Synthesis of some novel fused oxo- and thiopyrimidines via an intramolecular Friedel-Crafts reaction

Article abstract of DOI:10.1002/jhet.5570440309

(Chemical Equation Presented) 1H-Indeno[1,2-d]pyrimidine-2,5(3H,9bH)-dione derivatives 2(a-i) and 2,3-dihydro-2-thioxo-1H-indeno[1,2-d]pyrimidine-5(9bH)- ones 2(j-q) were synthesized via an intramolecular Friedel-Crafts reaction between the aryl and ester group of ethyl 6-methyl-4-aryl-2-oxo-1,2,3,4- tetrahydropyrimidine-5-carboxylates 1a-i, and their thioxo analogs using AlCl₃ and acetyl chloride in nitrobenzene. Yields of the products, after washing with THF, were of the order of 45-69%. IR and NMR spectroscopy together with elemental analysis were used for identification of these compounds.

Full text of DOI:10.1002/jhet.5570440309

May-Jun 2007
557
Synthesis of Some Novel Fused Oxo- and Thiopyrimidines via an
Intramolecular Friedel-Crafts Reaction
Akbar Mobinikhalediꢀ1, Naser Foroughifar1, Abdollah Javidan2 and Ehsan Amini2
1) Chemistry Department, Arak University, Dr. Beheshti Ave, Arak, Iran
2) Chemistry Department, Imam Hossein University, Tehran, Iran
email: akbar_mobini@yahoo.com
Received April 14, 2006
G
G
O
EtOOC
NH
AlCl3
NH
CH3COCl/C6H5NO2
N
H
z
N
H
z
1H-Indeno[1,2-d]pyrimidine-2,5(3H,9bH)-dione derivatives 2(a-i) and 2,3-dihydro-2-thioxo-1H-
indeno[1,2-d]pyrimidine-5(9bH)-ones 2(j-q) were synthesized via an intramolecular Friedel-Crafts
reaction between the aryl and ester group of ethyl 6-methyl-4-aryl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-
carboxylates 1a-i, and their thioxo analogs using AlCl3 and acetyl chloride in nitrobenzene. Yields of the
products, after washing with THF, were of the order of 45-69%. IR and NMR spectroscopy together with
elemental analysis were used for identification of these compounds.
J. Heterocyclic Chem., 44, 557 (2007).
7
4'
G
G
INTRODUCTION
8
6
3'
2'
5'
6'
9
Recently the Biginelli reaction has been extended for
preparation of a large number of pyrimidines [1]. It is well
documented that various compounds containing
pyrimidine ring, are associated with diverse pharmacol-
ogical activities such as antitumor [2], antiviral [3],
anticancer [4], anti-inflammatory [4], antifolate [5],
antimicrobial [6], antifungal [7] and antiproliferative [8]
activities. Over the past decade many pyrimidines with
appropriate functional groups have emerged as
antihypertensive agents [9-12] and potent calcium channel
blockers [13-14]. In addition, several marine alkaloids
with interesting biological activities contain the
dihydropyrimidine-5-carboxylate moiety [10]. The most
convenient preparation method of simple pyrimidines
include one-pot reaction of ꢁ-ketoester or ꢁ-diketone,
arylaldehyde and (thio)urea using a photochemical [15] or
microwave irradiation [16-18]. However, because of the
incessant interest in this field new efficient synthesis of
novel pyrimidine derivatives are still sought [19-22]. In
view of these reports and continuation of our studies on
the synthesis of pyrimidines [15-18,23,24] we wish to
report the synthesis of some fused pyrimidines using an
intramolecular electrophilic substitution reaction.
5
1'
4
NH
O
5
EtOOC
1
NH
3
AlCl3
6
4
2
z
2
z
CH3COCl/C6H5NO2
N
H
N
H
2
1
1a) G= H, Z=O
1j) G= H, Z=S
1b) G= 3-Cl, Z=O
1c) G= 2-NO2, Z=O
1d) G= 3-NO2, Z=O
1e) G= 4-Br, Z=O
1f) G= 4-F, Z=O
1g) G= 4-Cl, Z=O
1h) G= 4-CH3, X=O
1i) G= 4-(CH3)2CH, X=O
1k) G= 3-Cl, Z=S
1l) G= 2-NO2, Z=S
1m) G= 3-NO2, Z=S
1n) G= 4-Br, Z=S
1o) G= 4-F, Z=S
1p) G= 4-Cl, Z=S
1q) G= 4-CH3, X=S
Scheme 1
and thioxopyrimidine derivatives as shown in Scheme 1.
