Chemistry Reference
In-Depth Information
PG
2
HN
PG
1
PG
2
Tandem
aza-ene-type reaction
N
HN
G
1
P
+
2
N
*
RH
G
PG
2
R
H
*
*
1st aza-ene
Cyclization
PG
2
PG
1
PG
2
PG
1
PG
2
NH
N
2nd aza-ene
NH
HN
N
G H
≠
R
G
*
G H, G = H
R
H
*
*
≠
Scheme 8D.39.
O
O
H
BINOL-Ti
1
(10 mol %)
AgClO
4
(20 mol %)
MS 4A
O
H
H
+
O
O
O
CH
2
Cl
2
, 0°C, 24 h
trans
cis
80 (84% ee) : 20 (74% ee)
50% yield
Scheme 8D.40.
O
O
OO
OH
OH
EtO
EtO
box-Cu
18b
(20 mol %)
OEt
+
MS 4A
CH
2
Cl
2
, r.t., 2 h
trans cis
>50 (91% ee) : 1
81% yield
Scheme 8D.41.
The Cr complex-catalyzed ene reaction leads prenylated 1,3-dialdehydes to
bicyclo[3.2.1]octanes products bearing quaternary carbon centers as single diastereo-
mers in high enantioselectivities (Scheme 8D.42 ).
8D.6 ENE - TYPE CYCLIZATION
8D.6.1. Chiral Rh Catalysts
The fi rst catalytic asymmetric cyclization of 1,6-enynes using cationic chiral Rh(I) com-
plexes prepared
in situ
by a combination of [Rh(diphosphine)Cl]
2
and 1.0 equiv AgSbF
6
is reported by Zhang et al. (Scheme 8D.43) [73]. Reactions proceed smoothly at room
