Synthesis of 2-aryl-6H,7H-[1,3]oxazolo[5,4-d]pyrimidine-7-thione and 2-aryl-6H,7H-[1,3]thiazolo[5,4-d]pyrimidine-7-thione using 2- aroylaminomalonodiamide

Full text of DOI:10.1134/S1070363213030298

ISSN 1070-3632, Russian Journal of General Chemistry, 2013, Vol. 83, No. 3, pp. 572–576. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © A.O. Gurenko, O.V. Shablykin, V.S. Brovarets, 2013, published in Zhurnal Obshchei Khimii, 2013, Vol. 83, No. 3, pp. 521–524.
LETTERS
TO THE EDITOR
Synthesis of 2-Aryl-6H,7H-[1,3]oxazolo[5,4-d]pyrimidine-7-thione
and 2-Aryl-6H,7H-[1,3]thiazolo[5,4-d]pyrimidine-7-thione
Using 2-Aroylaminomalonodiamide
A. O. Gurenko, O. V. Shablykin, and V. S. Brovarets
Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine,
ul. Murmanskaya 1, Kiev, 02660 Ukraine
e-mail: brovarets@bpci.kiev.ua
Received October 18, 2012
DOI: 10.1134/S1070363213030298
Oxazolo- and thiazolopyrimidines have a biological
significance, since they are the structural analogs and
antagonists of purine bases. Among them substances
were found, which inhibit enzymes [1, 2] and possess
fungicidal [3] and antiviral [4] activity.
165.85 ppm, respectively. The signal of the pyrimidine
carbon atom bonded to the chlorine atom is observed
in the range of 153.63–154.02 ppm. The treatment of
compounds IVa–IVc with sodium hydrosulfide in
ethanol at 50°C gives rise to 2-aryl-6H,7H-[1,3]oxa-
zolo[5,4-d]pyrimidine-7-thiones Va–Vc. A charac-
teristic feature of the 13C NMR spectra of these com-
pounds is an appearance of the signal of the C=S
moiety in the range of 176.33–176.65 ppm.
There are two strategic approaches to construct the
azolopyrimidine system: via cyclization of the
pyrimidine ring on an azole or by fusion of azole ring
with the pyrimidine. In this work we used two
approaches using 2-aroylaminomalonodiamides Ia–Ic
as the starting materials [5]. In this case, the target
products were 2-aryl-6H,7H-[1,3]oxazolo[5,4-d]pyri-
midine-7-thiones Va–Vc and 2-aryl-6H,7H-[1,3]thi-
azolo[5,4-d]pyrimidine-7-thiones VIa–VIc. The reac-
tions sequence I→II→IV→V has as the initial reac-
tion that of 2-aroylaminomalonodiamides Ia–Ic with
ethyl formate in the presence of sodium ethoxide to
form 5-aroylamino-6-hydroxypyrimidin-4-ones IIa–
IIc. The 13C NMR spectra of these compounds contain
the characteristic signals of the C5 and C6 atoms of the
pyrimidine ring in the ranges of 102.87–103.34 and
The boiling of 2-aroylaminomalonodiamides Ia–Ic
with 2 eq of phosphorus pentasulfide in pyridine leads
to sulfurization of the amide groups and
heterocyclization into 5-amino-2-aryl-1,3-thiazol-4-
carboxthioamides IIIa–IIIc. The structure of the latter
was proved by the spectral data (appearance of two
singlets of thioamide groups in the range of 8.78–8.94
ppm in the 1H spectra and the presence of the signal of
thiourea group at δC 183.90–187.29 ppm in the 13C
NMR spectra) and their conversion into 2-aryl-6H,7H-
[1,3]thiazolo[5,4-d]pyrimidine-7-thiones VIa–VIc via
the boiling in triethylorthoformate.
1
165.75–165.85 ppm, respectively. In the H NMR
1
The H and 13C NMR spectra of compounds VIa–
spectra there are no signals of the primary amide
groups, and the singlet of С2H proton appears in the
range of 8.04–8.07 ppm.
