Rhenium-Catalyzed Arylation-Acyl Cyclization between Enol Lactones and Organomagnesium Halides: Facile Synthesis of Indenones

A set of rhenium-catalyzed arylation-acyl cyclizations between (hetero)arylmagnesium halides and enol lactones through a cascade C(sp(2))-C(sp(2))/C(sp(2))-C(sp(2)) bond formation under mild reaction conditions has been developed. Indeed, a wide range of functional groups on both organomagnesium halides and enol lactones is well tolerated by the simple rhenium catalysis, thus furnishing polyfunctionalized indenones in one-pot fashion and with complete control of the regioselectivity. Moreover, this approach also provides a straightforward synthetic route to neolignan and (iso)pauciflorol F. Mechanistic studies demonstrated that the reaction involves a sequence of syn-carborhenation and intramolecular nucleophilic addition.