Synthesis of N-functionalized carbodiimides, hydantoins, 1,3-diazetidines, and imidazolidine derivatives from N-vinylic phosphazenes derived from β-amino acids

Article abstract of DOI:10.3987/COM-01-9264

Synthesis of N-vinylic carbodiimides through Aza-Wittig reaction of N-vinylic phosphazenes with isocyanates is reported. These heterocumulenes are used for the preparation of unsymmetrical ureas and nitrogen heterocycles such as hydantoins, 1,3-diazetidines, imidazolidinones, and bis-imidazolidinone azines.

Full text of DOI:10.3987/COM-01-9264

HETEROCYCLES, Vol. 55, No. 9, pp. 1641 - 1652, Received, 5th June, 2001
SYNTHESIS
OF
N-FUNCTIONALIZED
AND
CARBODIIMIDES,
IMIDAZOLIDINE
HYDANTOINS,
1,3-DIAZETIDINES,
DERIVATIVES FROM N-VINYLIC PHOSPHAZENES DERIVED
FROM ß-AMINO ACIDS
a*
a
Francisco Palacios, Marta Legido, Itziar Pérez de Heredia, José María
a
b
Ezpeleta, and Gloria Rubiales
a
a
Departamento de Química Orgánica, Facultad de Farmacia, Universidad del País Vasco,
Apartado 450, 01080 Vitoria, Spain
*
E-mail: qoppagaf@vf.ehu.es
b
Departamento de Física Aplicada. Facultad de Farmacia. Universidad del País Vasco,
Apartado 450, 01080 Vitoria, Spain
Abstract- Synthesis of N-vinylic carbodiimides through Aza-Wittig reaction of N-
vinylic phosphazenes with isocyanates is reported. These heterocumulenes are used
for the preparation of unsymmetrical ureas and nitrogen heterocycles such as
hydantoins, 1,3-diazetidines, imidazolidinones, and bis-imidazolidinone azines.
1
The utility of N-vinylic phosphazenes has been demonstrated as key intermediates in the preparation of
2-4
5
heterocycles
context, we have used the Aza-Wittig reaction of N-vinylic phosphazenes with carbonyl compounds leading
2e 2a,d
and for the construction of the framework of pharmacologically active alkaloids. In this
to a very efficient method for the preparation of 2-azadienes derived from α- and β-amino acids.
Following on from our studies of the reactivity and synthetic utility of phosphazenes, here we wish to
explore the reactivity of N-vinylic phosphazenes (1) derived from β-amino acids or dehydroaspartic esters,
6
towards isocyanates to obtain N-functionalized carbodiimides and unsymmetrical ureas and to explore
their usefulness in the synthesis of heterocyclic compounds such as 1,3-diazetidines and C-5 unsaturated 2-
iminoimidazolones. The presence of an alkoxycarbonyl group as substituent on the exocyclic double bond
of these heterocycles could allow the synthesis of cyclic or acyclic derivatives of these compounds through
well known transformations of the alkoxycarbonyl group.
It is well known that the reaction of carbodiimides with an appropriate nucleophile such as H O and NH or
2
3
7
their derivatives leads to ureas or guanidines, respectively. Unsymmetrically substituted urea is a frequent
8a
structural feature of many biologically active compounds such as enzyme inhibitors and peptide
8b
analogues. Recently, compounds containing this functional group have been tested showing many
8c
other biological activities.
Moreover, unsymmetrically substituted ureas have been used as key

9a,b
intermediates in the synthesis of acyclic
9c,d
and heterocyclic compounds
and several methods for the
9e-g
preparation of unsymmetrical ureas in solution or solid phase have been published.
