Microwave-assisted solid-phase synthesis of 4,5-dihydroxy-1,3-dialkyl-4,5- diarylimidazolidine-2-thione and thiohydantoins

Article abstract of DOI:10.1080/00397911.2010.503000

4,5-Dihydroxy-1,3-dialkyl-4,5-diarylimidazolidine-2-thione are obtained in good yields from the 1:1 addition reaction between benzil derivatives and thiourea derivatives in the solid phase. These compounds undergo smooth rearrangement followed by a hydrogen shift to produce thiohydantoins in excellent yields.

Full text of DOI:10.1080/00397911.2010.503000

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Microwave-Assisted Solid-Phase
Synthesis of 4,5-Dihydroxy-1,3-
dialkyl-4,5-diarylimidazolidine-2-thione
and Thiohydantoins
Mohammad M. Ghanbari a , Gholam H. Mahdavinia b , Javad Safari c ,
Hossein Naeimi c & Mehdi Zare b
a Chemistry Department, Islamic Azad University, Sarvestan Branch,
Sarvestan, Iran
b Chemistry Department & Chemistry Scientific Society, Islamic Azad
University, Marvdasht Branch, Marvdasht, Iran
c Chemistry Department, Kashan University, Kashan, Iran
Published online: 14 Jun 2011.
To cite this article: Mohammad M. Ghanbari , Gholam H. Mahdavinia , Javad Safari , Hossein Naeimi
& Mehdi Zare (2011): Microwave-Assisted Solid-Phase Synthesis of 4,5-Dihydroxy-1,3-dialkyl-4,5-
diarylimidazolidine-2-thione and Thiohydantoins, Synthetic Communications: An International Journal
for Rapid Communication of Synthetic Organic Chemistry, 41:16, 2414-2420
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Synthetic Communications1, 41: 2414–2420, 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.503000
MICROWAVE-ASSISTED SOLID-PHASE SYNTHESIS
OF 4,5-DIHYDROXY-1,3-DIALKYL-4,5-
DIARYLIMIDAZOLIDINE-2-THIONE AND
THIOHYDANTOINS
Mohammad M. Ghanbari,1 Gholam H. Mahdavinia,2
Javad Safari,3 Hossein Naeimi,3 and Mehdi Zare2
1Islamic Azad University, Sarvestan Branch, Chemistry Department,
Sarvestan, Iran
2Islamic Azad University, Marvdasht Branch, Chemistry Department &
Chemistry Scientific Society, Marvdasht, Iran
3Chemistry Department, Kashan University, Kashan, Iran
GRAPHICAL ABSTRACT
Abstract 4,5-Dihydroxy-1,3-dialkyl-4,5-diarylimidazolidine-2-thione are obtained in good
yields from the 1:1 addition reaction between benzil derivatives and thiourea derivatives
in the solid phase. These compounds undergo smooth rearrangement followed by a hydrogen
shift to produce thiohydantoins in excellent yields.
Keywords 5-5-Diarylthiohydantoin; 4,5-dihydroxy-1,3-dialkyl-4,5-diarylimidazolidine-
2-thione; microwave; solid phase
INTRODUCTION
Thiohydantoins and their derivatives represent an important class of bio-
logically active molecules having broad medicinal and agrochemical applications.
Furthermore, many thiohydantoins are responsible for inhibition of fatty acid
hydrolases, glycogen phosphorylases, amylases, and serine proteases.[1–3]
Applications of microwave irradiation in a variety of organic reactions have
rapidly increased as a result of short reaction time and operational simplicity.[4–8]
As part of our current studies on the development of new routes in heterocyclic
Received May 18, 2010.
Address correspondence to Mohammad M. Ghanbari, Department of Chemistry, Islamic Azad
University, Sarvestan Branch, Sarvestan, Iran. E-mail: M.Mehdi.ghanbari@gmail.com
2414

