The formation of 1,2,4-triazolylimidazolidine-2,4-diones in reactions of 3-aryl-1,2,4-triazin-5(2H)-ones with alkylureas

Article abstract of DOI:10.1023/B:RUCB.0000011873.81934.d0

Recyclization of the addition products of alkylureas to 3-aryl-1,2,4-triazin-5(2H)-ones affording 1,2,4-triazole derivatives was found to occur in Ac₂O.

Full text of DOI:10.1023/B:RUCB.0000011873.81934.d0

Russian Chemical Bulletin, International Edition, Vol. 52, No. 10, pp. 2161—2166, October, 2003
2161
The formation of 1,2,4ꢀtriazolylimidazolidineꢀ2,4ꢀdiones in reactions
of 3ꢀarylꢀ1,2,4ꢀtriazinꢀ5(2H )ꢀones with alkylureas
D. G. Beresnev, G. L. Rusinov,ꢀ A. Yu. Ponomareva, and O. N. Chupakhin
I. Ya. Postovskii Institute of Organic Synthesis, Ural Division of the Russian Academy of Sciences,
20 ul. S. Kovalevskoi, 620219 Ekaterinburg, Russian Federation.
Fax: +7 (343 2) 74 1189. Eꢀmail: chupakhin@ios.uran.ru
Recyclization of the addition products of alkylureas to 3ꢀarylꢀ1,2,4ꢀtriazinꢀ5(2H )ꢀones
affording 1,2,4ꢀtriazole derivatives was found to occur in Ac2O.
Key words: 1,2,4ꢀtriazinꢀ5(2H )ꢀones, ureas, 6ꢀureidoꢀ1,2,4ꢀtriazines, 1,2,4ꢀtriazolylꢀ
imidazolidineꢀ2,4ꢀdiones, 1,2,4ꢀtriazoles, nucleophilic addition to azines.
Scheme 1
Transformations at the unsubstituted carbon atom in
azaaromatic compounds in reactions with nucleophilic
reagents (AN and SN reactions, teleꢀ and cineꢀsubstituꢀ
H
tions) are promising for the modification of the structures
of heterocyclic compounds.1 Reactions of bifunctional
nucleophiles with azines often result in 1,2ꢀcyclization2,3
H
due to tandem processes ANꢀAN, ANꢀSNipso, SNHꢀSN
,
and SNHꢀSNipso. The atom bearing a good leaving funcꢀ
tion (halogen, alkoxy group, etc.) along with the unꢀ
substituted carbon atom is an additional electrophilic cenꢀ
ter. The use of the carbonyl group for annelating a new
ring to the azine ring is less common and is represented by
several examples in the quinoxalinone and cinnolinone
series.4 In the present work, we studied a possibility of
involvement of the carbonyl group of 1,2,4ꢀtriazinꢀ5(2H )ꢀ
ones in the tandem transformations. Urea derivatives preꢀ
viously employed in the syntheses of 6ꢀazapurines acꢀ
cording to an SNHꢀSNipso scheme from 5ꢀmethoxyꢀ1,2,4ꢀ
triazine5,6 were used as dinucleophiles.
Mixtures of organic acids and anhydrides are the most
favorable medium for the reactions of 1,2,4ꢀtriazinꢀ
5(2H )ꢀones with nucleophiles.7,8 These conditions enꢀ
able sufficient activation of the substrate for the nucleoꢀ
philic attack and stabilization of the reaction products.
The reactions of triazinones 1—3 with ureas 4a—c in a
mixture of Ac2O with CF3COOH afford nucleophilic adꢀ
dition products to the unsubstituted C atom of the triꢀ
azine ring 5—7 (Scheme 1).
In the case of N,N´ꢀdimethylurea (4c), adducts 5—7
could not be isolated in the pure state, because their furꢀ
ther transformations occur even at room temperature. The
presence of compounds 5с and 6c can be detected in the
1H NMR spectra of reaction mixtures by the appearance
of the С(6)—H signals at δ 5—6, this region being characꢀ
teristic of the addition products. The reactions of triꢀ
azinones 1—3 with methylꢀ (4а) or propylureas (4b) afꢀ
ford more stable adducts, which were isolated in the anaꢀ
i. Ac2O, CF3COOH.
Ar = Ph (1, 5), 4ꢀTol (2, 6), 2ꢀPy (3, 7);
R1 = H, R2 = Me (a); R1 = H, R2 = Prn (b); R1 = R2 = Me (c)
lytically pure state and characterized. Based on the
1H NMR spectroscopic data, we established that the adꢀ
dition of nonsymmetrical ureas 4а,b occurred regioꢀ
selectively, as should be expected, involving the unꢀ
substituted amino group.