On the other hand,
guanidines with an ester group on the α position can undergo cyclization to give 2-aminoimidazolone or 2-
10
iminoimidazolone, which are a structural feature of several marine products such as hymenialdisine
11a-c
(2),
11d
aplysinopsine (3),
11e
and dispacamide (4) alkaloids (Figure 1)
12
isolated from marine
sponges. These metabolites exhibit an interesting pharmacological activity and have been the subject of
13
several syntheses. The common characteristic of this group of natural products is the presence of a ring
of C-5 unsaturated 2-iminoimidazolone connected through an exocyclic double bond to other heterocyclic
and acyclic systems.
NH
NH
HN
HN
HN
NH
Me
NH
Me
N
O
O
N
O
Br
Br
N
H
N
H
NH
NH
N
H
O
O
4: Dispacamide
2: Hymenialdisine
3: Aplysinopsine
Figure 1
The Aza-Wittig reaction of phosphazene (1a) with isocyanates in CHCl afforded the α, β-unsaturated
3
carbodiimides (5a-c) derived from β-amino esters (Scheme 1) in high yields (Table 1, Entries 1-3). Vinylic
heterocumulenes (5a-c) were isolated after column chromatography as a single isomer that was assigned as
E according to configuration of N-vinylic phosphazene (1a). However, small amounts of ureas (6a) and
(6b) were obtained (~10%) during purification of compounds (5a) and (5b). Complete transformation of
these carbodiimides (5a,b) into unsymmetrically substituted ureas (6a,b) (Scheme 1) was achieved by
stirring the former in CH Cl /H O (Table 1, Entries 4,5).
2
2
2
When phosphazenes (1b,c) derived from dehydroaspartic esters14 were used, carbodiimides (5d-f) could
1
be observed by H-NMR. But all attempts to purify the heterocumulenes (5d-f) by column
chromatography were unsuccessful, as they were readily converted into hydantoin derivatives (7a-c)
(Scheme 1) in high yields (Table 1, Entries 6-8). Compounds (7) were characterized on the basis of their
NMR spectroscopic data and MS spectrometry and were consistent with hydantoin structures. Formation of
hydantoins (7) can be explained by addition of water to heterocumulenes (5d-f) during the column
chromatography purification process to give the intermediate ureas (6) and subsequent cyclocondensation.
Consequently, carbodiimides (5d-f) were not isolated and crude reaction mixtures were satisfactorily used
without purification for the following purposes. These carbodiimides were obtained as a single isomer that
was assigned as Z form according to the configuration of phosphazenes (1b,c) and of the products
obtained by subsequent reactions of N-vinylic carbodiimides and nucleophiles.

4
O
R
4
N
R
4
PPh R
2
R -N=C=O
N
H
NH
H O , CH Cl
2
N
C
2
2
N
2
R
Me
1
2
1
2
R
R
( R = Me, R = H,
3
C O Me
2
1
3
R
R
R = CO Me)
2
3
R
1
6a,b
5
1
2
3
1a R= Ph, R = Me, R = H, R = CO Me
2
1
2
3
1b R= Ph, R = R = CO Me, R =H
2
1
2
3
1c R= Me, R = R = CO Me, R =H
2
column chromatography
1
2
3
(R =R = CO Me, R = H)
2
O
O
4
4
R
R
N
NH
N
H
NH
- MeOH
C O Me
2
C O Me
2
MeO C
2
O
6
7a-c
Scheme 1
Table 1. Carbodiimides (5), Ureas (6), Hydantoins (7) and 1,3-Diazetidines (8)
1
3
4
o
m p [ C]
2
a
Entry
Compd
R
R
R
R
Yield (%)
CO Me
2
1
2
5a
5b
5c
6a
6b
7a
7b
7c
8a
8b
8c
Me
Me
Me
-
H
H
H
-
Et
Pr
Ph
Et
78
67
80
74
65
48
60
40
81
S79
73
oil
oil
oil
oil
oil
CO Me
2
CO Me
2
3
4
-
-
-
-
-
5
-
-
Pr
Et
6
-
-
156-158
153-155
235-237
93-95
7
-
-
Pr
Ph
Et
8
-
-
CO Et
2
9
H
H
H
H
CO Me
2
10
11
Me
Me
Et
oil
CO Me
2
Ph
145-147
a
After recrystallization from CH Cl -hexane.