MICROWAVE SYNTHESIS OF THIOHYDANTOINS
2415
Scheme 1. Synthesis of compounds 3 and 4.
Table 1. Solid-phase synthesis of 4,5-dihydroxy-1,3-dialkyl-4,5-diarylimidazolidine-2-thione and
thiohydantoins
Product
Ar
C6H5
R
R0
Yield (%)
Mp (ꢀC)
3a
3b
3c
4a
4b
4c
4d
4e
4f
Me
Me
Et
H
Me
Me
Et
H
95
92
85
98
97
93
96
95
98
90
87
88
146–147
132–133
108–110
229–231
94–96
4-MeC6H4
C6H5
C6H5
4-MeC6H4
2-ClC6H4
4-ClC6H4
2-NO2C6H4
4-NO2C6H4
C6H5
H
H
H
H
135–137
234–236
168–170
265–266
181–182
152–153
183–184
H
H
H
H
H
H
4g
4h
4i
Me
Me
Me
H
4-MeC6H4
4-ClC6H4
H
H
systems,[9–11] we report an efficient synthesis of 4,5-dihydroxy-1,3-dialkyl-4,5-
diarylimidazoliodine-2-thiones 3 and thiohydantoins 4.
The reaction of benzils 1 and thioureas 2 in the presence of sodium hydroxide
(NaOH) leads to dioles 3, which undergo intramolecular reaction in microwave
irradiation to produce 4 in excellent yields (Scheme 1 and Table 1).
RESULTS AND DISCUSSION
The reaction of the benzils 1 with the alkyl thioureas 2 under microwave
irradiation (100 W) in the presence of the sodium hydroxide in the solid phase pro-
ceeded smoothly to afford the target compounds 3 and 4 in 78–98% yield (Scheme 1).
The structures of compounds 3 were confirmed by elemental analyses and infrared
1
1
(IR), H and 13C NMR, and mass spectral data. Thus, the H NMR spectrum of
each of the isolated dioles 3 exhibited OH protons signal at about 3.0–4.5 ppm.
Further evidence was obtained from the 13C NMR spectra, which displayed
N(C)OH carbon resonances at about 90–100 ppm. The mass spectra of 3 displayed
the molecular ion peaks at appropriate m=z values.
Dioles 3 undergo a smooth reaction to produce thiohydantoins 4 (Scheme 1).
Structure 4 was assigned to the isolated products on the basis of their elemental
1
1
analyses and IR, H and 13C NMR, and mass spectral data. Thus, the H NMR
spectrum of each of the isolated products exhibited a NH proton signal(s) at about

2416
M. M. GHANBAIR ET AL.
Scheme 2. Plausible mechanism for the formation of compounds 3 and 4.
9.0–12.5 ppm. Further evidence was obtained from the 13C NMR spectra, which dis-
=
played a C O carbon signal at about 162–175 ppm and C S carbon signal at about
=
180–184 ppm.
Although we have not yet established the mechanism of formation of 3 and 4 in an
experimental manner, a possible explanation is proposed in Scheme 2.[12] Presumably, the
ionic intermediate 5, formed from the sodium hydroxide and the thioureas, is attacked by
1 to produce 5-dihydroxy-1,3-dialkyl-4,5-diarylimidazolidine-2-thione 3. Dioles 3 elimin-
ate water to produce the intermediates 6, which apparently under goes rearrangement fol-
lowed by a hydrogen shift to produce the final products 4 in excellent yields.
In summary, we have prepared novel thiohydantoins via a one-pot reaction
between benzils and thioureas in the presence of a strong base such as sodium
hydroxide. Finally, the proposed procedure for the preparation of thiohydantoin
derivatives is advantageous because of its experimental simplicity, short reaction
time, and excellent yields.
EXPERIMENTAL
Thioureas 2 and sodium hydroxide were obtained from Fluka and were used
without further purification. Benzil 1 was prepared by known methods.[13–15] The
microwave oven used for this work was an ETHOS-MR (800 W, 180 ꢀC) operating
at 2450 MHz. Melting points (uncorrected) were measured on an Electrothermal
9100 apparatus. Elemental analyses for C, H, N, and S were performed using a
Heraeus CHN-O-Rapid analyzer. The experimental data were in good agreement
1
with the calculated values. H and 13C NMR spectra (CDCl3) were measured with
a Bruker DRX-500 Avance spectrometer. IR spectra were recorded on a Shimadzu
IR-460 spectrometer.
General Procedure for the Preparation of Dioles 3
A mixture of 1 mmol of 1 and 2 mmol of 2 was placed into an open glass
container, 0.080 g (2 mmol) of sodium hydroxide was added, and the mixture was