It is noteworthy that the presence of a strong acid, as
well as in other similar cases,7,8 is prerequisite for the
addition of urea. If the reaction is carried out in a mixture
of Ac2O and AcOH, only trace amounts of products 5—7
are detected after 5 h. The dependence of the transformaꢀ
tion rate on the acid strength is related, most probably, to
the fact that it is the protonated 2ꢀacylꢀ1,2,4ꢀtriazinone
formed in situ that is the reacting species. This is conꢀ
firmed by the result of the reaction of 2ꢀacylꢀsubstituted
derivative 8 with urea 4а. Probably, this reaction includes
the formation of unstable adduct 9 containing the acyl
group in position 2 of the triazine ring followed by the
acylotropic rearrangement to more stable 1ꢀacyl derivaꢀ
tive 5а (Scheme 2).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2047—2052, October, 2003.
1066ꢀ5285/03/5210ꢀ2161 $25.00 © 2003 Plenum Publishing Corporation

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Russ.Chem.Bull., Int.Ed., Vol. 52, No. 10, October, 2003
Beresnev et al.
Scheme 2
tion of compounds 5—7 to azapurinone of the type 11
occurs.
Scheme 4
Annelation of the imidazole ring could be expected
for compounds 5—7 on heating, as it has previously been
observed, e.g., for the addition products of ureas to
5ꢀmethoxyꢀ1,2,4ꢀtriazine (Scheme 3).5,6 In this case, the
transformations of adducts 10 included the intramolecuꢀ
lar substitution of the methoxy group to form Nꢀacetyl
derivative 11 followed by elimination of acetaldehyde to
give azapurinone 12.
i. Ac2O, 70 °C → 110 °C.
Starting
comꢀ
Ar
R1
R2
R3
—
Products
(yield (%))
pounds
13—15
16—18
5a
5b
Ph
Ph
H
H
Me
Prn
Me
Prn
Me
Prn
Me
Me
—
16 (40)
16 (13)
17 (52)
17 (22)
18 (12)
—
Ac 13b (20)
—
6a
6b
7a
7b
1, 4c
2, 4c
4ꢀTol
4ꢀTol
2ꢀPy
2ꢀPy
Ph
H
H
H
H
—
Ac 14b (7)
Ac 15a (20)
Ac 15b (26)
Me 13c (46)
Me 14c (44)
Scheme 3
Me
—
—
4ꢀTol Me
It was established that 3ꢀarylꢀ1,2,4ꢀtriazoles 16—18
represent the decomposition products of compounds
13—15: 1,2,4ꢀtriazole 16 identical to that synthesized by
a different method9 was obtained in 61% yield by refluxꢀ
ing individual 5ꢀtriazolylimidazolidineꢀ2,4ꢀdione 13c in
Ac2O (Scheme 5).
Scheme 5
R1, R2 = H, Me
Heating of compounds 5—7 or a mixture of comꢀ
pound 1 (2) with urea 4с in Ac2O at 70—110 °С produces
derivatives of 5ꢀtriazolylimidazolidineꢀ2,4ꢀdione 13—15
and 3ꢀarylꢀ1,2,4ꢀtriazole 16—18 (Scheme 4). No cyclizaꢀ

Reactions of 1,2,4ꢀtriazinꢀ5ꢀones with ureas
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 10, October, 2003
2163
Table 1. Reaction conditions and characteristics of compounds 13—15 and 16—18
Starting
Reaction conditions Proꢀ Yield
M.p.
MS,
compound
ducts
(%)
/°C
m/z (Irel (%))
T/°C
τ/h
5а
5b
70
90
70
90
110
70
90
110
70
90
110
70
10
10
12
10
10
12
10
1
10
10
10
9
16
40
83—85*
201 (25); 172 (4); 159 (100); 130 (4); 118 (41); 104 (7);
91 (5.5); 63 (3.5); 56(29)
13b
20 125—126 341 (27.2); 299 (3); 159 (100); 118 (13); 104 (8);
77 (4); 56 (14)
13
52 103—104 215 (25); 173 (100); 132 (28); 118 (8); 91 (5); 77 (4);
65 (2); 56 (18.5)
16
17
**
**
6а
6b
7а
14b
7
188—190 355 (28); 313 (3); 173 (100); 132 (26); 118(10);
91 (8); 56 (17)
***
88—89
17
15а
22
20
***
314 (84); 272 (35); 160 (100); 132 (51); 119 (5); 105 (30);
91 (11); 78 (31.5); 64 (10); 56 (11)
202 (23); 160 (100); 132 (49); 119 (6); 105 (23); 91 (12);
78 (29); 64 (7); 56 (11)
342 (29); 300 (9); 160 (100); 132 (43); 119 (6); 105 (26);
91 (9); 78 (16); 64 (7); 56 (17)
90
15
18
12
26
105
7b
70
90
110
15
10
10
15b
78—80
* The m.p. of triazole 16 coincides with the published data.9
** The m.p. and mass spectrum are identical to the corresponding characteristics for compound 16 obtained from
compound 5а.
