Novel phosphoranes containing urea derivatives: Synthesis and characterization

Article abstract of DOI:10.1080/10426500802446710

N-Acetyl-N'-methyl urea or ethyl urea in the presence of an acetylenic ester and a desired phosphine functioned as a NH-acid and added to the triple bond in a chemoselective reaction. One of the obtained products underwent lactonization to the correspondi

Full text of DOI:10.1080/10426500802446710

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Phosphorus, Sulfur, and Silicon
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Novel Phosphoranes Containing
Urea Derivatives: Synthesis and
Characterization
Davood Aghaei Afshar a & Mohammad Reza Islami a
a Department of Chemistry , Shahid Bahonar
University , Kerman, Iran
Published online: 04 Sep 2009.
To cite this article: Davood Aghaei Afshar & Mohammad Reza Islami (2009)
Novel Phosphoranes Containing Urea Derivatives: Synthesis and Characterization,
Phosphorus, Sulfur, and Silicon and the Related Elements, 184:9, 2238-2246
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Phosphorus, Sulfur, and Silicon, 184:2238–2246, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500802446710
Novel Phosphoranes Containing Urea Derivatives:
Synthesis and Characterization
Davood Aghaei Afshar and Mohammad Reza Islami
Department of Chemistry, Shahid Bahonar University, Kerman, Iran
N-Acetyl-Nꢀ-methyl urea or ethyl urea in the presence of an acetylenic ester and
a desired phosphine functioned as a NH-acid and added to the triple bond in
a chemoselective reaction. One of the obtained products underwent lactonization
to the corresponding imidazolidine containing ylide moiety when heated in the
presence of a base such as triethyl amine.
Keywords N-Acetyl-Nꢀ-methyl urea; chemoselective reaction; phosphoranes
INTRODUCTION
The various families of phosphorus compounds are particularly excit-
ing because of indications that they may generate many opportunities
for applied chemistry. The phosphoranes are good examples of such
molecules that apply in the synthesis of organic compounds.1–5 They
are of interest as building blocks for the preparation of alkenes,6 hetero-
cyclic compounds,7,8 and natural products.9 In addition, imidazolidine-
2,4-diones and their derivatives show interesting medicinal activities
since they have indicated therapeutic applications in drugs, such as
HIV protease inhibitors,10 antiarrhythmic properties,11 antihyperten-
sive activity,12 phenytion for the action of different types of epileptic
seizures,13 nilutamide,14 a nonsteroidal orally active antiandrogen in
the therapy of metastatic prostate cancer, and azimilide15 as an antiar-
rhythmic.
In spite of the fact that the applications of phosphorus ylides in
the synthesis of drugs16 and organic compounds and the application of
imidazolidines in organic chemistry as heat-resistant polymera for elec-
trical conductors17 and their interesting biological activities,18 there is
Received 9 July 2008; accepted 3 September 2008.
We thank the Shahid Bahonar University for financial support as a Grant-in-Aid for
Scientific Research.
Address correspondence to Mohammad Reza Islami, Department of Chemistry,
Shahid Bahonar University, Kerman 76169, Iran. E-mail: mrislami@mail.uk.ac.ir
2238

Novel Phosphoranes Containing Urea Derivatives
2239
still a search for the preparation of new compounds of these families,
and this has become an attractive strategy for synthetic chemists to
produce such materials in an effective manner from available precur-
sors. Here, we present our findings towards this goal (Scheme 1).
SCHEME 1 Synthesis of imidazolidine-2,4-dione derivatives: (i) Br2/KOH; (ii)
Ph3P, DMAD or DEAD; (iii) Et3N, heat.
RESULTS AND DISCUSSION
Acetamide reacted with bromine in the presence of KOH to give N-
acetyl-Nꢀ-Methyl urea 119 via a Hoffmann rearrangement.20–22 The for-
mation of compounds 2a–b may be explained in terms of the Michael ad-
dition of Ph3P to the triple bond of the acetylenic esters, and subsequent
protonation of the formed carbanion by NH acid in a chemoselective
manner to give intermediate 1. This intermediate readily undergoes
a second Michael addition to give an imide including polyfunctional
groups. The mechanism is shown in Scheme 2.
SCHEME 2

