UNEXPECTED DEOXYGENATION OF 2,2,6,6-TETRAMETHYLPIPERIDINE-1-OXYL (TEMPO) BY THIYL RADICALS THROUGH THE FORMATION OF ARYLSULPHINYL RADICALS

2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO), upon reaction with thiophenols, undergoes deoxygenation leading mainly to the formation of tetramethylpiperidinium arylsulphinates and arylsulphonates. Other identified products of the reaction are aryldisulphides, 2,2,6,6-tetramethylpiperidine, S-aryl-arylthiosulphonates, N-arylsulphinyl- and N-arylsulphonyl-2,2,6,6-tetramethylpiperidine. The formation of the reaction products is discussed on the basis of the interaction of arylsulphinyl and arylsulphonyl radicals with TEMPO as well as on the basis of the evolution of the arylsulphinyl radical itself.