2
2
All attempts to obtain carbodiimides using phosphazene (1d) (Scheme 2) were unsuccessful when
Phenyl isocyanate was used. However, when ethyl isocyanate was used, 1,3-diazetidine-2,4-diimine (8a)

1
(R =R =H, R =CO Et, R =Et) was obtained (Scheme 2, Table 1, Entry 9). Formation of this four
2
3
4
2
15a,16
membered hetetocycle could be explained by "in situ" dimerization of carbodiimide (5g).
First
indications of this 1,3 diazetidine structure were obtained by MS spectrometry where compound (8a)
13
+
1
showed the molecular peak at m/z = 336 (M ). H and C NMR spectra showed only two different signal
for ethyl groups corresponding to CO Et and Et N and one signal for the two vinylic CH respectively,
2
2
which suggest a symmetrical structure. In order to test if functionalized carbodiimides (5) could be
precursors of 1,3-diazetidines (8), the dimerization of some isolated carbodiimides (5) was explored. When
4
4
N-vinylic carbodiimides (5a) (R =Et) and (5c) (R =Ph) were refluxed in toluene 1,3-diazetidines (8b) and
(8c) were obtained (Scheme 2, Table 1, Entries 10 and 11). In those cases, MS spectrometry of the 1,3-
+
diazetidines (8b,c) showed a peak at M /2, which is in agreement with the literature.
16
4
R
N
PPh Me
2
4
C
R -N=C=O
N
N
r t
1
R
1
R
1
4
3
3
R = H, R =Et, R = CO Et
2
R
3
5g
R
1d
4
R
3
N
R
R
C
1
R
N
4
N
R
N
, Toluene
N
1
N
3
R
4
R
1
4
3
1
5a R =Me, R = Et, R = CO Me
2
R
3
1
4
3
R
5c R =Me, R = Ph, R = CO Me
2
8a-c
Scheme 2
In order to enhance the synthetic use of N-functionalized heterocumulenes (5), the reaction of crude
carbodiimides (5d-f) with nitrogen nucleophiles such as amines was explored. Heterocumulenes (5d-f),
generated “ in situ” by reaction of phosphazenes with isocyanates, were allowed to react with amines at
room temperature affording the iminoimidazolones (10) or (11) (Scheme 3) as single isomers (Table 2,
Entries 1, 3-4), except when carbodiimide (5d) reacted with propylamine, where a mixture of two isomers
(10b) and (11b) of vinylic iminoimidazolone was obtained in a ratio of 46:54 (10b/11b) (Table 2, Entry
2). The structure of both isomers will be discussed later on.

5
4
4
R
R
R
HN
N
HN
C
4
5
5
R
H N-R
2
R
N
N
NH
N
NH
C O Me
2
C O Me
2
C O Me
2
MeO C
2
MeO C
2
MeO C
2
4
5d R = Et
4
9
5e R = Pr
4
5f R = Ph
- MeOH
- MeOH
4
R =Pr
4
5
R
H N-NH
2
2
R
N
N
MeO C
2
5
R
4
N
NH
R
N
NH
HN
Pr
N
O
N
C O Me
2
N
N
C O Me
2
O
O
O
NH
Pr
11
10
C O Me
2
12
Scheme 3
1
13
The structural constitutions of iminoimidazolones (10) were inferred from the H and C NMR spectral
data and confirmed for compound (10a) on the basis of X-Ray diffraction analysis. Figure 2 shows an
ORTEP representation17 of compound (10a), and the configuration between the exocyclic methoxycarbonyl
group and the amino group in the ring is cis. Comparing with the NMR spectroscopic data found for the
olefinic proton in compounds (10) and (11) and compound (10a), a cis configuration was assumed for all
iminoimidazolones. These olefinic protons in all iminoimidazolones appeared at δ = 5.61-5.67 as singlets.