The Lewis acid, AlCl3, is used as a catalyst in this reaction
to produce the electrophilic species (acylium ion).
However the role of acetyl chloride in this reaction is
unknown. It is documented that the presence of an excess
amount of acetyl chloride increases the yield of product
considerably [25]. However the experiment was
unsatisfactory in the absence of the acetyl chloride. We
suggest that acetyl chloride, as cocatalyst, may interact
with the EtO- group and makes it as a better leaving
group.
RESULTS AND DISCUSSION
Starting ethyl 6-methyl-4-aryl-2-oxo-1,2,3,4-tetrahydro-
pyrimidine-5-carboxylates 1a-i and their thioxo analogs
were synthesized using literature procedures [15-18].
Intramolecular Friedel-Crafts acylation of 1 in the
presence of AlCl3 and acetyl chloride afforded fused oxo-
1
The H NMR spectra of 2a-i and 2j-q are very similar
1
to each other due to structural similarity. The H NMR
spectra data of all synthesized compounds are consistent

558
A. Mobinikhaledi, N. Foroughifar, A. Javidan and E. Amini
Vol 44
with their structures. For example the 1H NMR spectrum of
2a shows singlets at 2.31, 5.38, 8.18 and 9.44 ppm, which
attributed to the resonance of the methyl group, CH of
pyrimidine ring and two NH protons respectively. These
signals are shifted downfield with respect to those of starting
material due to loss of the electron releasing OEt group.
149.2, 152.5, 167.4. Anal Calcd. for C12H9N3O4: C, 55.60; H, 3.47;
N, 16.21%. Found: C, 55.71; H, 3.78; N, 16.51%.
7-Bromo-4-methyl-1H-indeno[1,2-d]pyrimidine-2,5(3H,
9bH)-dione (2e). Yield 51%, mp 265-266 °C; IR (KBr): ꢀ=
3248, 3109, 2933, 1707, 1641, 1529 cm-1; 1H NMR (DMSO-d6):
ꢁ (ppm) = 2.13 (s, 3H, CH3), 5.34 (s, 1H, CH), 7.77-7.87 (m,
3H, Harom), 8.26 (bs, 1H, NH), 9.262 (bs, 1H, NH); 13C-NMR
(DMSO-d6): ꢁ (ppm) = 15.5, 51.6, 107.5, 122.2, 125.2, 127.4,
135.8, 141.9, 145.7, 148.0, 155.2, 185.6. Anal Calcd. for
C12H9N2O2Br: C, 49.15; H, 3.07; N, 9.56%. Found: C, 49.43; H,
3.32; N, 9.21%.
1
Also absence of the H NMR signals related to the OEt
group resonance is a good support to the expected reaction.
EXPERIMENTAL
7-Fluoro-4-methyl-1H-indeno[1,2-d]pyrimidine-2,5(3H,
9bH)-dione (2f). Yield 52%, mp 283-284 °C; IR (KBr): ꢀ=
1
3248, 3200, 3138, 2964, 1716, 1680, 1612 cm-1; H NMR
Melting points were determined on an electrothermal digital
melting point apparatus.1H NMR spectra were recorded on a
Bruker (300 MHz) Spectrometer. The IR spectra were recorded
on Galaxy FT-IR 500 Spectrometer. Reactions were monitored
by thin layer chromatography. All materials were used as they
received. Starting pyrimidine compounds 1a-q were synthesized
using literature procedures [15-18].
(DMSO-d6): ꢁ (ppm) = 2.30 (s, 3H, CH3), 5.35 (s, 1H, CH),
7.38-7.98 (m, 3H, Harom), 8.27 (bs, 1H, NH), 9.62 (bs, 1H, NH);
Anal Calcd. for C12H9N2O2F: C, 62.07; H, 3.88; N, 12.07%.
Found: C, 62.34; H, 3.49; N, 11.77%.
7-Chloro-4-methyl-1H-indeno[1,2-d]pyrimidine-2,5(3H,
9bH)-dione (2g). Yield 55%, mp 280-281 °C; IR (KBr): ꢀ=
1
3327, 3294, 3021, 2981, 1711, 1693, 1621 cm-1; H NMR
General procedure for the synthesis of 2. A mixture of 6-
methyl-4-aryl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate
(DMSO-d6): ꢁ (ppm) = 2.19 (s, 3H, CH3), 5.32 (s, 1H, CH),
7.21-7.63 (m, 3H, Harom), 8.20 (bs, 1H, NH), 9.87 (bs, 1H, NH).
