Synthesis of New N-Hydroxy-6-methyluracil-5-carboximidoyl Chloride Derivatives

Article abstract of DOI:10.1134/S1070428019030084

N-Hydroxy-6-methyluracil-5-carboximidoyl chloride was synthesized for the first time, and its halogenation and reactions with amines (imidazole, aniline) were studied. The reaction of the title compound with sodium azide gave the corresponding N-hydroxyca

Full text of DOI:10.1134/S1070428019030084

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2019, Vol. 55, No. 3, pp. 325–329. © Pleiades Publishing, Ltd., 2019.
Russian Text © The Author(s), 2019, published in Zhurnal Organicheskoi Khimii, 2019, Vol. 55, No. 3, pp. 380–385.
Synthesis of New N-Hydroxy-6-methyluracil-5-carboximidoyl
Chloride Derivatives
I. B. Chernikovaa,* I. Z. Sagadatovab, M. S. Yunusova, and R. F. Talipovb
a Ufa Institute of Chemistry, Ufa Federal Research Center, Russian Academy of Sciences,
pr. Oktyabrya 71, Ufa, 450054 Bashkortostan, Russia
*e-mail: inna.b.chernikova@yandex.ru
b Bashkir State University, ul. Zaki Validi 32, Ufa, 450076 Bashkortostan, Russia
Received October 29, 2018; revised November 11, 2018; accepted December 16, 2018
Abstract—N-Hydroxy-6-methyluracil-5-carboximidoyl chloride was synthesized for the first time, and its
halogenation and reactions with amines (imidazole, aniline) were studied. The reaction of the title compound
with sodium azide gave the corresponding N-hydroxycarboximidoyl azide. The Z isomer of the latter was
stable, and it did not undergo isomerization to the E isomer, which prevented transformation to 1-hydroxy-
tetrazole. 6-Methyluracil-5-carbaldehyde oxime was readily acylated at the oxime oxygen atom.
Keywords: 6-methyluracil, carboximidoyl chloride, nucleophilic substitution, azide, nitrile.
DOI: 10.1134/S1070428019030084
Interest in pyrimidine derivatives continuously
increases as their role in biological processes and
practically useful properties have been revealed.
An important research line in the field of chemical
modifications of pyrimidine bases is the development
of simple and efficient methods for the introduction of
functional groups into the heterocycle. Some uracil
derivatives modified at the C5=C6 double bond were
shown to exhibit high pharmacological activity with
a broad spectrum of action. 5-Halouracils constitute
base units of many medicines; they also attract interest
due to the fact that these compounds are produced
in vivo during various inflammatory processes, which
could lead to mutations related to nucleic acid damage
and hence to oncological diseases [1–2]. In view of the
above stated, search for efficient and practical methods
of synthesis of uracil derivatives is an important
problem.
Herein, we report the results of our study on the
synthesis and halogenation of N-hydroxy-6-methyl-
uracil-5-carboximidoyl chloride (3). The reaction of
6-methyluracil-5-carbaldehyde 1 [3] with hydroxyl-
amine hydrochloride in the presence of sodium acetate
gave the corresponding oxime 2 which was subjected
to chlorination with HCl–H2O2 in methylene chloride
at room temperature (3 h) [4]. We thus obtained target-
ed hydroximoyl chloride 3 in 90% yield (Scheme 1).
Compound 3 remained unchanged under the above
oxidative halogenation conditions in a two-phase
system, as well as under the conditions described in
[5]. On the other hand, the chlorination of 3 with
molecular chlorine in chloroform involved the uracil
Scheme 1.
O
O
O
Cl
O
Cl
Cl
CHO
Me
i
ii
iii
HN
HN
HN
NOH
HN
NOH
NOH
95%
90%
85%
Me
OH
O
N
H
O
N
H
Me
O
N
H
Me
O
N
H
1
2
3
4
Reagents and conditions: i: NH2OH·HCl (10 eqquiv), AcONa (12 equiv), H2O, r.t., 5 h; ii: 34% aq. HCl (3 equiv), 33% aq. H2O2
(4 equiv), CH2Cl2, r.t., 3 h; iii: Cl2, CHCl3, r.t., 2.5 h.
