Chemistry Reference
In-Depth Information
OH
H
133
(20 mol %)
N
EtO
2
C
CN
EtO
2
C
CN
SO
2
Ph
+
O
Toluene, -25
C
SO
2
Ph
89-96%, 93-97% ee
R
°
R
N
R = Ph, 4-Me-Ph, 4-MeO-Ph, 4-F-Ph,
4-Cl-Ph, 4-Br-Ph, 3-Cl-Ph,
2-naphthyl, 2-thienyl
133
Scheme 8A.74.
CF
3
NC
COO Et
COOEt
O
R
2
S
134
(10% mol %
)
Toluene, 4A MS
-60
R
1
R
1
+
R
2
O
CN
H
H
CF
3
°
C, 96 h
N
R
1
=aryl,R
2
=alkyl,aryl
R
1
=alkyl, R
2
=aryl
61-99%, 82-97% ee
134
Scheme 8A.75.
using
Cinchona
alkaloid catalyst
135
. These highly functionalized catalytic products
could be manipulated to give a wide range of useful intermediates, which were diffi cult
to obtain via other procedures (Scheme 8A.76).
Ph
3
Si
R
1
O
2
C
R
2
R
1
O
2
C
+
135
(10 mol %)
O
O
NC
*
OH
NC
H
CH
2
Cl
2
,-20
°
C
H
N
R
1
=Me,Et,Bn,t-Bu
R
2
H
N
R
2
= Me, n-Hex, allyl,-Pr,Et
(CH
2
)
3
OTBSi, t-Bu, Bn
72-95%, 39-56% ee
135
Scheme 8A.76.
8A.3.8. Conjugate Addition of Indoles
Austin and MacMillan [149] successfully employed chiral imidazolidinone catalyst
110
to perform highly enantioselective asymmetric conjugate addition of indoles to enals,
yielding the corresponding β-indolyl aldehydes in high yields and good enantioselectivi-
ties (Scheme 8A.77 ).
Chiral thiourea catalysts such as
136
and
137
were reported in asymmetric conjuga-
tion addition of indole to nitro-olefi n. Recently, Ricci et al. reported that chiral thiourea
