Octafluorotoluene

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Reaction of Metal Diethylnitroxides With ‎Pentafluoropyridine, Pentafluorobenzene, ‎Octafluorotoluene and 2-Chloro-3- Or 5-Nitropyridine

Journal Title, Volume, Page: 
Journal of Fluorine Chemistry Volume 76, Issue 1, Pages 67–78
Year of Publication: 
1996
Authors: 
Waheed J. Jondi
Chemistry Department, University of Manchester Institute of Science and Technology, Manchester M60 1QD, UK
Current Affiliation: 
Department of Chemistry, Faculty of Science, An-Najah National University, Nablus, Palestine
Adrian J. Adamson
Chemistry Department, University of Manchester Institute of Science and Technology, Manchester M60 1QD, UK
Anthony E. Tipping
Chemistry Department, University of Manchester Institute of Science and Technology, Manchester M60 1QD, UK
Preferred Abstract (Original): 

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-OH2NEt2(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 SRNl 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 SRNl pathways.

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