A rapid and efficient microwave-assisted synthesis of hydantoins and thiohydantoins

Article abstract of DOI:10.1016/S0040-4020(03)00033-4

The present paper describes studies on the synthesis of the antiepileptic drug phenytoin, and of structurally related derivatives. First, the influence of the solvent has been investigated in the microwave-assisted synthesis of the drug, resulting in a yield improvement and a cleaner reaction. Second, a two-step reaction is described to synthesize selectively and in high yields phenytoin. The first step consists in microwave activation of the reaction of benzil with thiourea, the second step includes the conversion of the resulting 2-thiohydantoin to phenytoin using hydrogen peroxide. Moreover, microwave activation is a very convenient method for the synthesis of 3-alkylated phenytoin derivatives, resulting in a much more selective method than the previously reported procedure using alkylating agents.

Full text of DOI:10.1016/S0040-4020(03)00033-4

Tetrahedron 59 (2003) 1301–1307
A rapid and efficient microwave-assisted synthesis of hydantoins
and thiohydantoins
†
Giulio G. Muccioli,a Jacques H. Poupaert,a Johan Wouters,b Bernadette Norberg,b
,
Wolfgang Poppitz,c Gerhard K. E. Scribad and Didier M. Lamberta
,
*
a
´ ´
Laboratoire de Chimie pharmaceutique et de Radiopharmacie, Ecole de Pharmacie, Faculte de Medecine,
´
Universite catholique de Louvain, Avenue E. Mounier 73, UCL-CMFA 7340, B-1200 Bruxelles, Belgium
´
b
´ ´
Laboratoire de Chimie moleculaire structurale, Faculte des Sciences, Facultes universitaires Notre Dame de la Paix,
Rue de Bruxelles, 61, 5000 Namur, Belgium
cDepartment of Inorganic and Analytical Chemistry, University of Jena, August-Bebel-Strasse 2, D-07743 Jena, Germany
dDepartment of Pharmaceutical Chemistry, University of Jena, Philosophenweg 14, D-07743 Jena, Germany.
Received 20 September 2002; revised 18 November 2002; accepted 19 December 2002
Abstract—The present paper describes studies on the synthesis of the antiepileptic drug phenytoin, and of structurally related derivatives.
First, the influence of the solvent has been investigated in the microwave-assisted synthesis of the drug, resulting in a yield improvement and
a cleaner reaction. Second, a two-step reaction is described to synthesize selectively and in high yields phenytoin. The first step consists in
microwave activation of the reaction of benzil with thiourea, the second step includes the conversion of the resulting 2-thiohydantoin to
phenytoin using hydrogen peroxide. Moreover, microwave activation is a very convenient method for the synthesis of 3-alkylated phenytoin
derivatives, resulting in a much more selective method than the previously reported procedure using alkylating agents. q 2003 Elsevier
Science Ltd. All rights reserved.
1. Introduction
the cannabinoid receptors CB1 and CB2 using a phenytoin
derivative as template.10,11 Due to the growing interest of
medicinal chemists in the hydantoin scaffold, we developed
an efficient and rapid synthesis of phenytoin and related
compounds using microwave activation. Microwave
activation has received increasing interest in organic
synthesis because of rapid reaction rates, increased yields
and cleaner reaction conditions.12 Recently, several 1,5-
diphenyl hydantoins have been prepared by microwave-
assisted synthesis.13
The imidazolidine-2,4-dione, or hydantoin nucleus, is a
common 5-membered ring containing a reactive cyclic urea
core. This heterocycle is present in a wide range of
biologically active compounds including antiarrhytmics,1
anticonvulsant2 and antitumor3 agents. Among these agents,
phenytoin (3a, X¼O), or 5,5-diphenylhydantoin, is a well-
known therapeutic drug for the treatment of epileptic
seizures.4 More than 60 years since Merrit and Putnam
demonstrated that phenytoin was effective against
electrically induced seizures in the cat,5 the compound is
still the drug of choice for the treatment of generalised
tonic–clonic seizures (so-called grand mal epilepsy) and
focal motor seizures.6 Nowadays, phenytoin has found new
applications due to the neuro-and cardioprotective
properties.7,8
The most straightforward condition for the synthesis of
phenytoin is the base-catalysed condensation using benzil
(1) and urea (2a, X¼O) (Scheme 1), known as the Biltz
synthesis of phenytoin.14 Dunnavant and James showed that
the reaction proceeds via a benzilic rearrangement.15 The
authors also studied the optimal ratio being 1:2 in order to
reduce the side product 4a. Poupaert and co-workers
previously reported16 that the use of a two-phase system
such as aqueous KOH/n-BuOH and PEG 600 as phase
transfer catalyst drastically reduced the quantity of side-
product increasing the yield of phenytoin (87–93%). The
glycolureide 4a was obtained as a single diastereomer
possessing cis configuration.17
Imidazolidinediones are
a
common template in
combinatorial chemistry libraries.9 Recently, our group
initiated a medicinal chemistry research program targeting
Keywords: phenytoin; microwave activation; 5-aryl-3-alkyl-
imidazolidinediones.
