Chemistry Reference
In-Depth Information
L-3
or
L-4
Sc(DS)
3
(10 mol %) or
Sc[O
3
S(CH
2
)
10
CH
3
]
3
(1-10 mol %)
additive
OSiMe
3
O
R
1
aq. HCHO
+
R
3
*
R
3
HO
H
2
O, 0.5 M
5°C-rt, 20-110 h
R
2
R
1
R
2
(5.0 equiv)
O
O
O
O
O
HO
HO
CH
3
HO
HO
Ph
HO
Ph
Cl
81% yield, 91% ee
83% yield, 94% ee
91% yield, 91% ee
92% yield, 90% ee
83% yield, 90% ee
O
OH
O
OH
O
O
O
CH
3
S
t
Bu
HO
HO
S
t
Bu
HO
90% yield, 92% ee
84% yield, 91% ee
82% yield, 96% ee
73% yield, 91% ee
65% yield, 90% ee
O
-
O
-
N
+
N
+
OO
NN
HN
NH
t
Bu
t
Bu
OH
HO
L
-
3
L
-
4
Scheme 1.13.
aq. HCHO (5.0 equiv)
Sc(DS)
3
(10 mol %)
L-3
(12 mol %)
H
2
O, 1.0 M, 20 h
then centrifugation
3000 rpm, 20 min
Me
3
SiO
1
PI-Pd
(10 mol %)
H
2
(1 atm)
HO
BTF, 80
∞
C, 8 h
3
56%, 91% ee
Scheme 1.14.
1.2.1.5. Silica Gel-Supported Scandium with Ionic Liquid (Silica-Sc-IL)
A novel
heterogeneous scandium catalyst system, Silica-Sc-IL, has been developed (Scheme
1.15 ) [21] .
The catalyst
4
coated with an IL, [DBIm]SbF
6
, works effi ciently in Mukaiyama aldol
reaction in water (Scheme 1.16). The reaction proceeds much faster in water than in
organic solvents, without solvent or in the absence of IL.
These experiments clearly suggest that Silica-Sc-IL and IL forms hydrophobic reac-
tion environments in water (Scheme 1.17). It should be noted that water-labile reagents
