An efficient one-pot and solvent-free synthesis of chromeno[2,3-d] pyrimidine derivatives: Microwave assisted reaction

Article abstract of DOI:10.3987/COM-10-11929

An efficient synthesis of some new chromeno[2,3-d]pyrimidine derivatives has been described by a solvent-free, multi-component reaction in fairly high yields. The Japan Institute of Heterocyclic Chemistry.

Full text of DOI:10.3987/COM-10-11929

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HETEROCYCLES, Vol. 81, No. 5, 2010, pp. 1271 - 1278. © The Japan Institute of Heterocyclic Chemistry
Received, 24th February, 2010, Accepted, 1st March, 2010, Published online, 3rd March, 2010
DOI: 10.3987/COM-10-11929
AN EFFICIENT ONE-POT AND SOLVENT-FREE SYNTHESIS OF
CHROMENO[2,3-d]PYRIMIDINE
DERIVATIVES:
MICROWAVE
ASSISTED REACTION
Afsaneh Zonouzi,a Mojtaba Biniaza, Roghieh Mirzazadeh,a Merzieh Talebi,a
and Seik Weng Ngb
aSchool of Chemistry, University College of Science, University of Tehran,
Tehran, Iran, E-mail:zonouzi@khayam.ut.ac.ir
bDepartment of Chemistry, University of Malaya, 50603 Kuala Lumpour,
Malaysia
Abstract – An efficient synthesis of some new chromeno[2,3-d]pyrimidine
derivatives has been described by a solvent-free, multi-component reaction in
fairly high yields.
Development of multi-component reaction (MCRs) is of great interests in recent years since MCRs have
the advantages such as atom economy, high efficiency and selectivity as well as environmental
friendliness.1-3 On the other hand, microwave (MW) promoted reactions have shown environmentally
friendly nature, greater selectivity and enhanced reaction rate.4-8 Fused pyrimidine derivatives are an
important heterocyclic compounds which occur in many biological active products, useful as anticancer,9
antiplatelet,10 antimicrobial,11 antitumor,12 neuroprotective,13 DHFR inhibitory,14 antiviral15 and
antifungal16 activities. Various methods for the synthesis of pyrimidine derivatives have been
reported.17-27 Most of these methods require prolonged reaction times, isolation of intermediates,
complex synthetic pathways or generate moderate yields. Sakurai and coworker have already reported the
condensation of hydroxybenzaldehyde and methylene compounds such as benzoylacetonitrile, ethyl
cyanoacetate and ethyl acetoacetate in the presence of ammonia or ammonium acetate to give
benzoquinazoline derivatives in 28-35% yields.28 Meyer has reported the synthesis of pyranopyrimidine
derivatives by condensation of malonodiamidine dihydrochloride and aromatic aldehyde in 4-51%
yields.29

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HETEROCYCLES, Vol. 81, No. 5, 2010
One of the key areas of green chemistry is the elimination of catalysts and solvents. In today's world,
synthetic chemists in both academia and industry have a widespread current debate over the relative
"greenness" of different procedures.30 We have already reported multicomponent, one-pot synthetic
procedures for some new heterocyclic compounds.31-34 Now we wish to report multicomponent reaction
of malononitrile 1, salicylaldehydes 2, and secondary amines 3 in a 1:2:2 molar ratio under heat or
microwave irradiation (MWI) to afford a series of new chromeno[2,3-d]pyrimidines 4.
X
N
N
100 °C
O
R1
R1
X
10-12 h
CN
CN
N
OH
R1
H
+
+
2
O
N
H
OH
MW 100 °C
3-6 min
1
3
2
4
X= CH2, O
X= CH2, O
Table 1. Synthesis of products 4 under microwave irradiation and heat
Comp.
R1
Amine
Time (h)
(Δ)
12
Time (min)
Yield (%)
Yield (%)
MP
(°C)
187
210
216
250
226
219
195
231
Entry 4
(MW)
(Δ)
75
78
80
82
81
83
85
85
(MW)
90
a
b
c
H
H
piperidine
morpholine
piperidine
morpholine
piperidine
morpholine
piperidine
morpholine
6
6
5
5
4
4
3
3
11
92
Cl
12
86
d
e
Cl
12
88
Br
11
91
f
Br
10
89
g
h
MeO
MeO
10
96
10
95
X-Ray crystal structure of 4b was preformed to confirm unambiguously its highly functionalized
structure.35 The X-ray crystal structure shows the intramolecular O-H---N hydrogen bonding and
neighboring molecules are stabilized by intermolecular hydrogen bonds (Figure 1).

