Chemistry Reference
In-Depth Information
Tab. 4.34.
Synthesis of cyclic ureas 1068 from diamines and carbon dioxide
a
[778].
Starting amine RR
O
NH
Temp.
Time
Yield of ureas
b
˚C
h
%
R
R
O
H
H
150
12
85
150
24
0
c
80
24
17
Me
H
80
12
60
Ph
H
80
24
40
HOCH
2
CH
2
-
H
150
24
95
HOCH(CH
2
)CH
2
-
H
150
24
54
Me
Me
150
24
75
a
General reaction conditions: diamine/Ph
3
SbO/P
4
S
10
20/1.0/2.0
mmol, benzene (20 mL), CO
2
at 4.9 MPa, time 12 h;
b
Isolated yield;
c
In the absence of the catalytic system.
¼
N
CO
2
R'
NN
R
H
R
R'
Ph
3
SbO / P
4
S
10
O
1067
1068
Typical procedure. Imidazolidinone 1068 [778]:
A mixture of ethylenediamine (1.2 g,
20 mmol), Ph
3
SbO (1.0 mmol), and P
4
S
10
(2.0 mmol) was autoclaved under a
pressure of CO
2
(4.9 MPa). Imidazolidinone was isolated by column chromatogra-
phy (silica gel; eluent: ethyl acetate/hexane, 1:1, v/v); yield 1.5 g (85%).
Monitoring the reaction of primary amines with CO
2
by
13
C NMR spectroscopy
revealed that the reaction course involves thiolation of the carbamic acid 1059 to
give an intermediate antimony carbamate species 1069, followed by aminolysis of
the carbamothioic acid thus formed.
H
H
RNH
2
CO
2
NH
3
R
N
H
NS
RNH
2
R
R
Ph
3
SbO/P
4
S
10
O
O
1059
1069
H
H
Ph
3
SbO
NN
R
R
O
(30-100 %)
R = allyl, alkyl, phenyl
The approach described above exploits the aminolysis of thiol carbamic acids
under mild conditions, thereby by-passing the di
culties encountered in the un-