2240
D. A. Afshar and M. R. Islami
Due to much the greater acidity of the NH group of the imide rel-
ative to the NH group in an amide moiety, no other products were
formed under these conditions. The structures of compounds 2a–b are
1
assigned based on their IR, H NMR, and 13C NMR spectra and ele-
1
mental CHN-analyses data. The H and 13C NMR spectroscopic data
for these compounds exhibit a mixture of two rotational isomers.23–25
The main reason for this phenomenon is related to the resonance of
the carbanion of the ylide moiety with the adjacent carbonyl group of
1
the ester. The ratio of rotational isomers was determined from the H
1
NMR spectrum. As an example, the H NMR spectrum of compound
2a exhibits the mixture of these isomers as 80% and 20% for Z and E
isomers, respectively.
The spectrum of compound 2a shows six sharp lines (δ 1.98, 2.05,
3.05, 3.52, 3.76, 3.78) arising from the methyl of acetyl groups and
methoxy protons along with signals from the N-methyl protons at δ
2.88 and 2.83, which appear as two doublets (3JNH−H = 4.8) and the me-
thine protons at δ 5.04 and 5.00, which appear as two doublets (3JPH
=
17.7) for the major and minor geometrical isomers, respectively. The
13C NMR spectrum of compound 2a is in agreement with the proposed
1
structure. The H and 13C NMR spectra of 2b are similar to those of
compound 2a, except for the signals from the ester groups, which ap-
pear as characteristic resonance lines with the corresponding chemical
shifts.
Synthesis of Imidazolidine-2,4-dione Derivative
When compounds 2a–b were subjected to ring closure by heating in the
presence of a base such as triethyl amine, only 2a was exclusively lost
methanol to produce imidazolidine-2,4-dione derivative 3.
Since the other derivatives of compound 3 did not form in the same
reaction conditions, the reaction of N-ethyl urea, dialkyl acetylenedi-
carboxylate, and Ph3P was employed for synthesis of compounds 4a
and 4b in a chemoselective reaction manner.

Novel Phosphoranes Containing Urea Derivatives
2241
Similarly compounds 4a–b were subjected to ring closure upon heat-
ing in the presence of triethylamine; however, no reaction was observed
even a prolonged period. Although the reason of this observation is not
clear to us, it is possible that the steric hindrance of the ethyl sub-
stituent could be a factor.
Structure 3 was assigned on the basis of its elemental analyses and
IR, 1H, and 13C NMR spectral data. Compound 3 did not show the
absorption band of the NH group in the IR spectrum at 3354 cm−1, while
1
this absorption was detected in the IR spectrum of 2a. H NMR and
13C NMR spectra of compound 3 revealed a mixture of two rotational
isomers (Scheme 3).
SCHEME 3
In the 1H NMR spectrum of compound 3, protons of the acetyl
groups appeared as two singlets at δ 2.51and 2.49 along with two
signals arising from the methoxy groups at δ 3.10 and 3.46 for the
3Z and 3E isomers, respectively. Protons of N-methyl groups ap-
peared as two singlets at δ 3.05 and 3.07. The 1H NMR spectra of
2a and 3, which we believe are the result of ring closure of 2a,
are quite different. N-methyl protons of 3 appeared as two singlets,
1
whereas in the H NMR spectrum of 2a, these protons appeared as
two doublets due to the spin–spin splitting of the NH proton. The
13C NMR spectrum of compound 3 is in agreement with the proposed
structure.

2242
D. A. Afshar and M. R. Islami
1
The structures of compounds 4a–b were deduced from their IR, H
NMR, and 13C NMR spectra and elemental CHN-analyses data. The
1H and 13C NMR spectral data for these compounds exhibit a mixture
of two rotational isomers, and the ratio of the Z isomer is extremely
high in comparison to the E isomer. Probably the high yield of the Z
isomer compared to the E isomer is the result of hydrogen bonding via
a six-membered ring as shown:
CONCLUSION
In conclusion, N-acetyl Nꢀ-methyl urea was used as a precursor for the
synthesis of only one imidazolidine-2,4-dione derivative. The conver-
sion of ylides to imidazolidine-2,4-dione derivatives depended on the
substituent that was presented into the reactants. When the reactant
contains a methyl substituent, the reaction produces the expected prod-
uct. Although ylides were obtained in the first step of the reaction, when
bigger groups than methyl were used as a substituent on the acetylenic
ester or urea, the reaction does not go further even after refluxing the
reaction mixture for a long period.
EXPERIMENTAL
All common reagents and solvents were used as obtained from com-
1
mercial suppliers without further purification. The H and 13C NMR
spectra were recorded on a Bruker DRX-500 AVANCE (1H NMR at
500 MHz, and 13C NMR at 125.77 MHz). Melting points were obtained
on a Gallenkamp melting point apparatus and are uncorrected. Ele-
mental CHN analyses were performed by the University of Tarbiat
Moalem using a Heracus CHN-O Rapid analyzer. IR spectra were mea-
sured on a Mattson 1000 FT-IR spectrometer. Throughout this section,
* = for two rotamers.