VIc contain the same characteristic signals that in the
spectra of 2-aryl-6H,7H-[1,3]oxazolo-[5,4-d]pyrimi-
1
dine-7-thiones Va–Vc. Thus, in the H NMR spectra
The subsequent fusion of the five-membered oxa-
zole ring was performed by boiling 5-aroylamino-6-
hydroxypyrimidin-4-ones IIa–IIc in an excess of phos-
phorus oxychloride to give 2-aryl-7-chloro[1,3]oxa-
zolo[5,4-d]pyrimidines in 57–79% yields. In the 13C
NMR spectra the signals of the C5 and C6 atoms are
shifted downfield to 130.08–130.63 and 165.75–
there is the signal of the C2H proton of pyrimidine
fragment at 8.24–8.30 ppm, and the 13C NMR
spectrum contains the signals of the C=S moiety at δC
177.20–177.57 ppm.
Thiazolopyrimidines VIa–VIc were also obtained
by the reaction of phosphorus pentasulfide with 5-
572

SYNTHESIS OF 2-ARYL-6H,7H-[1,3]OXAZOLO[5,4-d]PYRIMIDINE-7-THIONE
573
O
H
N
O
H
N
S
NH2
NH2
Ar
N
S
HC(O)OEt
P2S5
NH
NH2
NH2
Ar
Ar
O
O
O
HO
IIа−IIc
N
Iа−Ic
IIIа−IIIc
P2S5
POCl3
HC(OEt)3
S
Cl
S
N
N
O
N
S
NaSH
EtOH
NH
N
NH
Ar
Ar
Ar
O
N
N
N
Vа−Vc
IVа−IVc
VIа−VIc
Ar = Ph (а), 4-MeC6H4 (b), 4-ClC6H4 (c).
aroylamino-6-hydroxypyrimidin-4-ones IIa–IIc in 10–
15% yields. The identity of the products VIa–VIc
obtained via the transformations II→VI and III→VI
was proved by comparing their IR and NMR spectra.
trum, δС, ppm: 103.15, 128.18, 128.68, 131.82, 134.64,
147.87, 154.18, 162.76, 165.79. Mass spectrum, m/z:
232 [M + 1]+. Found, %: C 57.28, H 3.81; N 18.09.
C11H9N3O3. Calculated, %: C 57.14; H 3.92; N 18.27.
M 231.
The structure of the obtained compounds is also
consistent with the data of elemental analysis and gas
chromatography-mass spectrometry. In addition, com-
pounds IVa, Va, VIa have been previously obtained
[6, 7].
5-(4-Methylbenzoylamino)-6-hydroxypyrimidin-
4-one (IIb). Yield 69%, mp 247–248°C. IR spectrum,
ν, cm–1: 1537, 1648, 2597, 3050, 3193, 3340, 3394. 1Н
NMR spectrum, δН, ppm: 2.37 s (3Н, CH3), 7.29 d
(2Н, С6H4, J 7.5 Hz), 7.86 d (2Н, С6H4, J 7.5 Hz), 8.04
s (1Н, CH), 9.13 s (1Н, NH). 13С NMR spectrum, dС,
ppm: 21.48, 103.34, 126.11, 128.21, 129.22, 129.96,
131.87, 141.70, 147.72, 168.91. Mass spectrum, m/z:
246 [M + 1]+. Found, %: C 58.51; H 4.40; N 17.29.
C12H11N3O3. Calculated, %: C 58.77; H 4.52; N 17.13.
M 245.
Thus, we demonstrated that the available 2-aroyl-
aminomalonodiamides can be used in the synthesis of
oxazolo- and thiazolo[5,4-d]pyrimidines, among which
it is possible to look for biologically active compounds.