*
Corresponding author. Tel.: þ32-2-764-73-47; fax: þ32-2-764-73-63;
e-mail: lambert@cmfa.ucl.ac.be
Present address: Institut de Recherches Microbiologiques Wiame—Av E
Gryzon 1, 1070 Brussels, Belgium.
The present study reports several improvements of the Biltz
reaction allowing the rapid synthesis of phenytoin and
†
0040–4020/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4020(03)00033-4

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G. G. Muccioli et al. / Tetrahedron 59 (2003) 1301–1307
Scheme 1. Synthetic routes to diphenylhydantoin and diphenylthiohydantoin. Method A: conventional route known as Biltz’s synthesis of phenytoin (3a) and
diphenylthiohydantoin (3b), obtained from benzil (1) and urea (2a) or thiourea (2b) in absence or presence of microwave activation. Method B: two-step
procedure for preparing phenytoin (3a) following the microwave-assisted condensation of benzile and thiourea (2b) giving diphenylthiohydantoin (3b)
followed by H2O2 oxidation in DMF/acetic acid at room temperature.
structurally related derivatives. First, we have investigated
the type of solvent in view of adapting the Biltz synthesis to
microwave activation. Secondly, we have developed a two-
step procedure via synthesis of the 2-thiophenytoin and
subsequent conversion into phenytoin resulting in the
virtual absence of the glycolureide side product 4a.
Finally, we have applied microwave activation to the
synthesis of N3-alkylated phenytoin derivatives including
2-thiophenytoin.
the ratio of products 3a and 4a, but rather affects the kinetics
of the reaction.16 Thus, while the reaction has been explored
regarding the stoichiometry15 and the type of the base, to the
best of our knowledge the role of the solvent has never been
studied in detail previously.
Frequently, solvent systems have to be adapted in order to
allow microwave-organic reaction enhancement
(MORE).20,21 Solvents useful for microwave activation
2. Results and discussion
2.1. Microwave activation of phenytoin synthesis
The Biltz synthesis is a common way to synthesise
phenytoin (3a, X¼O) starting from benzil and urea. Two
procedures, the classical one under thermal heating and a
new microwave-assisted approach, were compared using
the same reacting mixtures. We used a pulsed method18,19
for the microwave-activation in order to maximise the
microwave effect and to avoid the loss of solvent and
starting material due to the heating of the reaction mixture.
Nine microwave pulses were applied using a household
oven over a 30 min period. The time periods between pulses
allowed the cooling of the mixture.
The principal limitation of the Biltz synthesis of phenytoin
is the concomitant formation of 3 and 4 (Scheme 1). Under
homogeneous reaction conditions, using ethanol as solvent,
the yield of 3 is less than 50%. In ethanol/water mixtures the
yield of pure 3a never exceeds 55%. According to our
studies the yield of isolated 4a can be as high as 20%.
Changing the strength of the base does not significantly alter
Table 1. Solvent effect (% yield) in the microwave-assisted (microwave)
and the regular Biltz synthesis (thermal) of phenytoin (3)
Solvent
Microwavea
Thermal
DMSO
DMSO/H2Ob
Sulfolane
80
76
78
71
45
80
36
62
57
58
25
58
Sulfolane/H2Ob
Dioxane
Dioxane/H2Ob
The same composition of the reagents was used in each type of synthesis.
The reaction mixture was heated for 2 h under thermal reaction conditions
or submitted to nine 750 W pulses over a period of 30 min in the
microwave-assisted synthesis. Reactions were carried out at the same
temperature under both reaction conditions.