HETEROCYCLES, Vol. 81, No. 5, 2010
1273
Figure 1. X-Ray crystal structure of 4b
In this research initially 2-imino-2H-chromene-3-carbonitriles 5 (its synthesis and spectroscopic data has
been already reported36,37) was synthesized by one-pot reaction of malononitrile 1, salicylaldehyde
derivative 2, and catalytic amounts of secondary amine 3 within a few minutes at room temperature
under solvent-free condition. Addition of secondary amines 3 (~ 2 equiv.) and refluxing the reaction
mixture for 10-12 h or microwave irradiation for 3-6 min by using microwave oven,38 in this stage
produced the chromeno[2,3-d]pyrimidines 4 as solid products. The products 4 can be purified by
recrystalization from ethanol or methanol. Single crystals of 4b were obtained from a mixture of
methanol and acetone.
This procedure is optimized as following: Catalytic amounts of secondary amine 3 for preparation of
iminocoumarin 5 is necessary in the first step. It is the major component to produce the final products 4
in the second step and help to carry out the reaction under solvent-free conditions. The second step was
optimized by varying reaction time, temperature and molar ratio of secondary amines 3. The best results
were obtained when the secondary amines were used 1.7-2 equivalents and the reaction mixtures were
heated at 100 °C (180 W) for 3-6 minutes under microwave irradiation.38 For the best comparison we
performed the reaction using conventional heating (oil bath), we kept the quantities of the reactant
exactly the same as in the microwave-promoted reaction and performed the solvent less reaction in a 50
mL three-necked flask with a thermometer. The reaction mixture was heated at 100 °C for 10-12 h.
Moderate yields (75-85%) of the final products were obtained. Clearly, the microwave irradiation has
shortened the reaction times with yield enhancement.
In summary, we have reported here a new and effective methodology for the synthesis of some new
chromeno[2,3-d]pyrimidines with potential biological activities.

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HETEROCYCLES, Vol. 81, No. 5, 2010
This method has many dramatic advantages such as solvent-free synthesis, short reaction time, high yield
and simple procedure for purification of the only one product. In this one-pot, solvent-free procedure,
eight new bonds was formed and the new aromatic ring (pyrimidine) was produced. Microwave
irradiation improved the yields and shortened the reaction times. Further investigations of this method are
currently in progress to establish its scope and utility.
EXPERIMENTAL
Chemicals and solvents were obtained from Merck (Germany) and Fluka (Switzerland) and were used
without further purification. Microwave assisted reactions were carried out in microwave oven (ETHOS
1600, Milestone) with a power of 600 W specially designed for organic synthesis. Columns
chromatography were performed on silica Gel (0.015-0.04 mm, mesh-size) and TLC on precoated plastic
sheets (25 DCUV-254), respectively. Melting points were measured on Barnstead Electrothermal melting
point apparatus and were not corrected. Elemental analyses for C, H and N were performed using a
Thermo Finnigan Flash EA1112 instrument. IR spectra were measured on a Shimadzu FT-IR-4300
spectrophotometer as KBr discs. 1H NMR and 13C NMR spectra were determined in CDCl3 on a Brucker
500 spectrophotometer and chemical shifts were expressed in ppm downfield from tetramethylsilane.
Mass spectra were recorded on a Finnigan-MAT 8430 spectrometer at an ionization potential of 70 ev.
General Procedure:
To a magnetically stirred mixture of malononitrile 1 (1 mmol), salicylaldehyde derivatives 2 (2 mmol)
and morpholine or piperidine (0.2 mmol) were added at 5 °C, the reaction mixture was stirred for 5 min
then secondary amines 3 (~1.5 mmol) was added dropwise to the above mixture and stirred for 5-10 min
at room temperature and placed in a open glass container. Irradiation in a microwave oven38 at 100 °C for
3-6 min gave the solid products 4 were collected by filtration and recrystallized from EtOH or MeOH.
2-(4-(Piperidin-1-yl)-5H-chromeno[2,3-d]pyrimidin-2-yl)phenol (4a).
Light yellow crystals; mp 187 °C; νmax (KBr): 3043 (O−H), 1622, 1605 (C=N), 1257, 1151, 1110 (C-O)
cm-1; δH (500 MHz, CDCl3): 1.77-1.81 (6H, m, 3CH2 of piperidine), 3.45-3.47 (4H, m, 2CH2 of
piperidine), 3.93 (2H, s, CH2), 6.94-6.97, 7.00-7.02, 7.11-7.14, 7.21-7.31, 7.36-7.40, 8.44-8.46 (8H, 6m,
aromatic), 13.50 (1H, brs, OH); δC (125 MHz): 24.79, 26.36, 49.93, (CH2 of piperidine), 26.04 (CH2),
97.91, 117.47, 117.96, 119.02, 119.22, 119.97, 124.80, 128.59, 128.98, 129.62, 133.21, 151.01, 160.86,
162.39, 165.59 (aromatic); MS: m/z: 359, 331, 275, 181, 84; Anal. Calcd for C22H21N3O2: C, 73.52; H,
5.89; N, 11.69. Found: C, 73.51; H, 5.88; N, 11.71.
2-(4-(Morpholino-5H-chromeno[2,3-d]pyrimidin-2-yl)phenol (4b).
Light yellow crystals; mp 210 °C; νmax (KBr): 3038 (O−H), 1630, 1609 (C=N), 1250, 1109, 1015 (C-O)
cm-1; δH (500 MHz, CDCl3): 3.45-3.56, 3.94-3.96 (8H, 2t, J= 4.73 Hz, CH2 of morpholine), 3.98 (2H, s,

