Chiral Silver Alkoxide Catalyzed Asymmetric Aldol Reaction Of Alkenyl Esters With Isatins

A catalytic enantioselective aldol reaction of alkenyl esters with isatins was achieved using a DM-BINAP center dot AgOTf complex as the chiral precatalyst and N,N-diisopropylethylamine as the base precatalyst in the presence of methanol or 2,2,2-trifluoroethanol. Optically active 3alkylated 3-hydroxy-2-oxindoles having up to 98% ee were diastereoselectively obtained in moderate to high yields not only from cyclic alkenyl esters but also from acyclic ones through the in situ generated chiral silver enolates.