Reactions of Anodically Generated Methoxystilbene Cation Radicals: The Influence of Ortho-Substituted Vinyl and Formyl Groups
2019
Chong, Kam-Weng | Thomas, Noel F. | Low, Yun-Yee | Kam, Toh-Seok
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.
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