Figure 1. Structures of S-ethyl-5,500-diphenyl-2-thiohydantoin (5), 3-alkyl-
2-thiohydantoins (6), 3-alkyl-5,5 -di(para-substitutedphenyl)hydantoins
(7–16). Excepted for compound 5, all compounds have been prepared
from benzil and alkylureas or alkylthiourea under microwave activation.
a
Experiments done in triplicate.
40:100, v/v.
b

G. G. Muccioli et al. / Tetrahedron 59 (2003) 1301–1307
1303
Scheme 2. Proposed mechanism of condensation of benzile and alkylurea followed by the benzylic rearrangement.
are dipolar solvents especially those with a high boiling
point.22 We first investigated solvents such as DMSO and
DMF because we have obtained a yield of 3a of up to 62%
in earlier studies when using DMSO–water mixtures. Using
microwave activation, with the same solvent composition
and temperature (,1108C) than in the thermal reaction, the
yield of 3a was somewhat improved (76%) and a diminution
in the side product (4a) yield was observed. In addition, the
reaction was complete after 30 min instead of 2 h under
classical thermal conditions. Actually, when we performed
the thermal reaction under reflux for only 30 min (reacting
time of the microwave-assisted reaction) nearly 50% of the
starting benzil was recovered and the phenytoin yield was as
low as 26%. It is noteworthy that in the microwave-assisted
reaction after the first 90 s pulse, 40% of the benzil was still
present and the phenytoin yield was 40% instead of 76% at
the end of the pulse sequence. When the reaction was
performed in DMSO under microwaves the yield of 3a
slightly increased to 80%. Similar results were obtained
with sulfolane and dioxane (Table 1). However, DMF gave
much lower yields. This can be explained by the extensive
hydrolysis of DMF under the highly basic conditions and
high temperatures which rapidly depletes the KOH
concentration in the reaction mixture.
separation procedures to obtain pure N3-alkylated com-
pounds.8 In view of obtaining a rapid and efficient synthesis
of these derivatives, microwave activation has been applied
to reaction mixtures containing different benzil and
alkylated (thio)urea derivatives allowing us to obtain the
N3-alkyl (thio)hydantoin in a good yield. The new hydantoin
derivatives 7–16 (Fig. 1) have been prepared from the
cor0responding alkylureas and either 4,4-dichlorobenzil or
4,4 -dibromobenzil. The proposed mechanism (Scheme 2) is
similar to the mechanism of the classical Biltz synthesis of
phenytoin.23 The alkylurea derivatives were prepared by
reaction of potassium cyanate and the corresponding
alkylamines.24 Interestingly, the microwave-assisted pro-
cedure gave easy access to 3-alkyl-2-thiohydantoin. Under
alkylating conditions, treatment of 3b (X¼S) with
iodoethane mainly yields the S-ethyl derivative 5, while
reaction of ethylthiourea gave N-ethyl-2-thio-phenytoin 6.
The structures of compounds 5 and 6 (Fig. 1) gave distinct
1H NMR and 13C NMR spectra. The position of the alkyl
substituent was confirmed by X-ray analysis. ORTEP
diagrams of 5 and 6 in the asymmetric unit are presented
in Figures 2 and 3, respectively.
3. Conclusions
2.2. Synthesis of phenytoin via the 2-thiophenytoin
Microwave activation of the Biltz synthesis of phenytoin
improves both, yield and time reaction. Albeit yields under
In our efforts to improve and extend the scope of the Biltz
synthesis of phenytoin without microwave activation, we
noticed that the reaction of benzil with thiourea in ethanolic
KOH did not yield any 4b. In addition, the presence of water
in the reaction mixture increased the yield of 3b (X¼S) with
a corresponding decrease of 4b. In the microwave-assisted
procedure, DMSO was chosen because of its high boiling
point and solvating power. The reaction of benzil (1) with
thiourea (2b, X¼S) in DMSO using aqueous KOH as
catalyst gave the 2-thiohydantoin derivative (3b, X¼S) in
high yield (92%). Moreover, the thioglycolureide (4b) was
virtually absent from the reaction mixture. After precipi-
tation, the crude product 3b was oxidized to phenytoin (3a)
using hydrogen peroxide in DMF/acetic acid at room
temperature in good yields (95%). In conclusion, the
combination of this two-step procedure and the use of
microwaves allowed to obtain phenytoin in high yield and
by minimal work-up.