5-Aroylamino-6-hydroxypyrimidin-4-ones (IIa–
IIc). To a solution of 4.60 g (0.20 mol) of sodium in
150 ml of anhydrous ethanol was added 0.10 mol of 2-
aroylaminomalonodiamide Ia–Ic and 18.56 ml (0.23 mol)
of ethyl formate. The mixture was heated with stirring
for 2 h. Then ethanol was evaporated in a vacuum, and
to the residue was added water (100 ml). The un-
reacted 2-aroylaminomalonodiamide Ia–Ic was filtered
off. The filtrate was acidified with hydrochloric acid to
pH 5, the formed precipitate was filtered off, and
compounds IIa–c were analyzed without further
purification.
5-(4-Chlorobenzoylamino)-6-hydroxypyrimidin-
4-one (IIс). Yield 58%, mp 258°C. IR spectrum, ν,
1
cm–1: 1546, 1648, 2597, 3059, 3332. Н NMR spec-
trum, δН, ppm: 7.57 d (2Н, С6H4, J 6.8 Hz), 7.97 d
(2Н, С6H4, J 6.8 Hz), 8.06 s (1Н, CH), 9.31 s (1Н,
NH), 12.05 br. s (2H, NH, OH). 13С NMR spectrum,
δС, ppm: 102.87, 128.79, 129.38, 130.09, 133.50,
136.63, 147.93, 162.83, 164.75. Mass spectrum, m/z:
266 [M]+. Found, %: C 49.98, H 3.11; Cl 13.21; N
15.66. C11H8ClN3O3. Calculated, %: C 49.73; H 3.04;
Cl 13.35; N 15.82. M 266.
5-Benzoylamino-6-hydroxypyrimidin-4-one (IIa).
1
Yield 58%, mp 217–218°C. Н NMR spectrum, δН,
ppm: 7.45–7.98 m (5Н, С6H5), 8.07 s (1Н, CH), 9.24 s
5-Amino-2-aryl-1,3-thiazole-4-carbothioamides
(IIIa–IIIc). To a suspension of 4.45 g (0.02 mol) of
(1Н, NH), 12.08 br. s (2Н, NH, OH). 13С NMR spec-
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GURENKO et al.
phosphorus pentasulfide in 20 ml of anhydrous pyri-
dine was added 0.01 mol of compound IIa–IIc. The
mixture was refluxed for 2 h, then diluted with water
(50 ml) and acidified with hydrochloric acid to pH 5.
The formed precipitate was filtered off and suspended
in 60 ml of 5% aqueous NaOH. The mixture was
refluxed for 3 min and cooled. The precipitate was
filtered off. The additional amount of thioamides IIIa–
IIIc was obtained by acidification of the mother liquor
to pH 1. The formed precipitate was filtered off and
suspended in 20 ml of ethanol. After reflux for 6 h, the
precipitate was filtered off, washed with water, and
recrystallized from ethanol.
heated for 5 h. Then phosphorus oxychloride was distilled
off in vacuum. The residue was poured onto ice and
neutralized with sodium hydrogen carbonate to pH 7.
The precipitate was filtered off and dried. The substances
IVa–IVc were analyzed without further purification.
2-Phenyl-7-chloro[1,3]oxazolo[5,4-d]pyrimidine
(IVa). 57% yield, mp 155–156°C (mp 152°C [6]). IR
1
spectrum, ν, cm–1: 16128, 1713, 1914, 1973, 3060. Н
NMR spectrum, δН, ppm: 7.64–34 m (5Н, С6H5), 8.93
s (1Н, СН). 13С NMR spectrum, δС, ppm: 125.33,
128.64, 130.08, 131.14, 134.08, 149.38, 153.87, 163.51,
165.85. Mass spectrum, m/z: 232 [M]+. Found, %: C
57.29, H 2.68; Cl 15.17; N 18.22. C11H6ClN3O. Calcu-
lated, %: C 57.04; H 2.61; Cl 15.31; N 18.14. M 232.
5-Amino-2-phenyl-1,3-thiazole-4-carbothioamide
(IIIa). Yield 69%, mp 194–195°C. IR spectrum, ν, cm–1:
1522, 1564, 1639, 3194, 3275, 3403. 1Н NMR
spectrum, δН, ppm: 7.33–7.95 m (5Н, С6H5), 8.75 s
(2Н, NH2), 8.84 s [1Н, C(S)NH2], 8.92 s [1Н, C(S)NH2].
