Synthesis and in vitro microbiological evaluation of novel series of 8-hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-phenyl-3H-chromeno [2,3-d]pyrimidin-4(5H)-one derivatives catalyzed by reusable silica-bonded N-propylpiperazine sulfamic acid

Article abstract of DOI:10.1007/s11164-013-1419-2

Abstract Silica-bonded propylpiperazine-N-sulfamic acid is employed as a recyclable catalyst for the synthesis of a series of 8-hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-phenyl-3H-chromeno[2,3-d]pyrimidin-4(5H)-one derivatives by the condensation of 2-amino-3-c

Full text of DOI:10.1007/s11164-013-1419-2

Res Chem Intermed
DOI 10.1007/s11164-013-1419-2
Synthesis and in vitro microbiological evaluation
of novel series of 8-hydroxy-2-(2-oxo-2H-chromen-3-yl)-
5-phenyl-3H-chromeno [2,3-d]pyrimidin-4(5H)-one
derivatives catalyzed by reusable silica-bonded
N-propylpiperazine sulfamic acid
•
M. Ghashang S. Sheik Mansoor K. Aswin
•
Received: 26 May 2013 / Accepted: 20 September 2013
Ó Springer Science+Business Media Dordrecht 2013
Abstract Silica-bonded propylpiperazine-N-sulfamic acid is employed as a
recyclable catalyst for the synthesis of a series of 8-hydroxy-2-(2-oxo-2H-chromen-
3-yl)-5-phenyl-3H-chromeno[2,3-d]pyrimidin-4(5H)-one derivatives by the con-
densation of 2-amino-3-cyano-7-hydroxy-4-phenyl-4Hchromene derivatives with
coumarin-3-carboxylic acid. The heterogeneous catalyst was used for four runs.
This method has the advantages of high yields, a cleaner reaction, simple meth-
odology, short reaction times, and easy work-up. All the compounds were evaluated
for their in vitro antimicrobial activity against different bacterial and fungal strains.
Keywords Silica-bonded N-propylpiperazine sulfamic acid (SBPPSA) Á
Chromeno[2,3-d]pyrimidin-4(5H)-one Á 2-amino-4H-chromene Á
4-(dimethylamino)pyridine (DMAP) Á Malononitrile Á Microbiological
evaluation
Introduction
Coumarins form an important class of compounds, which occupy a special role in
nature. They belong to the flavonoid class of plant secondary metabolites, which
have been found to exhibit a variety of biological activities, usually associated with
low toxicity, and have raised considerable interest because of their potential
beneficial effects on human health. [1]. These compounds are considered as
M. Ghashang
Faculty of Sciences, Najafabad Branch, Islamic Azad University, Najafabad,
Esfahan, Iran
S. S. Mansoor (&) Á K. Aswin
Bioactive Organic Molecule Synthetic Unit, Research Department of Chemistry,
C. Abdul Hakeem College, Melvisharam 632 509, Tamil Nadu, India
e-mail: smansoors2000@yahoo.co.in
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M. Ghashang et al.
‘privileged structures’ in medicinal chemistry due to their immense potentiality.
Coumarin derivatives have anti-tuberculosis [2], anti-HIV [3], antibacterial,
antioxidant [4], and anti-inflammatory [5] properties, and are used as mushroom
tyrosinase inhibitors [6] and cytotoxicity agents [7]. They are also present or used in
perfumes and cosmetics [8], alcoholic beverages [9], and laser dyes [10]. Due to
their wide range of biological and other applications, in recent times various
research groups have made considerable efforts to synthesize these compounds.
Coumarin derivatives were first synthesized via the Perkin reaction in 1868, and
many simple coumarins are still derived from this method. From the literature, it has
been found that a number of methods have been reported so far for the synthesis of
coumarin derivatives [11–15]. Most of these procedures require refluxing for hours
in organic solvents, the use of expensive catalysts, and tedious work-up. In view of
these observations, there is further scope to develop a synthetic methodology using
a less expensive and environmentally benign catalyst.
In recent times, it has been found that heterogeneous catalysts have gained in
interest since they are less expensive, non-toxic, easily available, and environmen-
tally acceptable. They can be conveniently handled and removed from the reaction
mixture, thus making the experimental procedure simple and eco-friendly. Recently,
silica-bonded propylpiperazine N-sulfamic acid (SBPPSA) has emerged as mild,
water-tolerant, inexpensive, and environmentally compatible heterogeneous cata-
lyst, reported by Niknam et al. [16] for the synthesis of 1,2,4,5-tetrasubstituted
imidazoles. SBPPSA has also been used as a catalyst for the synthesis of a-
aminonitriles [17] and for cyanation reactions [18].