On the other hand, the iminic structure assumed for the exocyclic N in compounds (10) and (11) is
confirmed by comparing with the structure found for compound (10a), analyzed by X-Ray diffraction, and
10
with the studies of Talaty et al.
7b
The annelation leading to iminoimidazolidinones can be explained by a cyclocondensation across the ester
functionality in the intermediate (9) with loss of alcohol (Scheme 3). Although the cyclization could take
place through both imino groups, the higher nucleophilicity of the N-alkylimino group could explain the
selective process that leads to iminoimidazolidinones as a single isomer (10) or (11), regardless of the
carbodiimides and amines used in the process. When both imino groups in the intermediate guanidine (9)
are alkyl substituted, there is no selectivity in the cyclocondensation process and two iminoimidazolidinones
(10b) and (11b) are obtained. The structure of componds (10b) and (11b) were assigned by means of
1
their H NMR spectral data. In compound (10b), the protons of N-CH in the propyl group appeared at δ
2
= 3.55 as a triplet, and the protons of N-CH in the ethyl group appeared at δ = 3.29 as a quartet.
2
Similarly, the N-CH of the propyl group in iminoimidazolidinone (10a) shows absorptions at δ = 3.69. It
2

can be assumed that isomer (10b) has the propyl group attached to the nitrogen on the cycle. In the case of
the isomer (11b), however, the N-CH in the propyl group appeared at δ = 3.20 as a triplet whereas the N-
2
CH in the ethyl group appears as a quartet at δ =3.65, which is consistent with an ethyl group on the
2
nitrogen of the ring.
Figure 2. ORTEP view of compounds (10a) and (12)
Table 2. Iminoimidazolones (10) and (11)
4
5
o
m p [ C]
a
Entry
Compd
Starting
R
R
Solvent Time Yield%
compound
CHCl
1
2
3
10a
10b/11b
10c = 11c
11d
5f
5d
5e
5e
Ph
Et
Pr
Pr
Pr
H
60 h
3 h
1 h
1 h
60
76-77
3
CH Cl
2
30/35 92-94/ 89-90
2
2
2
CH Cl
2
Pr
Pr
60
53
82-83
CH Cl
2
4
128-129
a
After recrystallization from CH Cl -hexane.
2
2
Finally, we aimed to extend this methodology to the preparation of bisheterocyclic compounds by using
reagents with two nucleophilic centers such as hydrazine. Reaction of N-vinylic carbodiimides with
hydrazine could lead to symmetrical bis-imidazolidinone azines. Thus, we performed the reaction of
carbodiimide (5f) with hydrazine in ethanol which afforded azine (12) in 31% yield (Scheme 3). The
structure of this compound was characterized by its spectral data and was confirmed by X-Ray diffraction
analysis. An ORTEP representation17 of molecule (12) is given in Figure 2, where a planar disposition of

both heterocycles can be observed. These types of compounds have received considerable interest because of
18
their potential as materials for electroluminescence purposes and in the non-linear optics (NLO) field.
Table 3. Selected spectral data for compounds (5-12)
a
Compd
1
13
a
b
c
H-NMR (CDCl )
3
δ (ppm)
C-NMR (CDCl )
3
δ (ppm)
IR
-1
υ (cm )
MS
(m/z)
3
+
5a
1.31 (t, 3H,
CH ), 2.37 (s, 3H, CH ), (CH ), 50.6 (OCH ), 108.3
J
= 7.3 Hz, 16.6 (CH ), 19.2 (CH ), 41.5
2146 (N=C=N)
1715 (C=O)
168 (M , 35 %)
HH
3
3
3
3.44 (q, 2H,
3
= 7.3 Hz, (=CH), 132.5 (C=), 155.4
2
3
3
J
HH
CH ), 3.64 (s, 3H, OCH ), (N=C=N), 167.4 (C=O)
2
5.50 (s, 1H, =CH).
