Reactions of Anodically Generated Methoxystilbene Cation Radicals: The Influence of Ortho-Substituted Vinyl and Formyl Groups

The present investigation represents
a continuation of studies on the effect of ortho′-substitution
on the reactivity of anodically generated methoxystilbene cation radicals.
Whereas previous studies have focused on the effect of ortho′-substituted
nucleophilic groups such as OH, NH2, CH2OH,
CH2NH2, and COOH, the present study extends
the investigation to ortho′-substituted vinyl and formyl groups.
The results show that when the ortho′-substituent is a vinyl
group, the products include a bisdihydronaphthalene derivative and
a doubly bridged, dibenzofused cyclononane from direct trapping of
a bis carbocation intermediate. In the presence of an additional 3-methoxy
substituent, the products are the tetracyclic chrysene derivatives.
When the ortho′-substituent is a nonnucleophilic formyl group,
the products include fused indanylnaphthalenes and indanylbenzopyran
aldehydes. When an additional 3-methoxy group is present, an unusual
fused benzofluorene-dibenzoannulene product is obtained. Mechanistic
rationalization for the formation of the various products is presented.
The results have contributed to a deeper understanding of how the
reactivity of the methoxystilbene cation radicals is affected by the
nature of the ortho′-substituents.