As part of continuing effort in our laboratory towards the development of
environmentally friendly procedures for the synthesis of biologically active
heterocyclic molecules [19–24], we now describe the synthesis of 8-hydroxy-
2-(2-oxo-2H-chromen-3-yl)-5-phenyl-3H-chromeno[2,3-d]pyrimidin-4(5H)-one
derivatives using SBPPSA as an efficient novel heterogeneous catalyst. These
compounds were synthesized using 2-amino-3-cyano-7-hydroxy-4-phenyl-4Hchro-
mene derivatives and coumarine-3-carboxylic acid using 4-(dimethylamino)pyri-
dine (DMAP) as an efficient catalyst.
Experimental
Apparatus and analysis
Chemicals were purchased from Merck, Fluka, and Aldrich. All yields refer to
isolated products unless otherwise stated. 1H NMR (500 MHz) and 13C NMR
(125 MHz) spectra were obtained using a Bruker DRX-500 Avance at ambient
temperature, using TMS as internal standard. FT-IR spectra were obtained as KBr
discs on a Shimadzu spectrometer. Mass spectra were determined on a Varion–
Saturn 2000 GC/MS instrument. Elemental analysis was measured by means of
Perkin Elmer 2400 CHN elemental analyzer flowchart.
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Synthesis and in vitro microbiological evaluation of novel series
Preparation of the catalyst (SBPPSA)
Silica-bonded propylpiperazine-N-sulfamic acid was prepared by the reaction of
3-piperazine-N-propylsilica (3-PNPS) and chlorosulfonic acid in chloroform as
reported in the literature [16], and 0.2 g of SBPPSA is equal to 0.24 mmol of H?.
General procedure for the synthesis of 2-amino-3-cyano-7-hydroxy-4-substituted-
4Hchromene derivatives
A mixture of resorcinol (0.110 g, 1 mmol), aldehyde derivatives (1 mmol),
malononitrile (0.066 g, 1 mmol), ethanol (5 mL), and DMAP (10 mol %) was
stirred at 60 °C for the appropriate time. After completion of the reaction (TLC
monitoring), the DMAP was filtered off and the solvent was evaporated. The catalyst
was washed with dichloromethane and vacuumed to remove CH2Cl2, and the
resulting catalyst was reused directly for the next run. The filtrate was concentrated to
dryness, and the crude solid product was crystallized from EtOH to afford the pure
2-amino-3-cyano-7-hydroxy-4-substituted-4H-chromene derivatives.
Spectral data for new compounds (4a–j)
2-Amino-3-cyano-7-hydroxy-4-phenyl-4Hchromene (4a)
IR (KBr, cm-1): 3,433 (OH), 3,350 (NH2), 2,202 (CN), 1,666 (C=C vinyl nitrile),
1,591 (C=C aromatic); 1H NMR (500 MHz, DMSO-d6): d 4.95 (s, 1H, CH), 6.24 (s,
2H, NH2), 6.57 (d, J = 4.0 Hz, 1H, Ar–H), 6.75 (dd, J = 4.0 Hz, J = 8.0 Hz, 1H,
Ar–H), 6.88 (d, J = 8.0 Hz, 1H, Ar–H), 7.18–7.34 (m, 5H, Ar–H), 9.60 (s, 1H, OH)
ppm; 13C NMR (125 MHz, DMSO-d6): d 30.4, 58.5, 103.5, 111.0, 117.5, 124.4,
126.3, 127.8, 129.6, 130.4, 143.3, 155.7, 159.5, 176.3 ppm. MS (ESI): m/z 265
(M?H)?. Anal. Calcd. for C16H12N2O2: C, 72.72; H, 4.54; N, 10.60 %. Found: C,
72.66; H, 4.52; N, 10.61 %.
2-Amino-3-cyano-7-hydroxy-4-(4-chlorophenyl)-4Hchromene (4b)
IR (KBr, cm-1): 3,442 (OH), 3,344 (NH2), 2,212 (CN), 1,662 (C=C vinyl nitrile),
1,588 (C=C aromatic); 1H NMR (500 MHz, DMSO-d6): d 4.88 (s, 1H, CH), 6.29 (s,
2H, NH2), 6.62 (d, J = 4.0 Hz, 1H, Ar–H), 6.73 (dd, J = 4.0 Hz, J = 8.0 Hz, 1H,
Ar–H), 6.91 (d, J = 8.0 Hz, 1H, Ar–H), 7.28 (d, J = 7.4 Hz, 2H, Ar–H), 7.48 (d,
J = 7.4 Hz, 2H, Ar–H), 9.56 (s, 1H, OH) ppm; 13C NMR (125 MHz, DMSO-d6): d
29.8, 59.2, 104.6, 110.5, 118.0, 123.9, 125.7, 128.4, 129.0, 131.0, 144.0, 156.0,
158.9, 177.1 ppm. MS (ESI): m/z 299.45 (M?H)?. Anal. Calcd. for C16H11ClN2O2:
C, 64.33; H, 3.68; N, 9.38 %. Found: C, 64.22; H, 3.60; N, 9.30 %.
