Acyclic or Long-Bond Intermediate in the
Electron-Transfer-Catalyzed Dimerization of 4-Methoxystyrene
Lauren L. O'Nei
Olaf Wiest
10.1021/jo061745b.s001
https://acs.figshare.com/articles/journal_contribution/Acyclic_or_Long_Bond_Intermediate_in_the_Electron_Transfer_Catalyzed_Dimerization_of_4_Methoxystyrene/3048790
The electron-transfer-catalyzed dimerization of 4-methoxystyrene has long been a prototypical reaction
for the study of radical cation reactivity. The different possible pathways were explored at the B3LYP/6-31G* level of theory. Both [2 + 2] and [4 + 2] cycloadditions proceed via a stepwise pathway, diverging
at an acyclic intermediate and interconnected by a vinylcyclobutane-type rearrangement. The experimentally
observed stereoselectivity of the cycloaddition was traced to relatively high barriers for isomerization,
while the previously described “long-bond” intermediate could not be located at the higher level of theory.
CPCM calculations show that the highly exothermic [4 + 2] pathway becomes kinetically more favorable
in condensed phase. Time-dependent density functional theory calculations indicate that the different
possible intermediates have very similar absorption spectra, making the unambiguous assignment of the
experimentally observed transient absorption of 500 nm to a given species difficult.
2006-11-10 00:00:00
cycloaddition
theory calculations
pathway
CPCM calculations show
B 3LYP level
absorption spectra
cation reactivity
500 nm