Catalytic Enantioselective Vinylogous Allylic Alkylation of Coumarins.

An unprecedented, organocatalytic enantioselective vinylogous γ-allylic alkylation of 4-methylcoumarins has been developed. Using allylic carbonates as the allyl source, this reaction is catalyzed by Lewis basic dimeric Cinchona alkaloid (QD)2PHAL and proceeds exclusively in a γ- and branched-selective manner to produce densely functionalized coumarin derivatives generally in good yields with good to high enantioselectivities (up to 97:3 er).