Thiourea, oxidation

The hydroxyl-ion dependences suggest oxidation of substrate anions. Alkali-catalysed enolisation is the slow step of the oxidation of thioacetamide but is a fast pre-equilibrium in the thiourea oxidation. 

Only one report of a pyrazine-type compound apparently utilizing a thiourea has appeared. Tashika and Nitta248 found that the iodine/ thiourea oxidation of a-aminoacetophenone hydrochloride gave 2,5-diphenylpyrazine (113). The authors do not discuss the mechanism nor the function of the molar quantity of thiourea in the reaction. 

Oxidation of thioureas. The well-established synthesis of 1,2,4-thiadiazole derivatives by the oxidation of arylthioureas has been further studied by an examination of the oxidation products of mixtures of equimolar quantities of two thioureas. Oxidation of a mixture of syw-diarylthiourea and thiourea by hydrogen peroxide in acidified ethanol yields 3-amino-4-aryl-5-arylimino-A -1,2,4-thiadiazolines (42 R = H). These compounds are considered to be formed by the cyclization of amidino-thioureas (43), which can be isolated from the oxidation of mixtures of l-alkyl-3-arylthioureas and thiourea. The overall mechanism resembles that postulated for the formation of Hector s Bases. The oxidation of binary mixtures of sym-diaryl- and iV-alkyl-thioureas similarly furnishes the trisubstituted thiadiazolines (42 R = alkyl). ... 

Carbonylation of the tetrasubstituted bispropargyiic amine 23 using PdCP and thiourea under mild conditions affords the carboxylated pyrrolidine derivatives 24a and b in good yields. Thiourea is regarded as effective for the oxidative carbonylation of alkynes, but no oxidative carbonylation was observed in this case[21]. 

In many cases, the a-haloketone does not appear to be an intermediate in this reaction, since reagents such as sulfur trioxide, sulfuric, or 60% nitric add lead to 2-aminothiazole but with lower yields (11 to 43%). Formamidine disulfide [-S-C(=NH)NH2]2, a product of the oxidation of thiourea, seems to be the intermediate in this reaction, since upon treatment with ketones, it gives 2-aminothiazole (604). However, the true mechanism of this reaction has not yet been completely elucidated. 

Traditionally, these dyes are appHed from a dyebath containing sodium sulfide. However, development in dyeing techniques and manufacture has led to the use of sodium sulfhydrate, sodium polysulfide, sodium dithionite, thiourea dioxide, and glucose as reducing agents. In the reduced state, the dyes have affinity for cellulose (qv) and are subsequendy exhausted on the substrate with common salt or sodium sulfate and fixed by oxidation. 

Spray Pyrolysis. In spray pyrolysis, a chemical solution is sprayed on a hot surface where it is pyrolyzed (decomposed) to give thin films of either elements or, more commonly, compounds (22). Eor example, to deposit CdS, a solution of CdCl plus NH2CSNH2 (thiourea) is sprayed on a hot surface. To deposit Iu202, InCl is dissolved in a solvent and sprayed on a hot surface in air. Materials that can be deposited by spray pyrolysis include electrically conductive tin—oxide and indium/tin oxide (ITO), CdS, Cu—InSe2, and CdSe. Spray pyrolysis is an inexpensive deposition process and can be used on large-area substrates. 

Whiter fabrics are produced if an oxidative bleaching is followed by a reductive one this is often referred to as full bleaching. One such process involves a hydrogen peroxide oxidative bleaching, followed by addition of thiourea to the Hquor to generate thiourea dioxide for a reductive bleach in situ (115). 

Thiourea dioxide, or formamidine sulfinic acid, is an oxygenated thiourea derivative synthesized by the oxidation of thiourea with hydrogen peroxide. It has the chemical formula (NH2)NHCS02H and is tautomeric. 

Diborane reacts with ethylene oxide at —80° C to form diethoxyborane and a soHd polymer containing approximately eight ethylene oxide units per molecule (88). Potassium thiocyanate or thiourea react ia aqueous solution with ethylene oxide to give ethylene sulfide (89). 

Thiirane 1-oxide undergoes acid-catalyzed ring opening by ethanethiol to give ethyl 2-ethylthioethyl disulfide. Treatment of thiirane 1,1-dioxide with thiolate anions, sodium sulfide or thiourea gives /3-mercaptosulfinic acid derivatives (75S55). Thiiranium ions are attacked at carbon by most sulfur nucleophiles (79ACR282), but see Section 5.06.3.4.3 for exceptions. 

This thiourea, prepared from an amino acid and phenyl isothiocyanate, is cleaved by anhydrous trifluoroacetic acid (an N-COCF3 group is stable), and by oxidation (/72-CIC6H4CO3H, 0°, 1.5 h, 73% yield H2O2/ACOH, 80°, 80 min, 44% yield). ... 

Tropolone has been made from 1,2-cycloheptanedione by bromination and reduction, and by reaction with A -bromosuccinimide from cyolo-heptanone by bromination, hydrolysis, and reduction from diethyl pimelate by acyloin condensation and bromination from cyclo-heptatriene by permanganate oxidation from 3,5-dihydroxybenzoic acid by a multistep synthesis from 2,3-dimethoxybenzoic acid by a multistep synthesis from tropone by chlorination and hydrolysis, by amination with hydrazine and hydrolysis, or by photooxidation followed by reduction with thiourea from cyclopentadiene and tetra-fluoroethylene and from cyclopentadiene and dichloroketene. - ... 

Ethylene glycol Ethylene glycol dinitrate Ethylene oxide Ethylene thiourea Ethylenimine... 

Like the reaction of ketones, the interaction of triflic anhydride with thiourea and substituted thioureas also gives dicationic triflates (equations 40 and 41) however, two sulfur atoms form the bndge in this case This result indicates that triflic anhydride is acting as an oxidizing reagent toward thiourea [89]. 

The DPA ester is formed from the acid chloride in pyridine (40-96% yield). It is cleaved oxidatively by treatment with NBS followed by thiourea (40-88% yield). ... 

However, Sahasrabudhey thinks that the compound formed from 5-amino-1,2,3,4-thiatriazole does not have the composition CSN2H3CI, but (CSN2H4C1)2, and is in fact the dihydrochloride of formamidine disulfide, the oxidation product of thiourea. This con-... 

A variation of the general method for the synthesis of 2-amino-selenazoles is to avoid the use of the free a-halogenocarbonyl compound and in its place react the corresponding ketone and iodine with selenourea.This procedure is also taken from thiazole chemistry. By contrast with thiourea, the reaction with selenourea needs a longer reaction time and the work up of the reaction mixture is somewhat more difficult. Usually an excess of the ketone is used. In the preparation of 2-amino-4-( n-nitrophenyl)selenazole, a very high yield, calculated on the amount of iodine used, was obtained. To explain this peculiar result, the oxidative action of the nitro group was invoked. This liberates free iodine from some of the hydrogen iodide eliminated in the condensation reaction, and the free iodine then re-enters into the reaction. 

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