3
3
+
5b
0.96 (t, 3H,
CH ), 1.65 (m, 2H, CH ), (CH ), 48.0 (NCH ), 50.6
J
= 7.3 Hz, 11.1 (CH ), 19.3 (CH ), 24.3
2143 (N=C=N)
1712 (C=O)
182 [M , 33 %]
HH
3
3
3
2
2
2
2.39 (s, 3H, CH ), 3.35 (t, (OCH ), 108.0 (=CH), 136.9
3
3
= 7.3 Hz, NCH ), (C=), 155.4 (N=C=N), 167.3
3
2H,
3.64 (s, 3H, OCH ), 5.54 (s, (C=O)
J
HH 2
3
1H, =CH).
+
5 c
5d
2.40 (s, 3H, CH ), 3.63 (s, 20.1 (CH ), 51.1 (OCH ),
2141 (N=C=N)
1718 (C=O).
216 [M ,100%]
3
3
3H, OCH ), 5.62 (s, 1H, 110.8 (=CH), 124.4, 126.3,
3
3
=CH), 7.05-7.29 (m, 5H, Ar). 129.7, 133.0 (Ar), 136.9 (C=),
152.7 (N=C=N), 167.2 (C=O)
+
(5d + Ph PO): 3.76 (s, 3H, (5d + Ph PO): 51.7 (OCH ),
2132 (N=C=N)
1742 (C=O)
260 [M , 37 %]
3
OCH ), 3.87 (s, 3H, OCH ), 53.7 (OCH ), 114.2 (=CH),
3
3
3
6.41 (s, 1H, =CH), 7.18 - 7.70 120.5-134 (Ar + C=), 138.2
3
3
(m, 20H, Ar).
(N=C=N), 163.5 (C=O), 164.6
(C=O)
+
5 e
5 f
6a
(5e + Ph PO): 1.19 (t, 3H, (5e + Ph PO): 16.2 (CH ),
2157 (N=C=N)
1736 (C=O)
212 [M , 78%]
3
= 7.2 Hz, CH ), 3.41 40.9 (CH ), 51.4 (OCH ),
3
3
3
J
HH
(q, 2H,
3 2 3
J = 7.2 Hz, CH ), 53.2 (OCH ), 112.0 (=CH),
HH 2 3
3.59 (s, 3H, OCH ), 3.70 (s, 128-134 (Ar + C=), 140.3
3
3
3H, OCH ), 6.14 (s, 1H, (N=C=N), 163.8 (C=O), 165.3
3
=CH), 7.39-7.70 (m, 15 H, (C=O)
Ar)
+
(5f + Ph PO): 0.93 (t, 3 H, (5f + Ph PO): 11.1 (CH ),
3
2150 (N=C=N)
1726 (C=O)
226 [M , 42%]
3
3
3
J
= 7.2 Hz, CH ), 1.65 23.9, (CH ), 47.4 (NCH ),
HH
(m, 2H, CH ), 3.43 (t, 2H, 51.3 (OCH ), 53.1 (OCH ),
3 2 2
3
2
3
3
J
= 6.8 Hz, NCH ), 3.68 111.7 (=CH), 128-134 (Ar +
HH
(s, 3H, OCH ), 3.79 (s, 3H, C=), 140.4 (N=C=N), 163.8
2
3
OCH ), 6.20 (s, 1H, =CH), (C=O), 164.9 (C=O)
3
7.39-7.70 (m, 15 H, Ar)
3
HH
+
1.10 (t, 3H,
J
= 7.2 Hz, 15.2 (CH ), 21.9 (CH ), 35.4
3327 (NH)
1680 (C=O)
186 [M , 19%]
3
3
CH ), 2.31 (s, 3H, CH ), (CH ), 50.9 (OCH ), 92.5
3
3.20 (m, 2H, CH ), 3.61 (s, (=CH), 153.8 (C=), 157.5
3
2
3
2
3H, OCH ), 4.60 (s, 1H, NH), (C=O), 170.4 (C=O)
3
4.73 (s, 1H, =CH), 10.50 (s,
1H, NH)

Table 3. Continued
