The reaction of 1,2-diones with ureas - A synthesis of 4-(1-substituted)alkylimidazol-2-ones

Article abstract of DOI:10.1071/CH99130

The reaction between glyoxal and ureas or thioureas in formic acid in the presence of sulfmates gives 4-arylsulfonylimidazol-2-ones such as (3b) and (3e). Labile 4-arylsulfonyl-5-hydroxyimidazolidin-2-ones (2a-c) may be isolated. Acyclic or cyclic 1,2-diketones react with ureas in the presence of selected nucleophiles to give side-chain substituted imidazol-2-ones (5a-e). CSIRO 2000.

Full text of DOI:10.1071/CH99130

C S I R O P U B L I S H I N G
Australian Journal
of Chemistry
Volume 53, 2000
© CSIRO Australia 2000
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Aust. J. Chem., 2000, 53, 73–76
Short Communications
The Reaction of 1,2-Diones with Ureas—
a Synthesis of 4-(1-Substituted)alkylimidazol-2-ones
Andris J. LiepaA,B and Denis M. J. WrightA
A CSIRO Molecular Science, Bayview Ave, Clayton, Vic. 3169.
B Author to whom correspondence should be addressed.
The reaction between glyoxal and ureas or thioureas in formic acid in the presence of sulfinates gives 4-arylsul-
fonylimidazol-2-ones such as (3b) and (3e). Labile 4-arylsulfonyl-5-hydroxyimidazolidin-2-ones (2a–c) may be iso-
lated. Acyclic or cyclic 1,2-diketones react with ureas in the presence of selected nucleophiles to give side-chain
substituted imidazol-2-ones (5a–e).
Keywords. Synthesis; ureas; thioureas; imidazolones; diones; glyoxal.
The reaction between 1,2-dicarbonyl compounds and
simple ureas can provide1 an array of condensation products.
In the simplest example, glyoxal is known2 to react with urea
to provide 4,5-dihydroxyimidazolidin-2-one (1a), isolable in
good yield.
roform was sufficient to cause a very rapid and efficient
transformation into the imidazolone (3b). This synthesis
generated only one of the two possible imidazolone prod-
ucts, (3b), with selectivity seemingly arising from a require-
ment to minimize interactions between the two bulky groups.
However, ethylurea, a somewhat less sterically demanding
precursor, likewise gave a single isomer (3c). N.O.e. exper-
iments carried out on (3c) indicated interactions between the
alkene proton and the methylene of the ethyl group provid-
ing verification of the assumed 1,3-disubstitution pattern.
It was further found that 4-ethoxyphenylurea reacted with
glyoxal in warm formic acid to give a mixture of isomers,
presumably (3d) and its regioisomer, in a ratio of approxi-
mately 3: 2. However, regioselectivity was observed from
the same reaction components when they were reacted over
24 h in 30% aqueous acetic acid at room temperature to
afford the intermediate imidazolidinone (2d) as a single
isomer. Asolution of this compound in (D)chloroform for 24
h at room temperature was converted quantitatively into a
single imidazolone isomer (3d).
It seemed likely that reactive intermediates of this kind
might incorporate suitably chosen nucleophiles to afford an
assortment of novel products suitable for biological testing.
Indeed, it has recently been shown3 that (1a) may be reacted
with an arylsulfinic acid to form a labile 4-arylsulfonyl-5-
hydroxyimidazolidin-2-one (2a) which readily dehydrates to
the 4-arylsulfonyl-1,3-dihydroimidazol-2-one (3a).
When t-butylurea was warmed with a solution of aqueous
glyoxal and formic acid in the presence of sodium p-tolue-
nesulfinate for 25 min the imidazolone (3b) was obtained in
82% yield as a single regioisomer. The same components at
room temperature for 7 h in aqueous acetic acid gave the pre-
cursor (2b) analogous to the findings of Shutalev and
Sivova.3
Surprisingly, a solution of (2b) in a mixture of (D6)-
dimethyl sulfoxide and (D)chloroform showed peaks
attributable only to (3b). Despite its origins in dilute acetic
acid, the trace of mineral acid normally present in (D)chlo-
It seemed likely that condensations of this type should
also provide a useful route to imidazolo-2-thiones. Indeed,
reaction was found to occur readily between 1,3-dimethyl-
Manuscript received 29 September 1999
© CSIRO 2000
10.1071/CH99130 0004-9425/00/010073

74
Short Communications
thiourea and glyoxal in aqueous acetic acid containing
sodium p-toluenesulfinate to afford the anticipated imida-
zolo-2-thione (3e) in 70% yield.