13С NMR spectrum, δС, ppm: 123.16, 126.94, 128.35,
129.29, 132.09, 142.73, 150.66, 183.90. Found, %: C
51.29; H 3.92; N 17.61; S 27.40. C10H9N3S2. Cal-
culated, %: C 51.04; H 3.85; N 17.86; S 27.25.
2-(4-Methylphenyl)-7-chloro[1,3]oxazolo[5,4-d]-
pyrimidine (IVb). Yield 79%, mp 163–164°C. IR
1
spectrum, ν, cm–1: 1600, 1616, 2216, 3038. Н NMR
spectrum, δН, ppm: 2.43 s (3Н, СH3), 7.46 d (2Н,
С6H4, J 7.6 Hz), 8.13 d (2Н, С6H4, J 7.6 Hz), 8.88 s
(1Н, СH). 13С NMR spectrum, δС, ppm: 21.79, 122.47,
128.59, 130.63, 131.40, 144.70, 149.06, 153.63, 163.66,
165.75. Mass spectrum, m/z: 266 [M]+. Found, %: C
58.83, H 3.35; Cl 14.59; N 17.24. C12H5ClN3O. Cal-
culated, %: C 58.67, H 3.28; Cl 14.43; N 17.10. M 266.
5-Amino-2-(4-methylphenyl)-1,3-thiazole-4-car-
bothioamide (IIIb). Yield 75%, mp 222–223°C. IR
spectrum, ν, cm–1: 1500, 1564, 1664, 3197, 3292, 3431
1Н NMR spectrum, δН, ppm: 2.34 s (3Н, CH3), 7.26 d
(2Н, С6H4, J 5.6 Hz), 7.75 d (2Н, С6H4, J 5.6 Hz), 8.71
s (2Н, NH2), 8.78 s [1Н, C(S)NH2], 8.87 s [1Н,
C(S)NH2]. 13С NMR spectrum, δС, ppm: 21.40, 126.05,
126.37, 129.98, 130.72, 139.55, 144.48, 160.20, 187.19.
Mass spectrum, m/z: 250 [M + 1]+. Found, %: C 52.73;
H 4.49; N 16.79; S 25.61. C10H9N3S2. Calculated, %: C
52.98; H 4.45; N 16.85; S 25.72. M 249.
7-Chloro-2-(4-chlorophenyl)[1,3]oxazolo[5,4-d]-
1
pyrimidine (IVc). Yield 79%, mp 180–181°C. Н
NMR spectrum, δН, ppm: 7.72 d (2Н, С6H4, J 8.3 Hz),
8.24 d (2Н, С6H4, J 8.3 Hz), 8.93 s (1Н, СН). 13С
NMR spectrum, δС, ppm: 124.17, 130.25, 130.35,
131.32, 138.94, 149.54, 154.02, 162.61, 165.78. Mass
spectrum, m/z: 246 [M]+. Found, %: C 49.81; H 1.85;
Cl 26.73; N 15.71. C11H5Cl2N3O. Calculated, %: C
49.65; H 1.89; Cl 26.65; N 15.79. M 246.
5-Amino-2-(4-chlorophenyl)-1,3-thiazole-4-carbo-
thioamide (IIIc). Yield 86%, mp 209–210°C. IR spec-
trum, ν, cm–1: 1521, 1561, 1641, 1910, 3184, 3289,
3431. 1Н NMR spectrum, δН, ppm: 7.49 d (2Н, С6H4, J
6.7 Hz), 7.88 d (2Н, С6H4, J 6.7 Hz), 8.78 s (2Н, NH2),
8.89 s [1Н, C(S)NH2], 8.94 s [(1Н, C(S)NH2]. 13С
NMR spectrum, dС, ppm: 126.59, 127.69, 129.43,
132.25, 134.20, 142.80, 160.65, 187.29. Mass spec-
trum, m/z: 270 [M]–. Found, %: C 44.38; H 3.07; Cl
13.19; N 15.45; S 23.82. C10H8ClN3S2. Calculated, %: C
44.52; H 2.99; Cl 13.14; N 15.58; S 23.77. M 270.