2.3. Synthesis of phenytoin derivatives
In our studies to synthesize N3-alkylated phenytoin
derivatives, we noted that alkylation resulted, in addition
to the desired N3-alkylated derivatives, in N1-alkyl and
O-alkyl (or S-) side products often requiring tedious
Figure 2. ORTEP diagram (50% probability) of S-ethyl-5,50-diphenyl-2-
thiohydantoin.

1304
G. G. Muccioli et al. / Tetrahedron 59 (2003) 1301–1307
were recorded on a Finnigan MAT 44S, with an ionisation
voltage of 70 eV.
Suitable crystals of compounds 5 and 6 obtained by
recrystallization in ethanol were mounted with a quartz
fibre on a goniometer head of a CAD4 Nonius diffract-
ometer. After determination of the cell parameter using 25
well-centred reflections, complete diffraction data sets were
collected.Thestructureswere solvedusingdirectmethodsand
refined by full matrix least squares on F 2 using the program
Shelxl97.25 All non-hydrogen atoms were treated anisotropi-
cally while a riding model was applied for the hydrogens.
Analytical correction for absorption was introduced.
4.1.1. Compound 5. Colourless plate (0.41£0.27£
˚
0.08 mm), monoclinic, P21/c, a¼6.066(1) A, b¼
˚
˚
18.587(1) A, c¼14.579(1) A, a¼90.08, b¼113.02(1)8,
g¼90.08, V¼1512.9(3) A , Z¼4, m¼1.89 mm21, Dx¼
3
˚
1.301 g cm23
,
l
(Cu Ka)¼1.54178 A, F(000)¼624,
˚
T¼290 K, 3264 unique reflections (Rint¼0.0286), 195
refined parameters, R1¼0.0400 for 2977 Fo.4s(Fo),
R1¼0.0503 for all data (3264) and wR2¼0.1098,
Figure 3. ORTEP diagram (50% probability) of 3-ethyl-5,50-diphenyl-2-
thioxo-imidazolidin-4-one.
3
3
˚
˚
GOF¼S¼1.054, Drmin¼20.282 e/A , Drmax¼0.199 e/A .
microwave-assisted conditions were quite satisfactory
(74%), a two-step synthesis was developed in order to
reduce the formation of the glycolureide side product
resulting in a further improvement of the yield (87.4%, total
yield). This rapid method of synthesizing phenytoin can be
very useful for the synthesis of radiolabelled phenytoin
analogs with short half-lives.
4.1.2. Compound 6. Colourless plate (0.44£0.18£
˚
0.15 mm), monoclinic, P21/c, a¼10.535(1) A, b¼
˚
˚
12.360(1) A, c¼12.207(1) A, a¼90.08, b¼105.95(1)8,
g¼90.08, V¼1528.3(2) A , Z¼4, m¼1.87 mm21, Dx¼
3
˚
1.288 g cm23, l (Cu Ka)¼1.54178 A, F(000)¼624, T¼
˚
290 K, 2985 unique reflections (Rint¼0.0130), 196 refined
parameters, R1¼0.0338 for 2687 Fo.4s(Fo), R1¼0.0382
for all data (2985) and wR2¼0.0965, GOF¼S¼1.032,
3
3
˚
˚
Furthermore, using the corresponding alkylureas or
alkylthioureas, the same microwave-assisted procedure
gives rapid and efficient access to new N3-alkyl-5,50-
diarylhydantoins or N3-alkyl-5,50-diaryl-2-thiohydantoins.
This convenient procedure will allow a further increase of
the diversity within the imidazolidinedione family.
Drmin¼20.192 e/A , Drmax¼0.270 e/A .
4.1.3. 5,50-Diphenyl-imidazolidine-2,4-dione (3a, X5O).
Classical method. To a solution of 20.2 g of benzil (1,
96.2 mmol) and 12.69 g of urea (2a, 167 mmol) in 40 ml of
DMSO 25 ml of 1.2 M aqueous KOH were added under
stirring. The resulting mixture was refluxed for 2 h and
poured into cold water. The precipitate was filtrated and the
filtrate was acidified with glacial acetic acid. The resulting
precipitate was collected, dried and recrystallized from
ethanol. Yield¼60%, mp 295–2968C. Spectral data similar
to a commercial sample of the product (Acros Organics,
17173–0050).