Anal Calcd. for C12H9N2O2Cl: C, 57.95; H, 3.62; N, 11.27.
Found: C, 57.32; H, 3.79; N, 11.01%.
4,7-Dimethyl-1H-indeno[1,2-d]pyrimidine-2,5(3H,9bH)-
dione (2h). Yield 65%, mp 273-274 °C; IR (KBr): ꢀ= 3310,
3335, 3290, 3005, 1712, 1686, 1615 cm-1; 1H NMR (DMSO-d6):
ꢁ (ppm) = 1.90 (s, 3H, CH3), 2.28 (s, 3H, CH3), 5.30 (s, 1H,
CH), 7.46-8.17 (m, 3H, Harom), 8.18 (bs, 1H, NH), 9.47 (bs, 1H,
NH); 13C-NMR (DMSO-d6): ꢁ (ppm) = 15.1, 21.0, 51.6, 107.5,
122.2, 129.4, 137.2, 138.8, 142.9, 145.7, 147.0, 155.2, 187.2.
Anal Calcd. for C13H12N2O2: C, 68.42; H, 5.26; N, 12.28. Found:
C, 68.16; H, 5.55; N, 12.53%.
7-Isopropyl-4-methyl-1H-indeno[1,2-d]pyrimidine-2,5(3H,
9bH)-dione (2i). Yield 69%, mp 263-264 °C; IR (KBr): ꢀ=
3290, 3190, 2995, 1720, 1690, 1610 cm-1; 1H NMR (DMSO-d6):
ꢁ (ppm) = 1.49 (s, 6H, 2 x CH3 ipropyl), 1.84 (s, 3H, CH3), 2.7
(m, 1H, CH, isopropyl), 5.10 (s, 1H, CH), 6.45-6.83 (m, 3H,
Harom), 9.28 (bs, 1H, NH), 10.05 (bs, 1H, NH). Anal Calcd. for
C15H16N2O2: C, 70.31; H, 6.25; N, 10.94. Found: C, 70.52; H,
6.03; N, 11.15%.
or
6-methyl-4-aryl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-
carboxylate (0.001 mol), 1, anhydrous aluminum chloride (0.005
mol), acetyl chloride ( 0.005 mol) and nitrobenzene (2 ml) was
heated at 90 °C for 4-5 h. The solution was poured into 15-20 ml
of ice-cooled water, 5 ml hydrochloric acid (37%) and 15 ml
petroleum ether were added, and stirred for 3 h. The precipitate
was collected by filtration and washed with THF to give pure
product 2.
4-Methyl-1H-indeno[1,2-d]pyrimidine-2,5(3H,9bH)-dione
(2a). Yield 45%, mp 230-231 °C; IR (KBr): ꢀ= 3345, 3284,
1
1700, 1685, 1630cm-1; H NMR (DMSO-d6): ꢁ (ppm) = 2.31
(s, 3H, CH3), 5.38 (s, 1H, CH), 7.48-7.87 (m, 4H, Harom), 8.18
(bs, 1H, NH), 9.44 (bs, 1H, NH); 13C-NMR (DMSO-d6):ꢁ
(ppm) = 13.9, 51.3, 107.2, 121.9, 124.5, 128.0, 132.6, 139.1,
146.1, 146.2, 154.8, 186.6. Anal Calcd. for C12H10N2O2: C,
67.29; H, 4.67; N, 13.08%. Found: C, 67.51; H, 4.79; N,
12.85%.
8-Chloro-4-methyl-1H-indeno[1,2-d]pyrimidine-2,5(3H,9bH)-
dione (2b). Yield 51%, mp 273-274 °C; IR (KBr): ꢀ= 3345, 3284,
1
1707, 1680, 1628 cm-1; H NMR (DMSO-d6): ꢁ (ppm) = 2.29 (s,
2,3-Dihydro-4-methyl-2-thioxo-1H-indeno[1,2-d]pyrimi-
dine-5(9bH)-one (2j). Yield 49%, mp 225-226 °C; IR (KBr): ꢀ=
3H, CH3), 5.38 (s, 1H, CH), 7.50-8.21 (m, 3H, Harom), 8.27 (bs,
1H, NH), 9.62 (bs, 1H, NH); 13C-NMR (DMSO-d6):ꢀ (ppm) =
13.9, 51.0, 106.9, 123.7, 124.8, 128.4, 137.2, 137.9, 146.8, 147.9,
154.5, 185.2. Anal Calcd. for C12H9N2O2Cl: C, 57.72; H, 4.01; N,
11.22%. Found: C, 57.50; H, 4.16; N, 11.53%.
