Enantioselective Synthesis of α-Allyl-α-aryldihydrocoumarins and 3-Isochromanones via Pd-Catalyzed Decarboxylative Asymmetric Allylic Alkylation.

An enantioselective Pd-catalyzed DAAA of α-aryl-β-oxo esters has been developed employing the (R,R)-ANDEN-phenyl Trost ligand to prepare a series of α-aryl-α-allyldihydrocoumarins and 3-isochromanones. A variety of aryl groups were successfully employed to afford the dihydrocoumarin and 3-isochromanone products in high yields up to 95% and ee's up to 96%. Under these conditions, substrates containing di- and mono-ortho-substituted aryl groups gave the highest levels of enantioselectivities. This work represents the first example of the enantioselective preparation of all-carbon quaternary α-allyl-α-aryl dihydrocoumarins and 3-isochromanones.