MICROWAVE SYNTHESIS OF THIOHYDANTOINS
2417
irradiated in a microwave oven at a power of 100 W over a period of 1.5 min. The hot
mixture was then poured into ice water, and the precipitate was filtered off. The fil-
trate was acidified with concentrated hydrochloric acid, and the precipitate of 3 was
filtered off, dried for 2 days in a desiccator over calcium chloride, and recrystallized
from ethanol.
Selected Data
4,5-Dihydroxy-1,3-dimethyl-4,5-diphenylimidazolidine-2-thione (3a). White
powder; mp 146–147.5 ꢀC; yield: 0.30 g (95%); IR (KBr) (nmax=cmꢁ1): 3333 (OH),
=
1520 (C C). Anal. calcd. (%) for C17H18N2O2S (314.40): C, 64.94; H, 5.77; N,
1
8.91; S, 10.20. Found: C, 65.10; H, 5.56; N, 8.61; S, 10.51. H NMR (300 MHz,
CDCl3): d ¼ 3.13 (6 H, s, 2 Me), 4.17 (2 H, s, 2 OH), 6.94–7.18 (10 H, m, CH).13C
NMR (75 MHz, CDCl3): d ¼ 30.9 (2 Me), 96.0 (2C), 127.2 (4 CH), 128.4 (4 CH),
=
129.0 (2 CH), 136.1 (2 C), 184.8 (C S).
4,5-Dihydroxy-1,3-dimethyl-4,5-dip-tolylimidazolidine-2-thione (3b). White
=
powder; IR (KBr) (nmax=cmꢁ1): 3335 (OH), 1524 (C C). Anal. calcd. (%) for
C17H18N2O2S (314.4): C, 64.94; H, 5.77; N, 8.91; S, 10.20. Found: C, 64.90; H,
1
5.87; N, 8.86; S, 10.40. H NMR (300 MHz, CDCl3): d ¼ 2.34 (6 H, s, 2 Me), 3.12
(6 H, s, 2 Me), 4.15 (2 H, s, 2 OH), 7.30–7.73 (8 H, m, CH).13C NMR (75 MHz,
CDCl3): d ¼ 21.5 (2 Me), 30.9 (2 Me), 96.0 (2C), 128.2 (4 CH), 129.4 (4 CH),
=
135.0 (2 C), 137.1 (2 C), 184.8 (C S).
4,5-Dihydroxy-1,3-diethyl-4,5-diphenylimidazolidine-2-thione (3c). White
=
powder; IR (KBr) (nmax=cmꢁ1): 3330 (OH), 1515 (C C). Anal. calcd. (%) for
C19H22N2O2S (342.46): C, 66.64; H, 6.48; N, 8.18; S, 9.36. Found: C, 66.10; H,
6.56; N, 8.31; S, 9.71. EIMS: m=z (%) 342 (Mþ, 4), 324 (64), 265 (100), 189 (67),
1
3
165 (38), 77 (33). H NMR (300 MHz, CDCl3): d ¼ 1.33 (6 H, t, JHH ¼ 6.9 Hz,
2 Me), 3.33 (2 H, dt,3JHH ¼ 6.9 Hz, JHH ¼ 12.2 Hz, CH2), 3.92 (2 H, dt, JHH
¼
2
3
6.9 Hz, JHH ¼ 12.2 Hz, CH2), 4.33 (2 H, s, 2 OH), 6.89–7.52 (10 H, m, CH).13C
2
NMR (75 MHz, CDCl3): d ¼ 15.4 (2 Me), 40.2 (2 CH2), 96.8 (2C), 127.5 (4 CH),
=
128.2 (4 CH), 128.7 (2 CH), 136.4 (2 C), 184.0 (C S).
General Procedure for the Preparation of 4
A mixture of 1 mmol of 1 and 0.152 g (2 mmol) of thiourea was placed into an
open glass container, 0.080 g (2 mmol) of sodium hydroxide was added, and the mix-
ture was irradiated in a microwave oven at a power of 100 W over a period of
1.5 min. The hot mixture was then poured into ice water, and the precipitate was
filtered off. The filtrate was acidified with concentrated hydrochloric acid, and the
precipitate of 4 was filtered off, dried for 2 days in a desiccator over calcium chloride,
and recrystallized from ethanol.
Selected Data
5,5-Diphenyl-2-thioxoimidazolidin-4-one (4a, C15H12N2OS). White pow-
der; mp 229–231 ꢀC; yield: 0.26 g (98%); IR (KBr) (nmax=cmꢁ1): 3250 (NH), 1735