Novel Phosphoranes Containing Urea Derivatives
2243
Dimethyl 2-Acetyl(methylamino)carbonyl)amino-3-(1,1,1-
triphenyl-λ5-phosphanylidene) Succinate 2a: General
Procedure
At ambient temperature, dimethyl acetylenedicarboxylate (0.24 mL,
2 mmol) was added dropwise to a stirred solution of triphenylphos-
phine (0.53 g, 2 mmol) and acetyl methyl urea (0.23 g, 2 mmol) in a
mixture of hexane/ethyl acetate (3:2). After the addition was complete
(approximately 30 min), the mixture was stirred for an additional 1
h and was subsequently filtered. The solid collected in the filter was
washed thoroughly with ethyl acetate to give a white powder.
0.99 g, mp 162–163◦C, yield 95%; IR (KBr) (ν max, cm−1): 1741, 1716,
1
1666, and 1641 (C O). Isomer (Z) (80%) H NMR (CDCl3): δ 1.98 (s,
CH3), 2.88 (d, 3JNH−H = 4.8 Hz NCH3), 3.05 and 3.78 (s, 2 OCH3), 5.04
3
(1H, d, JPH = 17.7 Hz, P C CH), 7.38–7.69 (30H, m, Ar)∗ , 6,95 (1H,
br.s, NH)*. 13C NMR (CDCl3): δ 22.90 (CH3), 27.42 (NCH3), 39.96 (d,
1JPC = 123.5, P C), 49.20 and 52.69 (2 OCH3), 57.35 (d, 2JPC =16.8 Hz
3
P C-CH), 125.96 (d,1JPC = 91.9 Hz, Cipso), 128.67(d, JPC = 12.5 Hz,
Cmeta), 132.28 (d,4JPC = 2.6 Hz, Cpara), 133.62 (d,2JPC = 9.8 Hz, Cortho),
2
156.62 and 169.29 (C O), 170.24 (d, JPC = 12.7 Hz, C O)*, 173.22
(d,3JPC = 14.6Hz, C O)*. Isomer (E) (20%), 1H NMR (CDCl3) : δ 2.05 (s,
CH3), 2.83 (d, 3JHH 4.8 Hz, NCH3), 3.52 and 3.76 (s, 2 OCH3), 5.01 (1H,
3
d, JPH = 17.6 Hz, P C-CH). 13C NMR (CDCl3): δ 22.35 (CH3), 27.40
(NCH3), 50.25 and 52.20 (2 OCH3), 56.77 (d, 2JPC = 16.8 Hz P C-CH),
125.48 (d,1JPC = 90.7 Hz, Cipso), 128.44 (d,3JPC = 12.1 Hz, Cmeta), 131.86
4
(d, JPC = 2.5 Hz, Cpara), 133.78 (d,2JPC = 9.7 Hz, Cortho). Anal. Calcd.
For C28H29N2O6P (520): C, 64.61; H, 5.57; N, 5.38%. Found: C, 64.42;
H, 5.11; N, 5.41%.
Diethyl 2-Acetyl (Methyl Amino) Carbonyl) Amino-3-(1,1,1-
triphenyl-λ5 phosphanylidene) Succinate 2b
1.03 g, mp 160–162◦C, yield 92%; IR (KBr) (ν
1690, and 1641 (C O). Isomer (Z) (88.2%), H NMR (CDCl3): δ 0.45
cm−1): 1765, 1741,
max,
1
3
3
(t, 3H, JHH = 7.0 Hz, CH3), 1.32 (t, 3H, JHH = 7.1 Hz, CH3), 2.00
3
(s, CH3), 2.89 (d, JNH−H = 4.7 Hz, CH3), 3.57–4.36(8H, m, 4OCH2)*,
5.04 (1H, d, JPH = 18.3 Hz, P C-CH), 7.45◦7.72 (30H, m, Ar)∗ .13C
3
NMR (CDCl3): δ 13.98, 14.22 and 22.89 (3 CH3), 27.48 (NCH3), 39.87
(d, 1JPC = 122.3, P C)*, 57.35 (d, 2JPC = 16.9 Hz P C-13CH), 57.92 and
61.41 (2 OCH2)*, 126.17 (d,1JPC = 91.8 Hz, Cipso)*, 128.58 (d,3JPC
=
12.3 Hz, Cmeta)*, 132.21 (d, 4JPC = 2.6 Hz, Cpara)*, 133.71 (d,2JPC = 9.8
Hz, Cortho)*, 156.75 and 169.23 (2 C O), 169.77 (d, JPC = 12.6 Hz,
2
C O)*, 172.71 (d,3JPC = 14.3Hz, C O)*. Isomer, (E) (11.8%),1H NMR

