Synthesis of 1,2′-Spirobi[indene]-1,3-diones by Pd(II)-Catalyzed C-H Activation and Alkynes Annulation Reaction

An intermolecular annulation reaction of 2-aryl-1,3-indandions with alkynes was reported using Pd(OAc)2 to access spirobi[indene]-1,3-diones. Under palladium catalysis, the substrates form a homocoupling dimer intermediate through a catalytic dehydrogenative cross-coupling process. The palladium(II) species could come from dimer or 2-aryl-1,3-indandion. Notably, this pathway is not typically observed in enol-directed formal sp3 C-H functionalization/oxidative annulation palladium chemistry. This transformation provides a route to access a class of functionalized spiro carbocyclic indenes. image