Substrate- and Reagent-Controlled Dimerization of Vinyl <i>para</i>-Quinone Methides

Substrate and reagent-controlled dimerization of vinyl <i>para</i>-quinone methides (VPQMs) is reported. When subjected to Brønsted acidic conditions, VPQM dimerization occurs via a formal 1,8-addition to provide griffipavixanthone (GPX)-type congeners. Under optimized Lewis acidic conditions, a change in regioselectivity affords limonene-containing dimers by a 1,6-addition/cyclization process. This divergent reactivity has been explored on several substrates of differing complexity, providing access to analogues of the natural product griffipavixanthone (GPX) as well as a range of novel, substituted limonene dimers.