2-Amino-3-cyano-7-hydroxy-4-(4-bromophenyl)-4Hchromene (4c)
IR (KBr, cm-1): 3,428 (OH), 3,340 (NH2), 2,196 (CN), 1,672 (C=C vinyl nitrile),
1,590 (C=C aromatic); 1H NMR (500 MHz, DMSO-d6): d 4.99 (s, 1H, CH), 6.16 (s,
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M. Ghashang et al.
2H, NH2), 6.64 (d, J = 4.0 Hz, 1H, Ar–H), 6.78 (dd, J = 4.0 Hz, J = 8.0 Hz, 1H,
Ar–H), 6.95 (d, J = 8.0 Hz, 1H, Ar–H), 7.36–7.50 (m, 4H, Ar–H), 9.52 (s, 1H, OH)
ppm; 13C NMR (125 MHz, DMSO-d6): d 30.7, 58.7, 103.9, 111.2, 117.4, 124.3,
126.4, 127.5, 129.2, 131.3, 143.8, 155.8, 159.3, 177.4 ppm. MS (ESI): m/z 343.9
(M?H)?. Anal. Calcd. for C16H11BrN2O2: C, 55.99; H, 3.21; N, 8.16 %. Found: C,
55.88; H, 3.15; N, 8.11 %.
2-Amino-3-cyano-7-hydroxy-4-(4-fluorophenyl)-4Hchromene (4d)
IR (KBr, cm-1): 3,440 (OH), 3,330 (NH2), 2,199 (CN), 1,659 (C=C vinyl nitrile),
1,580 (C=C aromatic); 1H NMR (500 MHz, DMSO-d6): d 5.09 (s, 1H, CH), 6.22 (s,
2H, NH2), 6.62 (d, J = 4.0 Hz, 1H, Ar–H), 6.77 (dd, J = 4.0 Hz, J = 8.0 Hz, 1H,
Ar–H), 6.90 (d, J = 8.0 Hz, 1H, Ar–H), 7.20–7.44 (m, 4H, Ar–H), 9.59 (s, 1H, OH)
ppm; 13C NMR (125 MHz, DMSO-d6): d 30.5, 59.0, 104.4, 110.8, 118.6, 123.8,
125.8, 127.9, 129.4, 130.9, 144.1, 156.4, 158.7, 176.8 ppm. MS (ESI): m/z 283
(M?H)?. Anal. Calcd. for C16H11FN2O2: C, 68.08; H, 3.90; N, 9.93 %. Found: C,
68.02; H, 3.84; N, 9.94 %.
2-Amino-3-cyano-7-hydroxy-4-(4-methylphenyl)-4Hchromene (4e)
IR (KBr, cm-1): 3,430 (OH), 3,352 (NH2), 2,214 (CN), 1,660 (C=C vinyl nitrile),
1
1,575 (C=C aromatic); H NMR (500 MHz, DMSO-d6): d 2.18 (s, 3H, CH3), 4.85
(s, 1H, CH), 6.12 (s, 2H, NH2), 6.58 (d, J = 4.0 Hz, 1H, Ar–H), 6.69 (dd,
J = 4.0 Hz, J = 8.0 Hz, 1H, Ar–H), 6.80 (d, J = 8.0 Hz, 1H, Ar–H), 7.22 (d,
J = 7.4 Hz, 2H, Ar–H), 7.49 (d, J = 7.4 Hz, 2H, Ar–H), 9.60 (s, 1H, OH) ppm; 13
C
NMR (125 MHz, DMSO-d6): d 18,9, 29.7, 58.3, 103.2, 111.8, 117.4, 123.5, 126.2,
128.2, 128.9, 131.4, 143.5, 155.9, 158.5, 177.2 ppm. MS (ESI): m/z 279 (M?H)?.
Anal. Calcd. for C17H14N2O2: C, 73.38; H, 5.03; N, 10.07 %. Found: C, 73.25; H,
5.01; N, 10.01 %.
