Potassium ferricyanide oxidations

Dimethylcarbodihydrazide (280) reacts with aldehydes to afford 1,5-dimethyltetrahydro-l,2,4,5-tetrazin-6-ones (281), which can be oxidized by silver oxide, potassium ferricyanide or lead dioxide to yield radicals (282) related to the verdazyls these can be transformed into tetrahydro-l,2,4,5-tetrazines (283) by hydrogenation over palladium (80AG766). 

K20s02(0H)4 can be used as the nonvolatile form of osmium and this can be mixed with the oxidant, potassium ferricyanide, and the ligand to allow ease of use. 

Potassium ferricyanide-mediated oxidation Potassium ferricyanide is a relatively mild inorganic oxidizing reagent that is used widely for the conversion of bis(thiol) to disulphides (5, 6, 8). Since K3Fe(CN)g is slightly light sensitive, reactions are best conducted in the dark. Oxidation side products are possible when Met or Trp residues are present in the substrate (89,90). 

As an example, the strong oxidant potassium ferricyanide or hydrogen peroxide oxidizes thiamin to fluorescent thiochrome. 

An important mode of oxidation for -phenylenediamines is the formation of ben2oquinonediimines, easily obtained by oxidation with silver oxide in ether solution (17). DHmines undergo 1,4 additions with amines to generate tri- and tetraamines which readily oxidi2e in air to highly conjugated, colored products. An example of this is the formation of Bandrowski s base [20048-27-5] when -phenylenediamine is oxidi2ed with potassium ferricyanide (18). 

Methylpyridinium quaternary salts, such as (12), undergo oxidation in alkaline solution in the presence of potassium ferricyanide to give 2-pyridones, eg, A/-methyl-2-pyridone [694-85-9] (16). Frequendy nucleophilic attack at position 2 by excess hydroxide leads to ring opening this and synthetically useful recycli2ations have been reviewed (17). 

AH formulations of vitamin E must show low acidity, and contain not more than 0.004% heavy metals (reported as Pb) and not more than 10 ppm Pb. Eormulations that contain RRR-a-tocopherol must have a specific rotation of +24 ° for the oxidation product with alkaline potassium ferricyanide. 

The most suitable oxidizing agent is potassium ferricyanide, but ferric chloride, hydrogen peroxide ia the presence of ferrous salts, ammonium persulfate, lead dioxide, lead tetraacetate or chromate, or silver and cupric salts may be useful. Water mixed, eg, with methanol, dimethylformamide, or glycol ethers, is employed as reaction medium. 

Again, as with pyridopyrimidines, the main reaction is oxidation of di- or poly-hydro derivatives to fully aromatic structures, often merely by air or oxygen. In some cases the reagent of choice is mercury(II) oxide, whilst other reagents used include sulfur, bromine, chloranil, chromium trioxide-acetic acid, hydrogen peroxide, and potassium ferricyanide, which also caused oxidative removal of a benzyl group in the transformation (306) (307)... 

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... 

The indolinol character of eseretholemethine is indicated by the fact that the methiodide on treatment with picric acid yields a diquaternary pierate (m.p. 170°) with the loss of the hydroxyl group. More definite proof is afforded by the oxidation of eseretholemethine with ammoniaeal silver nitrate or potassium ferricyanide, when a dehydroeseretholemethine (oxyeseretholemethine of Polonovski), pierate, m.p. 199°, is produced which is assumed to have formula (VI), since on exhaustive methylation it yields trimethylamine and an unsaturated product (deep-red pierate, m.p. 103°), which absorbs two atoms of hydrogen, forming 5-ethoxy-l 8-dimethyl-S-ethyl-2-indolinone (VII), colourless cubes, m.p. 68°. The... 

A -Piperideine-N-oxide was obtained along with a dimeric product by oxidation of N-hydroxypiperidines with mercuric acetate or potassium ferricyanide (107-109). 2l -Pyrroline-N-oxide is formed by oxidation of N-ethylpyrrolidine with hydrogen peroxide with simultaneous formation of ethylene (110). 

Marazano and co-workers have also applied the reactions of tryptamine with various Zincke salts, including 115 (Scheme 8.4.39), in the synthesis of pyridinium salts such as 116. This type of product is useful for further conversion to dihydropyridine or 2-pyridone derivatives. For example, in a different study, Zincke-derived chiral pyridinium salts could be oxidized site-selectively with potassium ferricyanide under basic conditions as a means of chiral 2-pyridone synthesis (117 —> 118, Scheme 8.4.40). 

Dihydroquinazolincs are oxidized to quinazolines with alkaline potassium ferricyanide (see Section VI,A,1). 

Fig. 3. Cation-exchange chromatography of protein standards. Column poly(aspartic acid) Vydac (10 pm), 20 x 0.46 cm. Sample 25 pi containing 12.5 pg of ovalbumin and 25 pg each of the other proteins in the weak buffer. Flow rate 1 ml/min. Weak buffer 0.05 mol/1 potassium phosphate, pH 6.0. Strong buffer same +0.6 mol/1 sodium chloride Elution 80-min linear gradient, 0-100% strong buffer. Peaks a = ovalbumin, b = bacitracin, c = myoglobin, d = chymotrypsinogen A, e = cytochrom C (reduced), / = ribonuclease A, g = cytochrome C (oxidised), h = lysozyme. The cytochrome C peaks were identified by oxidation with potassium ferricyanide and reduction with sodium dithionite [47]...

Potassium ferricyanide in oxidative decarboxylation, 40, 86 Potassium permanganate for oxidation of (trialkylmethyl)amines to tri-alkylnitromethanes, 43,87 Pregnenolone acetate, conversion to 3/3-acetoxyetienic acid, 42, 5 Propane, 2,2-dibotoxy-, 42,1 Propargylsuccinic anhydride, by-product in addition of maleic anhydride to allcne, 43, 27... 

---