Chemistry Reference
In-Depth Information
Ph
Ph
O
O
Me
O
H
P
159
Me
O
O
Ph
Ph
Ph
Ph
O
TMSCl, NaI, CH
3
CN, reflux
Phosphite
159
O
O
HO
R
Me
P
O
P
NO
2
NO
2
HO
TMEDA, Et
2
Zn,
THF, -78°C
Me
CH
2
Cl
2
/H
2
O, r.t.
65-94%
O
NO
2
O
R
R
Ph
Ph
86-91%
ee = 81-95%
de = 84-96%
MeO
R =
,
Fe
,
MeO
,
,
,
OMe
Scheme 8A.102.
studies, they developed a useful organocatalyst cinchonidine
160
for this reaction and
obtained 75% ee (Scheme 8A.103) [186]. A bifunctional catalysis mechanism was
proposed.
H
N
OH
N
SH
O
O
Bu
t
160
+
S
Bu
t
Scheme 8A.103.
Deng et al. identifi ed that the dihydroquinidinepyrimidine catalyst (DHQD)
2
PYR
77
was effective for the asymmetric conjugate addition of (
S
) - nucleophiles to cyclic enones
(Scheme 8A.104) [187]. This reaction afforded the corresponding Michael adducts in
high yields and enantioselectivities when a wide variety of six- to nine-membered cyclic
enones and substituted cyclopentenones as well as cyclohexenone were used as the
acceptors. Because of the absence of hydrogen donor functionalities in
77
, this catalyst
was unable to promote the conjugate addition through a bifunctional catalysis mecha-
nism similar to that proposed for
160
.