2-Amino-3-cyano-7-hydroxy-4-(4-methoxyphenyl)-4Hchromene (4f)
IR (KBr, cm-1): 3,426 (OH), 3,335 (NH2), 2,206 (CN), 1,674 (C=C vinyl nitrile),
1,578 (C=C aromatic); 1H NMR (500 MHz, DMSO-d6): d 3.66 (s, 3H, OCH3), 5.04
(s, 1H, CH), 6.20 (s, 2H, NH2), 6.63 (d, J = 4.0 Hz, 1H, Ar–H), 6.77 (dd,
J = 4.0 Hz, J = 8.0 Hz, 1H, Ar–H), 6.84 (d, J = 8.0 Hz, 1H, Ar–H), 7.30 (d,
J = 7.4 Hz, 2H, Ar–H), 7.46 (d, J = 7.4 Hz, 2H, Ar–H), 9.55 (s, 1H, OH) ppm; 13
C
NMR (125 MHz, DMSO-d6): d 29.2, 55,8, 59.5, 104.5, 110.6, 118.1, 124.6, 125.5,
127.7, 128.7, 131.1, 144.2, 156.1, 159.0, 176.5 ppm. MS (ESI): m/z 295 (M?H)?.
Anal. Calcd. for C17H14N2O3: C, 69.39; H, 4.76; N, 9.52 %. Found: C, 69.27; H,
4.71; N, 9.42 %.
2-Amino-3-cyano-7-hydroxy-4-(4-nitrophenyl)-4Hchromene (4g)
IR (KBr, cm-1): 3,448 (OH), 3,341 (NH2), 2,200 (CN), 1,655 (C=C vinyl nitrile),
1,581 (C=C aromatic); 1H NMR (500 MHz, DMSO-d6): d 5.07 (s, 1H, CH), 6.17 (s,
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Synthesis and in vitro microbiological evaluation of novel series
2H, NH2), 6.56 (d, J = 4.0 Hz, 1H, Ar–H), 6.72 (dd, J = 4.0 Hz, J = 8.0, 1H, Ar–
H), 6.90 (d, J = 8.0 Hz, 1H, Ar–H), 7.22 (d, J = 7.4 Hz, 2H, Ar–H), 7.51 (d,
J = 7.4 Hz, 2H, Ar–H), 9.59 (s, 1H, OH) ppm; 13C NMR (125 MHz, DMSO-d6): d
30.9, 58.8, 103.9, 111.0, 117.9, 123.7, 126.5, 127.3, 129.5, 130.8, 144.3, 155.5,
158.6, 177.3 ppm. MS (ESI): m/z 310 (M?H)?. Anal. Calcd. for C16H11N3O4: C,
62.13; H, 3.56; N, 13.59 %. Found: C, 62.01; H, 3.54; N, 13.56 %.
2-Amino-3-cyano-7-hydroxy-4-(4-hydroxyphenyl)-4Hchromene (4h)
IR (KBr, cm-1): 3,427 (OH), 3,444 (OH), 3,337 (NH2), 2,195 (CN), 1,668 (C=C
vinyl nitrile), 1,594 (C=C aromatic); 1H NMR (500 MHz, DMSO-d6): d 4.85 (s, 1H,
CH), 6.22 (s, 2H, NH2), 6.64 (d, J = 4.0 Hz, 1H, Ar–H), 6.74 (dd, J = 4.0 Hz,
J = 8.0 Hz, 1H, Ar–H), 6.83 (d, J = 8.0 Hz, 1H, Ar–H), 7.34 (d, J = 7.4 Hz, 2H,
Ar–H), 7.57 (d, J = 7.4 Hz, 2H, Ar–H), 9.52 (s, 1H, OH), 9.69 (s, 1H, OH) ppm;
13C NMR (125 MHz, DMSO-d6): d 29.3, 59.1, 104.0, 110.8, 118.4, 123.9, 125.9,
128.3, 129.1, 131.6, 143.6, 156.3, 158.8, 176.6 ppm. MS (ESI): m/z 281 (M?H)?.
Anal. Calcd. for C16H12N2O3: C, 68.57; H, 4.28; N, 10.00 %. Found: C, 68.50; H,
4.22; N, 10.02 %.