HETEROCYCLES, Vol. 81, No. 5, 2010
1275
CH2), 6.96-6.98, 7.02-7.04, 7.16-7.18, 7.22-7.24, 7.29-7.30, 7.40-7.44, 8.43-8.45 (8H, 7m, aromatic),
13.38 (1H, brs, OH); δC (125 MHz): 26.04 (CH2), 49.14, 67.11 (CH2 of morpholine), 94.07, 117.62,
118.10, 119.38, 119.51, 125.03, 128.98, 128.84, 129.66, 133.51, 151.90, 160.81, 162.40, 165.92
(aromatic); MS: m/z: 361, 275, 268, 182, 95, 92, 86; Anal. Calcd for C21H19N3O3: C, 69.79; H, 5.30; N,
11.63. Found: C, 69.77; H, 5.33; N, 11.65.
4-Chloro-2-(7-chloro-4-(piperidin-1-yl)-5H-chromeno[2,3-d]pyrimidin-2-yl)phenol (4c).
Light yellow crystals; mp 216 °C; νmax (KBr): 3074 (O−H), 1644, 1634 (C=N), 1250, 1208, 1180, 1097
(C-O), 871, 825 (C-Cl) cm-1; δH (500 MHz, CDCl3): 1.80-1.81 (6H, m, CH2 of piperidine), 3.46-3.47 (4H,
m, CH2 of piperidine), 3.89 (2H, s, CH2), 6.90-6.92, 7.12-7.14, 7.22-7.24, 7.28-7.31, 8.36-8.37 (6H, 5m,
aromatic), 13.31 (1H, brs, OH); δC (125 MHz): 24.71, 26.34, 49.93 (CH2 of piperidine), 25.96 (CH2),
97.41, 118.76, 119.49, 119.92, 121.47, 124.15, 128.70, 128.73, 128.76, 129.82, 133.04, 149.45, 159.43,
161.40, 165.55 (aromatic); MS: m/z: 429, 427, 345, 343, 308, 229, 215, 127, 84; Anal. Calcd for
C22H19Cl2N3O2: C, 61.69; H, 4.47; N, 9.81. Found: C, 61.68; H, 4.47; N, 9.83.
4-Chloro-2-(7-chloro-4-(merpholin-4-yl)-5H-chromeno[2,3-d]pyrimidin-2-yl)phenol (4d).
Light yellow crystals; mp 250 °C; νmax (KBr): 3165 (O−H), 1656, 1648 (C=N), 1274, 1245, 1182, 1118
(C-O), 898, 906 (C-Cl) cm-1; δH (500 MHz, CDCl3): 3.52-3.54, 3.94-3.96 (8H, 2t, J = 4.23 Hz, 4CH2 of
morpholine), 3.91 (2H, s, CH2), 6.91-6.93, 7.13-7.15, 7.23-7.27, 7.29-7.32, 8.33-8.34 (6H, 5m, aromatic),
13.00 (1H, brs, OH); δC (125 MHz): 25.92 (CH2), 49.08, 67.04 (CH2 of morpholine), 97.72, 118.85,
119.63, 119.74, 120.98, 124.27, 128.75, 128.95, 130.06, 133.28, 149.25, 159.38, 161.53, 165.26
(aromatic); MS: m/z: 431, 429, 345, 343, 301, 215, 127, 86; Anal. Calcd for C21H17Cl2N3O3: C, 58.62; H,
3.98; N, 9.77. Found: C, 58.60; H, 3.97; N, 9.79.
4-Bromo-2-(7-bromo-4-(piperidin-1-yl)-5H-chromeno[2,3-d]pyrimidin-2-yl)phenol (4e).
Yellow crystals; mp 226 °C; νmax (KBr): 3068 (O−H), 1640, 1593 (C=N), 1249, 1181, 1089 (C-O), 900,
811 (C-Br) cm-1; δH (500 MHz, CDCl3): 1.79-1.81 (6H, m, CH2 of piperidine), 3.46-3.47 (4H, m, CH2 of
piperidine), 3.92 (2H, s, CH2), 6.87-6.89, 7.09-7.11, 7.38-7.40, 7.43-7.45, 8.52-8.53 (6H, 5m, aromatic),
13.36 (1H, brs, OH); δC (125 MHz): 24.70, 26.33, 49.96 (CH2 of piperidine), 25.91 (CH2), 95.06, 111.30,
117.30, 119.21, 119.97, 122.00, 131.68, 131.71, 131.75, 135.95, 159.94, 163.21, 166.57 (aromatic); MS:
m/z: 519, 517, 515, 433, 431, 343, 259, 171, 84, 57; Anal. Calcd for C22H19Br2N3O2: C, 51.09; H, 3.70; N,
8.12. Found: C, 51.11; H, 3.72; N, 8.15.
4-Bromo-2-(7-bromo-4-(merpholin-4-yl)-5H-chromeno[2,3-d]pyrimidin-2-yl)phenol (4f).
Yellow crystals; mp 219 °C; νmax (KBr): 3046 (O−H), 1618, 1603 (C=N), 1216, 1176, 1106, 1018 (C-O),
898, 867 (C-Br) cm-1; δH (500 MHz, CDCl3): 3.41-3.43, 3.81-3.83 (8H, 2t, J = 4.55 Hz, CH2 of
morpholine), 3.90 (2H, s, CH2), 6.75-6.77, 6.97-6.99, 7.28-7.30, 7.31-7.33, 8.36-8.37 (6H, 5m, aromatic),
12.95 (1H, brs, OH); δC (125 MHz): 25.57 (CH2), 48.86, 66.81 (CH2 of morpholine), 97.79, 111.00,

