Photocyclisations of o-iodobenzyl-indanones and tetralones infer the intermediacy of triplet aryl cations

Abstract

Photocyclisations of aryl iodides to 2-indanones and 2-tetralones give different outcomes to analogous radical reactions implicating the intermediacy of triplet aryl cations. Additions to 2-indanones generally give dibenzoisochromenones by sequential cyclisation, CO extrusion and electrocyclisation. By contrast, 2-tetralones produce benzo[a]phenalenones by ortho-cyclisation.