Pyridine-Hydrazone Ligands in Asymmetric Palladium-Catalyzed 1,4- and 1,6-Additions of Arylboronic Acids to Cyclic (Di)enones

Abstract

Catalysts generated by combinations of Pd(TFA)2 and enantiomerically pure pyridine-hydrazone ligands have been applied to the 1,4-addition of arylboronic acids to β-substituted cyclic enones, building all-carbon quaternary stereocenters in high yields and enantioselectivities (up to 93% ee). The developed methodology allows the efficient introduction of ortho-substituted aryl groups in β-position of cyclopentanone cores, giving scaffolds present in a broad range of biologically active natural products. These Pd(II)-complexes served also as catalysts in the 1,6-addition of arylboronic acids to cyclic dienones, affording complete regioselectivities, moderate yields and good enantioselectivities (up to 80% ee).