohler synthesis, alkyl ureas may be obtained. They are of different t es as illustrated by the following formulas showing their relationship to urea. 

Frechet and coworkers have reported the development of a functionalized polymer monolith for use in parallel solution phase synthesis in continuous flow applications [10]. In this report, the authors outline the preparation of an azalac-tone-functionalized monolith for scavenging nucleophiles. This method involves the preparation of a macroporous polyfchloromethylstyrene co-divinylbenzene) monolith via the polymerization of the relevant mixture of monomer, initiator and porogen. These are allowed to react with a free radical initiator (4-cyanovaleric acid), followed by reaction with the monomer of choice, to synthesize the functionalized monolith. The authors have thus prepared monoliths functionalized with VAZ to provide an azalactone-functionalized monolith. These monoliths were then demonstrated to completely remove amines after flowing a solution of amine in THF through the monolith for 30 min. They have also reported the reaction of these monoliths with alcohols as well. A small demonstration library of ureas was prepared and after 8 min of residence time up to 76% of the alkyl amines were found to be scavenged (Scheme 8.6). 

C-labeled carbamoyl compounds can be prepared by using a selenium-mediated reaction with [ carbon monoxide. The urea formation works excellent in the case of cyclizations but in other cases satisfactorily only with primary amines (Kihlberg et al. 2002). Since selenium is practically insoluble in most solvents the use of primary alkyl amines or tetrabutylammonium fluoride is necessary for the formation of soluble and reactive complexes with selenium. Except for ring closures, rhodium-promoted carbonylations are probably more useful than the corresponding selenium reactions (Ohad et al. 2009). 

Isocyanates derived from the higher aliphatic amides react more rapidly with the haloamide salts than with water and alkali, so that, when these amides are subjected to the Hofmann reaction in aqueous mediiun, only small amounts of the expected amines are formed. Although amines arise from the hydrolysis of the alkyl acyl ureas, they are largely oxidized to nitriles by the excess of hypobromite present. 

The storage stability of pre-condensates based on phenol-formaldehyde usually poses no problem. This is not the case with amino-resin pre-condensates. Technically significant are only the reaction products of urea, urea derivatives, and melamine with formaldehyde. The hydroxyl alkyl amines formed in an addition reaction... 

Chem. Descrip. Urea, n-alkyl dimethyl benzyl ammonium chloride (20%), alkyl dimethyl ethylbenzyl ammonium chloride (20%) and Dimethyl Cl 15 alkyl amine Ionic Nature Cationic... 

Urea derivadves are of general interest in medicinal chemistry. They may be obtained cither from urea itself (barbiturates, sec p. 306) or from amines and isocyanates. The latter are usually prepared from amines and phosgene under evolution of hydrogen chloride. Alkyl isocyanates are highly reactive in nucleophilic addidon reactions. Even amides, e.g. sulfonamides, are nucleophilic enough to produce urea derivatives. 

A wide selection of amino resin compositions is commercially available. They are all alkylated to some extent in order to provide compatibiUty with the other film formers, and formulation stabiUty. They vary not only in the type of amine (melamine, urea, ben2oguanamine, and glycolutil) used, but also in the concentration of combined formaldehyde, and the type and concentration of alkylation alcohol (/ -butanol, isobutyl alcohol, methanol). 

Alkylation of the protected azetidinyl bromide 61 with the anion from m-trifluormethyl-phenol gives ether 62. Removal of the N-(alpha-methylbenzyl)- protecting group by catalytic hydrogenation gives the secondary amine 63. Reaction of that compound with methyl isocyanate gives the anticonvulsant urea fluzinamide (64) [14]. 

As yet, a number of experiments have failed to convert ureas 205 such as N-phenylurea or imidazolin-2-one by silylation amination with excess amines R3NHR4 such as benzylamine or morpholine and excess HMDS 2 as well as equivalent amounts of NH4X (for X=C1, I) via the silylated intermediates 206 and 207 in one reaction step at 110-150°C into their corresponding guanidines 208 with formation of NH3 and HMDSO 7 [35] (Scheme 4.13). This failure is possibly due to the steric repulsion of the two neighbouring bulky trimethylsilyl groups in the assumed activated intermediate 207, which prevents the formation of 207 in the equilibrium with 206. Thus the two step Rathke-method, which demands the prior S-alkylation of 2-thioureas followed by amination with liberation of alkyl-mercaptans, will remain one of the standard syntheses of guanidines [21, 35a,b,c]. 

The soluble polymer support was dissolved in dichloromethane and treated with 3 equivalents of chloroacetyl chloride for 10 min under microwave irradiation. The subsequent nucleophilic substitution utilizing 4 equivalents of various primary amines was carried out in N,N-dimethylformamide as solvent. The resulting PEG-bound amines were reacted with 3 equivalents of aryl or alkyl isothiocyanates in dichloromethane to furnish the polymer-bound urea derivatives after 5 min of micro-wave irradiation (Scheme 7.75). After each step, the intermediates were purified by simple precipitation with diethyl ether and filtration, so as to remove by-products and unreacted substrates. Finally, traceless release of the desired compounds by cyclative cleavage was achieved under mild basic conditions within 5 min of micro-wave irradiation. The 1,3-disubstituted hydantoins were obtained in varying yields but high purity. 

Several syntheses of l,3-dioxoperhydropyrrolo[l,2-c]imidazoles have been developed using different strategies. a-Substituted bicyclic proline hydantoins were prepared by alkylation of aldimines 135 of resin-bound amino acids with a,tu-dihaloalkanes and intramolecular displacement of the halide to generate cr-substituted prolines 136 and homologs (Scheme 18). After formation of resin-bound ureas 137 by reaction of these sterically hindered secondary amines with isocyanates, base-catalyzed cyclization/cleavage yielded the desired hydantoin products <2005TL3131>. 

Unlike the urea- and melamine-formaldehyde resins, these wet strength agents are suitable for both neutral and alkaline pH. They are prepared by condensation of a dicarboxylic acid and bis (2-aminoethyl) amine, the free amino group is then alkylated with epichlorohydrin to give an aminochlorohydrin which exists in equilibrium with a 3-hydroxyazetidinium group (Figure 7.28). 

Since then, optically active a-aminophosphonates have been obtained by a variety of methods including resolution, asymmetric phosphite additions to imine double bonds and sugar-based nitrones, condensation of optically active ureas with phosphites and aldehydes, catalytic asymmetric hydrogenation, and 1,3-dipolar cycloadditions. These approaches have been discussed in a comprehensive review by Dhawan and Redmore.9 More recent protocols involve electrophilic amination of homochiral dioxane acetals,10 alkylation of homochiral imines derived from pinanone11 and ketopinic acid,12 and alkylation of homochiral, bicyclic phosphonamides.13... 

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