Compd
1
a
13
a
b
c
H-NMR (CDCl )
3
δ (ppm)
C-NMR (CDCl )
3
δ (ppm)
IR
-1
υ (cm )
MS
(m/z)
6b
3
11.2 (CH ), 21.6 (CH ), 23.0
3318 (NH)
1671 (C=O)
+
3
(CH ), 42.0 (NCH ), 50.6
3
0.90 (t, 3H,
J
= 7.2 Hz,
200 [M , 19%]
HH
CH ), 1.52 (m, 2H, CH ),
2
2
(OCH ), 92.2 (=CH), 153.8
3
2.35 (s, 3H, CH ), 3.15 (m,
2
3
3
2H, NCH ), 3.63 (s, 3H,
(C=), 157.26 (C=O), 170.0
(C=O)
2
OCH ), 4.76 (s, 1H, =CH),
3
5.63 (s, 1H, NH), 10.53 (s,
1H, NH)
7a
3
13.6 (CH ), 34.2 (CH ), 52.4
3269 (NH)
1737 (C=O)
1704 (C=O)
1675 (C=O)
+
3
(OCH ), 95.9 (=CH), 139.7
2
1.26 (t, 3 H,
J
= 7.2 Hz,
3
HH
198 [M , 56%]
HH
3
CH ), 3.67 (q, 2H,
J
= (C=), 153.6 (C=O), 162.5
(C=O), 167.4 (C=O)
3
7.2 Hz, CH ), 3.82 (s, 3H,
2
OCH ), 5.91 (s, 1H, =CH),
3
9.05 (s, 1H, NH)
3
7b
11.1 (CH ), 21.4 (CH ), 40.5
3270 (NH)
1732 (C=O)
1699 (C=O)
1673 (C=O)
+
3
(NCH ), 52.2 (OCH ), 95.6
2
0.87 (t, 3 H,
J
= 7.3 Hz,
212 [M , 31%]
HH
CH ), 1.63 (m, 2H, CH ),
2
3
3
2
(=CH), 139.5 (=C), 153.6
(C=O), 162.5 (C=O), 167.2
(C=O)
3
3.50 (t, 2H,
J
= 7.3 Hz,
HH
NCH ), 3.75 (s, 3H, OCH ),
2
3
5.85 (s, 1H, =CH), 8.86 (s,
1H, NH)
7 c
8a
(CDCl + DMSO-d ): δ = 50.3 (OCH ), 93.9 (=CH),
3280 (NH)
1739 (C=O)
1702 (C=O)
1677 (C=O)
+
3
3.79 (s, 3H, OCH ), 5.78 (s, 125.0, 126.9, 127.5, 129.6
6
3
246 [M , 68%]
3
(ar), 137.3 (C=), 152.0 (C=O),
160.6 (C=O), 164.0 (C=O)
1H, =CH), 7.41-7.54 (m, 5H,
ar), 11.18 (s, 1H, NH)
3
13.5 (CH ), 14.3 (CH ), 38.0
1708 (C=O)
1596 (C=N)
+
3
(NCH ), 60.2 (OCH ), 114.7
3
1.23 (t, 6H,
J
= 7.3 Hz,
3
HH
336 [M , 6%]
+
HH
2
2
168 [M /2, 63%]
CH ), 1.30 (t, 6H,
J
= (=CH), 144.8 (=CH), 153.5
(C=N), 167.3 (C=O)
3
7.2 Hz, CH ), 3.46 (q, 4H,
3
3
J
= 7.3 Hz, CH ), 4.21
2
HH
3
(q, 4H,
J
= 7.2 Hz, CH ),
HH 2
3
5.83 (d, 1H,
J
= 13.2 Hz,
3
HH
=CH), 7.85 (d, 2H,
13.2 Hz, =CH)
J
=
HH
8b
3
13.3
(-CH -CH ),
23.6
(CH ), 36.1 (CH ), 55.5
1679 (C=O)
1540 (C=N)
+
2
3
1.16 (t, 6H,
J
= 7.2 Hz,
168 [M /2, 74%]
HH
CH ), 2.11 (s, 6H, CH ),
3
(OCH ), 106.2 (=CH), 156.0,
2
3
3