4. Experimental
4.1. General procedures
All reagents were purchased from commercial sources
(Sigma-Aldrich or Acros, Belgium) and were used without
further purification. Solvents were of analytical grade. The
microwave oven used was a commercial household
microwave oven (Moulinexw FM1935G, frequency:
2450 MHz).
Microwave activation. 25 ml of 1.2 M aqueous KOH were
added to a mixture of 20.2 g of benzil (1, 96.2 mmol) and
10.03 g of urea (2a, 167 mmol) dissolved in 40 ml of
DMSO. Following an initial 90 s 750 W pulse the mixture
was stirred for 5 min. 30 s pulses were then applied at 6, 9,
12, 15, 18, 21, 24, and 30 min, the mixture was stirred
between pulses. The mixture was then poured into 300 ml of
cold water. The precipitate was filtrated and the filtrate was
acidified with glacial acetic acid. The white precipitate was
collected, dried and recrystallized from ethanol.
Yield¼74%. Mp 295–2968C. Spectral data similar to a
commercial sample of the product (Acros Organics, 17173–
0050).
Melting points (mp) were determined in open capillaries
using an Electrothermal 9100 apparatus and are uncorrected.
Infrared (IR) spectra were recorded using a Perkin–Elmer
FT-IR 286 spectrometer, values are reported as n in cm21
.
Nuclear magnetic resonance (1H NMR, 13C NMR) spectra
were recorded on a Bruker AM-300 spectrometer at room
temperature and analysed using the WIN NMR software
package. Chemical shifts (d) are reported relative to
tetramethylsilane peak set at 0.00 ppm. In the case of
multiplets the signals are reported as intervals. Signals were
abbreviated as s, singlet; d, doublet; t, triplet; m, multiplet.
Coupling constants were expressed in Hz. Mass spectra
4.1.4. 5,50-Diphenyl-2-thioxo-imidazolidin-4-one (3b,
X5S). The synthesis was performed as for 3a (X¼O),
with microwave activation but using thiourea (2b).

G. G. Muccioli et al. / Tetrahedron 59 (2003) 1301–1307
1305
Yield¼92%. Mp 238–2408C. Spectral data similar to a
commercial sample of the product (Sigma-Aldrich,
D21,425-6).
dibromobenzil (8.15 mmol) and 1.21 g of methylurea
(16.3 mmol). Yield¼45%. Mp 215–2168C. IR (KBr,
cm21) n 3218 (NH), 1769 (CvO), 1710 (CvO), 1480
(CvC). 13C NMR (300 Hz) d 24.59 (CH3), 68.39 (C),
121.76 (Carom.), 128.82 (CHarom.), 131.53 (CHarom.), 138.59
(Carom.), 155.28 (CvO), 172.55 (CvO). 1H NMR (300 Hz)
d 2.93 (m, 3H), 7.30 (d, J¼8.82 Hz, 4H), 7.61 (d,
J¼8.82 Hz, 4H), 9.69 (s, 1H). MS DCI (H2O): 425/100
[MþH]þ. Calcd for C16H12Br2N2O2: C, 45.32; H, 2.85; Br,
37.68; N, 6.61; O, 7.55%. Found: C, 45.17; H, 2.78; N,
6.43%.
4.1.5. Conversion of 5,50-diphenyl-2-thioxo-imidazolidin-
4-one (3b) into phenytoin (3a). To a solution of 2.68 g of
5,50-diphenyl-2-thiohydantoin (10 mmol) in DMF 1 ml of
glacial acetic acid and 2.5 ml of perhydrol 30% were added.
The reaction mixture was stirred for 24 h at room temperature
and poured onto ice. The precipitate was collected, dried, and
recrystallized from ethanol. Yield¼92%. Mp 294–2968C.
Spectral data were comparable to (3a, X¼O).
