Thiourea, desulfuration

When desulfurized with Pb02, l-aryI 3-(4-p-tolyl-2-thiazolyl)thioureas yield the heterocyclic guanidines (262) (Scheme 159) (299, 496, 497). 

The formation of a sulfur-containing ring was justified by the attack of the halogenated carbon of the cMoroacetyl derivative by the sulfur atom of thiourea, a fact in accordance with the results just discussed by Wallach (49,50) and Claus (51). The new formula (37) of thiohydantoine explained why, contrary to thiourea, its desulfuration was difficult. 

Carbodiimides have been prepared by desulfurization of thioureas by metal oxides, by sodium hypochlorite,4 or by ethyl chloroformate in the presence of a tertiary amine by halogena-tion of ureas or thioureas followed by dehydrohalogenation of the N,N -disubstituted carbamic chloride 8 and by dehydration of disubstituted ureas using -toluenesulfonyl chloride and pyridine.7 The method described above is a modification of that of Campbell and Verbanc. ... 

Except this particular example, the other possibilities such as the desulfurization of cyclic thioureas or the vacuum thermolysis of methoxy derivatives [1-5], has never been used for the preparation of chiral diaminocar-... 

Marcotrigiano et al.39 suggested that the desulfuration of thiourea in sodium hydroxide results in the formation of cyanamide, amidinourea, and guanidine at a pH below 12 they also suggested that the formed urea converts to ammonium cyanate and finally to ammonium carbonate (by hydrolysis). The pro-... 

Marcotrigiano, G. Peyronel, G. Battistuzzi, R. 1972. Kinetics of desulfuration of S-35-labeled thiourea in sodium hydroxide studied by chromatographic methods. /. Chem. Soc., Perkin Trans. 2 1539-1541. 

A novel route to synthesize l,3 -triazine-2,4(l//,3//)-diones through the desulfurization of thiocarboamides, such as 1,3-disubstituted 2-thioureas, trisubstituted thioureas and N-substituted thioamides by silver cyanate has been reported <00H(53)929>. Treatment of urazole 23 with one equivalent of sodium hydride under anhydrous conditions, followed by addition of dimethyl sulfate, leads to l,3,5-triazine-2,4-dione 24 in 80% yield . 

This procedure for the preparation of l-ethyl-3-(3-dimethyl-amino)propylcarbodiimide and its salts is a modification of one that has been published.4 Unsymmetrical carbodiimides have also been prepared by desulfurization of the corresponding thioureas with mercuric oxide3 or by dehydration of the corresponding ureas with -toluenesulfonyl chloride in pyridine.4 Unsymmetrical 1,3-disubstituted ureas are best prepared by the reaction... 

A critical study of the preparation of the two anomeric 6-desoxy-D-glucose tetraacetates (LXXXIV) from D-glucose has been made by Hardegger and Montavon.70 The final step, namely, the reduction of the two 6-iodo-6-desoxy-D-glucose tetraacetates (LXXXII) in high yield, proved to be particularly difficult and a variety of methods were studied. Highest yields were obtained when LXXXII was allowed to react with thiourea to form the S-substituted isothiuronium iodide (LXXXIII) which was then desulfurized with Raney nickel. In actual practice the 6-iodo derivative was refluxed briefly in amyl alcohol with thiourea and... 

Cyclic thiourea derivatives like l,3,4,5-tetramethylimidazole-2(3H)-thione— prepared by condensation of substituted thioureas with a-hydroxyketones—can be converted into the corresponding imidazolin-2-ylidene by desulfurization with sodium or potassium [Eq. (23)]. This method was used to prepare and isolate l,3-bis-neo-pentylbenzimidazolin-2-ylidene with Na/K. With LDA as the base it is also possible to generate free benzimidazolin-2-ylidenes in solution. ... 

Desulfurization of 1,3-disubstituted thioureas to the corresponding ureas with KO2 at room temperature in DMSO takes place in good to excellent yields . It is believed that this reaction proceeds by formation of a peroxysulfenate intermediate (equation 75). 