3.93 (s, 6H, OCH ), 3.95 (q,
3
162.4, 163.0
3
3
4H,
J
= 7.2 Hz, CH ),
HH 2
5.88 (s, 2H, =CH)
8 c
2.25 (s, 6H, CH ), 3.87 (s, 29.8 (CH ), 55.8 (OCH ),
1693 (C=O)
1540 (C=N)
+
3
6H, OCH ), 6.09 (s, 2H, 106.8 (=CH), 128.7-134.7 (ar
3
3
216[M /2, 100%]
3
=CH), 7.42-7.70 (m, 10H, Ar)
+ C=), 155.9 (C=N), 163.4
(C=O)

Table 3. Continued
Compd
1
a
13
a
b
c
H-NMR (CDCl )
3
δ (ppm)
C-NMR (CDCl )
3
δ (ppm)
IR
-1
υ (cm )
MS
(m/z)
3
+
10a 0.93 (t, 3H,
J
CH ), 1.72 (m, 2H, CH ), (NCH ), 51.3 (OCH ), 90.6
= 7.5 Hz, 10.8 (CH ), 20.9 (CH ), 40.6
3397 (NH)
1686 (C=O)
1640 (C=O)
287 [M , 11%]
HH
3
2
3
3.65 (s, 3H, OCH ), 3.69 (t, (=CH), 121.3 (ar), 124.0 (ar),
2
2
3
3
3
2H,
J
= 7.4 Hz, NCH ), 129.3 (ar), 140.7 (ar), 142.9
HH 2
5.66 (s, 1H, =CH), 6.90-7.35 (C=), 145.5 (C=N), 161.7
(m, 5H, Ar.), 8.97 (s, 1H, (C=O), 167.8 (C=O)
NH)
3
+
10b 0.85 (t, 3H,
J
CH ), 1.19 (t, 3H,
= 7.4 Hz, 11.1(CH ), 16.2 (CH ), 21.2
3
3104 (NH)
1730 (C=O)
1699 (C=O)
1672 (C=O)
239 [M , 40%]
HH
3
3
J
7.2 Hz, CH ), 1.61 (m, 2H, (NCH ), 51.7 (OCH ), 89.6
= (CH ), 40.8 (NCH ), 42.0
3
HH
2 2
3
CH ), 3.29 (q, 2H,
2
= (=CH), 141.9 and 142.5 (C= +
3
3
J
7.2 Hz, NCH ), 3.55 (t, 2H, C=N), 162.2 (C=O), 168.9
2
HH
2
= 7.3 Hz, NCH ), 3.72 (C=O)
3
J
(s, 3H, OCH ), 5.61 (s, 1H,
HH
2
3
=CH), 9.04 (s, 1H, NH)
3
+
10c= 0.85 (t, 3H,
11c CH ), 0.90 (t, 3H,
J
= 7.5 Hz, 11.2 (CH ), 11.8 (CH ), 21.2
3124 (NH)
1680 (C=O)
253 [M , 24%]
HH
3
= (CH ), 24.3 (CH ), 40.8
3
3
J
7.3 Hz, CH ), 1.6 (m, 4H, (NCH ), 49.3 (NCH ), 51.7
3
HH
2
2
3
CH ), 3.19 (t, 2H,
2
2
= (OCH ), 89.4 (=CH), 142.0
3
J
6.9 Hz, NCH ), 3.59 (t, 2H, (C=), 142.6 (N=C), 162.4
2
HH
3
2
= 7.3 Hz, NCH ), 3.72 (C=O), 169.0 (C=O)
3
J
(s, 3H, OCH ), 5.61 (s, 1H,
HH
2
3
=CH), 9.04 (s, 1H, NH)
3
+
11b 0.91 (t, 3H,
J
CH ), 1.17 (t, 3H,
= 7.4 Hz, 11.8 (CH ), 13.2 (CH ), 24.3
3
3270 (NH)
1746 (C=O)
1690 (C=O)
1666 (C=O)
239 [M , 21%]
HH
3
= (CH ), 34.2 (NCH ), 49.3
3
J
7.1 Hz, CH ), 1.60 (m, 2H, (NCH ), 51.6 (OCH ), 89.5
3
