Ferricyanide oxidations, alkaline

Alkali ferricyanides oxidize alkaline phenolphthalin solutions instantly. This same behavior is exhibited by insoluble metal ferricyanides that are decomposed by the free alkali in the phenolphthalin solution to produce alkali ferricyanide and insoluble hydrous metal oxide. A test for ferricyanide in the presence of other oxidizing materials is based on this behavior. The neutral or weakly acidified test solution is treated with zinc sulfate insoluble zinc ferricyanide separates. The washed precipitate is tested with phenolphthalin solution. 

Furoic acid has been made by oxidation of lactose followed by pyrolysis, by the oxidation of 2-acetylfuran, 2-methylfuran, or furfuryl alcohol using potassium ferricyanide in alkaline medium, and by other methods already listed. ... 

Oxysanguinarine, C2oH430gN, was isolated by Spath, Schlemmer, Schenck and Gempp by chromatographic analysis of blood root alkaloids, and was also prepared by oxidation of sanguinarine nitrate by potassium ferricyanide in alkaline solution. It was purified by crystallisation from... 

An interesting catalytic effect upon the alkaline ferricyanide oxidations of ketones is shown by osmium(VIII) tetroxide, the rate expression being... 

Skinner, W. A. Alaupovic, P. Oxidation products of vitamin E and its model, 6-hydroxy-2,2,5,7 8-pentamethyl-chroman. V. Studies of the products of alkaline ferricyanide oxidation. J. Org. Chem. 1963, 28, 2854—2858. 

Ferricyanide oxidation of 1,5-disubstituted thiocarbazones (116) give the mesoionic tetrazolium salts (117) under mild conditions (Eq. 21).190 This is in contrast to the strongly alkaline oxidation of carbazides leading to mercapto formazans as shown in Eq. 8 (Section 7.3.1.4). The heterocyclic triazine (118), obtained by the action of a diazonium salt on 2-... 

Paquette and co-workers synthesized the 5,11-dinitro isomer of 1,3-bishomopentaprismane (95) by treating the dioxime (94) with a buffered solution of m-CPBA in refluxing acetonitrile. A significant amount of lactone by-product (96) is formed during this step and may account for the low isolated yield of (95). Oxidative nitration of (95) with sodium nitrite and potassium ferricyanide in alkaline solution yields a mixture of isomeric trinitro derivatives, (97) and (98), in addition to the expected 5,5,11,11-tetranitro derivative (99), albeit in low yield. Incomplete reactant to product conversion in this reaction may result from the low solubility of either (97) or (98) in the reaction medium, and hence, incomplete formation of the intermediate nitronate anions. 

Olah and co-workers reported the synthesis of 2,2,5,5-tetranitronorbornane (127) from 2,5-norbornadiene (122). In this synthesis formylation of (122) with formic acid yields the diformate ester (123), which on treatment with chrominm trioxide in acetone yields 2,5-norbomadione (124). Formation of the dioxime (125) from 2,5-norbornadione (124) is followed by direct oxidation to 2,5-dinitronorbomane (126) with peroxytriflnoroacetic acid generated in situ from the reaction of 90 % hydrogen peroxide with TFAA. Oxidative nitration of 2,5-dinitronorbornane (126) with sodium nitrite and potassium ferricyanide in alkaline solution generates 2,2,5,5-tetranitronorbornane (127) in excellent yield. 

Tlie products of alkaline ferricyanide oxidation of pyridinophanium salts 62 (85CB4259) are pyridones 63 in relatively high yields, and traces of 48 (82TH2) (Scheme 13). Similarly, oxidation of 64 yields pyridones 69 almost... 

Only para coupling was observed during the alkaline ferricyanide oxidation of 4-hydroxy-3-(3-hydroxybenzoyl)benzoic acid. 7-Hydroxy-9-oxoxanthene-2-carboxylic acid (515) was obtained in 21% overall yield from methyl 4-hydroxybenzoate (78JCS(P1)876). The synthesis utilizes a photochemical Fries rearrangement of methyl 4-(3-methoxybenzoyloxy)benzoate to prepare the benzophenone (514 Scheme 189). A similar route was used to prepare 2-hydroxy-2 -methoxybenzophenones, which undergo intramolecular cyclization with loss of methanol on treatment with base. 

