Nitroxides reactions with thiyl radicals

Under photo-stimulation, isoindolyloxyl radical (5) abstracts primary, secondary, or tertiary hydrogens from unactivated hydrocarbons including cyclohexane, isobutane, or n-butane (Scheme l).23 The nitroxide (5) traps the resultant carbon-centred radical (R ) and so afford the A -aI koxyisoindo les (6). Blank photolysis experiments with no added hydrocarbon have shown some unprecedented / -fragmentation of (5) to afford the nitrone (7). A number of C60 nitroxide derivatives have been synthesized and characterized by ESR spectroscopy which show features common to nitroxide radicals.24 Reaction of nitroxide and thionitroxide radicals with thiyl radicals have been observed, from which sulfinyl, sulfonyl, and sulfonyloxy radicals were generated.25 The diisopropyl nitroxide radical was generated in the reaction of lithium diisopropylamide with a-fluoroacetate esters.26... 

The reaction of arenethiols with a stable prototype nitroxide (2,2,6,6-tetram-ethylpiperidine-l-oxyl, TEMPO) has been the subject of a detailed study [31]. The spontaneous reaction of nitroxide with thiols leads to the formation of 2,2,6,6-tetramethyIpiperidine as well as the corresponding piperidinium arylsul-finates and arylsulfonates in 70-80% yields (Scheme 4). Four other minor products containing sulfur were identified and allowed for a rationalization of the reaction mechanism. The key steps are discussed in terms of nitroxide and thiyl radical combination to form an intermediate which decomposes homolytically to piperidinyl and sulfinyl radicals followed by known chemistry. The PhSH/RjNO ... 

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