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O
O
Rh(acac)(C
2
H
4
)
2
(3 mol %)
44
(7.5 mol %)
ArB(OH)
2
, 3eq
Dioxane/H
2
O, 100°C
X
()
n
()
n
Ar
n
= 0,1,2
O
O
n
= 0,1,2; X = CH
2
or O
>98%
ee
P N
Ar = Ph, 2-FC
6
H
4
, 3-MeOC
6
H
4
,
3-MeC
6
H
4
, 4-MeC
6
H
4
,
44
O
O
4% Rh(acac)(eth)
2
10%
44
Ethanol, reflux, 2 h
BF
3
K
X
X
+
()
n
()
n
n
= 0,1,2; X = CH
2
or O
100% conv; up to 99%
ee
O
O
4% Rh(acac)(eth)
2
10%
44
+
ArBF
3
K
ethanol, reflux, 2 h
Ar
68-100% conv; 98-99%
ee
Ar = Ph, 4-MeC
6
H
4
, 3-ClC
6
H
4
,
3-MeOC
6
H
4
, thiophene
Scheme 8A.37.
O
O
Rh(acac)(C
2
H
4
)
2
(3 mol %)
(R)
-
45
(7.5 mol %)
(ArBO)
3
, dioxane/H
2
O, 100°C
O
O
P
N
N
N
CO
2
Bn
CO
2
Bn
(R)
-45
R
100% conv; up to 99%
ee
Ar = Ph,
o
-MeC
6
H
4
,
p
-MeC
6
H
4
,
m
-MeC
6
H
4
,
p
-MeOC
6
H
4
,
p-
ClC
6
H
4
,
p-
FC
6
H
4
,
m,p
-(MeO)
2
C
6
H
3
Scheme 8A.38.
ligands
8
and
46
, excellent yields and high enantiomeric excesses were obtained at room
temperature (Scheme 8A.39 ).
Wu and Chong [56] reported the asymmetric conjugate additions of
B
- 1 - alkynyldi-
isopropylboronates to enones catalyzed by binaphthols, which could afford alkyne prod-
ucts with high yields and enantiomeric excesses. A possible mechanism was also proposed
as shown in Scheme 8A.40 .
8A.2.5. Conjugate Addition of Organoaluminum Reagents
Examples of enantioselective addition of trialkylaluminum reagents have been described
for cyclic [57,58] and acyclic [59,60] enones, and nitro-olefi ns [61] . In 2005, Alexakis
et al. reported a new way to build chiral quaternary centers, using 2-substituted
