4.25. Procedure for the aldol reaction of isatin with acetone
Amino oxazoline 9 (20 mol %) and acetone (4 eq) were mixed in
dry THF at 5–8 C and then stirred for 30 min. To this clear solution,
isatin (1 equiv) was added and stirred at the same temperature for
72 h. The solvent was then evaporated under reduced pressure after
which 20 mL of water was added to the crude mixture and extracted
with ethylacetate (3 20 mL). The combined organic layer was
dried over sodium sulfate and the solvent was evaporated on a ro-
tary evaporator. The crude material was purified by column chroma-
tography using 60–120 mesh silica gel and a mixture of ethylacetate
and petroleum ether as eluent to afford the aldol product.