***The m.p. and mass spectrum are identical to the corresponding characteristics for compound 17 obtained from
compound 6а.
The ratio of the transformation products of ureidoꢀ
triazines 5—7 depends on both the substituents in the
triazine ring (Ar) and the substituents in the ureido fragꢀ
ment (R1 and R2) (Scheme 1, Table 1). The presence of
either the pyridyl substituent in the triazole ring or two
methyl groups (R2 and R3) in the imidazolidine fragment
favor stabilization of 5ꢀtriazolylimidazolidineꢀ2,4ꢀdiones
13—15. For example, for R2 = R3 = CH3, after complete
conversion of the substrate, 1,2,4ꢀtriazoles 16 and 17 are
not yet formed: their formation requires prolonged (up to
15 h) refluxing in Ac2O.
of 6ꢀazapurines5,6 11 (isomers of compounds 13—15),
which can also be formed in the reaction. The NMR
spectra of compounds 11 and 13—15 differ only in the
values of chemical shifts of the resonance signals. In parꢀ
ticular, the signals of protons at the sp3ꢀC atom of the
heterocyclic system of compounds 13—15 exhibit the
downfield shift of 1.0—1.5 ppm compared to the correꢀ
sponding signals of the isomeric azapurines 11 (R1 = Me,
Ac; R2 = Me, Prn).
The structures of the resulting compounds were proved
on the basis of NMR and mass spectroscopic data. The
most characteristic resonance signal in the 1H NMR specꢀ
tra of ureidotriazines 5a,b—7a,b is the signal of C(6)H at
δ 5.7—6.0 in the form of a doublet with a spinꢀspin couꢀ
pling constant of 6.4—7.2 Hz. The spinꢀspin coupling of
the С(6)H protons of the triazine ring and NH group of
the ureido substituent in compounds 5—7 indicates that
the addition to 1,2,4ꢀtriazinꢀ5(2H )ꢀones involves the
unsubstituted amino group of urea (Table 2).
The 1H NMR spectra of 5ꢀtriazolylimidazolidineꢀ
2,4ꢀdiones 13—15 exhibit resonance signals of the aroꢀ
matic substituent and threeꢀproton singlets of the methyl
and acetyl groups, the proton at Csp3, and the R2 subꢀ
stituent (Table 3). A similar set of signals is characteristic
The proof of structures of compounds 13—15 was
based on the interpretation of their mass spectra
(Scheme 6). In the case of compound 11, the molecular
ion loses one (for R1 = Me) or two (for R1 = Ac) acetyl
groups upon fragmentation.6 The mass spectra of syntheꢀ
sized compounds 13, 14b, and 15a,b contain the peak of
the [М – 42]+ fragment corresponding to the loss of only
one acetyl group. The [М – 42]+ peak was not detected in

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Russ.Chem.Bull., Int.Ed., Vol. 52, No. 10, October, 2003
Beresnev et al.