Oxidation of aldoses and ketoses with ferricyanide under alkaline conditions involves the 1,2-enediol as an intermediate. Such an oxidation... 

Pyridone Formation by Alkaline Ferricyanide Oxidation or 3-Substituted Pyridinium Salts... 

Oxidants that operate according to this one-electron oxidation mechanism include potassium ferricyanide in alkaline solution, cobalt, copper complexes with dioxygen, and some enzymes. 

Benzofurazan oxide has been prepared by a thermal decomposition of o-nitrophenylazide 4-8 by oxidation of the dioxime of o-benzoquinone by dilute nitric acid or potassium ferricyanide in alkaline solution 4 and by oxidation of o-nitroaniline with sodium hypochlorite.9 The present synthesis is a modification of the methods of Noelting and Kohn 8 and of Zincke and Schwarz.4... 

Hiinig and Oette prepared azothiadiazoles (85) by oxidative coupling of 3-methyl-l,3,4-thiadiazolin-2(3)-one hydrazones (84) with phenols and diphenylamine. 84 was prepared by reaction of 2-methyl-thio-3-methyl-l,3,4-thiadiazolium ions (82) with benzhydrazide and hydrolysis of the first formed benzhydrazone (83). The coupling to 85 was performed with potassium ferricyanide in alkaline medium. 

Das and Rout claim to have prepared the imino forms (143) of several 2-toluidino-l,3,4-thiadiazoles (145) by oxidation of the corresponding 4-tolylthiose micarbazones (144) with iodine or potassium ferricyanide in alkaline solution. Later, Ramachander and Srinivasan repeated this synthesis in similar systems, but they also prepared the tautomers (145) by oxidation of 144 with ferric chloride. It is highly unlikely that individual tautomers like 143 and 145 should exist as separate compounds, particularly as they have crystallized from the same solvent, ethanol. The only proofs for the structure 143 are sulfur analyses, but it is evident from the melting points that 143 is identical neither with 145 nor with the isomeric triazolinethiones. Menin et al. tried to repeat the preparation of 143, though without success. 

Thiamine hydrochloride is stable in acid but unstable in aqueous solutions with a pH above S. Under lhe.se conditions. it undergoes decomposition and inactivation. Exposure of thiamine to the atmosphere or to oxidizing reagents such as hydrogen peroxide, permanganate, or alkaline potassium ferricyanide oxidizes it readily to ihiochromc, shown below. Thiochromc exhibits a vivid blue fluorescence hence, this reaction is the basis for the quantitative fluoro-metric assay of thiamine in the USP. 

Historically, assessment of thiamine status was by animal bioassay (the correction of bradycardia in thiamine-deficient rats) and later by microbiological assays using the fungus Phycomyces hlakesleeanus, yeast fermentation, or bacteria of the Staphylococcus, Streptococcus, or Lactobacillus species. Some bacterial microbiological assays are still in use in the food industry. Early chemical methods were often based upon the production of a fluorophore, thiochrome, when thiamine is oxidized with ferricyanide in alkaline solution, a property that is used in some modern chromatographic methods. 

Finally, ferricyanide oxidation of the tetrasubstituted pyrroles 37 (Scheme 12) under aqueous alkaline conditions gives high yields of the dimers 38, which dissociate into radicals (39) on heating.39... 

Oxysparteine was also the intermediate which furnished conclusive proof of the ring structure of all the Cw lupin alkaloids. Clemo, Morgan, and Raper in 1936 (260) announced the synthesis, from non-alkaloid starting materials, of a compound with structure XCV and established the identity of this compound with the d/-oxysparteine obtained by alkaline ferricyanide oxidation of dZ-sparteine. The s3Tithesis of dZ-oxy-sparteine (XCV) was accomplished as outlined below. The Claisen condensation of ethyl 2-pyridylacetate (XCVI) with ethyl orthoformate... 

Alkaline potassium ferricyanide oxidation of A/ -substituted pyridinium salts often is amethod of choice for the preparation of A -alkyl-2-pyridones. For example,... 

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