Ketone radical reactions dimethyl carbonates

Lipid-Protein-Carbohydrate Interactions. Evidence for such complex interaction was recently reported by Huang et al (36) who observed that the addition of corn lipids to zein and corn carbohydrates enhanced the formation of alkylpyrazines, indicating that lipid-derived free radicals may accelerate the rate of Maillard reactions. Two of the alkylpyrazines, identified in such mixtures after heating for 30 minutes at 180°C, have 5-carbon alkyl substitution at the pyrazine ring and could only be explained by interaction of lipid or lipid decomposition products. These authors suggested that condensation of amino ketones, formed by protein-carbohydrate interaction, may yield 3,6-dihydropyrazine which would in turn react with pentanal, a lipid oxidation product, to form 2,5-dimethyl-3-pentylpyrazine. 

In the GiflV reaction of cyclohexane in the presence of P(OMe)3, ketone and a new product were formed instead of the expected alcohol. This new product was identified as cyclohexyl dimethyl phosphate l, 49 jf a carbon-centered cyclohexyl radical was an intermediate, one would expect the catalytic conversion of trimethyl phosphite into trimethyl phosphate in the presence of dioxygen. The latter reaction was indeed observed when genuine cyclohexyl radicals were photochemically generated under similar conditions to those employed in the Gif reaction l. So, once again this demonstrates that Gif-oxidation does not produce free alkyl radicals. 

Tetrafluoroallene reacts with two moles of bistrifluoromethyl nitroxide at ambient temperature. The initial adduct (134) reacts further with the radical to give a ketone (135a) and the bistrifiuoromethylamino-radical, which may attack the allene at the central carbon atom since the enamine (136) is isolated in substantial yield. Alternatively, the enamine (136) may arise by reaction of the allene with perfluoro-(2,4-dimethyl-3-oxa-2,4-diazapentane) (135b), because the N—O—N compound was shown to react in this way with the allene at room temperature. The yield of the ketone rose to 89%, accompanied by an equimolar proportion of the N—O—compound, when the allene was treated with a six-fold excess of the nitroxide, further justifying the proposed reaction scheme (Scheme 29). 

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