It was of additional interest to evaluate the opportunities
for extending the scope of this reaction. Hence pyruvalde-
hyde, the simplest monoketo candidate, was also examined.
A mixture of t-butylurea, pyruvaldehyde and sodium p-tolue-
nesulfinate in aqueous acetic acid gave an acyclic product (4)
in which only the formyl group had reacted. By contrast,
under these conditions glyoxal gave the cyclic 5-hydroxyim-
idazolidinone (2b). Attempts to cyclize (4) under mildly
acidic conditions resulted in extensive decomposition.
With a dialkyl 1,2-diketone, on the other hand, an imida-
zol-2-one (5) is again formed but the nucleophile becomes
attached at the 1-position of one of the alkyl groups during
an anomalous substitution reaction (Scheme 1).
It was evident that the variety of products of type (5)
might easily be increased by using alternative nucleophiles.
Thus it was found that the thiol 2-mercaptopropionic acid
also reacted readily with a mixture of urea and hexane-3,4-
dione to give the expected product (5d).
Urea reacted, albeit slowly, with hexane-3,4-dione in
formic acid containing sodium p-toluenesulfinate to form
one major product. Surprisingly, one of the ethyl groups of
the diketone was transformed into a 1-substituted ethyl
group, bearing the toluenesulfonyl group as a substituent as
in (5a). A proposed sequence of events for the formation of
products of this kind is displayed in Scheme 1.
Benzotriazole has also received wide application as a ver-
satile nucleophile4 under acidic conditions and it also formed
the benzotriazole-substituted product (5e). However, routine
spectroscopic examination of (5e), expected to verify a 1,3-
relationship for the larger substituents as found with the
glyoxal condensations, led to the surprising discovery that
the substituents were, unexpectedly, in adjacent positions.
This was confirmed by n.O.e. experiments which showed an
interaction between the benzotriazole-substituted methylene
with the proximate methylene of the butyl group. Asequence
of events which may account for this unusual substitution is
suggested in Scheme 1.
A monosubstituted urea condenses reversibly with a sym-
metrical diketone to form an acyl imine (a) which can then
cyclize to (b) (Scheme 1). Under the prevailing acidic condi-
tions the cyclized intermediate would readily eliminate
water to form a stabilized N-acyl iminium species5 which in
turn readily loses a proton to form a methylene imidazolone
(d). This intermediate would be expected to be susceptible to
attack by a nucleophile at the methylene terminus to give the
final product (e). A 1,2- rather than the intuitive 1,3-substitu-
tion pattern is a consequence of the proposed mechanism.
This unexpected substitution pattern is in fact observed in
the formation of (5e).
The cyclic 1,2-dione cyclohexane-1,2-dione also partici-
pated in a similar manner in reactions with an N-alkyl-N ´-
arylurea and 1,3-dimethylthiourea to give (6a) and (6b)
respectively.
While this area of chemistry served to provide an inter-
esting variety of compounds for biological testing, none of
them exhibited sufficient activity in primary agrochemical
screens to warrant further investigation.
Likewise, 1,3-dimethylurea reacted with diacetyl
(butane-2,3-dione) in the presence of sodium p-toluenesulfi-
nate, forming (5b), while thiourea gave (5c).
To summarize, it is evident that alternate pathways can
prevail during an apparently simple condensation occurring
between a urea and a 1,2-dicarbonyl compound in the pres-
ence of a suitable nucleophile.
Thus, where the dicarbonyl compound consists of two
aldehyde groups (glyoxal), the initial product is a cyclic imi-
dazolidinone (2) which easily dehydrates and the nucle-
ophile is found attached directly to the resultant imidazolone
ring (3). With a monoaldehyde/monoketone combination
such as pyruvaldehyde the outcome is an acyclic condensa-
tion product (4).

