Chemistry Reference
In-Depth Information
R
2
O
O
67
(20 mol %), H
2
O
CH
2
Cl
2
,r.t.,24 h
R
1
NO
2
R
2
S
H
H
NO
2
+
H
N
R
1
CH
3
CH
3
Bn
H
H
O
NH
2
Up to 98% yield
Up to 50:1 syn/anti
Up to 99% ee
67
R
1
=aryl,alkyl
R
2
=aryl,alkyl
Scheme 8A.45.
O
O
O
O
Catalyst
+
H
Ph
H
Bn
O
CH
3
N
Ph
Ph
OT MS
Ph
Ph
OMe
HN
H
H
Bn
H
68
57
[6 9]
69
[81]
70
[82]
82% yield
>95% ee
78% yield
65% ee
52% yield
97% ee
52% yield
97% ee
Scheme 8A.46.
O
CH
3
O
N
R
71
(10 mo
l %)
Up to 99% yield
syn
/
trans
: up to 2/98
Up to 97% ee
O
•HCl
O
R
H
O
H
71
O
H
O
R
O
Up to 99% yield
cis
/
trans
: up to 89/11
Up to 99% ee
H
R=H,Ph,Me
72
(10 mol %)
N
H
2
S
H
F
3
CCO
2
72
Scheme 8A.47.
Hechavarria Fonseca and List achieved intramolecular conjugate addition of alde-
hydes to enones by employing MacMillan's imidazolidinone
71
[83] . The cysteine -
derived organocatalyst
72
[84] was also used in the intramolecular conjugate addition to
afford compounds containing three and two contiguous chiral centers in good yields and
with high diastereo - and enantioselectivities (Scheme 8A.47 ).
8A.3.2. Conjugate Addition of Ketones
A variety of chiral organocatalysts such as
Cinchona
alkaloid derivatives, chiral primary
and secondary amines, small peptides, and so on have been applied in asymmetric
