Treatment of the nitroxides Et₂NO⁻ M⁺(2a-c) (M = Na, Li, K) and (Et₂NO⁻)₂ Ba²⁺(2d) with pentafluoropyridine (3) at room temperature (1 d) gave in all cases the compounds Py-NEt₂(8), Py-ONEt₂(9), Py-NHEt (10) and Py-O⁻H₂NEt₂(11) (where Py = tetrafluoro-4-pyridyl) in the approximate ratio 1:30:30:35. The radical traps, 1,4-dinitrobenzene or galvinoxyl, retarded the reaction (5 d required for complete consumption of 3), but the same products were formed in a similar ratio and compounds 8–11were also formed by decomposition of the amine oxide Py-N+(Ō)Et₂(20) [synthesised by the route: 3 + Et₂NH → 8 (57%); 8+ (CF₃CO)₂O/H₂O₂→20 (81%) as the monohydrate]. It is proposed that the products8–11 arose mainly via an S_RNl mechanism involving single electron transfer (SET) from the nitroxide 2 to the substrate 3 leading to the radical anion (21) and hence the tetrafluoro-4-pyridyl radical (22) which reacted with 2 at nitrogen to afford the amine oxide 20. Major Meisenheimer rearrangement of 20 gave hydroxylamine 9, while minor rearrangement afforded the hydroxylamine Py-N(Et)OEt (23) which eliminated ethanal to yield the secondary amine 10. Competing deoxygenation of 20 gave the tertiary amine 8 and the salt 11 [synthesised by reaction of Py-OH (26) with Et₂NH] was formed via decomposition of 8 in light (or on heating) involving homolytic fission of the weak N-O bond. Treatment of 9with the acids AHF or CF₃SO₃H resulted in exothermic reaction and gave compounds 8 (27%, 11%), 10(16%, 18%) and 11 (13%, 25%) via competing protonation at oxygen and nitrogen.

The corresponding reactions of nitroxide 2a with the substrates C₆HF₅(4) and C₆F₅CF₃(5) afforded the salt 4-H-C₆F₄-O⁻ H₂NEt₂(12) (15%) and a mixture of the compounds 4-CF₃-C₆F₄-R [R = ONEt₂(13)(23%);R = NHEt (14) (2%);R = O⁻ H₂N+Et₂ (15) (12%)], respectively, while treatment of 2a with 2-chloro-3-nitropyridine (6) and 2-chloro-5-nitropyridine (7) gave the tertiary amines 2-N,N-diethylamino-3-nitropyridine (16) (35%) or 2-N,N-diethylamino-5-nitropyridine (18) (25%) together with N-(2-chloro-3-pyridyl)-N-(3-nitro-2-pyridyl)amine (17) (13%) or N-(2-chloro-5-pyridyl)-N-(5-nitro-2-pyridyl)amine (19)(27%) via presumed S_RNl pathways.