2-Amino-3-cyano-7-hydroxy-4-(3-hydroxyphenyl)-4Hchromene (4i)
IR (KBr, cm-1): 3,438 (OH), 3,452 (OH), 3,348 (NH2), 2,198 (CN), 1,657 (C=C
vinyl nitrile), 1,586 (C=C aromatic); 1H NMR (500 MHz, DMSO-d6): d 4.98 (s, 1H,
CH), 6.25 (s, 2H, NH2), 6.66 (d, J = 4.0 Hz, 1H, Ar–H), 6.76 (dd, J = 4.0 Hz,
J = 8.0 Hz, 1H, Ar–H), 6.92 (d, J = 8.0 Hz, 1H, Ar–H), 7.22–7.38 (m, 4H, Ar–H),
9.48 (s, 1H, OH), 9.65 (s, 1H, OH) ppm; 13C NMR (125 MHz, DMSO-d6): d 30.0,
59.7, 103.7, 111.5, 117.7, 124.0, 125.4, 127.6, 129.7, 130.7, 144.2, 156.7, 159.4,
176.8 ppm. MS (ESI): m/z 281 (M?H)?. Anal. Calcd. for C16H12N2O3: C, 68.57; H,
4.28; N, 10.00 %. Found: C, 68.59; H, 4.27; N, 10.01 %.
2-Amino-3-cyano-7-hydroxy-4-(4-N,N-dimethylaminophenyl)-4Hchromene (4j)
IR (KBr, cm-1): 3,440 (OH), 3,343 (NH2), 2,210 (CN), 1,670 (C=C vinyl nitrile),
1,576 (C=C aromatic); 1H NMR (500 MHz, DMSO-d6): d 2.58 (s, 6H, CH3), 4.88 (s,
1H, CH), 6.18 (s, 2H, NH2), 6.61 (d, J = 4.0 Hz, 1H, Ar–H), 6.71 (dd, J = 4.0 Hz,
J = 8.0 Hz, 1H, Ar–H), 6.87 (d, J = 8.0 Hz, 1H, Ar–H), 7.25 (d, J = 7.4 Hz, 2H,
Ar–H), 7.51 (d, J = 7.4 Hz, 2H, Ar–H), 9.60 (s, 1H, OH) ppm; 13C NMR (125 MHz,
DMSO-d6): d 29.5, 44.4, 58.0, 105.0, 110.1, 118.8, 123.1, 126.2, 128.0, 128.9, 131.0,
143.7, 155.2, 158.4, 177.5 ppm. MS (ESI): m/z 308 (M?H)?. Anal. Calcd. for
C18H17N3O2: C, 70.35; H, 5.54; N, 13.68 %. Found: C, 70.30; H, 5.51; N, 13.66 %.
General procedure for the synthesis of 8-hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-
phenyl-3H-chromeno[2,3-d]pyrimidin-4(5H)-one derivatives by SBPPSA
A mixture of 2-amino-3-cyano-7-hydroxy-4-phenyl-4Hchromene 4a–j (1 mmol),
coumarin-3-carboxylic acid (1 mmol), and SBPPSA (0.2 g, equal to 0.24 mmol of
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M. Ghashang et al.
H?) were heated at 60 °C for about 3.0–3.5 h (Scheme 2). After completion of the
reaction as indicated by TLC, 2 mL of water was added and stirred at room
temperature for 20 min. The precipitated product was filtered, washed with water,
dried, and purified over column chromatography using silica gel (230–400 mesh)
with n-hexane and ethyl acetate (8:2) as eluent. The aqueous layer containing catalyst
was recovered, washed with acetone, dried and reused for subsequent reactions
without loss in its activity and product yield.
Recycling and reusing of the catalyst
The catalyst was recovered by evaporation of the water, washed with hexane, dried
at 50 °C under vacuum for 1 h and reused in another reaction without appreciable
reduction in the catalytic activity.
Spectral data for the synthesized compounds (6a–j)
8-Hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-phenyl-3H-chromeno[2,3-d]pyrimidin-
4(5H)-one (6a)
IR (KBr, cm-1): 3,466 (OH), 3,418 (NH), 1,703 (CO of lactone), 1,651 (CO of
1
ketone), 1,622 (CO of lactam), 1,600 (CN), 1,202 (C–O–C); H NMR (500 MHz,
CDCl3) d: 5.12 (s, 1H, CH), 6.66 (d, J = 4.0 Hz, 1H, Ar–H), 6.78 (dd, J = 4.0 Hz,
J = 8.0 Hz, 1H, Ar–H), 6.88 (d, J = 8.0 Hz, 1H, Ar–H), 7.18 (d, J = 7.2 Hz, 2H,
Ar–H), 7.36–7.55 (m, 3H, Ar–H), 7.72–7.82 (m, 4H, Ar–H), 8.22 (s, 1H, Coumarin
H), 9.28 (s, 1H, NH), 9.44 (s, 1H, OH) ppm; 13C NMR (125 MHz, CDCl3) d: 30.4,
102.6, 104.8, 110.3 117.1, 121.4, 124.8, 125.7, 126.1, 126.9, 127.5, 128.1, 128.5,
129.6, 130.6, 143.5, 146.7, 150.6, 156.0, 158.1, 162.1, 162.5, 164.4, 168.1 ppm;
MS(ESI): m/z 437 (M?H)?; Anal. Calcd for C26H16N2O5: C, 71.56; H, 3.67; N,
6.42 %. Found: C, 71.44; H, 3.61; N, 6.43 %.