Short Communications
75
n.m.r. δ (CDCl3) 1.56, s, 9H, But; 2.40, s, 3H, ArCH3; 7.05, s, 1H, CH;
7.28, d, J 8.4 Hz, Ar; 7.88, d, J 8.4 Hz, Ar; 11.58, br s, 1H, NH. 13C
n.m.r. δ (CDCl3) 21.6, 28.0, 56.5, 116.1, 120.3, 127.7, 129.9, 137.5,
144.6, 153.9.
1-Ethyl-4-(p-tolylsulfonyl)-1,3-dihydroimidazol-2-one (3c)
This was prepared in a similar manner from sodium p-toluenesulfi-
nate (2 g, 11.2 mmol), glyoxal (1.6 ml) and ethylurea (0.88 g, 10.0
mmol) in formic acid (5 ml, 98%) at 80°C for 15 min and recrystallized
from aqueous methanol gave the product (1.77 g, 66%) as colourless
needles, m.p. 188–190°C (Found: C, 54.2; H, 5.1; N, 10.4.
C12H14N2O3S requires C, 54.1; H, 5.3; N, 10.5%). 1H n.m.r. δ (CDCl3)
1.36, t, J 7.3 Hz, CH2CH3; 2.44, s, CH3; 3.76, q, J 7.3 Hz, CH2CH3;
7.03, s, CH; 7.34, d, J 8.4 Hz, 2H, Ar; 7.91, d, J 8.4 Hz, 2H, Ar; 11.32,
br s, NH. 13C n.m.r. δ (CDCl3) 14.5, 21.6, 38.8, 117.7, 121.3, 127.6,
130.0, 137.5, 144.7, 153.8.
Experimental
Melting points were determined on a Reichert Kofler hot-stage
micro-melting point apparatus and are uncorrected. Microanalyses
were performed by Campbell Microanalytical Laboratory, Otago, New
Zealand. Infrared spectra were recorded on a Perkin Elmer 842 spec-
trophotometer and refer to KBr disks. Proton n.m.r. and 13C n.m.r.
spectra were recorded at 200 and 50.3 MHz respectively on a Bruker
AC-200 spectrometer or at 250 and 62.9 MHz on a Bruker AC250
instrument. Chemical shifts (δ) are measured in ppm. High-resolution
chemical ionization mass spectra were obtained on a Jeol JMS-DX303
mass spectrometer. Low-resolution chemical ionization mass spectra
were obtained on a Micromass Platform II mass spectrometer. Radial
thin-layer chromatography was performed on a Harrison Research
Chromatotron (7924T) using 4-mm thick silica plates (silica gel 60
PF254, Merck No. 7749). Light petroleum refers to the fraction with a
b.p. of 40–60°C.
1-(4-Ethoxyphenyl)-4-phenylsulfonyl-1,3-dihydroimidazol-2-one (3d)
The compound was prepared from 4-ethoxyphenylurea (1.8 g, 10.0
mmol), glyoxal (1.6 ml, 40%) and sodium benzenesulfinate in formic
acid (10 ml, 98%) at 80°C for 15 min and recrystallized from methanol
to give the product (1.94 g, 56%), m.p. 204–206°C (Found: C, 59.1; H,
4.5; N, 8.3. C17H16N2O4S requires C, 59.3; H, 4.7; N, 8.1%). 1H n.m.r.
δ (CDCl3) 1.42, t, J 6.9 Hz, CH3; 4.04, d, J 6.9 Hz, CH2; 6.86, m, 2H,
Ar; 7.23, s, 1H, Ar; 7.40–8.01, m, 6H, Ar; 11.45, br s, NH. 13C n.m.r. δ
(CDCl3) 14.7, 63.8, 115.1, 118.2, 121.6, 124.3, 127.7, 128.1, 129.4,
133.8, 140.0, 152.8, 158.2.
trans-1-t-Butyl-5-hydroxy-4-(p-tolylsulfonyl)imidazolidin-2-one (2b)
1,3-Dimethyl-4-(p-tolylsulfonyl)-1,3-dihydroimidazolo-2-thione (3e)
To a mixture of hydrated sodium p-toluenesulfinate (2 g, 11.2 mmol)
in acetic acid (3 ml) and water (5 ml) containing t-butylurea (1.16 g, 10
mmol) was added a solution of glyoxal in water (1.6 ml, 40%). The
mixture was stirred at room temperature whereupon it became nearly
homogeneous and then rapidly precipitated a copious amount of colour-
less solid. After 7 h the mixture was diluted with water (5 ml), stirred 30
min longer and then filtered and washed on the filter with water to
afford the product as a microcrystalline colourless powder (1.61 g, 51%
based on urea), m.p. 153–155°C (dec.) (Found: C, 53.8; H, 6.5; N, 9.2.