2-Aryl-6H,7H-[1,3]oxazolo[5,4-d]pyrimidine-7-
thiones (Va–c). To a solution of 0.1 mol of compound
IVa–IVc in 925 ml of ethanol was added 20.75 g
(0.28 mol) of sodium hydrosulfide monohydrate. The
mixture was refluxed for 2.5 h. The precipitate was
filtered off. Compounds Va–Vc were analyzed without
further purification.
2-Phenyl-6H,7H-[1,3]oxazolo[5,4-d]pyrimidine-
7-thione (Va). Yield 85%, mp 287–288°C (mp 292°C
[6]). IR spectrum, ν, cm–1: 1510, 1617, 1684, 1939,
1
2-Aryl-7-chloro[1,3]oxazolo[5,4-d]pyrimidines
(IVa–IVc). A mixture of 230 ml (2.48 mol) of phos-
phorus oxychloride and 0.1 mol of compound IIa–IIc was
3038, 3111 Н NMR spectrum, δН, ppm: 7.55–8.21 m
(5Н, С6H5), 8.40 s (1Н, СН), 14.37 s (1Н, NН). 13С
NMR spectrum, δС, ppm: 125.95, 127.64, 129.93,
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SYNTHESIS OF 2-ARYL-6H,7H-[1,3]OXAZOLO[5,4-d]PYRIMIDINE-7-THIONE
575
132.83, 134.50, 148.53, 159.82, 160.55. 176.54. Mass
spectrum, m/z: 230 [M + 1]+. Found, %: C 57.75; H
3.02; N 18.21; S 14.09. C11H7N3OS. Calculated, %: C
57.63; H 3.08; N 18.33; S 13.99. M 229.
165.31, 177.57. Mass spectrum, m/z: 246 [M + 1]+.
Found, %: C 53.71; H 2.82; N 17.21; S 26.01.
C11H7N3S2. Calculated, %: C 53.85; H 2.88; N 17.13;
S 26.14. M 245.
2-(4-Methylphenyl)-6H,7H-[1,3]oxazolo[5,4-d]-
pyrimidine-7-thione (Vb). Yield 80%, mp 267–268°C.
1Н NMR spectrum, δН, ppm: 2.39 s (3Н, СH3), 7.39 d
(2Н, С6H4, J 7.0 Hz), 7.99 d (2Н, С6H4, J 7.0 Hz), 8.32
s (1Н, СН), 14.23 s (1Н, NН). 13С NMR spectrum, dС,
ppm: 21.68, 123.11, 127.54, 130.41, 134.47, 143.10,
148.26, 159.59, 160.71, 176.33. Mass spectrum, m/z:
244 [M + 1]+. Found, %: C 50.19; H 2.34; Cl 13.40; N
15.99; S 12.22. C11H6ClN3OS. Calculated, %: C 50.10;
H 2.29; Cl 13.44; N 15.93; S 12.16. M 243.
2-(4-Methylphenyl)-6H,7H-[1,3]thiazolo[5,4-d]-
pyrimidine-7-thione (VIb). Yield 73% (method a),
15% (method b), mp 219–220°C. IR spectrum, ν, cm–1:
1
1517, 1570, 2836, 3280. Н NMR spectrum, δН, ppm:
2.39 s (3Н, СH3), 7.38 d (2Н, С6H5, J 7.8 Hz), 7.92 d
(2Н, С6H5, J 7.8 Hz), 8.29 s (1Н, СН). 13С NMR
spectrum, δС, ppm: 21.57, 129.16, 129.99, 131.51,
136.90, 146.49, 148.59, 159.05, 164.21, 177.20. Mass
spectrum, m/z: 260 [M + 1]+. Found, %: C 55.70; H
3.44; N 16.27; S 24.84. C12H9N3S2. Calculated, %: C
55.57; H 3.50; N 16.20; S 24.73. M 259.
