Experiment and Theory of Bimetallic Pd-Catalyzed α‑Arylation and Annulation for Naphthalene Synthesis

We report the synthesis of bimetallic Pd­(I) and Pd­(II) complexes with bidentate 2-phosphinoimidazole ligands and their catalytic activity to generate substituted naphthalenes. This process involves the coupling of an aryl iodide and 2 equiv of a ketone via sequential ketone α-arylation and then annulation to generate disubstituted and tetrasubstituted naphthalenes in a regioselective manner. Excellent substrate scope for both aryl iodide and ketone partners is demonstrated, including that for heteroaryl iodides. Bimetallic Pd complexes are much more reactive than monometallic Pd catalysts in this transformation. Density functional theory calculations, isotope effect experiments, and substrate competition experiments were used to examine bimetallic mechanisms, reactivity, and selectivity.