Chemistry Reference
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O
Ti cat
3
(1 mol %)
O
H
+
H
2
Et
Ph
Toluene, r.t., 30-48 h
Ph
CO
2
Et
3a
3b
3c
94.4% ee (91%)
9.8% ee (32%)
96.5% ee (>99%)
HO
HO
OH
OH
OH
OH
HO
HO
2
2
c
HO
OH
HO
OH
2b
Scheme 8D.4.
O
i
Pr
H
O
O
Ti(O
i
Pr)
4
HO
HO
Ti
O
O
O
i
Pr
H
Linker
Linker
n
3
2
OH
OH
Scheme 8D.5.
8D.3.2. Chiral Pd, Pt, and Ni catalysts
Mikami et al. reported square-planar dicationic late transition metal complexes
(
PP
* - M
2+
: M = Pd, Pt) bearing
C
2
-symmetric diphosphine ligands as highly effi cient
asymmetric Lewis acid catalysts instead of early transition metal Lewis acid catalysts. A
chiral cationic (
S
) - BINAPs - Pd complex
4
has been developed for the asymmetric car-
bonyl - ene reaction with 1,1 - disubstituted olefi ns (Scheme 8D.6 ) [26] . The combination