2418
M. M. GHANBAIR ET AL.
þ
=
=
(C O), 1524 (C C). EIMS: m=z (%). 268 (M , 100), 239 (62), 180 (98), 104 (69), 77
(70). 1H NMR (300 MHz, CDCl3): d ¼ 6.91–7.82 (10 H, m, CH), 11.10 (1 H, s, NH),
11.82 (1 H, s, NH). 13C NMR (75 MHz, CDCl3): d ¼ 74.2 (C), 127.7 (2CH), 127.9 (4
=
=
CH), 129.5 (4 CH), 131.4 (2 C), 162.6 (C O), 180.5 (C S).
2-Thioxo-5,5-dip-tolylimidazolidin-4-one (4b). White powder; mp 94–
96 ꢀC; yield: 0.29 g (97%); IR (KBr) (nmax=cmꢁ1): 3244 (NH), 1760 (C O), 1520
=
=
(C C). Anal. calcd. (%) for C17H16N2OS (296.10): C, 68.89; H, 5.44; N, 9.45; S,
10.82. Found: C, 68.97; H, 5.36; N, 9.61; S, 10.51. EIMS: m=z (%) 296 (Mþ, 100),
253 (80), 211 (40), 194 (90), 91 (73), 65 (38). 1H NMR (300 MHz, CDCl3):
d ¼ 2.22 (6 H, s, 2 Me), 6.80–7.73 (8 H, m, CH), 11.28 (1 H, s, NH), 12.10 (1 H,
s, NH).13C NMR (75 MHz, CDCl3): d ¼ 21.3 (2 Me), 74.2 (C), 127.9 (4 CH),
=
=
129.5 (4 CH), 135.4 (2 C), 137.7 (2 C), 162.6 (C O), 180.5 (C S).
5,5-Bis(2-chlorophenyl)-2-thioxoimidazolidin-4-one (4c, C15H10N2OSCl2).
Yellow powder; mp 135–137 ꢀC; yield: 0.31 g (93%); IR (KBr) (nmax=cmꢁ1): 3150
1
=
=
(NH), 1750 (C O), 1524 (C C). H NMR (300 MHz, CDCl3): d ¼ 7.27–7.80 (8 H,
m, CH), 11.30 (1 H, s, NH), 12.20 (1 H, s, NH). 13C NMR (75 MHz, CDCl3):
d ¼ 74.6 (C), 127.8 (2 CH), 127.9 (2 CH), 129.5 (2 CH), 129.9 (2 CH), 133.4 (2 C),
=
=
141.4 (2 C), 162.6 (C O), 180.5 (C S).
5,5-Bis(4-chlorophenyl)-2-thioxoimidazolidin-4-one (4d, C15H10N2OSCl2).
White powder; mp 234–236 ꢀC; yield: 0.32 g (96%); IR (KBr) (nmax=cmꢁ1): 3150
1
=
=
(NH), 1690 (C O), 1524 (C C). H NMR (300 MHz, CDCl3): d ¼ 7.27–7.90 (8 H,
m, CH), 11.40 (1 H, s, NH), 12.32 (1 H, s, NH). 13C NMR (75 MHz, CDCl3):
=
d ¼ 77.4 (C), 129.3 (4 CH), 129.9 (4 CH), 131.5 (2 C), 138.4 (2 C), 162.6 (C O),
=
180.8 (C S).
5,5-Bis(2-nitrophenyl)-2-thioxoimidazolidin-4-one (4e). Brown powder;
mp 168–170 ꢀC; yield: 0.34 g (95%); IR (KBr) (nmax=cmꢁ1): 3050 (NH), 1690
=
=
(C O), 1524 (C C). Anal. calcd. (%) for C16H12N4O5S (372.36): C, 51.61; H,
3.25; N, 15.05; S, 8.61. Found: C, 50.92; H, 3.38; N, 15.21; S, 9.11. 1H NMR
(300 MHz, CDCl3): d ¼ 7.20–7.90 (8 H, m, CH), 9.20 (1 H, s, NH), 11.91 (1 H, s,
NH).13C NMR (75 MHz, CDCl3): d ¼ 74.0 (C), 127.2 (2 CH), 129.9 (2 CH), 135.5
=
=
(2 CH), 138.4 (2 C), 148.5 (2 C), 172.6 (C O), 181.5 (C S).
5,5-Bis(4-nitrophenyl)-2-thioxoimidazolidin-4-one (4f). Brown powder;
mp 265–266 ꢀC; yield: 0.35 g (98%); IR (KBr) (nmax=cmꢁ1): 3150 (NH), 1700
=
=
(C O), 1520 (C C). Anal. calcd. (%) for C16H12N4O5S (372.36): C, 51.61; H,
3.25; N, 15.05; S, 8.61. Found: C, 48.98; H, 3.36; N, 15.61; S, 8.41. 1H NMR
(300 MHz, CDCl3): d ¼ 7.27–7.80 (8 H, m, CH), 9.30 (1 H, s, NH), 11.89 (1 H, s,
NH).13C NMR (75 MHz, CDCl3): d ¼ 74.2 (C), 121.7 (4 CH), 129.9 (4 CH), 145.5
=
=
(2 C), 146.4 (2 C), 174.6 (C O), 181.9 (C S).
3-Methyl-5,5-diphenyl-2-thioxoimidazolidin-4-one (4g). White powder;
mp 94–96 ꢀC; yield: 0.25 g (90%); IR (KBr) (nmax=cmꢁ1): 3286 (NH), 1711 (C O),
=
=
1499 (C C). Anal. calcd. (%) for C16H14N2OS (282.36): C, 68.06; H, 5.00; N,
9.92; S, 11.36. Found: C, 67.90; H, 5.06; N, 9.82; S, 11.41. EIMS: m=z (%) 282
(Mþ, 100), 225 (8), 193 (3), 180 (54), 167 (37), 105 (32), 77 (30). 1H NMR
(300 MHz, CDCl3): d ¼ 3.14 (3 H, s, Me), 7.07–7.19 (10 H, m, CH), 7.90 (1 H, s,