325

CHERNIKOVA et al.
zole was observed under these conditions, and the
326
Scheme 2.
initial compound remained unchanged. The presence
of an azido group in molecule 7 was confirmed by the
IR spectrum which displayed a strong absorption band
at 2127 cm–1. Presumably, hydroximoyl azide was
formed as stable Z isomer which failed to isomerize
to the E isomer, so that no 1-hydroxytetrazole was
obtained.
O
X
i or ii
HN
NOH
3
O
N
Me
H
5, 6
5, X = 1H-imidazol-yl (yield 98%); 6, X = PhNH (83%).
Reagents and conditions: i: imidazole (2 equiv), MeOH,
r.t., 5 h; ii: aniline (2 equiv), MeOH, r.t., 8 h.
By treatment of azide 7 with acetic anhydride at
70°C we obtained nitrile 8 as the only product
(Scheme 4), whereas in the reaction of 7 with trifluoro-
acetic anhydride at room temperature the initial com-
pound was recovered from the reaction mixture. We
failed to obtain O-acyl derivatives of 7. Nitrile 8 was
also formed in quantitative yield when compound 7 in
DMF was heated for 2 h at 100°C. The formation of
nitrile 8 from azide 7 is likely to follow a mechanism
outlined in Scheme 4. Tselinskii et al. [8, 9] previously
described the transformation of aromatic hydroximoyl
azides to nitriles.
ring with the formation of 85% of 5-chloro derivative
4 (Scheme 1); no 5-bromo derivative was formed in
the bromination of 3 under similar conditions.
Reaction with amines are the most studied trans-
formations of hydroximoyl chlorides. As might be
expected, compound 3 reacted with imidazole and
aniline to afford the corresponding amide oximes 5 and
6 (Scheme 2).
With the goal of obtaining previously unknown
1-hydroxytetrazoles containing an uracil fragment,
hydroximoyl chloride 3 was treated with sodium azide
in water at room temperature; we thus isolated hy-
droximoyl azide 7 (Scheme 3). It is known that reac-
tions of hydroximoyl chlorides with sodium azide are
stereospecific and that only the Z isomers are obtained
[6]. The Z isomers of hydroximoyl chlorides are fairly
stable, and they do not undergo spontaneous cycliza-
tion to 1-hydroxytetrazoles. On the other hand, by
the action of HCl they readily isomerize to unstable
E isomers which undergo cyclization to 1-hydroxy-
tetrazoles [7–9]. However, no cyclization of 7 to tetra-
In order to obtain a dioxime derivative, hydroxi-
moyl chloride 3 was treated with a solution of hy-
droxylamine hydrochloride in water in the presence of
sodium acetate at room temperature for 5 h; as a result,
N,N′-dihydroxyamidine 9 was formed as a mixture of
syn and anti isomers in an overall yield of 28%
(Scheme 5). By prolonging the reaction time to 20 and
40 h, we succeeded in improving the yield of 9 to 42
and 45%, respectively. Compound 9 failed to undergo
chlorination in a two-phase system.
It is known that aldehyde oximes react with acetic
anhydride to give generally nitriles [10]. However, in
Scheme 3.
N
O
N3
O
N
N
i
N
HN
NOH
HN
3
85%
OH
O
N
H
Me
O
N
H
Me
7
Reagents and conditions: i: NaN3, H2O, r.t., 2 h.
Scheme 4.
HN
:
O
N
O
O
O
CN
Me
ii
i or iii
N
HN
NOH
HN
HN
7
O
N
H
Me
O
N
H
Me
O
N
H
8
Reagents and conditions: i: Ac2O, 70°C, 2 h, yield 51%; ii: (CF3O)2O, r.t., 2 h; iii: DMF, 100°C, 2 h, yield 99%.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 55 No. 3 2019

SYNTHESIS OF NEW N-HYDROXY-6-METHYLURACIL-5-CARBOXIMIDOYL
Scheme 5.
