Chemistry Reference
In-Depth Information
D-Glucose
O
O
OEt
HO
HO
AcO
AcO
c)
AcO
d)
AcO
a), b
)
O
O
OH
AcO
72%
AcO
81%
AcO
HO
79%
AcO
OH
OAc
Br
81
82
80
16
e), f)
85%
O
OEt
O
OEt
g)
TrO
TrO
70%
O
HO
PPh
2
84
83
(a) Ac
2
O, NaOAc. (b) HBr, HOAc. (c) Zn, CuSO
4
, HOAc. (d) BF
3
* Et
2
O, CH
2
Cl
2
. (e) MeOH, H
2
O, Et
3
N. (f) TrCl,
pyridine. (g) Ph
2
PCl, Et
3
N, THF.
Scheme 12.14
Synthesis of a
gluco
-configured olefin-phosphinite ligand.
O
OEt
TrO
O
PPh
2
84
O
O
1.5 mol%[RhCl(CH
2
=CH
2
)
2
]
2
, 3.3 mol% ligand*
+
Ph-B(OH)
2
KOH, dioxane, H
2
O
*
n
n
Ph
n=1, 2
n = 2
80% > 99%ee (
R
)
n = 1
82% 99%ee (
R
)
Scheme 12.15
Rhodium-catalyzed addition of phenylboronic acid to enones.
12.5
Conclusions
The use of carbohydrate derivatives as chiral ligands has had a modest impact on
copper-catalyzed conjugated additions of organometallic reagents to
-
unsaturated carbonyl compounds compared to the extensive use of these ligands
in other catalytic asymmetric reactions. Furthermore, the a priori advantageous
modular nature of carbohydrate-derived ligands have not afforded improved
results in the asymmetric conjugate addition with regard to other kinds of ligands
that have led to very high degrees of enantioselectivity.
α
,
β
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