Synthetic approach to flavanones and flavones via ligand-free palladium(II)-catalyzed conjugate addition of arylboronic acids to chromones

The remarkable catalytic effects of Fe(OTf)(3) in the context of the Pd(II)-catalyzed conjugate addition of arylboronic acids to chromones were observed to yield a variety of flavanones under mild conditions. The addition of catalytic amounts of DDQ and KNO2 to the reactions exclusively yielded flavone analogs. The reaction scope for the transformation was fairly broad, affording good yields of a wide range of flavanones and flavones, which are privileged structures in many biologically active compounds.