C14H20N2O4S requires C, 53.8; H, 6.5; N, 9.0%). 1H n.m.r. δ ((CD3)2SO)
0.99, s, But; 2.40, s, ArCH3; 4.41, d, J 2.9 Hz, CH; 5.15, d, J 7.7 Hz, CH;
6.69, d, J 7.7 Hz, OH (exch. D2O); 7.47, d, J 8.0 Hz, 2H, Ar; 7.72, d, J
8.0 Hz, 2H, Ar; 8.03, d, J 2.9 Hz, NH (exch. D2O). 13C n.m.r. δ
((CD3)2SO, Bruker AC250) 21.1, 27.6, 51.7, 78.2, 79.3, 129.3, 129.8,
131.8, 145.2, 157.2.
This was obtained from the reaction between 1,3-dimethylthiourea
(1.04 g, 10.0 mmol), glyoxal (1.6 ml, 40%) and sodium p-toluenesulfi-
nate (2.0 g, 11.2 mmol) in formic acid (7 ml, 98%) at 80°C for 1 h.
Recrystallization from methanol gave the product as colourless prisms
(2.2 g, 70%), m.p. 131–133°C (Found: C, 49.5; H, 5.6; N, 8.9%.
1
C12H14N2O2S2·CH3OH requires C, 49.7; H, 5.8; N, 8.9%). H n.m.r. δ
(CDCl3) 2.44, s, ArCH3; 3.41, s, 3H, CH3OH; 3.59, s, NCH3; 3.63, s,
NCH3; 7.35, m, 2H, Ar; 7.48, s, CH; 7.77, m, Ar. 13C n.m.r. δ
(CDCl3/(CD3)2SO) 20.8, 32.0, 34.7, 124.6, 126.6, 126.9, 129.5, 135.7,
144.8, 166.0.
1-t-Butyl-3-[2-oxo-1-(p-tolylsulfonyl)propyl]urea
(4; Ar = 4-MeC6H4)
A mixture of t-butylurea (0.58 g, 5.0 mmol), hydrated sodium p-
toluenesulfinate (1 g, 5.6 mmol), water (2.5 ml) and acetic acid (3 ml)
was stirred at room temperature until it became homogeneous. A solu-
tion of methylglyoxal (1 g, 40% aqueous) was added and the solution
allowed to stand. The product started to separate as colourless needles
within 30 min. After 6 h the mixture was diluted with 70% aqueous
ethanol (5 ml), stirred for 30 min, collected by filtration and washed
lightly with aqueous EtOH on the filter to give colourless needles (0.71
g, 44%). Although the product was colourless when freshly prepared,
within a few days it had acquired a pink coloration. Attempted recrys-
tallization led to decomposition. M.p. 155–157°C (dec.). νmax 1688,
trans-1-(4-Ethoxyphenyl)-5-hydroxy-4-phenylsulfonylimidazolidin-2-
one (2d)
A mixture of sodium benzenesulfinate (2 g, 12.2 mmol), glyoxal
(1.6 ml, 40% aq.), 4-ethoxyphenylurea (1.8 g, 10.0 mmol) and water (5
ml) in acetic acid (9 ml) was stirred for 4 days, diluted with water (20
ml) and stirring continued until crystallization was complete. The
product was collected by filtration to give a single regioisomer as a
colourless powder (2.1 g, 57%) (decomposes upon attempted recrystal-
1
1
1366s cm–1. H n.m.r. δ (CDCl3) 1.00, s, But; 2.34, s, ArCH3; 2.53, s,
lization), m.p. 149–150°C. H n.m.r. δ ((CD3)2SO) 1.29, t, J 6.9 Hz,
CH3; 3.95, q, J 6.9 Hz, 2H, CH2; 4.80, s, 1H, CH; 5.45, s, 1H, CH; 6.80,
d, J 8.4 Hz, Ar; 6.99, d, J 8.4 Hz, Ar; 7.63–7.93, m, 5H, Ar; 8.61, br s,
1H, NH. 13C n.m.r. δ ((CD3)2SO) 14.6, 63.1, 77.6, 80.7, 114.2, 123.5,
129.3, 129.5, 130.1, 134.6, 134.7, 156.0. Mass spectrum m/z 363.3.
