Ureas methylureas

Urea, methylurea, and dimethylureas react with glyoxylic acid and its methyl ester to give a-substituted hydantoic acid derivatives (16) and substituted allantoic acid derivatives (17), which can be cyclized to 5-substituted hydantoins (18). Although allantoin (18) formation from urea and... 

A mechanism consistent with the results of a kinetic study has been proposed for the oxidation of cysteine by BAT in H2S04. The RuCls-catalysed oxidations of urea, methylurea and ethylurea to the corresponding hydrazines by BAT and BAB in HCl solution are first order each in oxidant, substrate, and catalyst and fractional order in H+. The same observations were made for the oxidation of a range of substituted alcohols [RCH2CH2OH (R = H, OEt, OMe, NH2, Cl and Br)] under the same conditions (with BAT), except that an inverse first-order dependence on H+ concentration was observed mechanisms consistent with the kinetic data have been proposed for these reactions. The oxidation of some 5-substituted indoles by BAT catalysed by osmium(Vni) affords the corresponding oxindoles. The reaction is first order each in substrate and BAT, fractional order in Os(VIII), and inverse first order in HO . The Hammett correlation of substituent effects and proton-inventory studies in H2O-D2O mixtures showed the involvement of a single exchangeable proton of OH ion in an electron-deficient transition state. 

Studies which have involved Lewis acid-base adducts of organoboranes include the following the adducts of phenyl boron dichloride with tetrasulphur tetranitride, dibromomethylborane and bromodimethylborane with pyridine, 4-methylpyridine, trimethylamine and trimethylphosphine, monoalkylboranes with A AWW -tetramethylethylenediamine, diethylboron esters of alkane-nitronic acids with pyridine, and triarylboranes with guanidine,urea, methylurea, and thiourea. ... 

An alternative method of preparation involves the interaction of methylamine hydrochloride with urea to give methylurea, followed by interaction with nitrous acid as above ... 

Meihylamine hydrochloride method. Place 100 g. of 24 per cent, methyl-amine solution (6) in a tared 500 ml. flask and add concentrated hydrochloric acid (about 78 ml.) until the solution is acid to methyl red. Add water to bring the total weight to 250 g., then introduce lSO g. of urea, and boil the solution gently under reflux for two and three-quarter hours, and then vigorously for 15 minutes. Cool the solution to room temperature, dissolve 55 g. of 95 per cent, sodium nitrite in it, and cool to 0°. Prepare a mixture of 300 g. of crushed ice and 50 g. of concentrated sulphuric acid in a 1500 ml. beaker surrounded by a bath of ice and salt, and add the cold methylurea - nitrite solution slowly and with mechanical stirring and at such a rate (about 1 hour) that the temperature does not rise above 0°. It is recommended that the stem of the funnel containii the methylurea - nitrite solution dip below the surface of the acid solution. The nitrosomethylurea rises to the surface as a crystalline foamy precipitate. Filter at once at the pump, and drain well. Stir the crystals into a paste with about 50 ml. of cold water, suck as dry as possible, and dry in a vacuum desiccator to constant weight. The yield is 55 g. (5). 

The reaction conditions can be varied so that only one of those monomers is formed. 1-Hydroxy-methylurea and l,3-bis(hydroxymethyl)urea condense in the presence of an acid catalyst to produce urea formaldehyde resins. A wide variety of resins can be obtained by careful selection of the pH, reaction temperature, reactant ratio, amino monomer, and degree of polymerization. If the reaction is carried far enough, an infusible polymer network is produced. 

Miscellaneous urea herbicides (chlorobromuron (3,4(bromo-3-chlorophenyl)-1 -methoxy-1 -methylurea), Chlorotoluron (3(3 chlorotoluyl) dimethyl urea), Diuron (N-(3,4 chlorophenyl) N,N dimethyl urea), Monolinuron (3(4, chlorophenyl-1-methoxy-1 -methylurea), Linuron (3,(3,4 dichlorophenyl)-1 -1 -methoxy-1 -methylurea) Chloroxuron (3, (3,4 dichlorophenyl-1,1 dimethylurea)... 

Reaction with amines gives substituted ureas (cf. methylurea p. 271) —with hydrazine for example, semicarbazide ... 