Oxidative desulfurization of the thiourea moiety is known to occur by an in vivo metabolism which forms the corresponding carbonyl compound, although there is no direct evidence for involvement of any activated oxygen species like superoxide, which is distributed widely in living cells. It was found that various thiocarbonyl derivatives such as thioureas, thioamides and thiocarbamates were readily desulfurized with 51 to the corresponding carbonyl compounds in almost quantitative yields at —35°C in CH3CN (equation 82). Desulfurization of thiourea with 02 was previously reported but the yields were comparatively low. ... 

A. Desulfurization of Thioureas with Metal Oxides and Other Metallic Compounds. 215... 

V-(Arylsulfonamidino)thioureas (108) afford the expected 5-amino-3-sulfonamido-l,2,4-thiadiazoles (109). The cyclization occurs almost quantitatively under the influence of bromine, but fails with hydrogen peroxide, which cleaves part of the starting material to sulfonylguanidine (110), and desulfurizes part to sulfonamidinourea (111).116. 

Desulfuration.1 The reaction of K02 with o-nitrobenzenesulfonyl chloride results in a peroxysulfur reagent that converts thioureas, thioamides, and thiocar-bamates in CH3CN at -30° into the corresponding carbonyl compounds. Example ... 

This method is a modification of the procedure described by Taylor and Ehrhart.2 Formamidine has previously been prepared (as its hydrochloride) from hydrogen cyanide via the formimino ether, which is then treated with ammonia,3 or by desulfurization of thiourea in the presence of ammonium chloride.4 The methosulfate salt of formamidine has been reported to be formed by reaction of formamide with dimethyl sulfate.8... 

Desulfuration.4 Thioureas and thioamides are converted into ureas and amides in 60 80% yield by reaction with KOz crown ether in DMF at 25°. lixamples ... 

The kinetics of the oxidation of l-phenyl-2-thiourea by chlorite, in aqueous acidic media, are strongly influenced by the pH and show a complex acid dependence. The proposed mechanism involves HOC1 as a major intermediate whose autocatalytic production determines the observed kinetics of the reaction. The oxidation involved the formation of two stable intermediates, the sulfinic acid and the sulfonic acid, on the pathway towards total desulfurization to form phenylurea. A comprehensive 29-reaction scheme has been proposed to describe the observed complex kinetics.96 The oxidation of trimethylthiourea (TMTU) by chlorite in slightly acidic media is very fast. The oxidation of TMTU proceeds through the formation of sulfinic acid then to the sulfoxylate anion. The direct reaction of chlorine dioxide and TMTU is autocatalytic and is also inhibited by acid. A series of 28 reactions have been proposed to describe the mechanism.97... 

A-Oxidation -Oxidation P-Oxidation Desulfuration Nicotine, dimethylaniline, imipramine Thiobenzamide, phorate, thiourea Diethylphenylphosphine Fonofos Alcohol Dehydrogenase... 

The first synthesis of carbodiimides was reported by Weith in 1873. However, carbodiimides were already synthesized by Hinterberger and Zinin in 1852, and Biziro in 1861. The earlier authors obtained carbodiimides by desulfurization of 1,3-disubstituted thioureas but did not recognize their structure. 

Isothiocyanates are also major starting materials for carbodiimides either by converting them into 1,3-disubstituted thiourea intermediates, which are subsequently desulfurized, or by treating them with iminophosphoranes. 

The synthesis of carbodiimides by desulfurization of 1,3-disnbstitnted thioureas is the most general method of synthesis because dialkyl-, alkylaryl- anddiarylcarbodiimides with the same or different substituents are obtained. The desnlfurization of N,N -disubstituted thioureas 1 with yellow mercuric oxide is the classical method of synthesis of carbodiimides 2 used by Weith in 1873. ... 

In addition to dialkyl-, alkylaryl- and diarylcarbodiimides, heterocyclic carbodiimides, such as l,4-dioxan-2-ylcarbodiimides 6 are obtained by desulfurization of the corresponding thiourea 5. ... 

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