CH3; 5.90, d, J 9.51 Hz, CH (exch. D2O); 6.88, d, J 9.51 Hz, NH (exch.
D2O); 7.26, d, J 8.05 Hz, 2H, Ar; 7.73, d, J 8.05 Hz, 2H, Ar. 13C n.m.r.
δ (CDCl3) 21.7, 28.8, 31.1, 50.2, 75.4, 129.77, 129.80, 133.4, 145.6,
153.6, 197.6. High-resolution mass spectrum (Found: m/z, 327.1362.
Calc. for C15H23N2O4S: m/z, 327.1378).
1-t-Butyl-4-(p-tolylsulfonyl)-1,3-dihydroimidazol-2-one (3b)
4-Ethyl-5-[1-(p-tolylsulfonyl)ethyl]-1,3-dihydroimidazol-2-one (5a)
To a solution of hydrated sodium p-toluenesulfinate (2 g, 11.2
mmol) in formic acid (3 ml, 98%) was added a solution of glyoxal in
water (1.6 ml, 40%) followed by t-butylurea (1.16 g, 10.0 mmol). The
homogeneous solution was warmed at 80°C for 5 min, whereupon a
mass of colourless crystals separated, and then left to cool to room tem-
perature. The mixture was diluted with aqueous ethanol (10 ml, 50%),
stirred for 2 h and the precipitate collected by filtration to give the
product as colourless needles (2.1 g, 82%), m.p. 232–234°C (Found: C,
56.8; H, 6.1; N, 9.4. C14H18N2O3S requires C, 57.1; H, 6.2; N, 9.5%). 1H
A mixture of hydrated sodium p-toluenesulfinate (2 g,11.2 mmol),
urea (0.64 g, 13.9 mmol) and hexane-3,4-dione (1.14 g, 8.9 mmol) in
aqueous formic acid (9 ml, 45%) was stirred at room temperature for 2
h and then warmed to 80°C and held at this temperature for 4 h, during
which time the distinct yellow colour of the diketone disappeared. The
solution was cooled to room temperature, diluted with water (2 ml),
stirred until compound began to precipitate and a further portion of
water (2 ml) added.After 4 h the precipitate (1.69 g, 57%) was collected

76
Short Communications
and recrystallized from acetonitrile/ether, m.p. 130–132°C (Found: C,
57.2; H, 6.0; N, 9.5. C14H18N2O3S requires C, 57.1; H, 6.2; N, 9.5%).
1H n.m.r. δ (CDCl3) 0.79, t, J 7.3 Hz, CH2CH3; 1.67, d, J 7.3 Hz,
CHCH3; 1.78–2.05, m, CH2CH3; 2.40, s, ArCH3; 4.04, q, J 7.3 Hz,
CHCH3; 7.29, d, J 8.0 Hz, 2H, Ar; 7.62, d, J 8.0 Hz, 2H, Ar; 9.22, br s,
NH; 10.32, br s, NH. 13C n.m.r. δ (CDCl3) 12.2, 12.6, 16.9, 21.6, 56.6,
109.6, 125.4, 128.8, 129.7, 133.7, 145.1, 155.0.
1-(4-Ethoxyphenyl)-5-methyl-4-(p-tolylsulfonylmethyl)-1,3-
dihydroimidazol-2-one (5f)
This was obtained from 4-ethoxyphenylurea (1.8 g, 10.0 mmol),
butane-2,3-dione (0.86 g, 10.0 mmol) and hydrated sodium p-toluene-
sulfinate (2 g, 11.2 mmol) in formic acid (7 ml, 98%) at 80°C for 2 h.
