Darstellung und Umwandlung von 1-Hydroxyindolin-2-onen

The photolytical behaviour of 2-(4-tert-butyl-2-nitrophenyl)-2-methylpropanoic acid has been investigated. While its crystals are photostable due to unfavourable conformational parameters in the solid state, irradiation in methanol gives a 1-hydroxyindolin-2-one and a hydroxylamine in an unspecific reaction. Photolysis of the sodium carboxylate rapidly leads to decomposition products, indicating a change in reaction mechanism. The (-)-menthyl ester shows the typical photochemical behavior of o-tert-butylnitrobenzenes. The (-)-menthyl group as chiral auxiliary did not lead to any diastereomeric exess in the main photoproduct. 2-(4-tert-Butyl-2-nitrosophenyl)-2-methylpropanoic acid did not act as a classical nitroso spin trap for various radicals. With 2-cyano-2-propyl radicals, however, addition of two radicals is observed with formation of an N-oxide. Surprisingly, an analogous product is found even with the highly hindered 2-(3,5-di-tert-butyl-2-nitrosophenyl)-2-methylpropanoic acid. Although postulated as intermediate, a nitroxide, being the expected product of spin trapping, could not be isolated in either case.


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