Cyclic ketones, autoxidation

According to Quinkert, photoexcited cyclic ketones may be transformed to open-chain unsaturated carboxylic acids in the presence of molecular oxygen. This reaction may compete efficiently with a-cleavage and secondary transformations thereof. Thus, both stereo iso meric 17-ketones (109) and (110) yield as much as 20% of the unsaturated acid (111) when irradiated in benzene under a stream of oxygen. This photolytic autoxidation has been used notably for partial syntheses of naturally occurring unsaturated 3,4-seco-acids from 3-oxo triterpenes (for references, see ref. 72). 

The autoxidation of cyclic ketones with dirhenium decacarbonyl under basic catalytic conditions produces dicarboxylic acids (68-73%) bicyclic ketones are converted into keto carboxylic acids and, when one ring is aromatic, quinones are obtained, e.g. 1-tetralone produces 2-hydroxy-1,4-naphthaquinone (93%), and H02C(CH2)4C0(CH2)3C02H (85%) is obtained from 1-decalone via a cyclic triketone [5]. 

Despite problems with acyclic ketones, the reaction is quite useful for cyclic ketones and the corresponding secondary alcohols, the dicarboxylic acid being prepared in good yield. The formation of adipic acid from cyclohexanone (shown above) is an important industrial procedure. Acid dichromate and permanganate are the most common oxidizing agents, although autoxidation (oxidation with... 

Wallace and Schriesheim dried the solvent by distillation under nitrogen over Linde I3X molecular sieve (calcined under N at 350° for 4 hrs.) and stored it in a dry box equipped with a moisture conductivity cell. They found it superior to DMF or tetramethylurea as solvent for base-catalyzed (KOH or NaOH) autoxidation of thiols and disulfides to sulfonic acids. It is superior also for base-catalyzed autoxidation of alkylthiophenes and toluene, and of 5-0,2 cyclic ketones to the corresponding dibasic acids."... 

It follows that any carbonyl compound which undergoes facile enolization is prone to spontaneous autoxidation. Thus, /Ijy-unsaturated ketones [6b, 30] and cyclic 1,3-diketones [31] readily autoxidize under neutral conditions as illustrated by the examples in Scheme 13 [30, 31]. Although enols may be involved in these reactions, direct C-H abstraction is also feasible [30]. 

Sodium hydroxide I chiral quaternary ammonium salts triethyl phosphite Cyclic a-hydroxyketones from ketones Asym. autoxidation under phase transfer catalysis... 

Unsaturated lipids produce qualitatively similar products when thermally oxidized or autoxidized at low temperatures. These include a series of aldehydes, ketones, acids, esters, alcohols, hydrocarbons, lactones, cyclic compounds, dimers and polymers. However, quantitative pattern of the decomposition products formed at high temperatures is different from that of autoxidation, varying widely depending on the nature of the substrate and parameters of heat treatment (Nawar, 1985 Pokorny, 1989). Unsaturated fatty acids are much more susceptible to oxidation than their saturated analogs. According to Frankel (1980), at 25 to 80 °C, relative proportions of isomeric hydroperoxides isolated from each substrate varies with the oxidation temperature, however, their qualitative pattern remains the same. At oxidation temperatures higher than 80°C, isolation and quantitation of hydroperoxide intermediates is difficult due to their extreme heat sensitivity. Furthermore, the primary decomposition products are unstable and rapidly undergo further oxidative decomposition. As the oxidative process continues, a variety of possible reaction mecha-... 

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