327
proton and carbon signals of the solvent. The IR
spectra were recorded on a Shimadzu IR Prestige-21
spectrometer from samples dispersed in mineral oil.
The atmospheric pressure chemical ionization (APCI)
mass spectra were obtained with a Shimadzu LCMS-
2010 EV instrument [syringe injector, solvent aceto-
nitrile–chloroform, eluent acetonitrile–water (95:5),
flow rate 0.1 mL/min; positive and negative ion
detection, capillary voltage 4.5 kV and –3.5 kV,
respectively; APCI interface temperature 250°C, heater
temperature 200°C, vaporizer temperature 230°C;
interface capillary voltage 25 to –25 V; nebulizer gas
nitrogen, flow rate 2.5 L/min]. Elemental analysis was
performed on a Euro 3000 analyzer. The melting
points were measured in glass capillaries.
O
NHOH
OH
i
ii
HN
N
3
45%
O
N
H
Me
9
Reagents and conditions: i: NH2OH·HCl (1 equiv), AcONa
(2 equiv), H2O, r.t., 40 h; ii: 34% aq. HCl (3 equiv), 33% aq.
H2O2 (4 equiv), CH2Cl2, r.t., 3 h.
some cases, the reaction can be stopped at the stage of
formation of O-acyl derivatives under milder con-
ditions [11]. These cases are typical of syn oximes for
which, in contrast to their anti isomers, 1,2-elimination
is hindered. The acylation of oxime 2 with 3-(1,3-di-
oxo-1,3-dihydro-2H-isoindol-2-yl)propanoyl chloride
afforded 80% of O-acyl derivative, which may be
related to a sufficiently high stability of the syn isomer
of 2 (Scheme 6).
6-Methyl-2,4-dioxo-1,2,3,4-tetrahydropyrimi-
dine-5-carbaldehyde oxime (2). Aldehyde 1, 0.20 g
(1.3 mmol), was added in one portion to a solution of
0.90 g (13 mmol) of hydroxylamine hydrochloride and
1.28 g (15.6 mmol) of sodium acetate in 5.00 mL of
distilled water, and the mixture was stirred for 5 h at
room temperature. The precipitate was filtered off,
washed with distilled water, dried, and recrystallized
from methanol. Yield 0.20 g (95%), white needles,
Scheme 6.
O
N
O
2
+
1
mp >265°C (decomp., from MeOH). H NMR spec-
trum, δ, ppm: 2.30 s (3H, CH3), 7.95 s (1H, CH=N),
10.91 s (1H, NOH), 11.12 s (1H, N1H), 11.22 s (1H,
N3H). 13C NMR spectrum, δC, ppm: 18.93 (CH3),
102.76 (C5), 143.81 (CH=N), 150.44 (C2), 152.62 (C6),
163.59 (C4). Found, %: C 42.50; H 4.08; N 24.98.
C6H7N3O3. Calculated, %: C 42.61; H 4.17; N 24.84.
M 169.14.
Cl
O
4"
O
O
3"
0°C to r.t., 5 h
80%
2'
7"
1"
O
N
1'
4
HN
N
3'
2
6
O
O
O
N
H
Me
N-Hydroxy-6-methyl-2,4-dioxo-1,2,3,4-tetra-
hydropyrimidine-5-carboximidoyl chloride (3).
Oxime 2, 0.20 g (1.2 mmol), was dissolved in 2.00 mL
of methylene chloride, 0.33 mL (3.6 mmol) of
34% aqueous HCl was added with stirring at room
temperature, and 0.48 mL (4.8 mmol) of 33% hydro-
gen peroxide was then added dropwise. The mixture
was stirred for 3 h at room temperature, and the
precipitate was filtered off, washed with distilled
water, dried, and recrystallized from methanol. Yield
0.22 g (90%), white needles, mp >210°C (decomp.,
10
Thus, we have shown that N-hydroxy-6-methyl-
uracyl-5-carboximidoyl chloride is inactive toward
oxidative halogenation and bromination and that its
chlorination with molecular chlorine gives 5-chloro
derivative. 1-Hydroxytetrazole cannot be obtained
from hydroximoyl azide 7 because of the high stability
of the Z isomer of the latter. 6-Methyluracil-5-carb-
aldehyde oxime is readily acylated at the oxime
oxygen atom.