Table 2. Data of the 1H NMR spectra of ureidotriazines 5—7 (400 MHz, DMSOꢀd6)
Comꢀ
pound
δ (J/Hz)
NHtriazole
С(6)—H
Ar
Ac
(s, 3 H) (br.s, 1 H)
6ꢀR
5а
5b
5.80 (d, 1 H, J = 7.1)
5.81 (d, 1 H, J = 7.2)
7.87—7.89 (m, 2 H);
7.41—7.49 (m, 3 H)
7.87—7.89 (m, 2 H);
7.41—7.49 (m, 3 H);
2.31
2.31
11.28
11.28
7.17 (d, 1 H, J = 7.1); 5.79 (q, 1 H, J = 4.6);
2.54 (d, 3 H, J = 4.6)
7.06 (d, 1 H, J = 7.2); 5.9 (t, 1 H, J = 5.6);
2.87—2.92 (m, 2 H); 1.32—1.39 (m, 2 H);
0.83 (t, 3 H, J = 7.6)
6а
6b
7а
5.93 (d, 1 H, J = 7.2);
5.93—5.97 (m, 2 H)*
5.76 (d, 1 H, J = 6.8)
7.78 (d, 2 H, J = 8.4);
7.29 (d, 2 H, J = 8.4);
2.29 (s, 3 H)
7.78 (d, 2 H, J = 8.4);
7.29 (d, 2 H, J = 8.4);
2.28 (s, 3 H);
2.36
2.36
2.35
11.3
11.31
10.28
7.24 (d, 1 H, J = 7.2); 5.82 (q, 1 H, J = 3.7);
2.48 (d, 3 H, J = 3.7)
7.12 (d, 1 H, J = 7.2); 5.93—5.97 (m, 2 H);
2.85—2.89 (m, 2 H); 1.29—1.34 (m, 2 H);
0.78 (t, 3 H, J = 7.4)
7.26 (d, 1 H, J = 6.8); 5.84 (q, 1 H, J = 4.5);
2.51 (d, 3 H, J = 4.5)
8.65 (dd, 1 H,
J = 1.7; 4.8);
8.12 (d, 1 H, J = 8.1);
7.94 (ddd, 1 H,
J = 1.7; 8.1; 7.8);
7.52 (ddd, 1 H,
J = 0.9; 4.8; 7.8)
8.64 (d, 1 H, J = 4.6);
8.12 (d, 1 H, J = 8);
7.93 (ddd, 1 H,
7b
5.74 (d, 1 H, J = 6.4);
2.35
10.28
7.15 (d, 1 H, J = 6.4); 5.95 (t, 1 H, J = 5.6);
2.84—2.89 (m, 2 H); 1.32—1.38 (m, 2 H);
0.82 (t, 3 H, J = 7.5)
J = 1.3; 7.7; 8.0);
7.51 (ddd, 1 H,
J = 0.9; 4.6; 7.7)
* The С(6)—H signal is overlapped with the NH signal of the ureido substituent.
the mass spectra of compounds 13с and 14c, which makes
it possible to make choice in favor of the structure of
5ꢀtriazolylimidazolidineꢀ2,4ꢀdione.
The fragmentation of the molecular ion of compounds
13с and 14с and the [М – 42]+ ion of compounds 13b,
14b, and 15a,b (see Scheme 6) is accompanied by the
1
Table 3. Data of the H NMR spectra of compounds 13—15 (400 MHz, DMSOꢀd6)
Comꢀ
pound
δ (J/Hz)
СH
Ar
R2; R3; Me
(s, 1 H)
13b
14b
15а
6.66
6.67
6.72
8.00—7.90 (m, 2 H); 7.38—7.47 (m, 3 H)
3.46—3.68 (m, 2 H); 2.68, 2.49 (both s, 3 H each);
1.56—1.92 (m, 2 H); 0.96—1.2 (m, 3 H)
3.54—3.63 (m, 2 H); 2.71, 2.56 (both s, 3 H each);
1.72—1.77 (m, 2 H); 1.03 (t, 3 H, J = 7.4)
3.14, 2.7, 2.5 (all s, 3 H each)
7.79, 7.17 (both d, 2 H each, J = 8.0);
2.47 (s, 3 H)
8.59 (dd, 1 H, J = 1.8; 4.8);
8.01 (dd, 1 H, J = 1.1; 8.1);
7.82 (ddd, 1 H, J = 1.8; 8.1; 7.7);
7.35 (ddd, 1 H, J = 1.1; 4.8; 7.7)
8.59 (dd, 1 H, J = 0.8; 4.8);
7.97 (d, 1 H, J = 8.0); 7.81 (ddd, 1 H,
J = 0.8; 8.0; 7.7); 7.35 (ddd, 1 H,
J = 1.1; 4.8; 7.7)
15b
6.75
3.56—3.61 (m, 2 H); 2.7, 2.5 (both s, 3 H each);
1.7—1.75 (m, 2 H); 1.01 (t, 3 H, J = 7.4)
13c
14c
6.38
6.42
7.95—7.97 (m, 2 H); 7.37—7.42 (m, 3 H)
7.81, 7.17 (both d, 2 H each, J = 8.2);
2.32 (s, 3 H)
3.04, 2.8, 2.59 (all s, 3 H each)
3.00, 2.77, 2.57 (all s, 3 H each)

Reactions of 1,2,4ꢀtriazinꢀ5ꢀones with ureas
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 10, October, 2003
2165
Scheme 6
elimination of the imidazole ring and formation of 3ꢀarylꢀ
1,2,4ꢀtriazole ions, whose peak in all spectra, except for
that of 13c, are characterized by the maximum intensity.