Recrystallization from aqueous methanol gave the product (2.13 g,
55%), m.p. 244–245°C (Found: C, 62.2; H, 5.5; N, 7.5. C20H22N2O4S
requires C, 62.2; H, 5.7; N, 7.3%). 1H n.m.r. δ ((CD3)2SO) 1.26, s, CH3;
1.34, t, J 7.0 Hz, CH2CH3; 2.41, s, ArCH3; 4.03, q, J 6.9 Hz, CH2CH3;
4.33, s, CH2SO2; 6.92–7.07, m, 4H, NAr; 7.44, d, J 8.0 Hz, 2H, SO2Ar;
7.67, d, J 8.0 Hz, 2H, SO2Ar; 10.02, br s, NH. 13C n.m.r. δ (Bruker
AC250 MHz spectrometer, (CD3)2SO) 8.5, 14.6, 21.1, 52.1, 63.3,
105.0, 114.6, 120.5, 127.4, 128.3, 128.8, 129.7, 135.0, 144.6, 152.6,
157.7.
1,3,4-Trimethyl-5-(p-tolylsulfonylmethyl)-1,3-
dihydroimidazol-2-one (5b)
This was recrystallized from aqueous methanol, m.p. 86–87°C
(Found: C, 56.8; H, 6.5; N, 9.5. C14H18N2O3S requires C, 57.1; H, 6.2;
1
N, 9.5%). H n.m.r. δ (CDCl3) 1.60, s, CH3; 2.43, s, ArCH3; 3.05, s,
NCH3; 3.12, s, NCH3; 4.10, s, CH2; 7.31, d, J 8.0 Hz, 2H, Ar; 7.63, d, J
8.0 Hz, 2H, Ar. 13C n.m.r. δ (CDCl3) 8.3, 21.6 (2×C), 27.6, 52.0, 105.8,
121.1, 128.5, 129.9, 134.7, 145.3, 153.2.
3-Methyl-1-phenyl-4-phenylsulfonyl-1,3,4,5,6,7-hexahydro-
benzimidazol-2-one (6a)
A mixture of sodium benzenesulfinate (1.8 g, 11.0 mmol), cyclo-
hexane-1,2-dione (1.1 g, 9.8 mmol) and 1-methyl-3-phenylurea (1.5
g, 11.2 mmol) in formic acid (10 ml, 98%) was reacted over 7 days at
room temperature. The product (1.37 g, 44%) was recrystallized from
aqueous methanol, m.p. 148–150°C (Found: C, 65.5; H, 5.5; N, 7.5.
C20H20N2O3S requires C, 65.2; H, 5.5; N, 7.6%). νmax 2920, 1690,
4-Methyl-5-(p-tolylsulfonylmethyl)-1,3-dihydroimidazolo-2-
thione (5c)
This was obtained from the reaction between thiourea (0.76 g, 10.0
mmol), butane-2,3-dione (0.86 g, 7.3 mmol) and hydrated sodium p-
toluenesulfinate (2 g, 11.2 mmol) in formic acid (7 ml, 98%) at room
temperature for 6 days. The product (1.88 g, 70%) was recrystallized
from aqueous methanol–ethyl acetate, m.p. 260–262°C (Found: C,
49.4; H, 4.2; N, 10.6. C11H12N2O2S2 requires C, 49.2; H, 4.5; N, 10.4%).
1
1135 cm–1. H n.m.r. δ (CDCl3) 1.59–2.30, m, 3×CH2; 3.33, s, CH3;
4.18, d, J 5.1 Hz, CH; 7.23–7.46, m, 5H, Ar; 7.53–7.73, m, Ar;
7.86–7.91, m, 2H, Ar. 13C n.m.r. δ (CDCl3) 16.8, 20.1, 24.3, 28.7,
58.3, 109.6, 123.7, 126.7, 127.7, 128.9, 129.2, 129.3, 134.1, 134.5,
137.8, 153.3.
1H n.m.r. δ ((CD3)2SO) 1.47, s, CH3; 4.26, s, CH2; 7.61, m, 5H, Ar. 13
n.m.r. δ ((CD3)2SO) 7.9, 51.1, 112.0, 125.7, 128.2, 129.4, 134.2, 137.8,
C
160.1.
