Oxidative splitting

Another method to achieve selectivity in oxidative splitting of C C bonds to carbonyl groups is controlled epoxidation followed by periodate cleavage (J.P. Nagarkatti, 1973). 

Conversion of Cyclic to Acyclic Structures. Upon oxidation, the aromatic rings of lignin may be converted direcdy to acycHc stmctures, eg, muconic acid derivatives, or indirectly by oxidative splitting of o-quinoid rings. Further oxidation creates carboxyUc acid fragments attached to the lignin network. 

Oxidizing splitting of olefinic side chains forms dione 22 from benzal 21 (62CPB366) and aldehyde 10a from quaternized and Hofmann-degraded... 

Benzal acetones, in general, are readily oxidized by alkaline peroxide solution via epoxides (see XXI, XXII in Figure 14) which might even be isolated in some cases when mild conditions are used. Under more drastic conditions, however, the oxidation proceeds to the corresponding benzoic acids. Since active oxygen compounds (peroxides) are formed when 6,6 -bicreosol is oxidized, the proposed benzal acetone intermediate (XVII) seems to be oxidatively split into the corresponding salicylic acid (V) and acetone. 

Ito T, Shinohara H, Hatta H, Nishimoto S-l (1999) Radiation-induced and photosensitized splitting of C5-C5 -linked dihydrothymine dimers product and laser flash photolysis studies on the oxidative splitting mechanism. J Phys Chem A 103 8413-8420 ItoT, Shinohara H, Hatta H, Fujita S-l, Nishimoto S-l (2000) Radiation-induced and photosensitized splitting of C5-C5 -linked dihydrothymine dimers. 2. Conformational effects on the reductive splitting mechanism. J Phys Chem A 104 2886-2893 ItoT, Shinohara H, Hatta H, Nishimoto S-l (2002) Stereoisomeric C5-C5 -linked dehydrothymine dimers produced by radiolytic one-electron reduction of thymine derivatives in anoxic solution structural characteristics in reference to cyclobutane photodimers. J Org Chem 64 5100-5108 Jagannadham V, Steenken S (1984) One-electron reduction of nitrobenzenes by a-hydroxyalkyl radicals via addition/elimination. An example of an organic inner-sphere electron-transfer reaction. J Am Chem Soc 106 6542-6551... 

In anodic elimination reactions two substituents X, e.g., hydrogen or C02, are oxidatively split off from the substrate to yield double or triple bonds (Eq. (136) )... 

Tab. 4.5.2. Stereoselectivity of the oxidative splitting of pyrimidine cyclobutane dimers. ...

Simons process — Electrochemical polyfluorination reactions of organic compounds are the only efficient way to industrial production of perfluorinated compounds. The reaction proceeds in the solution of KF in liquid HF (b.p. 19.5 °C), where the starting substances as alcohols, amines, ethers, esters, aliphatic hydrocarbons and halo-hydrocarbons, aromatic and heterocyclic compounds, sulfo- or carboxylic acids are dissolved. During anodic oxidation, splitting of the C-H bonds and saturation of the C=C bonds occur and fluorine atoms are introduced. 

Plants. Degradation principally involves ester hydrolysis, O-demethylation, and oxidative splitting of the double bond... 

The synthesis of isolongistrobine also started with the imidazole ester 126, which in three steps was converted to the amino alcohol 129. Acylation with 4-pentenoyl chloride gave the amide alcohol 133. Oxidation of 133 with chromium trioxide in aqueous pyridine yielded the 4-pentene carboxamide 134. Oxidative splitting of the vinyl group of 134 with sodium periodate... 

Peroxidases Used as an enzymatic rinse process after reactive dyeing, oxidative splitting of hydrolysed reactive dyes on the fibre and in the liquor, providing better wet fastness, decolourised waste water and potentially toxic decomposition compounds (aromatic nitro-compounds)... 

Since both oxidative splitting of the double bond and aldol condensation represent reliable and general reactions, their sequence serves as an efficient route for the transformation of readily available cyclohexene systems e.g. formed via the Diels-Alder reaction or Robinson annulation) into functionalized cyclopentene derivatives. This standard operational mode is extensively used in total syntheses. One of the numerous examples, the synthesis of helminthosporal 463, the sesquiterpenoid toxin of fungi, is shown in Scheme 2.150. In the initial phases of the synthesis, commercially available (—)-carvomenthone 464 was transformed into 465 via Michael reaction with methyl vinyl ketone to give 466 and subsequent intramolecular aldol condensation. 

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