4.1.10. 5,50-Bis-(4-bromo-phenyl)-3-ethyl-imidazolidine-
2,4-dione (9). As described for 6 from 3 g of 4,40-
dibromobenzil (8.15 mmol) and 1.43 g of ethylurea
(16.3 mmol). Yield¼51%. Mp 215–2168C. IR (KBr,
cm21) n 3211 (NH), 1772 (CvO), 1712 (CvO), 1489
(CvC). 13C NMR (300 Hz) d 13.00 (CH3), 33.13 (CH2),
68.00 (C), 121.64 (Carom.), 128.62 (CHarom.), 131.47
(CHarom.), 138.39 (Carom.), 154.83 (CvO), 172.17 (CvO).
1H NMR (300 Hz) d 1.07–1.12 (m, 3H), 3.44–3.51 (m,
2H), 7.28 (d, J¼8.82 Hz, 4H), 7.63 (d, J¼8.82 Hz, 4H), 9.70
(s, 1H). MS DCI (H2O): 439/100 [MþH]þ. Calcd for
C17H14Br2N2O2: C, 46.61; H, 3.22; Br, 36.48; N, 6.39; O,
7.3%. Found: C, 46.63; H, 3.24; N, 6.31%.
4.1.6. S-Ethyl-5,50-diphenyl-2-thiohydantoin (5). The
alkylation has been previously describ0ed for the 5-50-
diphenylhydantoin.10 Briefly, 3 g of 5,5 -diphenyl-2-thio-
hydantoin (11.2 mmol) was dissolved in 10 ml of anhydrous
DMF. K2CO3, 6.17 g (4.7 mmol) and iodo-ethane, 1.75 g
(11.2 mmol) were added and the mixture stirred overnight.
The mixture was poured into 150 ml of water. The resulting
precipitate was collected, dried and recrystallized from
ethanol. Yield¼42%. Mp 182–1848C. 13C NMR (300 Hz) d
14.88 (CH3), 23.87 (CH2), 78.13 (C), 126.62 (CHarom.),
127.46 (CHarom.), 128.30 (CHarom.), 140.53 (Carom.), 159.55
1
(C2), 181.94 (CvO). H NMR (300 Hz) d 1.35–1.39 (t,
J¼7.35 Hz, 3H), 3.18–3.25 (q, J¼7.35 Hz, 2H), 7.31–7.37
(m, 10H), 11.52 (s, 1H). MS DEI: 296/100 [M]þ.
4.1.11. 5,50-Bis-(4-bromo-phenyl)-3-butyl-imidazolidine-
2,4-dione (10). As described for 6 from 3 g of 4,40-
dibromobenzil (8.15 mmol) and 1.89 g of butylurea
(16.3 mmol). Yield¼55%. Mp 151–1528C. IR (KBr,
cm21) n 3217 (N–H), 2954 (C–H), 1768 (CvO), 1713
(CvO), 1488 (CvC). 13C NMR (300 Hz) d 13.23 (CH3),
19.05 (CH2), 29.34 (CH2), 37.75 (CH2), 68.16 (C), 121.67
(Carom.), 128.66 (CHarom.), 131.50 (CHarom.), 138.62
(Carom.), 155.12 (CvO), 172.46 (CvO). 1H NMR
(300 Hz) d 0.82–0.87 (m, 3H), 1.16–1.23 (m, 2H), 1.47–
1.52 (m, 2H), 3.41–3.46 (m, 2H), 7.27 (d, J¼8.82 Hz, 4H),
7.63 (d, J¼8.82 Hz, 4H), 9.70 (s, 1H). MS DCI (H2O):
467/100 [MþH]þ. Calcd for: C19H18Br2N2O2: C, 48.95; H,
3.89; Br, 34.28; N, 6.01; O, 6.86%. Found: C, 48.65; H,
3.81; N, 5.93%.
4.1.7. 3-Ethyl-5,50-diphenyl-2-thioxo-imidazolidin-4-one
(6). 25 ml of 1.2 M aqueous KOH were added to a mixture
of 3 g of benzil (14.3 mmol) and 2.97 g of ethylthiourea
(28.6 mmol) dissolved in 30 ml of DMSO. The resulting
solution was subjected to a 90 s 750 W microwave pulse and
stirred for 5 min. 30 s pulses were applied at 6, 9, 12, 15, 18,
21, 24, and 30 min, and the mixture was stirred between
pulses. The mixture was poured into 300 ml of cold water.