Soil/Plant In soils and plants, monuron is demethylated at the terminal nitrogen atom coupled with ring hydroxylation forming 3-(2-hydroxy-4-chlorophenyl)urea and 3-(3-hydroxy-4-chloro-phenyl)urea (Hartley and Kidd, 1987). Wallnbefer et al. (1973) reported that the soil microorganism Rhizopus Japonicus degraded monuron into 3-(4-chlorophenyl)-l-methylurea. However, in the presence of Pseudomonas or Arthrobacter sp., monuron degraded to 2,4-di-chloroaniline, sj/ 3-bis(3,4-dichlorophenyl)urea, and unidentified metabolites (Janko et al., 1970). The reported half-life in soil is 166 d (Jury et al., 1987). 

Davis studied the dehydration of urea nitrates as a route to iV-nitroureas. The nitrate salt of iV-methylurea undergoes dehydration-rearrangement on treatment with concentrated sulfuric acid to give Af-nitro-A -methylurea in 42 % yield. In this compound the nitro and methyl groups are attached to the same nitrogen and so its hydrolysis can provide a route to methylnitramine. In contrast, the nitrate salts of ethyl, n-propyl, n-butyl and n-amyl ureas, give iV-nitro-A -ethylurea (49 %), A -nitro-A -propylurea (60 %), iV-nitro-iV -butylurea (67 %) and iV-nitro-A -amylurea (67 %), respectively, on treatment with concentrated sulfuric acid. 

Factors influencing the choice of synthetic routes to pyrimidines depend very much upon the substitution pattern of the desired product. For pyrimidines unsubstituted at the 4- and 6-positions, a two-component ring synthesis reaction involving a 1,3-dialdehyde and a urea or amidine derivative is the most straightforward route, but only if the dialdehyde is readily available. For example, synthesis of 2-chloro-5-(2-pyridyl)pyrimidine 989, an intermediate in the synthesis of a selective PDE-V inhibitor, was achieved in two steps in 40% overall yield by condensation of 2-(2-pyridyl)malondialdehyde 987 with methylurea, followed by demethylation/chlorination of the pyrimidinone 988 with a mixture of POCI3 and PCls <20070PD237>. 

Figure 9.12 Plot of log Ki0Q versus log Kiow for a alkylated and ha-logenated (R, = alkyl, halogen) phenylureas (R2 = R3 = H A, halogen, see margin below), phe-nyl-methylureas (R2 = CH3, R3 = H, d), and phenyl-dimethylureas (R2 = R3 = CH3, ). The slope and intercept of the linear regression using all the data is given in Table 9.2 (Eq. 9-26i) each subset of ureas would yield a tighter correlation if considered alone (e.g., Eq. 9-26j).

Dixon et al. (35) have proposed a mechanism for urease catalysis (Fig. 3) based on studies of the reactions with the poor substrates formamide, acetamide, and iV-methylurea. They suggest that the two nickel ions are both in the active site, one binding urea and the other a hydroxide ion which acts as an efficient nucleophile. This implies that the nickel ions are within 0.6 nm (1 nm = 10 A) of each other so far it... 

The enzyme urease catalyzes the hydrolysis of urea to form carbamate ion (equation 32). At pH 7.0 and 38 °C, the urease-catalyzed hydrolysis of urea is at least 1014 times as fast as the spontaneous hydrolysis of urea. Jack bean urease is a nickel(II) metalloenzyme502 with each of its six identical subunits containing one active site and two metal ions, and at least one of these nickel ions is implicated in the hydrolysis. It has been suggested503 that all substrates for urease (urea, N-hydroxyurea, 7V-methylurea, semicarbazide formamide and acetamide) are activated towards nucleophilic attack on carbon as a result of O-coordination to the active nickel(II) site as in (155). Nickel(II) ions have been found504 to promote the ethanolysis and hydrolysis of N-(2-pyridylmethyl)urea (Scheme 39) and this system is considered to be a useful model for the enzyme. 

This reaction differs from the spontaneous hydrolysis of urea to ammonium and cyanate, which is 1024 times slower. Urease is a highly specific and efficient enzyme. Its other substrates, of which the best are semicarbazide, formamide, acetamide, and A-methylurea, are hydrolyzed at very low rates [39],... 

Huber, G., Gemes, E. (1981) Decomposition of urea herbicide linuron (3-(3,4-dichlorophenyl)-l-methoxy-l-methylurea) in water of Lake Balaton. Hungar. J. Ind. Chem. 9, 113. 

Cyanophenanthrene is reduced by methylureas to the 9,10-dihydro-9-cyanophenanthrene (Tsujimoto et al., 1979a). Since the ureas do not quench... 