2-(4-Chlorophenyl)-6H,7H-[1,3]oxazolo[5,4-d]-
pyrimidine-7-thione (Vс). Yield 88%, mp 295–296°C
(decomp.). IR spectrum, ν, cm–1: 1537, 1567, 1609,
2-(4-Chlorophenyl)-6H,7H-[1,3]thiazolo[5,4-d]-
pyrimidine-7-thione (VIc). Yield 87% (method a),
13% (method b), mp 252°C. IR spectrum, ν, cm–1:
1
1904, 2208, 3040, 3084 Н NMR spectrum, δН, ppm:
7.66 d (2Н, С6H4, J 4.8 Hz), 8.11 d (2Н, С6H4, J
4.8 Hz), 8.38 s (1Н, СН). 13С NMR spectrum, δС, ppm:
124.79, 129.33, 130.03, 137.56, 139.47, 148.65,
159.82, 162.07, 176.65. Found, %: C 50.19; H 2.33; Cl
13.38; N 15.98; S 12.09. C11H6ClN3OS. Calculated, %:
C 50.10; H 2.29; Cl 13.44; N 15.93; S 12.16.
1
1548, 1591, 1679, 1870, 2740, 2845, 2964, 3123. Н
NMR spectrum, δН, ppm: 7.62 d (2Н, С6H4, J 6.7 Hz),
8.04 d (2Н, С6H4, J 6.7 Hz), 8.24 s (1Н, СН). 13С
NMR spectrum, δС, ppm: 129.16, 129.99, 131.51,
136.90, 146.49, 148.59, 159.05, 164.21, 177.20. Mass
spectrum, m/z: 280 [M]+. Found, %: C 47.32; H 2.11;
Cl 12.75; N 15.10; S 22.98. C11H6ClN3S2. Calculated,
%: C 47.22; H 2.16; Cl 12.67; N 15.02; S 22.92. M
280.
2-Aryl-6H,7H-[1,3]thiazolo[5,4-d]pyrimidine-7-
thiones (VIa-VIc). a. To 0.1 mol of compound IIIa–
IIIc was added 260 ml (1.57 mol) of triethyl-
orthoformate and the mixture was refluxed for 8 h.
After cooling the formed precipitate was filtered off,
washed with diethyl ether, and analyzed without
further purification.
The NMR spectra were recorded on a Bruker
AVANCE DRX-500 spectrometer [500 MHz (1Н), 125
MHz (13С)] using DMSO-d6 as a solvent and TMS as
an internal reference. The IR spectra were taken on a
Vertex 70 spectrometer from KBr pellets. The melting
points were determined on a Fisher Johns instrument.
The GC-MS spectra were recorded on a HPLC Agilent
1100 Series chromatograph equipped with a diode
matrix with an Agilent LC\MSD SL mass selective
detector. The GC-MS (APCI) parameters are as
follows: column Zorbax SB-C18 (1.8 µm×4.6×15 mm,
PN 821975-932); solvents: A acetonitrile–water (95:5)
+ 0.1% TFA, B 0.1% aqueous TFA; eluent flow rate
3 ml min–1; injection volume 1 μl; UV detecting at
215, 254, 285 nm; scanning range of m/z 80–1000. The
reaction progress was monitored by TLC.
b. A mixture of 0.1 mol of compound IIa–IIc in
200 ml of anhydrous pyridine and 44.46 g (0.2 mol) of
phosphorus pentasulfide was refluxed for 5 h and
poured into water. The formed precipitate was filtered
off, dried, and recrystallized from an ethanol–DMF
mixture (1:1.5). The mixture of two samples of VIa–
VIc obtained by the methods a and b did not give the
melting point depression.
2-Phenyl-6H,7H-[1,3]thiazolo[5,4-d]pyrimidine-
7-thione (VIa). Yield 64% (method a), 10% (method
b), mp 239–240°C (mp 238–245°C [7]). IR spectrum,
1
ν, cm–1: 1522, 1542, 1653, 2865, 3000, 3129, 3245 Н
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129.94, 132.24, 132.80, 146.65, 148.66, 158.96,
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