1
from MeOH). H NMR spectrum, δ, ppm: 2.05 s (3H,
EXPERIMENTAL
CH3), 11.15 s (1H, N1H), 11.20 s (1H, N3H), 12.20 s
(1H, NOH). 13C NMR spectrum, δC, ppm: 17.07 (CH3),
106.72 (C5), 129.63 (C=N), 150.75 (C2), 154.46 (C6),
162.31 (C4). Mass spectrum: m/z 166 (Irel 100%)
[M – H – HCl]–. Found, %: C 35.29; H 2.81; Cl 17.55;
N 20.73. C6H6ClN3O3. Calculated, %: C 35.40; H 2.97;
Cl 17.41; N 20.64. M 203.58.
The H and 13C NMR spectra were recorded on
1
a Bruker Avance III spectrometer at 500.13 and
125.76 MHz, respectively (5-mm PABBO Z-gradient
probe, temperature 298 K, solvent DMSO-d6); the
chemical shifts were measured relative to the residual
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 55 No. 3 2019

CHERNIKOVA et al.
(C4). Found, %: C 55.26; H 4.51; N 21.71.
328
5-Chloro-N,6-dihydroxy-6-methyl-2,4-dioxo-
C12H12N4O3. Calculated, %: C 55.38; H 4.65; N 21.53.
M 260.25.
hexahydropyrimidine-5-carboximidoyl chloride (4).
Gaseous chlorine was passed over a period of 30 min
through a solution of 0.20 g (1.0 mmol) of hydroxi-
moyl chloride 3 in 10.00 mL of chloroform, and the
mixture was stirred for 2 h at room temperature. The
precipitate was filtered off, washed with chloroform,
dried, and recrystallized from methanol. Yield 0.21 g
(85%), white needles, mp 143°C (decomp., from
MeOH). 1H NMR spectrum, δ, ppm: 1.55 s (3H, CH3),
8.55 s (1H, N1H), 10.75 s (1H, N3H), 12.80 br.s. (2H,
OH). 13C NMR spectrum, δC, ppm: 24.20 (CH3), 78.62
(C5), 83.22 (C6), 134.32 (C7), 152.35 (C2), 164.67 (C4).
Mass spectrum, m/z (Irel, %): 254 (33) [M – H]–, 218
(100) [M – H – HCl]–. Found, %: C 28.08; H 2.57;
Cl 27.82; N 16.46. C6H7Cl2N3O4. Calculated, %:
C 28.15; H 2.76; Cl 27.69; N 16.41. M 256.04.
(Z)-N-Hydroxy-6-methyl-2,4-dioxo-1,2,3,4-tetra-
hydropyrimidine-5-carboximidoyl azide (7). A mix-
ture of 0.20 g (1.0 mmol) of hydroximoyl chloride 3
and 0.07 g (1.1 mmol) of sodium azide in 2.00 mL of
water was stirred for 5 h at room temperature. The
precipitate was filtered off, washed in succession with
distilled water and acetone, dried, and recrystallized
from methanol. Yield 0.18 g (85%), white needles,
mp 150°C (decomp., from MeOH). IR spectrum, ν,
cm–1: 3143–3328 (NH, OH), 2126 (N3), 1696–1707
(C=O), 1624–1635 (C=N). 1H NMR spectrum, δ, ppm:
2.05 s (3H, CH3), 11.30 br.s (2H, N1H, N3H),
11.40 br.s (1H, OH). 13C NMR spectrum, δC, ppm:
17.39 (CH3), 102.52 (C5), 138.42 (C=N), 150.79 (C6),
155.71 (C2), 163.18 (C4). Mass spectrum, m/z (Irel, %):
209 (23) [M – H]–, 181 (22) [M – H – N2]–, 150 (100)
[M – H2O – N3]–. Found, %: C 34.01; H 3.25; N 39.96.
