Thiosemicarbazide, oxidation

The starting semicarbazones were most often prepared directly from the a-keto acids. Godfrin proceeded from a-alkyl acetoacetates, which were converted by oxidation with nitrosylsulfuric acid to a-keto-acid oximes and the latter transformed to semicarbazones or thioseraicarbazones by applying semicarbazide or thiosemicarbazide. For glyoxylic acid semicarbazone a very convenient procedure was employed, making use of the hydrolysis of nonisolated chloral semicarbazone. ... 

To the purified, oxidized glycoprotein(s), add fluorescein-5-thiosemicarbazide to a final concentration of 0.5 mg/ml. 

Cyclodesulfurization of thiosemicarbazides, containing pyrazole <2002PS67> or benzofuran <2002PS863, 2004PS1577> units, by yellow mercuric oxide or by l,3-dibromo-5,5-dimethylhydantoin in the presence of potassium iodide <2006TL4889> afforded the respectively substituted oxadiazoles. 

Thus, (dimorpholinophosphoryl)formonitrile oxide undergoes 1,3-addition reactions with HC1, HI, primary and secondary amines, acylhydrazines, and even with thiourea or thiosemicarbazide (Scheme 1.13) (98). The former gives (dimor-pholinophosphoryl)isothiocyanate and urea. Those products might arise from a retro destruction of the unstable 1,3,5-oxathiazoline. The latter transforms to the isothiocyanate, the product of addition of a second molecule of thiosemicarbazide. (98). 

Amino-5-alkyl- or 5-phenyI-l,3,4-thiadiazoles are prepared most conveniently from thiosemicarbazide. For example, benzalthiosemicarbazone by oxidation with iron(III) chloride gives the 5-phenyl derivative. Thiosemicarbazide is also used in the synthesis of 2-amino-5-mercapto-l,3,4-thiadiazole by reaction with carbon disulfide. The product may be alkylated to yield the 5-alkylthio derivatives using a variety of alkylating agents (58MI11201). 

Oxygen can be transferred from the arene oxides to nitrogen-, sulfur-, or phosphorus-containing substrates like pyridine, thiourea, N-methyl-benzothiazol-2-thione, thioacetamide, thiosemicarbazide, thiols, thio ethers, triphenylphosphine,21,160,161 etc. Parent hydrocarbons are formed as products.162 Thus the dimethoxycarbonyl oxide 269 on heating with pyridine produces 9,10-dimethoxycarbonylphenanthrene (270). The reaction of 1 or its... 

Ahn, B., Rhee, S. G., and Stadtman, E. R. (1987) Use of fluorescein hydrazide and fluorescein thiosemicarbazide reagents for the fluorometric determination of protein carbonyl groups and for the detection of oxidized proteins on polyacrylamide gels. Anal. Biochem. 161,245— 257. 

This general approach to the 1,2,3,5-thiatriazole ring was also used to prepare l,2,3,5-thiatriazolidine-4-one-l-oxides 36 (X = 0) and 1,2,3,5-thiatriazolidinc l-thione-l-oxides 36 (X = S) by the reaction of semicarbazides 35 (X = O) and thiosemicarbazides 35 (X = S), respectively, with thionyl chloride in methylene chloride solution (Equation 10) <1979JHC895>. 

Carbonylation occurs by the oxidation of some amino acid side chains into ketone or aldehyde derivatives by reactions with compounds of lipid oxidation or by glycoxidation with reducing sugars. These protein-carbonyl compounds are markers of protein oxidation, and recently, several carbonylated proteins and protein oxidation sites in milk (96), meat (97), and fishes (98) have been identified using a classical bottom-up proteomics approach based on 2-DE and MS/MS. Specific labeling of protein carbonyls using fluorescein-5-thiosemicarbazide has been developed and combined with 2-DE and... 

Treatment of aromatic carboxaldehyde (diaminomethylene)hydrazones (105) with hot acetic anhydride or benzoyl chloride affords l,4-diacyl-3-acylamino-5-ary 1-4,5-dihydro- 1H-1,2,4-traizoles (106) in 75-95% yields. In contrast, when the 4-pyridine analog of 105 was employed, the unusual hemianimal triazole derivative (107) was obtained. The structures of the novel compounds were determined by spectral methods and in several cases by x-ray structural analysis. Mechanistic considerations are discussed [95M733]. The oxazole-1,2,4-triazole (108) was prepared by cyclization of the corresponding oxazolecarbonyl-thiosemicarbazide with bicarbonate, alkylation at the sulfur and oxidation to the sulfoxide with MCPBA [95JHC1235]. 

Cyclization in phosphorus oxychloride of semicarbazides (79 X = NHR) yields aminooxadiazoles (81) whereas thermolysis leads to loss of ammonia (when X = NH2) and formation of an oxadiazolinone (80). Cyclization to aminooxadiazoles (81) occurs when thiosemicarbazides (82) are heated with an oxidizing agent such as lead oxide. This reaction has been widely applied to the synthesis of aminooxadiazoles, sometimes in low yields, and has been used to prepare 2-amino-l,3,4-oxadiazole (81 R1 =R2 = H). 5-Methyl ethers of thiosemicarbazides (82) cyclize, with loss of methanethiol, to aminooxadiazoles (81) on heating, but in PPA cyclization to 2-methylthio-l,3,4-oxadiazoles occurs. 

A versatile route to 2-aminooxadiazoles (92), which generally proceeds in higher yield than oxidation of thiosemicarbazides (82), is the cyclization in aqueous or alcoholic solution of l-acyl-2-cyanohydrazines (91) prepared from acylhydrazines and cyanogen bromide (Scheme 16). Alternatively, hydrazines (91) are obtained by acylation of cyanohydrazines (66EGP52668). 

Similar ring closures can be carried out oxidatively. Aminooxadiazoles 583 are commonly prepared by oxidative cyclization of thiosemicarbazides 582 using iodine in alkaline solution (Scheme 262) <1999JFC(93)39, 2001CHE1102> or other reagents . 

Donaruma et al.28 reported the synthesis of some polymeric thiosemicarbazide-containing copper ions which are employed to reduce or oxidize various organic substrates (Eq. 9). 

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