The resulting precipitate was collected, dried and recrys-
tallized from ethanol. Yield¼56%. Mp 186.8–187.48C. IR
(KBr, cm21) n 3262 (NH), 1714 (CvO), 1495 (CvC),
1164 (CvS). 13C NMR (300 Hz) d 12.75 (CH3), 35.71
(CH2), 71.10 (C), 126.5524 (CHarom.), 128.43 (CHarom.),
128.75 (CHarom.), 138.13 (Carom.), 173.20 (CvS), 180.90
(CvO). 1H NMR (300 Hz) d 1.11–1.16 (m, 3H), 3.79–3.82
(m, 2H), 7.30–7.44 (m, 10H), 11.02 (s, 1H). MS DEI:
296/100 [M]þ.
4.1.12. 5,50-Bis-(4-bromo-phenyl)-3-pentyl-imidazoli-
dine-2,4-dione (11). As described for 6 from 3 g of 4,40-
dibromobenzil (8.15 mmol) and 2.12 g of pentylurea
(16.3 mmol). Yield¼54%. Mp 157–1588C. IR (KBr,
cm21) n 3215 (N–H), 2951 (C–H), 1766 (CvO), 1716
(CvO), 1490 (CvC). 13C NMR (300 Hz) d 13.36 (CH3),
21.13 (CH2), 26.62 (CH2), 27.79 (CH2), 37.75 (CH2), 67.97
(C), 121.41 (Carom.), 128.46 (CHarom.), 131.24 (CHarom.),
4.1.8. 3-Cyclohexyl-5,50-diphenyl-imidazolidine-2,4-
dione (7). As described for 6 from 3 g of benzil
(14.28 mmol) and 4.06 g of cyclohexylurea (28.56 mmol).
Yield¼58%. Mp 179–1808C. IR (KBr, cm21) n 3233 (NH),
1770 (CvO), 1715 (CvO), 1493 (CvC). 13C NMR
(300 Hz) d 24.88 (CH2), 25.47 (CH2), 29.15 (CH2), 50.83
(CH), 68.36 (C), 126.72 (CHarom.), 128.14 (CHarom.), 128.60
(CHarom.), 140.05 (Carom.), 155.39 (CvO), 173.24 (CvO).
1H NMR (300 Hz) d 1.09–1.29 (m, 3H), 1.58–1.62 (m,
3H), 1.74–1.78 (m, 2H), 2.06–2.14 (m, 2H), 3.82–3.86 (m,
1H), 7.38–7.42 (m, 10H), 9.45 (s, 1H). MS DCI (H2O):
335/100 [MþH]þ. Calcd for C21H20Cl2N2O2: C, 62.54; H,
5.00; Cl, 17.58; N, 6.95; O, 7.93%. Found: C, 62.3; H, 4.95;
Cl, 17.21; N, 6.86%.
1
138.43 (Carom.), 154.92 (CvO), 172.33 (CvO). H NMR
(300 Hz) d 0.76–0.80 (m, 3H), 1.13–1.27 (m, 4H), 1.46–
1.55 (m, 2H), 3.39–3.44 (t, J¼7.35 Hz, 2H), 7.28 (d,
J¼8.82 Hz, 4H), 7.61 (d, J¼8.82 Hz, 4H), 9.70 (s, 1H). MS
DCI (H2O): 481/100 [MþH]þ. Calcd for C20H20Br2N2O2:
C, 50.03; H, 4.20; Br, 33.28; N, 5.83; O, 6.66%. Found: C,
49.67; H, 4.11; N, 5.67%.
4.1.13. 5,50-Bis-(4-chloro-phenyl)-imidazolidine-2,4-
dione (12). As described 0 for 3 with the microwave
activation from 3 g of 4,4 -dichlorobenzil (10.79 mmol)
and 1.64 g of urea (21.57 mmol). Yield¼62%. Mp 318–
3208C. IR (KBr, cm21) n 3187 (NH),1772 (CvO), 1720
4.1.9. 5,50-Bis-(4-bromo-phenyl)-3-methyl-imidazoli-
dine-2,4-dione (8). As described for 6 from 3 g of 4,40-

1306
G. G. Muccioli et al. / Tetrahedron 59 (2003) 1301–1307
(CvO), 1490 (CvC). 13C NMR (300 Hz) d 69.23 (C),
128.43 (CHarom.), 128.62 (CHarom.), 132.02 (Carom.), 138.46
(Carom.), 155.73 (CvO), 174.17 (CvO). 1H NMR (300 Hz)
d 7.36 (d, J¼8.82 Hz, 4H), 7.49 (d, J¼8.82 Hz, 4H), 9.40 (s,
1H), 11.25 (s, 1H). MS DCI (H2O): 321/100 [MþH]þ.
