Pd(0)-Catalyzed Intermolecular Dearomatizing [3 + 2] Spiroannulation of Phenol-Based Biaryls and Allenes

Readily available phenol-derived biaryls reacted with allenes under palladium catalysis to provide a variety of highly valuable spiro[cyclohexane-1,1′-indene]-2,5-dien-4-ones. This new catalytic process, involving a key step of regioselective allylative dearomatization of phenol, proceeded efficiently through a [3 + 2] spiroannulation pathway by overcoming undesired β-hydride elimination. Preliminary asymmetric studies showed that high enantioselectivity could be realized by using a commercially available PHOX ligand. Moreover, the potential application of this method was exemplified by several further transformations.