Molybdenum-Quinone-Catalyzed Deoxygenative Coupling of Aromatic Carbonyl Compounds.

In the presence of triphenylphosphine as a mild reductant, the use of catalytic amounts of Mo(CO)6 and an ortho-quinone ligand enables the intermolecular reductive coupling of aromatic aldehydes and the intramolecular coupling of aromatic ketones to produce functionalized alkenes. Diaryl- and diheteroaryl alkenes are synthesized with high (E)-selectivity and a tolerance toward bromide, iodide, and steric hindrance. Intramolecular coupling of dicarbonyl compounds under similar conditions affords mono- and disubstituted phenanthrenes.