The Pd(II) complex (41) promotes stoichiometric alcoholysis of urea according to Scheme 8, giving the carbamate esters of the ligand (101). For methylurea as the substrate, the major product is the one with R = H (75%), while the product with R = Me is the minor one (25%). This intramolecular alcoholysis is 240-380 times faster than the intermolecular alcoholysis involving external attack of free ethanol. The O-bound 1,3-dimethylurea does not undergo any detectable intramolecular or catalytic alcoholysis, since the N-bound isomer, which is the much more reactive one, is practically absent due to steric reasons. 

N-bridging cyanate in low yields (17-23% after heating for 24 h Scheme 11). Conversion was found to proceed at comparable rates in ethanol or acetonitrile, and it was thus concluded that hydrolytic processes by traces of water do not play a role. Cyanate formation also was observed with Af-methylurea or 7/,7/-dimethylurea, but not with Af,A -dimethylurea or tetramethylurea, which shows that at least one NH2 group is essential for the elimination reaction to occur. A possible interpretation is that bridging of urea over the binuclear core through its O atom and one amino N atom is a key step for the conversion (58). This finding is in line with the discovery of urea-to-cyanate transformation for several pyrazolate-based dinickel complexes with urea bound in the N,0-bridging mode (see below). 

In a subsequent investigation using the same phtalazine-derived ligand framework, urea substrates having alkyl substituents at only one of the N atoms, (e.g., A-methylurea or MW-dimethylurea) were shown to undergo alkylamine elimination to form a dinickel cyanate complex (120). The rate constants for the elimination of methylamine or dimethylamine at 60°C were calculated to be... 

SYNS 3-(3,4-DICHLOOR-FENYL)-l-METHOXY-l-METHYLUREUM (DUTCH) 3-(3,4-DICHLORO-FENIL)-1-METOSSI-l-METIL-UREA (ITALIAN) 3-(3,4-DICHLOROPHENYL)-l-METHOXY-l-METHYLUREA N -(3,4-DICHLOROPHENYL)-N-METHOXY-N-METHYLUREA l-(3,4-DICHLOROPHENYL)3-METHOXY-3-METHYLUREE (FRENCH) N-(3,4-DICHLOROPHENYL)-N -METHYL-N -METHOXYUREA... 

SYNS METHYLNITROSO-HARNSTOFF (GERMAN) N-METHYL-N-NITROSO-HARNSTOFF (GERMAN) METHYLNITROSOUREA 1-METHYL-l-NITROSO-UREA METHYLNITROSOUREE (FRENCH) MNU N-NITROSO-N-METHYLCARBAMIDE N-NITROSO-N-METHYI HARNSTOFF (GERMAN) NITROSO-METHYLUREA N-NITROSO-N-METHYLUREA 1-NITROSO-l-METFtYLUREA NMH NMU NSC-23909 Q RCRA WASTE NUMBER U177 SKI 24464 SRI 859... 

When urea (or thiourea) reacts with a-hydroxy ketones or a-diketones the products are imidazolin-2-ones (or -thiones) (70AHC(12)103,66RCR122). The reaction is limited to the preparation of 4,5-alkyl(or aryl)- or l,4,5-trialkyl(or triaryl)-imidazoles since an oxygen or sulfur function appears at C-2. Benzoin condenses with iV-phenylthiourea in hexanol in the presence of catalytic quantities of HCl to give l,4,5-triphenylimidazoline-2-thione (131) in 50-60% yield (Scheme 69). While 1-methylurea can also take part in the reaction. 

The metabolism of methylamine is believed to occur in two stages. The amino group is initially dehydrogenated to an intermediate imine (methyl imine), which reacts spontaneously with water, forming the corresponding aldehyde (formaldehyde) and ammonia. The final metabolic products, reported to be formic acid and urea or methylurea, are excreted in the urine. To a lesser extent, methylamine is also metabolized to dimethylamine. Methylamine is a normal constituent of mammalian and human urine. 

Helferich and Kosche, by a modified Schoorl procedure, isolated certain products whose existence had been demonstrated earlier (see page 218) on the basis of optical-rotation studies. These included 1-L-arabinosylurea, 1,3-di-D-xylosylurea, and l-D-glucosyl-2-thiourea. They also prepared 1-D-glucosylurea, l-D-glucosyl-3-methylurea, and some derivatives (see Table III), and demonstrated the formation of a molecular compound (1 1) of 1-D-glucosylurea with urea, as independently reported by Hynd at about the same time. 

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