8-Hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-(4-chlorophenyl)-3H-chromeno[2,3-
d]pyrimidin-4(5H)-one (6b)
IR (KBr, cm-1): 3,472 (OH), 3,409 (NH), 1,700 (CO of lactone), 1,661 (CO of
1
ketone), 1,629 (CO of lactam), 1,605 (CN), 1,212 (C–O–C); H NMR (500 MHz,
CDCl3) d: 5.09 (s, 1H, CH), 6.58 (d, J = 4.0 Hz, 1H, Ar–H), 6.74 (dd, J = 4.0 Hz,
J = 8.0 Hz, 1H, Ar–H), 6.85 (d, J = 8.0 Hz, 1H, Ar–H), 7.38 (d, J = 7.4 Hz, 2H,
Ar–H), 7.54 (d, J = 7.4 Hz, 2H, Ar–H), 7.68–7.80 (m, 4H, Ar–H), 8.46 (s, 1H,
Coumarin H), 9.37 (s, 1H, NH), 9.66 (s, 1H, OH) ppm; 13C NMR (125 MHz,
CDCl3) d: 29.6, 101.7, 105.0, 111.5, 117.7, 121.7, 124.4, 124.9, 126.3, 126.7, 127.0,
128.3, 128.7, 129.3, 131.2, 144.0, 145.9, 151.3, 155.5, 158.7, 162.3, 162.6, 165.0,
167.8 ppm; MS(ESI): m/z 471.45 (M?H)?; Anal. Calcd for C26H15ClN2O5: C,
66.32 H, 3.19; N, 5.95 %. Found: C, 66.26 H, 3.14; N, 5.90 %.
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Synthesis and in vitro microbiological evaluation of novel series
8-Hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-(4-bromophenyl)-3H-chromeno[2,3-
d]pyrimidin-4(5H)-one (6c)
IR (KBr, cm-1): 3,468 (OH), 3,415 (NH), 1,708 (CO of lactone), 1,666 (CO of
1
ketone), 1,620 (CO of lactam), 1,590 (CN), 1,207 (C–O–C); H NMR (500 MHz,
CDCl3) d: 5.11 (s, 1H, CH), 6.67 (d, J = 4.0 Hz, 1H, Ar–H), 6.81 (dd, J = 4.0 Hz,
J = 8.0 Hz, 1H, Ar–H), 6.91 (d, J = 8.0 Hz, 1H, Ar–H), 7.28–7.42 (m, 4H, ArH),
7.60–7.75 (m, 4H, Ar–H), 8.36 (s, 1H, Coumarin H), 9.48 (s, 1H, NH), 9.56 (s, 1H,
OH) ppm; 13C NMR (125 MHz, CDCl3) d: 30.6, 101.9, 104.5, 111.7, 117.2, 120.9,
124.3, 125.5, 126.5, 127.0, 127.4, 128.5, 128.8, 129.1, 130.7, 144.3, 145.5, 151.4,
156.2, 158.3, 162.5, 163.0, 164.8, 168.4 ppm; MS(ESI): m/z 515.9 (M?H)?; Anal.
Calcd for C26H15BrN2O5: C, 60.59; H, 2.91; N, 5.44 %. Found: C, 60.55; H, 2.88;
N, 5.43 %.
8-Hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-(4-fluorophenyl)-3H-chromeno[2,3-
d]pyrimidin-4(5H)-one (6d)
IR (KBr, cm-1): 3,478 (OH), 3,411 (NH), 1,711 (CO of lactone), 1,655 (CO of ketone),
1,633 (CO of lactam), 1,588 (CN), 1,215 (C–O–C); 1H NMR (500 MHz, CDCl3) d:
5.21 (s, 1H, CH), 6.55 (d, J = 4.0 Hz, 1H, Ar–H), 6.74 (dd, J = 4.0 Hz, J = 8.0 Hz,
1H, Ar–H), 6.87 (d, J = 8.0 Hz, 1H, Ar–H), 7.33–7.45 (m, 4H, ArH), 7.77–7.88 (m,
4H, Ar–H), 8.40 (s, 1H, Coumarin H), 9.42 (s, 1H, NH) 9.55 (s, 1H, OH) ppm; 13C
NMR (125 MHz, CDCl3) d: 29.9, 102.0, 105.2, 112.0, 117.6, 121.1, 124.1, 125.7,
126.2, 126.9, 127.7, 128.7, 128.9, 129.5, 131.3, 144.1, 146.3, 150.9, 156.3, 158.4,
162.2, 163.2, 164.6, 167.7 ppm; MS(ESI): m/z 455 (M?H)?; Anal. Calcd for
C26H15FN2O5: C, 68.72; H, 3.30; N, 6.17 %. Found: C, 68.66; H, 3.25; N, 6.15 %.
