Efficient unimolecular deprotonation of aniline radical cations.
[reaction: see text] Deprotonation of the radical cations of aromatic amines, such as anilines, generally occurs much more slowly than other fragmentation reactions. Here we report a stereoelectronic effect involving twisting of the anilino group out of the plane of the benzene ring that results in a significantly increased rate of reactivity toward deprotonation. Quantitative studies of the rate constants for deprotonation as a function of aniline radical cation pKa (Brønsted plots) demonstrate that the effect is not simply due to a change in the reaction thermodynamics. By combining this stereoelectronic effect with covalent attachment of carboxylate as a base, aniline radical cations that undergo unimolecular deprotonation with rate constants as high as 10(8) s(-1), even in unfavorable protic media, are described.
Dombrowski
Gary W
GW
Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, USA.
Dinnocenzo
Joseph P
JP
Zielinski
Paul A
PA
Farid
Samir
S
Wosinska
Zofia M
ZM
Gould
Ian R
IR