4-Methyl-9-nitro-1H-indeno[1,2-d]pyrimidine-2,5(3H,9bH)-
dione (2c). Yield 51%, mp 295-296 °C; IR (KBr): ꢀ= 3320,
3202, 3049, 2931, 1706, 1696, 1670 cm-1; 1H NMR (DMSO-d6):
ꢁ (ppm) = 2.27 (s, 3H, CH3), 5.78 (s, 1H, CH), 7.31-7.87 (m,
3H, Harom), 8.23 (bs, 1H, NH), 9.29 (bs, 1H, NH); 13C-NMR
(DMSO-d6): ꢁ (ppm) = 16.9, 48.9, 107.5, 117.5, 123.2, 127.8,
128.0, 128.2, 129.1, 133.3, 138.6, 183.8. Anal Calcd. for
C12H9N3O4: C, 55.60; H, 3.47; N, 16.21%. Found: C, 55.49; H,
3.67; N, 16.30%.
4-Methyl-8-nitro-1H-indeno[1,2-d]pyrimidine-2,5(3H,9bH)-
dione (2d). Yield 60%, mp 282-283 °C. IR (KBr): ꢀ= 3229,
3126, 3050, 2937, 1710, 1699 cm-1; 1H NMR (DMSO-d6): ꢁ (ppm)
= 2.26 (s, 3H, CH3), 5.28 (s, 1H, CH), 7.63-8.15 (m, 3H, Harom),
8.22 (bs, 1H, NH), 9.26 (bs, 1H, NH); 13C-NMR (DMSO-d6): ꢁ
(ppm) = 18.3, 53.9, 99.4, 121.3, 122.7, 130.6, 133.4, 147.3, 148.2,
1
3300, 3250, 1700, 1680, 1620 cm-1; H NMR (DMSO-d6): ꢁ
(ppm) = 2.31 (s, 3H, CH3), 5.37 (s, 1H, CH), 7.24-8.04 (m, 4H,
Harom), 10.10 (bs, 1H, NH), 10.67 (bs, 1H, NH); 13C-NMR
(DMSO-d6): ꢁ (ppm) = 15.1, 52.5, 67.4, 123.7, 126.8, 128.9,
130.3, 132.8, 135.7, 147.4, 158.6, 186.7. Anal Calcd. for
C12H10N2OS: C, 62.61; H, 4.35; N, 12.17%. Found: C, 62.79; H,
4.60; N, 11.96%.
8-Choloro-2,3-dihydro-4-methyl-2-thioxo-1H-indeno[1,2-
d]pyrimidine-5(9bH)-one (2k). Yield 47%, mp 254-255 °C; IR
(KBr): ꢀ= 3420, 3140, 3050, 2972, 1662, 1560 cm-1; 1H NMR
(DMSO-d6): ꢁ (ppm) = 2.27 (s, 3H, CH3), 5.23 (s, 1H, CH),
7.23-7.71 (m, 3H, Harom), 7.86 (bs, 1H, NH), 8.23 (bs, 1H, NH).
Anal Calcd. for C12H9N2OSCl: C, 54.44; H, 3.40; N, 10.59%.
Found: C, 54.26; H, 3.15; N, 10.75%.
2,3-Dihydro-4-methyl-9-nitro-2-thioxo-1H-indeno[1,2-d]-
pyrimidine-5(9bH)-one (2l). Yield 45%, mp 289-290 °C; IR
(KBr): ꢀ= 3491, 3306, 1674, 1523 cm-1; 1H NMR (DMSO-d6): ꢁ
(ppm) = 2.28 (s, 3H, CH3), 5.91 (s, 1H, CH), 7.49-7.77 (m, 3H,

May-Jun 2007
Synthesis of Some Novel Fused Oxo- and Thiopyrimidines
559
Harom), 7.91 (bs, 1H, NH), 8.25 (bs, 1H, NH); Anal Calcd. for
C12H9N3O3S: C, 52.36; H, 3.72; N, 15.27%. Found: C, 52.03; H,
3.49; N, 15.57%.
derivatives were synthesized via an intramolecular
Friedel-Crafts reaction under mild conditions. The Lewis
acid, AlCl3, was used as a catalyst in this reaction to
produce the acylium ion.