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117.22, 118.93, 119.91, 120.19, 121.56, 131.45, 131.58, 135.77, 149.57, 159.65, 160.97, 163.96
(aromatic); MS: m/z: 521, 519, 517, 433, 431, 345, 268, 171, 86, 57; Anal. Calcd for C21H17Br2N3O3: C,
48.58; H, 3.30; N, 8.09. Found: C, 48.55; H, 3.32; N, 8.12.
4-Methoxy-2-(7-methoxy-4-(piperidin-1-yl)-5H-chromeno[2,3-d]pyrimidin-2-yl)phenol (4g).
Light yellow crystals; mp 195 °C; νmax (KBr): 3064 (O−H), 1643, 1616 (C=N), 1213, 1169, 1089, 1030
(C-O) cm-1; δH (500 MHz, CDCl3): 1.69-1.82 (6H, m, 3CH2 of piperidine), 3.44-3.46 (4H, m, 2CH2 of
piperidine), 3.83, 3.89 (6H, 2s, 2OMe), 3.92 (2H, brs, CH2), 6.74-6.75, 6.80-6.83, 6.93-6.95, 6.99-7.01,
7.12-7.15, 7.96-7.97 (6H, 6m, aromatic), 13.10 (1H, brs, OH); δC (125 MHz): 24.77, 26.36, 49.98 (CH2
of piperidine), 26.30 (CH2), 56.09, 56.47 (2CH3O), 97.54, 112.24, 113.36, 114.22, 118.22, 118.73,
118.87, 120.68, 121.22, 144.91, 152.56, 155.27, 156.66, 162.19, 164.97 (aromatic); MS: m/z: 419, 404,
387, 357, 304, 182, 91, 84; Anal. Calcd for C24H25N3O4: C, 68.72; H, 6.01; N, 10.02. Found: C, 68.71; H,
6.00; N, 10.05.
4-Methoxy-2-(7-methoxy-4-(morpholin-4-yl)-5H-chromeno[2,3-d]pyrimidin-2-yl)phenol (4h).
Light yellow crystals; mp 231 °C; νmax (KBr): 3044 (O−H), 1631, 1612 (C=N), 1262,1199, 1154, 1106,
1021 (C-O) cm-1; δH (500 MHz, CDCl3): 3.50-3.52, 3.93-3.95 (8H, 2t, J = 4.49 Hz, 4CH2 of morpholine),
3.58, 3.87 (6H, 2s, 2OCH3), 3.89 (2H, s, CH2), 6.52-6.55, 6.72-6.74, 6.77-6.78, 7.12-7.14, 8.33-8.35 (6H,
5m, aromatic), 13.41 (1H, brs, OH); δC (125 MHz): 26.36 (CH2), 49.11, 67.13 (CH2 of morpholine),
55.79, 55.94 (2OCH3), 96.72, 101.70, 102.52, 107.20, 111.37, 111.72, 128.25, 128.94, 129.46, 130.94,
151.57, 160.10, 162.32, 165.04 (aromatic); MS: m/z: 421, 406, 389, 335, 303, 298, 182, 92, 86; Anal.
Calcd for C23H23N3O5: C, 65.55; H, 5.50; N, 9.97. Found: C, 65.54; H, 5.52; N, 10.01.
ACKNOWLEDGEMENTS
The support of this study by the Research Council at the University of Tehran is gratefully
acknowledged.
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