Yh. Wang et al., RADICAL-ION PROBES - 9 - THE CHEMISTRY OF RADICAL CATIONS DERIVED FROM 9-CYCLOPROPYLANTHRACENE AND 9-BROMO-10-CYCLOPROPYLANTHRACENE, Journal of organic chemistry, 63(3), 1998, pp. 628-635
Reactions of radical cations generated from 9-cyclopropylanthracene (1
) and 9-bromo-10-cyclopropylanthracene (2) in the presence of methanol
have been investigated electrochemically. The major products arising
from oxidation of both substrates are attributable to CH3OH attack at
the aromatic ring (occurring at the radical cation stage for 2 and the
dication stage for 1) rather than CH3OH-induced cyclopropane ring ope
ning, which is estimated to be exothermic by 20 kcal/mol. Although rin
g-opened products are detected in some instances, these are found to a
rise from subsequent reaction of the primary oxidation products. These
observations are consistent with a proposed product-like transition s
tate for the nucleophile-induced ring opening of cyclopropylarene radi
cal cations in which the positive charge is localized on the cycloprop
yl group and nucleophile, and thus unable to derive stabilization from
the aromatic ring.