Chemistry Reference
In-Depth Information
NHSO
2
CF
3
NHSO
2
CF
3
Toluene
-78
16
(10% ee, 10 mol %)
°
C
Heterogeneous
mixture
Ti(O
i
-Pr)
4
E
t
MeO
MeO
CHO
OH
+
Et
2
Zn
Toluene, -78
°
C
93% ee
Scheme 12.25.
12.2.8. Miscellaneous Cycloadditions
Belokon and others developed the enantioselective alkylation of achiral Ni(II) complex
of glycine-derived Schiff's base for the synthesis of
α
- amino acid. The benzylation was
catalyzed by 2 - hydroxy - 2
-binaphthyl (NOBIN) of 30% ee under the basic
conditions, and chiral phenylalanine of more than 95% ee was obtained after acid treat-
ment (Scheme 12.26 ) [38] .
′
- amino - 1,1
′
O
O
Bn
O
O
(
R
)-NOBIN
(30% ee, 10 mol %)
N
Ni N
aq. HCl
Bn
O
N
Ni N
+
BnBr
N
N
NaOH, CH
2
Cl
2
, rt
H
2
N
OH
O
O
>95% ee
OH
NH
2
(
R
)-NOBIN
Scheme 12.26.
Oestreich and Rendler reported a reagent-controlled Pd-catalyzed reaction of nor-
bornene with chiral hydrosilane
17
of 54% ee to give hydrosilylated product in 69% ee
(Scheme 12.27) [39]. This is an unusual example of chiral transfer from silicon to carbon
along with NLE.
12.3. ASYMMETRIC AUTOCATALYSIS
12.3.1. Background
In 1953, Frank proposed a reaction mechanism, without showing any chemical structure
for the molecules, in which a chiral product acts as a chiral catalyst for its own produc-
tion (asymmetric autocatalysis) and prohibits the formation of its antipode [40]. In such