The fragmentation of this ion occurs according to the
scheme characteristic of triazoles.
Considering the recyclization mechanism and reasons
for the different behavior of 5ꢀmethoxyꢀ and 5ꢀoxo deꢀ
rivatives of 1,2,4ꢀtriazines, one may conclude that the
primary annelation of the imidazole ring occurs in both
cases (Scheme 7). In the case of 5ꢀmethoxyꢀ1,2,4ꢀtriꢀ
azines, σipsoꢀadduct 19 (R = Me) is stabilized by eliminaꢀ
tion of methanol, whereas for the 5ꢀoxo derivatives
(R = H) the triazine ring is cleaved followed by the inꢀ
tramolecular cyclization of intermediate 20 involving the
acyl group. Under more drastic conditions, compounds
13—15 undergo destruction to form 1,2,4ꢀtriazoles 16—18
and imidazolinediones 21.
The formation of imidazolinedione 21 (R2 = Prn) was
detected upon heating of ureidotriazine 7b in Ac2O. The
mass spectrum of compound 21 contains the peak of the
1
molecular ion m/z 242. The H NMR spectrum exhibits
resonance signals of the propyl substituent: of the methylꢀ
ene groups as multiplets at δ 3.38—3.48 and 1.58—1.64
and of the methyl group as a triplet at δ 0.92 (J = 7.4 Hz),
threeꢀproton singlets at δ 2.43 and 2.09, and a singlet of
the proton at δ 6.53.
Thus, we can state that, unlike 5ꢀmethoxyꢀ1,2,4ꢀtriꢀ
azine, 5ꢀoxo derivatives react with ureas with annelation
of the imidazole ring and subsequent recyclization of the
triazine system with ring contraction.
Scheme 7

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Russ.Chem.Bull., Int.Ed., Vol. 52, No. 10, October, 2003
Beresnev et al.
Table 4. Reaction conditions and characteristics of compounds
5a,b—7a,b
Experimental
The course of reactions and purity of the synthesized prodꢀ
ucts were monitored by TLC on plates with a fixed layer of
ARMSORB KSGKꢀUF using dichloromethane—methanol
(30 : 1) as the eluent and detection in the UV light. Lancaster
silica gel (230—400 mesh) was used for preparative column chroꢀ
matography. 1H NMR spectra were obtained on a Bruker
DRX 400 instrument (400 MHz) using Me4Si as the internal
standard. Mass spectra were recorded on a Varian MAT 311ꢀA
instrument with the FD/EI combined source (direct inlet of a
sample in the ion source, energy of ionizing electrons 70 eV).
Elemental analysis was carried out on a Carlo Erba 1108 anaꢀ
lyzer. Melting points were determined on a Boetius stage and
were not corrected.
Comꢀ
pound
τ/h Yield
M.p.
/°C
Found
Calculated
(%)
N
(%)
С
H
5а
5b
6а
6b
7а
7b
4
67
79
76
76
45
41
196—198
224—226
220—223
202—204
222—225
236—237
53.79 5.12 24.15
53.98 5.22 24.21
56.57 6.11 22.02
56.77 6.03 22.07
55.32 5.54 22.97
55.44 5.65 23.09
57.87 6.21 21.02
57.99 6.39 21.13
49.27 4.62 28.16
49.65 4.86 28.95
52.84 5.83 26.41
52.83 5.70 26.40
2
3
3
The starting triazinones 1—3 have been synthesized by a
previously described method.10
2.5
2
1ꢀAcetylꢀ6ꢀalkylureidoꢀ3ꢀarylꢀ1,4,5,6ꢀtetrahydroꢀ1,2,4ꢀ
triazinꢀ5ꢀones (5—7a,b) (general procedure). A mixture of 3ꢀarylꢀ
1,2,4ꢀtriazinꢀ5(2H )ꢀone10 (0.6 mmol), urea (0.6 mmol), Ac2O
(2 mL), and CF3COOH (0.06 mL) was stirred at ∼20 °C. The
precipitate that formed was filtered off, washed with diethyl
ether, and dried in air. The duration of the reaction, yields,
m.p., and elemental analysis data of compounds 5a,b—7а,b are
presented in Table 4.
