To gain access to prenylated hexahydroxanthenes, tandem cascade cyclization-electrophilic aromatic substitution reactions have been studied on substrates bearing allylic and propargylic substituents. Both BF 3·OEt2 and TMSOTf can be used to initiate this reaction sequence, resulting in different ratios of the C-2 and C-6 substitution products. Even though allylic transposition is observed in some cases, the results of a crossover experiment are consistent with an intramolecular reaction sequence. Taken together, these studies now allow preparation of either the C-2 or C-6 prenylated hexahydroxanthene products.
Bibliographical noteFunding Information:
Financial support from the ACS Division of Medicinal Chemistry (in the form of a predoctoral fellowship to J.J.T.), the University of Iowa Graduate College (in the form of a Presidential Fellowship to J.G.K.), the Roy J. Carver Charitable Trust , and the National Cancer Institute ( R41CA126020 via Terpenoid Therapeutics, Inc.) is gratefully acknowledged.
- Electrophilic aromatic substitution
- Tandem reactions