50616-99-4Relevant academic research and scientific papers
Distinguishing between Polar and Electron-Transfer Mechanisms for Reactions of Anions with Alkyl Halides
Bordwell, F. G.,Wilson, Craig A.
, p. 5470 - 5474 (2007/10/02)
9-Substituted fluorenide carbanions in the series 9-MeFl-, 9-MeO-Fl-, and 9-Me2N-Fl-, which have nearly the same basicities but become progressively easier to oxidize, were selected as a test trio to probe for electron-transfer (eT-) components or radical-pair intermediates in reactions with alkyl halides.The trio members were shown to undergo eT- at progressively faster rates (>102 rate span) with two different types of single-electron acceptors, as expected- On the other hand, with PhCH2Cl, i-BuBr, or i-BuI, SN2 products were formed in a rate order that was the reverse of that established as characteristic of eT-.Reactions of the more sterically hindered 9-i-Pr2N-Fl- ion with PhCH2Cl or i-BuI to give SN2 products were over 1400 times slower than those with 9-MeFl-, whereas the eT- rate with c-C6H10(NO2)Ts was eight times faster.On the other hand, reactions of the test trio with F3CCH2I, which is known to react slowly in SN2 reactions, gave the reactivity order characteristic of eT-, and radical-type products were formed.For this reaction, a plot of log kobsd vs.Eox(A-) for seven 9-G-Fl- ions, wherein the bulk and radical-stabilizing ability of G was varied, was linear.This result shows that Eox(A-) is a good measure of eT- ability and that eT- rates are insensitive to steric effects in either the donor or acceptor that cause larger rate retardations in polar SN2 reactions.
Carbanions: Electron Transfer vs. Proton Capture. 8. Use of Sterically Protected Aromatic Nitro Compounds as Base-Resistant, One-Electron Oxidants
Guthrie, Robert D.,Hartmann, Christa,Neill, Richard,Nutter, Dale E.
, p. 736 - 740 (2007/10/02)
The behavior of two sterically protected nitroarenes, 2,4,6-tri-tert-butylnitrobenzene and 1,1,4,4,5,5,8,8-octamethyl-1,2,3,4,5,6,7,8-octahydro-9-nitroanthracene, was studied in the presence of strong bases.These compounds are resistant to the oxygen-base-promoted reactions observed with nitrobenzene, but they retain the capacity to oxidize carbon bases such as 9-methoxyfluorenide and triphenylmethide ions.Alkyllithium compounds are converted to alkyl radicals but phenyllithium does not react.Unexpectedly, the radical anions formed when these nitro compounds serve as oxidants undergo slow denitration to the corresponding aryl radicals.