MICROWAVE SYNTHESIS OF THIOHYDANTOINS
2419
NH).13C NMR (75 MHz, CDCl3): d ¼ 27.6 (Me), 71.9 (C), 127.0 (2 CH), 128.1 (4
=
CH), 128.7 (4 CH), 138.5 (2 C), 167.6 (C O), 181.5 (C S).
=
3-Methyl-2-thioxo-5,5-dip-tolylimidazolidin-4-one (4h). White powder;
mp 94–96 ꢀC; yield: 0.27 g (87%); IR (KBr) (nmax=cmꢁ1): 3278 (NH), 1682 (C O),
=
=
1501 (C C). Anal. calcd. (%) for C18H18N2OS (310.41): C, 65.65; H, 5.84; N,
9.02; S, 10.33. Found: C, 66.90; H, 5.46; N, 8.61; S, 9.81. EIMS: m=z (%) 310
(Mþ, 100), 295 (2), 281 (8), 267 (11), 253 (11), 219 (23), 91 (27). 1H NMR
(300 MHz, CDCl3): d ¼ 2.36 (6 H, s, 2 Me), 3.33 (3 H, s, Me), 7.07–7.25 (8 H, m,
CH), 8.20 (1 H, s, NH). 13C NMR (75 MHz, CDCl3): d ¼ 22.2 (2 Me), 28.3 (Me),
=
72.5 (C), 127.1 (2 CH), 130.0 (4 CH), 130.7 (4 CH), 138.5 (2 C), 172.0 (C O),
=
183.1 (C S).
5,5-Bis(4-chlorophenyl)-3-methyl-2-thioxoimidazolidin-4-one (4i). White
powder; mp 148–150 ꢀC; yield: 0.31 g (88%); IR (KBr) (nmax=cmꢁ1): 3280 (NH),
=
=
1690 (C O), 1490 (C C). Anal. calcd. (%) for C16H12N2OSCl2 (351.25): C, 54.71;
1
H, 3.44; N, 7.98; S, 9.13. Found: C, 55.90; H, 3.26; N, 7.61; S, 9.81. H NMR
(300 MHz, CDCl3): d ¼ 3.35 (3 H, s, Me), 7.02–7.24 (8 H, m, CH), 8.27 (1 H, s,
NH). 13C NMR (75 MHz, CDCl3): d ¼ 28.8 (Me), 77.0 (C), 129.3 (4 CH), 129.9
=
(4 CH), 131.5 (2 C), 138.4 (2 C), 162.6 (C O), 181.8 (C S).
=
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