8-Hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-(4-methylphenyl)-3H-chromeno[2,3-
d]pyrimidin-4(5H)-one (6e)
IR (KBr, cm-1): 3,465 (OH), 3,422 (NH), 1,699 (CO of lactone), 1,650 (CO of
1
ketone), 1,638 (CO of lactam), 1,585 (CN), 1,209 (C–O–C); H NMR (500 MHz,
CDCl3) d: 2.28 (s, 3H, CH3), 5.18 (s, 1H, CH), 6.62 (d, J = 4.0 Hz, 1H, Ar–H), 6.73
(dd, J = 4.0 Hz, J = 8.0 Hz, 1H, Ar–H), 6.84 (d, J = 8.0 Hz, 1H, Ar–H), 7.40 (d,
J = 7.4 Hz, 2H, Ar–H), 7.52 (d, J = 7.4 Hz, 2H, Ar–H), 7.69–7.79 (m, 4H, Ar–H),
8.29 (s, 1H, Coumarin H), 9.24 (s, 1H, NH), 9.48 (s, 1H, OH) ppm; 13C NMR
(125 MHz, CDCl3) d: 19.7, 30.3, 101.5, 104.9, 112.1, 117.2, 120.7, 123.9, 124.6,
126.4, 127.1, 127.7, 128.0, 128.3, 129.4, 130.9, 143.7, 145.8, 151.2, 155.9, 158.6,
161.8, 162.7, 165.1, 168.5 ppm; MS(ESI): m/z 451 (M?H)?; Anal. Calcd for
C27H18N2O5: C, 72.00; H, 4.00; N, 6.22 %. Found: C, 72.03; H, 4.00; N, 6.17 %.
8-Hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-(4-methoxyphenyl)-3H-chromeno[2,3-
d]pyrimidin-4(5H)-one (6f)
IR (KBr, cm-1): 3,478 (OH), 3,410(NH), 1,710 (CO of lactone), 1,662 (CO of
1
ketone), 1,631 (CO of lactam), 1,603 (CN), 1,222 (C–O–C); H NMR (500 MHz,
123

M. Ghashang et al.
CDCl3) d: 3.54 (s, 3H, OCH3), 5.15 (s, 1H, CH), 6.68 (d, J = 4.0 Hz, 1H, Ar–H),
6.79 (dd, J = 4.0 Hz, J = 8.0 Hz, 1H, Ar–H), 6.88 (d, J = 8.0 Hz, 1H, Ar–H), 7.28
(d, J = 7.4 Hz, 2H, Ar–H), 7.41 (d, J = 7.4 Hz, 2H, Ar–H), 7.76–7.90 (m, 4H, Ar–
H), 8.35 (s, 1H, Coumarin H), 9.40 (s, 1H, NH), 9.40 (s, 1H, OH) ppm; 13C NMR
(125 MHz, CDCl3) d: 29.5, 56.3, 102.1, 105.3, 110.9, 117.4, 121.3, 123.7, 125.0,
125.8, 126.5, 127.0, 127.9, 128.6, 129.8, 131.4, 144.4, 146.0, 151.4, 156.1, 157.9,
161.9, 162.6, 165.4, 167.3 ppm; MS(ESI): m/z 467 (M?H)?; Anal. Calcd for
C27H18N2O6: C, 69.53; H, 3.86; N, 6.01 %. Found: C, 69.44; H, 3.82; N, 6.00 %.