C6H7N6O3. Calculated, %: C 34.13; H 3.34; N 39.80.
M 211.16.
6-Methyl-2,4-dioxo-1,2,3,4-tetrahydropyrimi-
dine-5-carbonitrile (8). a. A mixture of 0.20 g
(1.7 mmol) of azide 7 and 2.00 mL of acetic anhydride
was stirred for 2 h at 70°C. The mixture was cooled,
and the precipitate was filtered off, washed with
acetone, dried, and recrystallized from water. Yield
0.07 g (51%), beige needles.
b. A mixture of 0.20 g (1.7 mmol) of azide 7 and
2.00 mL of DMF was stirred for 2 h at 100°C. The
mixture was cooled, and the precipitate was filtered
off, washed with acetone, dried, and recrystallized
from water. Yield 0.14 g (99%), beige needles [10].
1H NMR spectrum, δ, ppm: 2.24 s (3H, CH3), 11.65 s
(1H, N1H), 11.95 s (1H, N3H). 13C NMR spectrum, δC,
ppm: 18.41 (CH3), 86.52 (C5), 114.83 (C≡N), 149.73
(C2), 161.17 (C4), 163.73 (C6). Found, %: C 47.52;
H 3.25; N 27.89. C6H5N3O2. Calculated, %: C 47.69;
H 3.33; N 27.81. M 151.12.
5-[(Hydroxyimino)(1H-imidazol-1-yl)methyl]-6-
methylpyrimidine-2,4(1H,3H)-dione (5). A mixture
of 0.20 g (1.0 mmol) of hydroximoyl chloride 3 and
0.14 g (2.0 mmol) of imidazole in 2.00 mL of
methanol was stirred for 5 h at room temperature. The
precipitate was filtered off, washed in succession with
a solution of sodium hydrogen carbonate, distilled
water, and methylene chloride, dried, and recrystal-
lized from methanol. Yield 0.23 g (98%), white
needles, mp >250°C (decomp., from MeOH). 1H NMR
spectrum, δ, ppm: 2.05 s (3H, CH3), 6.90 d (1H, 5′-H,
J = 1.5 Hz), 7.60 d (1H, 4′-H, J = 1.5 Hz), 8.25 s (1H,
2′-H), 11.25 s (1H, N1H), 11.45 s (1H, N3H), 12.65 br.s
(1H, OH). 13C NMR spectrum, δC, ppm: 17.20 (CH3),
104.09 (C5), 119.98 (C5′), 127.94 (C4′), 136.12 (C2′),
138.45 (C=N), 151.14 (C6), 155.40 (C2), 163.19 (C4).
Found, %: C 45.81; H 3.73; N 29.89. C9H9N5O3. Cal-
culated, %: C 45.96; H 3.86; N 29.78. M 235.20.
N′-Hydroxy-6-methyl-2,4-dioxo-N-phenyl-
1,2,3,4-tetrahydropyrimidine-5-carboximidamide
(6). A mixture of 0.20 g (1.0 mmol) of hydroximoyl
chloride 3 and 0.18 mL (2.0 mmol) of aniline in
2.00 mL of methanol was stirred for 8 h at room
temperature. The precipitate was filtered off, washed in
succession with a solution of sodium hydrogen carbon-
ate, distilled water, and methylene chloride, dried, and
recrystallized from methanol. Yield 0.21 g (83%), gray
needles, mp >233°C (decomp., from MeOH). 1H NMR
spectrum, δ, ppm: 1.98 s (3H, CH3), 6.90 t (1H, p-H,
J = 7.7 Hz), 7.15 t (2H, m-H, J = 7.7 Hz), 7.50 d (2H,
o-H, J = 7.7 Hz), 8.30 br.s (2H, NH, OH), 11.05 br.s
(2H, N1H, N3H). 13C NMR spectrum, δC, ppm: 17.31
(CH3), 103.36 (C5), 121.83 (Cp), 123.59 (Co), 129.05
(Cm), 146.27 (C=N), 150.94 (C6), 154.10 (C2), 162.63
(E,Z)-N,N′-Dihydroxy-6-methyl-2,4-dioxo-
1,2,3,4-tetrahydropyrimidine-5-carboximidamide
(9). Hydroximoyl chloride 3, 0.20 g (1.0 mol), was