2244
D. A. Afshar and M. R. Islami
(CDCl3): δ 1.16 (t, 3H, 3JHH = 6.9 Hz, CH3), 1.36 (t, 3H, 3JHH = 7.2 Hz,
CH3), 1.97 (s, CH3), 2.91 (d, 3JNH−H = 5.0 Hz, CH3), 5.00 (1H, d, 3JPH
=
17.1 Hz, P C-CH).13C NMR (CDCl3): δ 13.99, 14.83 and 22.40 (3 CH3),
2
26.45 (NCH3), 56.77 (d, JPC = 16.6 Hz P C-13CH). Anal. Calcd. for
C30H33N2O6P (548): C, 65.69; H, 6.02; N, 5.10%. Found: C, 65.50; H,
6.0; N, 5.04%.
Methyl 2-(3-Acetyl-1-methyl-2,5-dioxo-4-imidazolidinyl)-2-(1,
1,1-triphnyl-λ5-phosphanylidene) Acetate 3
Compound 2a (0.52 g, 1 mmol) was heated in boiling triethyl amine for
30 min, and compound 3 was subsequently filtered. The solid collected
in the filter was washed thoroughly with ethyl acetate to give a white
powder.
0.29 g, mp 180 ◦C (dc), yield 70%; IR (KBr) (ν max, cm−1): 1790, 1741,
1
1690, and 1641 (C O). Isomer (Z): (66%) H NMR (CDCl3): δ 2.51 (s,
CH3), 3.05 (s, NCH3), 3.11 (s, OCH3), 4.20 (1H, d, 3JPH = 12.9, Hz, P C-
CH), 7.49–7.81 (30H, m, Ar)∗ .13C NMR (CDCl3): δ 24.87 (CH3), 25.34
(NCH3), 40.39 (d, 1JPC = 134.3 Hz, P C), 48.93 (OCH3), 60.88 (d, 2JPC
18.4Hz P C-CH), 125.78 (d,1JPC = 93.4 Hz, Cipso), (128.52 (d,3JPC
=
=
12.3 Hz, Cmeta), 132.01 (d, 4JPC = 2.4 Hz, Cpara), 134.14 (d,2JPC = 8.4 Hz,
Cortho), 154.77 ( C O), 168.99 (d, 2JPC = 12.9 Hz, C O), 169.20 (C O),
1
173.97 (d,3JPC = 5.8 Hz, C O). Isomer (E) (34%), H NMR (CDCl3): δ
3
2.49 (s, CH3), 3.07 (s, NCH3), 3.4 (s, OCH3), 4.27(1H, d, JPH = 13.9
Hz, P C-CH). 13CNMR (CDCl3): δ 24.70 (CH3), 25.34 (NCH3), 40.82 (d,
2
1JPC = 142.5 Hz, P C), 50.23 (OCH3), 59.93 (d, JPC = 18.1 Hz, P C-
CH), 126.47 (d, 1JPC = 80.4 Hz, Cipso). 128.59 (d,3JPC = 12.2 Hz, Cmeta),
134.21 (d,2JPC = 10.2 Hz, Cortho), 132.12 (d, 4JPC = 2.3 Hz, Cpara), 154.87
2
and 168.78 (2 C O), 169.4 (d, JPC = 18.2 Hz, C O), 174.02 (d,3JPC
=
5.53 Hz, C O). Anal. Calcd For C27H25N2O5P (488): C, 66.39; H, 5.12;
N, 5.73%. Found: C, 65.75; H, 5.51; N, 5.28%.
Dimethyl 2-{[(Methyl Amino) Carbonyl]amino}-3-(1,1,1-
triphenyl-λ5-phosphanylidene) Succinate 4a
This compound was prepared by using the method as described for the
preparation of compound 2a.
0.95 g, mp 119–120◦C, yield 97%); IR (KBr) (ν
cm−1): 1741,
max,
1716, 1691, and 1617 (C O). Isomer (Z) (96%) 1H NMR (CDCl3):
3
δ 1.05 (3H, t, JHH = 7.1 Hz, CH3), 3.11 and 3.61 (6H, s,2 OCH3),
3.13–3.20 (4H, m, 2 NCH2)*, 4.52–4.63 (2H, m, P C-CH )*, 5.70 (2H,
d,3JHH = 8.4 Hz, NH), 6.15 (4H, br.s, 2NH2)*, 7.45–7.72 (30H, m,

