attractive unit with 70% ee
(syn:anti¼84:16). The aldol reaction of a-branched aliphatic aldehydes
7 as different aldol donors with isatins 5 using catalyst 1a
also gave the corresponding aldol products 8 in excellent enantioselectivities
(up to 94% ee), showing that catalyst 1 was applicable
for asymmetric aldol reactions of cycloalkanones, hydroxy
acetones, and a-branched aliphatic aldehydes as aldol donors and
aromatic aldehydes, isatins as aldol acceptors. Surprisingly, stereochemical
course of all reactions reported here was different
from that in the reaction of aromatic aldehydes with cycloalkanones,
indicating that our catalyst having a 2,6-difluorophenyl
moiety has unique properties (Fig. 1).