Ester-bond cleavage, oxidative

Both schemes accommodate the kinetics, the primary isotope effect and the induction factor, which indicates that Cr(IV) is the initial stage of reduction of the oxidant. RoCek s mechanism does not accord with the solvent isotope effect of 2.5 per proton, which has just the value to be expected for acid-catalysis, for the O-H bond cleavage should be subject to a primary isotope effect of about 7. The ester mechanism is not open to this criticim. 

Three of the alkaloids (55-57) were isolated from Corydalis incisa (63-65) and two (57, 58) from Hypecoum procumbens (66), where they coexist with the parent protoberberines. They are formed in plants by an oxidative C-6—N bond cleavage, possibly through an aldehyde intermediate 61. This assumption was supported by in vivo experiments in which ( )-tetrahydrocorysamine-8,/4-/2 (59) and (+ )-tetrahydrocoptisine-8,74-/2 (60) were fed to Corydalis incisa (67) to produce corydalic acid methyl ester-8-/ (55) along with corydamine-8-f (58) and corydalic acid methyl ester-8-/ (55) with corynoline-8-/ (62), a benzophenantridine alkaloid, respectively (Scheme 14). 

The typical metabolic reactions of pyrethroids are hydrolysis of an ester linkage and oxidation of an alkyl group or an aromatic ring in either acid or alcohol moiety, as shown in Fig. 6. The oxidative cleavage of the C=C bond of the prop-l-enyl... 

Furthermore, the mediator has been used for the bond cleavage of benzyl ethers, the oxidation of benzyl alcohol to benzaldehyde, the oxidation of toluene derivatives to benzoic acid esters, and the oxidation of aliphatic ethers [47]. 

Chemical Properties NG reacts chemically as a nitrate ester, saponifiable to glycerol by alka-lies (preferably with peroxide present), and hydrolyzed by nitric acid to glycerol. In general, side products tend (d be produced resulting from cleavage of the C—C bonds and oxidation of the alcohol functions... 

Under conditions simultaneously favorable for these equilibria and unfavorable for carbon-carbon bond cleavage, the specificity of the reaction is greatly increased. Oxidation of primary alcohol groups appears to proceed through the intermediate formation of an ester of nitric (or nitrous) acid. 

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