Novel Phosphoranes Containing Urea Derivatives
2245
Ar)∗. 13C NMR (CDCl3): δ 15.44 (2CH3)*, 35.23 (2 N-CH2)*, 43.94
1
2
(d, JPC 125.6 Hz, P C)*, 48.99, 51.96 (2 OCH3), 52.79 (d, JPC
=
16.9 Hz P C-CH)*, 126.98 (d,1JPC = 92.4 Hz, Cipso), 128.54 (d,3JPC
=
12.3 Hz, Cmeta)*, 132.08 (d, 4JPC = 2.6 Hz, Cpara)*, 133.82 (d,2JPC = 9.9
Hz, Cortho)*, 157.63 (C O), 170.75 (d, JPC =13.8 Hz, C O)*, 174.30
2
(d,3JPC = 12.6 Hz, C O)*. Isomer (E) (4 %),1H NMR (CDCl3): δ 1.24
(t, JHH = 7.1 Hz, CH3), 3.51 and 3.61 (2 OCH3).13C NMR (CDCl3): δ ,
3
49.93 and 51.95 (2 OCH3), 126.27 (d, 1JPC = 87.5 Hz, Cipso) Anal. Calcd.
For C27H29N2O5P (492): C, 65.8; H, 5.8; N, 5.69%. Found: C, 66.39; H,
5.97; N, 5.80%.
Diethyl 2 -{[(Methyl Amino) Carbonyl]amino}-3-(1,1,1-
triphenyl-λ5-phosphanylidene) Succinate 4b
(0.93 g, mp 174–175◦C, yield 90%); IR (KBr) (ν
cm−1): 1741, 1716,
max,
1691, and 1617 (C O). Isomer (Z) (88%)1H NMR (CDCl3): δ 0.43 (t,
3H, 3JHH = 7.1 Hz, CH3), 1.11 (t, 3H, 3JHH = 7.0 Hz, CH3), 1.17 (t, 3H,
3JHH = 7.0 Hz, CH3), 3.13–3.21 (4H, m, 2 CH2N)*, 3.63–4,13 (8H, m,
OCH2)*, 4.42–4.47 (2H, m, P C-CH)*, 5.65 (2H, d,3JHH = 6.9 Hz, NH)
6.12 (4H, br.s, 2 NH2)*, 7.42–7.72 (30H, m, Ar)∗ .13C NMR (CDCl3):
1
δ 13.89, 14.13 and 15.49 ( 3 CH3), 35.24 ( NCH3), 43.69 (d, JPC
=
128.4 Hz, P C)*, 52.81 (d, 2JPC = 16.4 Hz P C-13CH), 57.62 and 60.88
(2 OCH2), 126.85 (d,1JPC = 91.8 Hz, Cipso), 128.44 (d,3JPC = 12.3 Hz,
Cmeta), 131.96 (d, 4JPC = 2.4 Hz, Cpara), 133.93 (d, 2JPC = 9.8 Hz, Cortho)*,
157.70 (C O), 170.32 (d, 2JPC = 13.8 Hz, C O)*, 174.52 (d,3JPC = 12.6
Hz, C O). Isomer (E) (12%), 1H NMR (CDCl3): 1.21 (t, 3H, JHH
=
=
3
3
3
6.9 Hz, CH3), 1.23 (t, 3H, JHH = 7.0 Hz, CH3), 1.24 (t, 3H, JHH
6.9 Hz, CH3). 13C NMR (CDCl3): δ 14.14 and 15.11 (2 CH3), 35.25
(NCH2), 52.25 (d, 2JPC 16.2 Hz, P C-13CH), 58.03 and 60.86 ( 2 OCH2)
126.40 (d, 1JPC = 92.4 Hz, Cipso), 128.63 (d, 3JPC = 8.8 Hz, Cmeta), 132.04
(Cpara), 157.42(C O). Anal. Calcd. For C29H33N2O5P (520): C, 66.9; H,
6.3; N, 5.4%. Found: C, 67.39; H, 6.43; N, 5.25%.
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