A catalytic enantioselective aldol reaction of alkenyl esters with isatins was achieved
using an (S)-BINOL-derived chiral tin dibromide possessing a 4-tert-butylphenyl group at 3- and 3′-positions as the chiral pre-catalyst in the presence
of sodium methoxide and methanol. Optically active 3-alkylated 3-hydroxy-2-oxindoles
having up to 98% ee were diastereoselectively obtained in high yields not only from
cyclic alkenyl esters but also from acyclic ones under the influence of the in situ
generated chiral tin bromide methoxide.
Key words
aldol reaction - alkenyl ester - asymmetric catalysis - isatin - tin