added in one portion to a solution of 0.07 g (1.0 mmol)
of hydroxylamine hydrochloride and 0.16 g
(2.0 mmol) of sodium acetate in 4.00 mL of distilled
water, and the mixture was stirred for 40 h at room
temperature. The precipitate was filtered off, washed
with distilled water, dried, and recrystallized from
methanol. Yield 0.09 g (45%), gray needles, mp 191°C
1
(decomp., from MeOH). H NMR spectrum, δ, ppm:
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 55 No. 3 2019

SYNTHESIS OF NEW N-HYDROXY-6-METHYLURACIL-5-CARBOXIMIDOYL
329
2.05 s and 2.15 s (3H, CH3), 9.15 br.s (2H, OH),
11.60 br.s (3H, NH, N1H, N3H). 13C NMR spectrum,
δC, ppm: 17.64 and 18.20 (CH3), 92.38 and 92.75 (C5),
150.80 and 150.84 (C4), 158.59 and 160.05 (C=N),
158.86 and 158.88 (C2), 161.28 and 161.57 (C6). Mass
spectrum, m/z (Irel, %): 183 (18) [M – OH]–, 166 (26)
[M – H2O2]–, 150 (100) ([M – H2O2 – NH2]–. Found,
%: C 35.93; H 3.91; N 28.13. C6H8N4O4. Calculated,
%: C 36.00; H 4.03; N 27.99. M 200.15.
(Ufa Federal Research Center, Russian Academy of
Sciences) “Synthesis of Biologically Active Hetero-
cyclic and Terpenoid Compounds” (project no. AAAA-
A17-117011910025-6).
CONFLICT OF INTERESTS
The authors declare the absence of conflict of
interests.
2-[3-({[(6-Methyl-2,4-dioxo-1,2,3,4-tetrahydro-
pyrimidin-5-yl)methylidene]amino}oxy)-3-oxo-
propyl]-1H-isoindole-1,3(2H)-dione (10). A suspen-
sion of 0.25 g (1.5 mmol) of oxime 2 in 10.00 mL of
methylene chloride was cooled to 0–5°C, and a solu-
tion of 0.43 g (1.8 mmol) of 3-(1,3-dioxo-2,3-dihydro-
1H-isoindol-2-yl)propanoyl chloride in 5.00 mL of
methylene chloride was added dropwise. The mixture
was stirred for 2 h at 0–5°C and for 3 h at room
temperature and evaporated to dryness, the residue was
heated for 2 min in 25.00 mL of distilled water under
reflux, the mixture was filtered while hot, and the
precipitate was washed in succession with distilled
water and acetone, dried, and recrystallized from
methanol. Yield 0.44 g (80%), white needles,
mp 198°C (decomp., from MeOH). 1H NMR spectrum,
δ, ppm: 2.40 (3H, CH3), 2.90 t (2H, 2′-H, J = 6.9 Hz),
3.90 t (2H, 3′-H, J = 6.9 Hz), 7.80 m (2H, 5″-H,
6″-H), 7.90 m (2H, 4″-H, 7″-H), 8.35 s (1H, CH=N),
11.50 s (1H, N1H), 11.60 s (1H, N3H). 13C NMR spec-
trum, δC, ppm: 19.69 (CH3), 31.36 (C2′), 33.75 (C3′),
100.18 (C5), 123.52 (C4″, C7″), 132.01 (C3a″, C7a″),
134.87 (C5″, C6″), 150.46 (C6), 152.83 (CH=N), 157.19
(C2), 163.14 (C4), 168.03 (C1″, C3″), 169.02 (C1′).
Found, %: C 55.03; H 3.68; N 15.25. C17H14N4O6.
Calculated, %: C 55.14; H 3.81; N 15.13. M 370.32.
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FUNDING
This study was performed in the framework of
research program of the Ufa Institute of Chemistry
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 55 No. 3 2019