Semicarbazide, oxidation

Cyclohexanone shows most of the typical reactions of aUphatic ketones. It reacts with hydroxjiamine, phenyUiydrazine, semicarbazide, Grignard reagents, hydrogen cyanide, sodium bisulfite, etc, to form the usual addition products, and it undergoes the various condensation reactions that are typical of ketones having cx-methylene groups. Reduction converts cyclohexanone to cyclohexanol or cyclohexane, and oxidation with nitric acid converts cyclohexanone almost quantitatively to adipic acid. 

Pyridazine aldehydes and ketones with the carbonyl group at the ring or in a side chain react in the usual manner. They form hydrazones, semicarbazides, oximes, etc. Side-chain aldehydes can be easily oxidized to pyridazinecarboxylic acids with silver nitrate and side-chain ketones are oxidized to carboxylic acids by treatment with potassium permanganate or hydrogen peroxide. 

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. ... 

C ( propyl) N phenylmtrone to N phenylmaleimide, 46, 96 semicarbazide hydrochloride to ami noacetone hydiochlonde, 46,1 tetraphenylcyclopentadienone to diphenyl acetylene, 46, 44 Alcohols, synthesis of equatorial, 47, 19 Aldehydes, aromatic, synthesis of, 47, 1 /3-chloro a,0 unsaturated, from ke tones and dimethylformamide-phosphorus oxy chloride, 46, 20 from alky 1 halides, 47, 97 from oxidation of alcohols with dimethyl sulfoxide, dicyclohexyl carbodumide, and pyndimum tnfluoroacetate, 47, 27 Alkylation, of 2 carbomethoxycyclo pentanone with benzyl chloride 45,7... 

Reaction of 1 with semicarbazide hydrochloride gives the semicarbazone 4, in 74 % yield, which can be oxidized by selenium(IV) oxide to provide dibenzo[2,3 6,7]thiepino[4,5-rf][l,2,3]selenadi-azole (5) in 80 % yield. Thermolysis of selenadiazole 5 leads, with subsequent release of nitrogen, to diradical 6, which can either dimerize to 7 or lose selenium to give the intermediate cycloalkyne. The latter can be trapped by dienes as cycloadducts.93 Thus, the thermolysis of 5 in the presence of 2,3,4,5-tetraphenylcyclopenta-2,4-dienone gives the cycloadduct 1,2,3,4-tetraphenyltribenzo-[/ ,<7,/]thiepin (8) in 14% yield. 

The iji vitro experiments, using the S-9 fraction from livers of uninduced Fisher 344 rats, was complicated by the fact that it became apparent that formaldehyde production was a poor measure of the extent of metabolism. The reason for that was that the S-9 fraction apparently catalyzed the oxidation of formaldehyde to formate. Consequently, determination of formaldehyde in an S-9 catalyzed reaction consistently gave low values of nitrosamine metabolism. Many workers use semicarbazide to suppress formaldehyde loss. We found, however, that semicarbazide is not a neutral bystander. 

A flash photolysis method has been developed that prepares the MoVI-Fe11 state and thus allows the rate constants k3 and k 3 to be measured. Solutions containing 5-deazariboflavin, semicarbazide, and sulfite oxidase are subjected to 555 nm flash photolysis. The deazariboflavin is excited to a triplet state, which is then reduced by semicarbazide to form the 5-deazariboflavin semiquinone radical. This radical is then rapidly oxidized back to its parent species through the one-electron reduction of sulfite oxidase. 

Amenates acylated at the exocydic nitrogen are stable as solid compounds but decompose in aqueous solutions releasing NO. This decomposition depends on the pH and most importantly on their chemical structure [147, 152]. The proposed mechanism of NO-release is shown in Scheme 6.24. It is related to that postulated for sydnonimines. The main difference is that here 5-substituted amenates 128 are able to react with water to form acyclic nitroso semicarbazides 129 directly without needing enzymatic cleavage, and these intermediates release NO by an oxidative or thiol mediated mechanism that is not fully understood [153]. 

