NITROXIDES (AMINYL OXIDES) - XLI. FORMATION AND DIMERIZATION OF β-SULFONYL SUBSTITUTED VINYL NITROXIDES. CC-VERSUS OC-DIMERIZATION

Article abstract of DOI:10.1016/S0040-4020(01)89108-0

Upon oxidation of hydroxylamines 1a-c only nitrones 2a-c could be isolated although the nitroxides 3a-c were detected by ESR.Oxidation of 1f yields compound 5, the CC-dimer of 4.Whereas oxidation of 1d affords only 7d which arises from 3d by CC-dimerization and elimination of propylsulfinic acid, from vinyl nitroxide 3e products 7e, 8 and 9 are formed by CC-dimerization and subsequent reaction steps, as well as 11 which is formed via the intermediate OC-dimer 10.The reaction steps leading to the different products are discussed.The reactivity of vinyl nitroxides can be attributed to their tendency to undergo bond formation at the β-C-atom.Thus, in principle they can form CC-bonded dimers or OC-bonded dimers.For N-tert-butyl substituted vinyl nitroxides CC-dimerization was found to be preferred reaction pathway at room temperature.It has been assumed that OC-dimers can be formed in a reversible reaction.However, if there is no possibility to form a more stable product in a subsequent reaction step, OC-dimerization should be only an unproductive reaction pathway.To verify this assumption we have now studied the dimerization of the corresponding hydroxylamines 1.