1,3-Dimethyl-4-phenylsulfonyl-1,3,4,5,6,7-hexahydrobenzimidazolo-
2-thione (6b)
2-[1-(5-Ethyl-2-oxo-2,3-dihydro-1H-imidazol-4-yl)ethyl-2-
sulfanyl]propionic Acid (5d)
The crude material obtained from the reaction between cyclohex-
ane-2,3-dione (1.1 g, 9.8 mmol), 1,3-dimethylthiourea (1.04 g, 10.0
mmol) and sodium benzenesulfinate (1.8 g, 11.0 mmol) in formic acid
(6 ml, 98%) at 80°C over 6 h was purified by radial chromatography
(eluent CH2Cl2) to afford fawn needles (1.2 g, 39%), m.p 169–171°C
(Found: C, 56.1; H, 5.7; N, 8.6. C15H18N2O2S2 requires C, 55.8; H, 5.6;
N, 8.7%). 1H n.m.r. δ (CDCl3) 1.73–2.49, m, 3×CH2; 3.52, s, CH3; 3.58,
s, CH3; 4.22, d, J 4.75 Hz, CH; 7.54–7.74, m, 3H, Ar; 7.84–7.90, m, 2H,
Ar. 13C n.m.r. δ (CDCl3) 16.4, 19.6, 24.2, 31.6, 33.2, 57.8, 115.4, 128.7,
129.4, 129.9, 134.2, 137.6, 163.4.
This was isolated from the reaction between urea (0.6 g, 10.0
mmol), hexane-3,4-dione (1.14 g, 8.9 mmol) and 2-mercaptopropionic
acid (1.06 g, 10.0 mmol) in formic acid (6 ml, 98%) for 7 days as a 1 : 1
mixture of diastereoisomers (1.53 g), isomer A and isomer B. This was
recrystallized from aqueous methanol, m.p. 195–196°C (Found: C,
49.2; H, 6.4; N, 11.6. C10H16N2O3S requires C, 49.2; H, 6.6; N, 11.5%).
1H n.m.r. δ (CDCl3) 0.43, m, 2×CH3, isomer A and B; 0.59, d, J 7.3 Hz,
CH3, A; 0.70, d, J 6.9 Hz, CH3, B; 0.74, d, J 6.9 Hz, CH3, B; 0.81, d, J
7.3 Hz, CH3, A; 1.67, m, 2×CH2CH3, A and B; 2.31, q, J 7.3 Hz, CH, A;
2.55, q, J 6.9 Hz, CH, B; 3.36–3.48, m, 2×CH, A and B; 9.35, m, 4×NH,
A and B. 13C n.m.r. δ (CDCl3) (isomer A and B) 13.4, 13.7, 16.5, 16.7,
17.6, 19.4, 19.8, 33.3, 34.1, 38.7, 40.0, 115.8, 116.1, 119.6, 120.6,
154.5, 154.7, 174.0, 174.6.
Acknowledgments
We are indebted to DuPont at Stine–Haskell, Delaware,
for testing these compounds for possible crop protection
applications.
5-Benzotriazol-1-ylmethyl-1-butyl-4-methyl-1,3-
dihydroimidazol-2-one (5e)
This was isolated from the condensation between butylurea (1.2 g,
10.3 mmol), benzotriazole (1.6 g, 13.4 mmol) and butane-2,3-dione
(0.86 g, 10.0 mmol) in formic acid (7 ml, 98%) during 7 days.
Recrystallization from aqueous methanol–ethyl acetate gave the product
(0.97 g, 33%) m.p. 139–140°C (Found: C, 62.9; H, 6.6; N, 24.6.
C15H19N5O requires C, 63.1; H, 6.7; N, 24.5%). νmax 1614, 2957, 2871s
cm–1. 1H n.m.r. δ (CDCl3) 0.77, m, CH3; 1.17, m, CH2CH2CH3; 2.30, s,
CH3; 3.47, m, CH2CH2CH2CH3; 5.63, s, CH2N; 7.40, m, 3H, Ar; 8.05,
m, 1H, Ar; 10.66, br s, NH. 13C n.m.r. δ (CDCl3) 9.8, 13.6, 19.8, 31.5,
41.2, 41.9, 109.2, 111.2, 117.9, 120.2, 124.2, 127.8, 132.4, 146.3, 154.0.
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5