Potassium iodate is a fairly strong oxidizing agent that may be used in the assay of a number of pharmaceutical substances, for instance benzalkonium chloride, cetrimide, hydralazine hydrochloride, potassium iodide, phenylhydrazine hydrochloride, semicarbazide hydrochloride and the like. Under appropriate experimental parameters the iodate reacts quantitatively with both iodides and iodine. It is, however, interesting to observe here that the iodate titrations may be carried out effectively in the presence of saturated organic acids, alcohol and a host of other organic substances. 

In the reaction of l-hydroxy-2-oxo-l-cyclohexanecarboxamide and cyan-amide, the 2-aminooxazole 282 was formed. Treatment of 282 with hydrazine yielded the semicarbazide 283, which on iodine oxidation gave the perhydro-2,4-quinazolinedione 284 (87JPR177). Although the configuration of the product was not given, the cis annelation can be deduced from the published NMR data. 

The same ring system can be prepared from 1,2,4-trisubstituted semicarbazides or thiosemi-carbazides and SOCI2 to give 1,2,3,5-thiatriazolidine S -oxide (40) <79JHC895> (Equation (11)). 

Amine oxidases catalyze the oxidative deamination of both xenobiotic and biogenic amines, and thus have many critical biological functions. Two distinct classes differ in the nature of their prosthetic groups [1]. The flavin-(FAD flavin adenine dinucleotide)-dependent amine oxidases include monoamine oxidases (MAO A and B) and polyamine oxidases. Amine oxidases not containing FAD, the so-called semicarbazide-sensitive amine oxidases (SSAO), include both plasma amine oxidases and tissue amine oxidases. These contain quinonoid structures as redox cofactors that are derived from posttranslationally modified tyrosine or tryptophan side chains, topaoquinone frequently playing this role [2]. 

To another flask are added 1.22 gm (0.0059 mole) of the semicarbazone and 35 ml of alcohol. The mixture is refluxed and then 5.0 gm (0.048 mole) of sodium hydrosulfite in 25 ml of water is slowly added. The mixture immediately becomes a colorless solution which on concentration yields 1.12 gm (91 %) of the semicarbazide, m.p. 194°C dec. On exposure of the product to air in the solid form or in solution, oxidation occurs to yield the yellow semicarbazone, m.p. 250°-251°C dec. 

Selenium dioxide (see Selenium and selenium compounds) Selenium oxide (see Selenium and selenium compounds) Semicarbazide hydrochloride... 

Chromium(III) does become seven-coordinate in two complexes in which the organic ligands are formed by condensation respectively of 2,6-diacetylpyridine and semicarbazide,1125 and 2,6-pyridinedialdehyde and 6,6 -bis(or-2-hydroxyethylhydrazino)-2 2 -bipyridyl.550 Seven-coordinate complexes are formed by chromium in several oxidation states (Table 95). 

The anodic oxidation of a number of 1-arylmethylenesemicarbazides (60) has been studied in CH3CN-AcOH containing sulfuric acid.118 This method provides a convenient preparative route to either oxadiazole (61) or triazoli-none (62) derivatives. The reactions were very sensitive to the concentration of water and under ordinary conditions the oxadiazole (61) is formed in 85% yield by oxidation of l-(p-methoxybenzylidene)semicarbazide. By addition of acetic anhydride, in order to reduce the water content, the triazolinone derivative 62 was formed in 45% yield [Eq. (50)]. 

Semisynthetic enzymatic oxidation of peptide alcohols employs equine liver alcohol dehydrogenase. Amino alcohols with nonpolar side chains and Z-Om[CH2OH] worked as effective substrates while polar amino alcohols such as H-Arg[CH2OH] and H-Lys[CH2OH] failed as substrates. To attain complete oxidation, semicarbazide was present in the reaction mixture to immediately trap the aldehyde, and flavin mononucleotide was used to oxidize the NADH to NAD+, which serves to oxidize the alcohol 41] Configurational stability was confirmed by NMR spectroscopy as in the case of Ac-Phe[CH2OH], which was prepared by sodium borohydride reduction of Ac-Phe-H 4 1... 

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