Stereoselective cyclization of stilbene derived carbocations

Cyclodimerization of 2,6-dimethoxy-4-methylstilbene under acidic conditions affords the rotationally restricted 1,3-bis-(2,6-dimethoxy-4-methylphenyl)-2-phenyl-1,2,3,4-tetrahydronaphthalene. Nucleophilic addition of this stilbene to 1,4-benzoquinone and maleic anhydride, respectively, followed by an intramolecular cyclization yields dihydrobenzofuran derivatives and a trisubstituted butanolide, respectively. These stereoselective cyclizations involving stilbene derived carbocations apparently biomimic the cyclization of naturally occurring stilbenes during oxidative oligomerization.