2,3-Dihydro-4-methyl-8-nitro-2-thioxo-1H-indeno[1,2-d]-
pyrimidine-5(9bH)-one (2m). Yield 45%, mp 262-263 °C; IR
(KBr): ꢀ= 3345, 3412, 2922, 2850, 1655, 1525 cm-1; 1H NMR
(DMSO-d6): ꢁ (ppm) = 2.31 (s, 3H, CH3), 5.31 (s, 1H, CH),
7.65-8.26 (m, 3H, Harom), 9.47 (bs, 1H, NH), 10.59 (bs, 1H, NH).
13C-NMR (DMSO-d6): ꢁ (ppm) = 21.2, 57.4, 104.5, 125.0,
126.0, 126.7, 133.9, 134.4, 137.0, 149.5, 170.7, 178.5. Anal
Calcd. for C12H9N3O3S: C, 52.36; H, 3.72; N, 15.27%. Found: C,
52.66; H, 3.51; N, 15.46%.
7-Bromo-2,3-dihydro-4-methyl-2-thioxo-1H-indeno-
[1,2-d]pyrimidine-5(9bH)-one (2n). Yield 47%, mp
349-350 °C; IR (KBr): ꢀ= 3350, 3248, 3109, 2933, 1703,
1641, 1529 cm-1; 1H NMR (DMSO-d6): ꢁ (ppm) = 2.27 (s,
3H, CH3), 5.12 (s, 1H, CH), 7.18-7.75 (m, 3H, Harom), 9.72
(bs, 1H, NH), 10.31 (s, 1H, NH). Anal Calcd. for
C12H9N2OSBr: C, 46.60; H, 2.91; N, 9.06%. Found: C,
46.41; H, 3.26; N, 9.29%.
7-Fluoro-2,3-dihydro-4-methyl-2-thioxo-1H-indeno[1,2-d]-
pyrimidine-5(9bH)-one (2o). Yield 47%, mp 342-343 °C; IR
(KBr): ꢀ= 3245, 3120, 3040, 2940, 1705 cm-1; 1H NMR (DMSO-
d6): ꢁ (ppm) = 2.27 (s, 3H, CH3), 5.13 (s, 1H, CH), 7.15-7.44 (m,
3H, Harom), 9.62 (bs, 1H, NH), 10.31 (bs, 1H, NH). Anal Calcd.
for C12H9N2OSF: C, 58.06; H, 3.63; N, 11.29%. Found: C,
58.27; H, 3.39; N, 11.44%.
7-Chloro-2,3-dihydro-4-methyl-2-thioxo-1H-indeno[1,2-d]-
pyrimidine-5(9bH)-one (2p). Yield 46%, mp 319-320 °C; IR
(KBr): ꢀ= 3245, 3120, 3040, 2940, 1760, 1705 cm-1; 1H NMR
(DMSO-d6): ꢁ (ppm) = 2.11 (s, 3H, CH3), 5.12 (s, 1H, CH),
7.21-7.89 (m, 3H, Harom), 8.32 (bs, 1H, NH), 9.21 (bs, 1H, NH);
13C-NMR (DMSO-d6): ꢁ (ppm) = 21.5, 50.2, 104.2, 115.5,
115.8, 125.3, 128.8, 129.0, 135.4, 143.3, 172.4, 178.3. Anal
Calcd. for C12H9N2OSCl: C, 54.44; H, 3.40; N, 10.59. Found: C,
54.13; H, 3.65; N, 10.82%.
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2,3-Dihydro-4,7-dimethyl-2-thioxo-1H-indeno[1,2-d]pyrimi-
dine-5(9bH)-one (2q). Yield 53%, mp 259-260 °C; IR (KBr):
ꢀ= 3371, 3190, 3040, 2940, 1685 cm-1; 1H NMR (DMSO-d6): ꢁ
(ppm) = 2.30 (s, 3H, CH3), 2.39 (s, 3H, CH3), 5.32 (s, 1H, CH),
7.49-7.90 (m, 3H, Harom), 10.09 (bs, 1H, NH), 10.67 (bs, 1H,
NH); 13C-NMR (DMSO-d6): ꢁ (ppm) = 14.7, 21.3, 52.8, 108.7,
123.3, 126.2, 135.1, 139.3, 139.8, 143.6, 144.0, 179.4, 186.2.
Anal Calcd. for C13H12N2OS: C, 63.93; H, 4.91; N, 11.48.
Found: C, 64.27; H, 4.85; N, 11.53%.
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CONCLUSION
Some novel fused oxo- and thiopyrimidines including
1H-indeno[1,2-d]pyrimidine-2,5(3H,9bH)-dione and 2,3-
dihydro-2-thioxo-1H-indeno[1,2-d]pyrimidine-5(9bH)-one