Oxidation reagents and

Many people view the Skraup/Doebner-von Miller reaction as the worst witch s brew of all the heterocyclic syntheses. The reaction can be violently exothermic. A variety of oxidizing reagents and additives have been added in an effort to improve yields, including iron (III) and tin (IV) salts, nitrobenzenes, iodine and various acids such as boric and arsenic. Cohn s conditions for the Skraup reaction using an iron salt and boric acid in concentrated sulfuric acid are frequently employed. ... 

Lysenko Z, Wessling RA, Rose GD. Formulations containing stable nitrile oxide reagents and their use in coatings, composites, and moldings, PCT Int. Appl. WO 9703142 [Chem. Abstr. 1997 126 200214],... 

The first landmark was the successful synthesis and structural characterization of the cyclotrigermylium cations 2 and 19 by Sekiguchi and co-workers. This was achieved by reaction of trityl cation with the cyclotrigermenes 20 in the presence of weakly coordinating borate anions (Scheme 8). The trityl cation acts here as a one-electron oxidizing reagent and the resulting radical cation of 20 decomposes to the... 

Reactions with Strong Oxidizing Reagents and Acids... 

Primary alcohols are oxidized either to aldehydes or to carhoxylic acids, depending on the oxidizing reagents and conditions used. 

Cyclic ketones also can be cleaved by oxidation with KMn04 (Figure 17.33). Under these conditions, 1, -ketocarboxylic acids or 1, -dicarboxylic acids are formed. The mechanism of this reaction is not known in detail. It is known only that KMn04 serves as a three-electron oxidizing reagent and that it is reduced to Mn02. 

Recent results on the isomerization of epoxides to ketones accomplished via electrode-catalyzed, one electron-oxidizing reagents, and DCA-sensitized photoreaction under nitrogen atmosphere, seem to confirm this mechanistic pathway [142, 143]. On the other hand, the MCPBA oxidation of 42 affords the same reaction products 43, 44, through a plausible acid-catalyzed isomerization of the same intermediate 45 [144]. 

Several classes of compounds initiate cationic polymerizations of alkenes, including protonic acids, Lewis acids (usually in combination with a cation or proton source), stable carbenium ions, oxidizing reagents, and other strong electrophiles. This section attempts to explain the mechanism of initiation with quantitative information when available physical means of initiation (electric current, y-rays, field ionization and emission, nuclear chemical initiation) will not be discussed. 

Aminopyrazine was oxidized by hydrogen peroxide in acetic acid at 20° to 3-aminopyrazine 1 -oxide and at 50° for 15 hours to 2-aininopyrazine 1,4-dioxide (51%) (also obtained by similar oxidation of 3-aminopyrazine 1-oxide) (1189). m-Chloroperoxybenzoic acid was also used for the oxidation of 2-aminopyrazine to its 1-oxide (1258). The following aminopyrazine TV-oxides have been prepared by oxidation (reagent and conditions) 2-amino-3-methoxycarbonylpyrazine 1-oxide (m-chloroperoxybenzoic acid in chloroform at reflux) (880, 1222) 2-amino-5-chloro-3-methoxycarbonyl(and methylcarbamoyl)pyrazine 1-oxide (m-chloroperoxybenzoic acid in chloroform at reflux) (1222) 2-amino-5-bromo-3-methoxycarbonylpyrazine 1-oxide (wperoxyacetic acid) (906) 2-amino-3-bromo-5,6-dimethylpyrazine 1-oxide (peroxyacetic acid) (907) and 2,3-bis(pyridin-2 -yl)pyrazine 1,4-dioxide (hydrogen peroxide in sulfuric acid at room temperature) (754). 

Pass the reduced derivatized protein through Sephadex G-25 equilibrated with 100 mM sodium acetate buffer, pH 4.5, containing 100 mM NaCl to remove excess reagent, oxidized reagent and pyridine-2-thionine. 

Most commercial enone synthesis methods are not applicable to all desired enones. The acetylene condensation/hydration method can only make enones with even numbers of carbons, while formaldehyde condensation preferentially gives branched products at higher molecular weights. Other methods use expensive oxidation reagents and start with the allylic alcohols. Yet other methods use even more expensive reagents, " or electrochemical methods... 

The details of lignin structure are beyond the scope of this review. However, the polymer is held together by a wide variety of ether (C-O-C) and carbon-carbon bonds that are intrinsically strong and resistant to hydrolysis. Because of this stability, lignins can be isolated as the residue left when other wood components are dissolved in 72 wt % sulfuric acid. These polyphenols, however, are susceptible to oxidizing reagents and are readily removed from wood by bleaching. 

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