2H), 3.88–3.96 (m, 1H), 7.27 (d, J¼8.82 Hz, 4H), 7.39 (d,
J¼8.82 Hz, 4H) 9.67 (s, 1H). MS DCI (H2O): 403/100
[MþH]þ. Calcd for C21H20Cl2N2O2: C, 62.54; H, 5; Cl,
17.58; N, 6.95; O, 7.93%. Found: C, 62.3; H, 4.95; Cl,
17.21; N, 6.86%.
4.1.14. 5,50-Bis-(4-chloro-phenyl)-3-ethyl-imidazolidine-
2,4-dione (13). As described for 6 from 3 g of 4,40-
dichlorobenzil (10.79 mmol) and 1.9 g of ethylurea
(21.58 mmol). Yield¼50%. Mp 160–1618C. IR (KBr,
cm21) n 3215 (NH), 1766 (CvO), 1710 (CvO), 1490
(CvC). 13C NMR (300 Hz) d 13.00 (CH3), 33.19 (CH2),
68.00 (C), 128.36 (CHarom.), 128.62 (CHarom.), 133.09
(Carom.), 138.13 (Carom.), 154.89 (CvO), 172.76 (CvO).
1H NMR (300 Hz) d 1.06–1.11 (t, J¼7.35 Hz, 3H), 3.43–
3.49 (q, J¼7.35 Hz, 2H), 7.34 (d, J¼8.82 Hz, 4H), 7.48 (d,
J¼8.82 Hz, 4H), 9.69 (s, 1H). MS DCI (H2O): 349/100
[M]þ. Calcd for C17H14Cl2N2O2: C, 58.47; H, 4.04; Cl,
20.30; N, 8.02; O, 9.16%. Found: C, 58.27; H, 4.11; Cl,
20.1; N, 7.96%.
4.2. Supplementary material for X-ray analysis
Crystallographic data (structures 5 and 6) have been
deposited with the Cambridge Crystallographic Data Centre
as supplementary publication numbers CCDC 193953 and
CCDC 193954. Copies of data can be obtained, free of
charge, on application to CCDC (deposit@ccdc.cam.ac.uk).
Acknowledgements
One of us (G. M.) is very indebted to ‘Fonds pour la
`
formation a la Recherche dans l’Industrie et l’Agriculture
(FRIA)’, Belgium, for the award of a research fellowship.
This work was partially funded by a FRSM grant from the
Belgian National Fund for Scientific Research, a FSR grant
4.1.15. 5,50-Bis-(4-chloro-phenyl)-3-butyl-imidazolidine-
2,4-dione (14). As described for 6 from 3 g of 4,40-
dichlorobenzil (10.79 mmol) and 2.57 g of butylurea
(21.58 mmol). Yield¼55%. Mp 145–1468C. IR (KBr,
cm21) n 3217 (NH), 1769 (CvO), 1713 (CvO), 1489
(CvO). 13C NMR (300 Hz) d 13.26 (CH3), 19.22 (CH2),
29.44 (CH2), 37.85 (CH2), 68.06 (C), 128.43 (CHarom.),
128.69 (CHarom.), 133.15 (Carom.), 138.26 (Carom.), 155.15
(CvO), 172.55 (CvO). 1H NMR (300 Hz) d 0.82–0.87 (t,
J¼7.35 Hz, 3H), 1.17–1.24 (q, J¼7.35 Hz, 2H), 1.49–1.53
(m, 2H), 3.43–3.48 (t, J¼7.35 Hz, 2H), 7.37 (d, J¼8.82 Hz,
4H), 7.51 (d, J¼8.82 Hz, 4H), 9.74 (s, 1H). MS DCI (H2O):
377/100 [M]þ. Calcd for C19H18Cl2N2O2: C, 60.49; H, 4.81;
Cl, 18.79; N, 7.43; O, 8.48%. Found: C, 60.65; H, 4.89; Cl,
18.77; N, 7.3%.
´
from the Universite catholique de Louvain.
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