Multicomponent reactions - Zhu.pdf - Index of

Ph
H
N
O Me Ph
N
O
21
MeOH, –40°C, 0.10 M: (S) : (R) = 75 : 25
MeOH, –40°C, 2.0 M: (S) : (R) = 33 : 77
Ph
H
N
Scheme 1.10
O Me Ph
O
23
N
H
H
OBn
N
O
MeOH, 25°C, 0.40 M
(S) : (R) = 35 : 65
Ph
H
N
O Me Ph
1.4.2.2 Ferrocenylamines
At the beginning of the 1970s Ugi et al. [29] reported the use of (þ)-a-ferrocenylethylamine
25a in the condensation with iso-butyraldehyde, benzoic acid and tertbutylisocyanide
(Scheme 1.11). The Ugi adduct 26 could be obtained with different
diastereomeric excesses, varying solvent, concentration and temperature in analogy
[29] with the above described a-methylbenzylamine. Following this first study, different
a-ferrocenylalkylamines have been employed [30, 31] and improvements in
Fe
Chiral aux.
25a
25a
25b
25c
Menthyl =
Scheme 1.11
R H
25
NH 2
Amine
config.
(S)
(S)
(R)
(R)
R
Me
Me
i-Pr
Menthyl
N
H
O
22
MeOH, 25°C, 0.58 M
(S) : (R) = 40 : 60
AllO
O
PhCO 2H, tBu–NC
CHO
Temp.
– 60°C
0°C
–78°C
25°C
1.4 Asymmetric Intermolecular Ugi Reactions 9
H
N
O
O O
H
N
Me
N
OEt
H
O
N
O
24
CF3CH2OH, –30°C, 0.50 M
(S) : (R) = 95 : 5
Conc.
1.0
0.0375
0.05
1.0
Fe
Solvent
MeOH
MeOH
MeOH
CF3CH2OH R
Ph
OMe
N
Yield
[M] [%]
n.r.
90
97
46
*
H
N
O
O 26
(S) : (R)
(*)
38 : 62
79 : 21
99 : 1
82 : 18