Tandem Hock and Friedel-Crafts reactions allowing an expedient synthesis of a cyclolignan-type scaffold

Abstract

The Hock cleavage is an acid-catalyzed oxydative reaction involving allylic or benzylic hydroperoxides. Since it generates an electrophilic oxocarbenium species, it could be used in tandem processes in the presence of nucleophiles. Here, starting from benzyl(prenyl)malonate substrates, the prenyl moiety was first photooxygenated. The resulting hydroperoxide was directly engaged in a Hock cleavage by adding a Lewis acid in presence of an aromatic nucleophile to promote tandem Friedel-Crafts reactions, also involving the benzyl moiety of the substrate. This tandem sequence led in one pot to 1-aryltetraline products reminiscent of the cyclolignan natural product skeleton.