HH
2 2
3
CH ), 3.20 (t, 2H,
2
= (=CH), 142.0 and 142.3 (C= +
3
3
J
7.1 Hz, NCH ), 3.64 (q, 2H, C=N), 162.1 (C=O), 168.9
2
HH
2
7.1 Hz, NCH ), (C=O)
3
J
3.72 (s, 3H, OCH ), 5.61 (s,
=
HH
2
3
1H, =CH), 9.03 (s, 1H, NH)
3
HH
+
11d 0.89 (t, 3H,
J
= 7.4 Hz, 11.18 (CH ), 21.3 (CH ),
3390 (NH)
3257.5 (NH)
1673 (C=O)
211 [M , 8%]
3
2
CH ), 1.64 (m, 2H, CH ), 40.8 (NCH ), 53.4 (OCH ),
3
3
3.57 (t, 2H,
2
= 7.3 Hz, 91.5 (=CH), 141.5 (C=), 151.4
2
3
J
NCH ), 3.71 (s, 3H, OCH ), (N=C), 162.9 (C=O), 168.15
HH
2
5.67 (s, 1H, =CH)
3
(C=O)
3
1 2
0.92 (t, 6H,
CH ), 1.73 (m, 4H, CH ), (NCH ), 51.8 (OCH ), 91.4
J
= 7.4 Hz, 11.3 (CH ), 21.3 (CH ), 41.4
3423 (NH)
1679 (C=O)
1640 (C=O)
----
HH
3
2
3
3.68 (t, 4H,
2
= 7.0 Hz, (=CH), 139.8 (C=), 148.4
2
3
3
J
NCH ), 3.74 (s, 6H, OCH ), (N=C), 162.9 (C=O), 168.1
HH
2
5.69 (s, 2H, =CH)
3
(C=O)
a
b
c
Obtained on a Varian VXR 300 Spectrometer. Recorded in a Nicolet FTIR Magna 550. Obtained on a Hewlett
Packard 5890 Spectrometer.

In conclusion, this paper describes an easy and efficient access to heterocumulenes derived from β-amino
esters and dehydroaspartic esters. These carbodiimides (5) can serve as intermediates in the synthesis of
unsymmetrical ureas as well as new nitrogen containing heterocyclic compounds such as hydantoins (7),
diazetidines (8), iminoimidazolidinones (10) and (11) and symmetrical bis-imidazolidinone azine (12).
Compounds with these substructures could be very useful in the synthesis of biologically active derivatives
8-13
with interest in medicinal chemistry.
ACKNOWLEDGMENTS
The present work has been supported by the University of the Basque Country (UPV, 170.123-G11/99),
by the Dirección General de Investigación del Ministerio de Ciencia y Tecnología (Madrid DGI, BQU2000-
0217). M. Legido thanks the Dirección General de Enseñanza Superior e Investigación Científica (Madrid)
for a postdoctoral fellowship.
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