1ꢀAcetylꢀ6ꢀ(3ꢀmethylureido)ꢀ3ꢀphenylꢀ1,4,5,6ꢀtetrahydroꢀ
1,2,4ꢀtriazinꢀ5ꢀone (5a). A solution of 1ꢀacetylꢀ3ꢀphenylꢀ1,2,4ꢀ
triazinꢀ5(2H )ꢀone (8)10 (50 mg, 0.23 mmol) and Nꢀmethylurea
(4a) (17 mg, 0.23 mmol) in CF3COOH (2 mL) was kept at
∼20 °C for 4 days. The solvent was removed in vacuo, and the
residue was triturated with diethyl ether and recrystallized from
methanol. The yield was 36 mg (54%). The product was identiꢀ
cal to the sample of 5а obtained as described above.
1ꢀAcetylꢀ5ꢀmethylꢀ3ꢀphenylꢀ1,2,4ꢀtriazole (16). A solution
of 1,3ꢀdimethylꢀ5ꢀ(5ꢀmethylꢀ3ꢀphenylꢀ1,2,4ꢀtriazolꢀ1ꢀyl)imidꢀ
azolidineꢀ2,4ꢀdione (13с) (28 mg, 0.1 mmol) in Ac2O (1 mL)
was refluxed for 15 h, the solvent was removed in vacuo, and
the residue was recrystallized from methanol. The yield was
12 mg (61%). The product was identical to triazole 16 syntheꢀ
sized by another method.
This work was financially supported by the Russian
Foundation for Basic Research (Project Nos. 02ꢀ03ꢀ32627
and 00ꢀ03ꢀ32721) and the International Scientific Techꢀ
nical Center (Project No. 708).
5ꢀ(3ꢀArylꢀ5ꢀmethylꢀ1,2,4ꢀtriazolꢀ1ꢀyl)ꢀ1,3ꢀdimethylimidꢀ
azolidineꢀ2,4ꢀdiones (13c, 14c). A mixture of 3ꢀarylꢀ1,2,4ꢀ
triazinꢀ5(2H )ꢀone (1 or 2) (0.6 mmol) and N,N´ꢀdimethylurea
(4c) (0.6 mmol, 53 mg) was heated to 70 °С in Ac2O (3 mL) and
stirred at this temperature for 6 h. Then the mixture was heated
for 2.5 h at 90 °С and for 4 h at 110 °С. The solvent was
evaporated, and the resulting yellow oil was chromatographed
on a column with silica gel (CH2Cl2—MeOH (30 : 1) as the
eluent) and recrystallized from methanol.
Compound 13c. The yield was 46%, m.p. 183—184 °С.
Found (%): C, 57.10; H, 4.97; N, 23.63. C14H15N5O2. Calcuꢀ
lated (%): С, 58.94; H, 5.30; N, 24.55. MS, m/z (Irel(%)): 285
(31), 159 (9), 127 (100), 118 (9), 104 (12), 91 (6), 77 (13), 56 (14).
Compound 14c. The yield was 44%, m.p. 180—182 °С.
Found (%): С, 59.76; H, 6.10; N, 23.15. C15H17N5O2. Calcuꢀ
lated (%): С, 60.19; H, 5.72; N, 23.40.
1ꢀAcetylꢀ3ꢀalkylꢀ5ꢀ(3ꢀarylꢀ5ꢀmethylꢀ1,2,4ꢀtriazolꢀ1ꢀyl)imidꢀ
azolidineꢀ2,4ꢀdiones (13b, 14b, 15a,b) and 1ꢀacetylꢀ3ꢀarylꢀ5ꢀ
methylꢀ1,2,4ꢀtriazoles (16—18) (general procedure). Ureidoꢀ
triazines 5a,b—7а,b were heated in Ac2O with gradual inꢀ
crease in the temperature from 70 to 110 °С (temperatures and
duration of heating are indicated in Table 1). The solvent was
removed in vacuo, and the resulting oil was chromatographed
on a column with silica gel (CH2Cl2—MeOH (30 : 1) as the
eluent). 1,2,4ꢀTriazoles 16—18 were eluted first, and then comꢀ
pounds 13—15 were eluted (see Table 1). In the case of 7b,
5ꢀacetoxyꢀ1ꢀacetylꢀ3ꢀpropylimidazolineꢀ2,4ꢀdione 21 was also
isolated (5%).
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Received May 3, 2003;
in revised form September 2, 2003