Chemistry Reference
In-Depth Information
O
Et
*
O
H
3
C
t-
Bu
Et
2
Zn (1.1eq),
36
(1.2 mol %)
CuOTf (1.0 mol %), CH
2
Cl
2
, 0
P
OH
R
1
R
2
R
1
R
2
°
C
61-96%
ee
R
1
= Ph, 4-OMeC
6
H
4
, 4-ClC
6
H
4
,
i
Bu, Cy, n-hexyl, Me
R
2
= Ph, 4-OMeC
6
H
4
, 4-ClC
6
H
4
, 4-Me
2
NC
6
H
4
,
i
Pr,
4-CF
3
C
6
H
4
,1-naphthyl,
n
-pentyl,
t
-Bu, Me
36
Scheme 8A.26.
O
O
0.5% Cu(OTf)
2
,1% ligand
CH
2
Cl
2
1.2 Et
2
Zn
+
*
Et
O
O
Ph
Me
Ph
Ph
=
,
O
O
,
2-napht
CH
3
H
86% ee;
R =
N
O
49% ee
R =
O
O
P
R
Ligand =
O
O
R =
54% ee
1-napht
O
Ph
O
P
R
82% ee
R =
96% ee;
R =
Ligand =
O
O
O
O
Scheme 8A.27.
phosphoramidite complex
37
as chiral ligand with high enantioselectivity (Scheme
8A.28 ) [38] .
Br ä se and H ö fener [39] presented the fi rst copper - free asymmetric 1,4 - addition of
diethylzinc or diisopropylzinc to
- unsaturated aldehydes. This methodology supple-
mented the spectrum of synthetic methods for
α
,
β
β
- chiral aldehydes (Scheme 8A.29 ).
8A.2.3. Conjugate Addition of Organolithium Reagents
Organolithium reagents are highly reactive species that can be used in various organic
transformations, especiallly carbon-carbon formation. Thus, organolithium-based asym-
metric conjugate addition methodologies are of high interests. In this section, we focus
on the recent progress in enantioselective conjugate addition of organolithium reagents
with achiral - activated olefi n under the control of external chiral ligands or chiral
catalysts.