8-Hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-(4-nitrophenyl)-3H-chromeno[2,3-
d]pyrimidin-4(5H)-one (6g)
IR (KBr, cm-1): 3,460 (OH), 3,413 (NH), 1,705 (CO of lactone), 1,667 (CO of
1
ketone), 1,625 (CO of lactam), 1,591 (CN), 1,218 (C–O–C); H NMR (500 MHz,
CDCl3) d: 5.05 (s, 1H, CH), 6.65 (d, J = 4.0 Hz, 1H, Ar–H), 6.80 (dd, J = 4.0 Hz,
J = 8.0 Hz, 1H, Ar–H), 6.93 (d, J = 8.0 Hz, 1H, Ar–H), 7.39 (d, J = 7.4 Hz, 2H,
Ar–H), 7.54 (d, J = 7.4 Hz, 2H, Ar–H), 7.67–7.84 (m, 4H, Ar–H), 8.40 (s, 1H,
Coumarin H), 9.33 (s, 1H, NH), 9.51 (s, 1H, OH) ppm; 13C NMR (125 MHz,
CDCl3) d: 29.8, 101.9, 104.7, 111.6, 117.3, 120.5, 124.2, 125.4, 126.1, 126.7, 127.3,
127.8, 128.7, 129.7, 131.6, 143.6, 145.4, 150.9, 155.8, 157.8, 161.7, 162.4, 164.3,
168.0 ppm; MS(ESI): m/z 482 (M?H)?; Anal. Calcd for C26H15N3O7: C, 64.86; H,
3.19; N, 8.73 %. Found: C, 64.78; H, 3.16; N, 8.75 %.
8-Hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-(4-hydroxyphenyl)-3H-chromeno[2,3-
d]pyrimidin-4(5H)-one (6h)
IR (KBr, cm-1): 3,480 (OH), 3,461 (OH), 3,417 (NH), 1,692 (CO of lactone), 1,653
1
(CO of ketone), 1,629 (CO of lactam), 1,595 (CN), 1,210 (C–O–C); H NMR
(500 MHz, CDCl3) d: 5.22 (s, 1H, CH), 6.56 (d, J = 4.0 Hz, 1H, Ar–H), 6.76 (dd,
J = 4.0 Hz, J = 8.0 Hz, 1H, Ar–H), 6.86 (d, J = 8.0 Hz, 1H, Ar–H), 7.34 (d,
J = 7.4 Hz, 2H, Ar–H), 7.45 (d, J = 7.4 Hz, 2H, Ar–H), 7.59–7.81 (m, 4H, Ar–H),
8.37 (s, 1H, Coumarin H), 9.41 (s, 1H, NH), 9.44 (s, 1H, OH) 9.62 (s, 1H, OH) ppm;
13C NMR (125 MHz, CDCl3) d: 30.6, 102.3, 105.4, 110.8, 116.8, 121.5, 124.5,
125.6, 126.3, 126.9, 127.6, 128.2, 128.8, 129.0, 130.6, 144.5, 146.2, 151.0, 155.6,
157.7, 162.4, 162.9, 164.7, 168.2 ppm; MS(ESI): m/z 453 (M?H)?; Anal. Calcd for
C26H16N2O6: C, 69.03; H, 3.54; N, 6.19 %. Found: C, 69.00; H, 3.50; N, 6.20 %.
8-Hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-(3-hydroxyphenyl)-3H-chromeno[2,3-
d]pyrimidin-4(5H)-one (6i)
IR (KBr, cm-1): 3,477 (OH), 3,455 (OH), 3,420 (NH), 1,698 (CO of lactone), 1,663
1
(CO of ketone), 1,636 (CO of lactam), 1,608 (CN), 1,206 (C–O–C); H NMR
(500 MHz, CDCl3) d: 5.03 (s, 1H, CH), 6.67 (d, J = 4.0 Hz, 1H, Ar–H), 6.77 (dd,
J = 4.0 Hz, J = 8.0 Hz, 1H, Ar–H), 6.87 (d, J = 8.0 Hz, 1H, Ar–H), 7.36–7.45
(m, 4H, ArH), 7.61–7.74 (m, 4H, Ar–H), 8.27 (s, 1H, Coumarin H), 9.28 (s, 1H,
NH), 9.38 (s, 1H, OH), 9.60 (s, 1H, OH) ppm; 13C NMR (125 MHz, CDCl3) d: 30.2,
123

Synthesis and in vitro microbiological evaluation of novel series
101.8, 104.6, 111.5, 116.7, 120.9, 123.9, 124.7, 126.5, 126.8, 127.4, 128.4, 128.9,
129.9, 130.3, 143.9, 145.8, 150.7, 156.2, 158.4, 162.3, 163.1, 164.5, 167.6 ppm;
MS(ESI): m/z 453 (M?H)?; Anal. Calcd for C26H16N2O6: C, 69.05; H, 3.53; N,
6.11 %. Found: C, 69.03; H, 3.54; N, 6.19 %.
8-Hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-(4-N,N-dimethylaminophenyl)-3H-
chromeno[2,3-d]pyrimidin-4(5H)-one (6j)
IR (KBr, cm-1): 3,468 (OH), 3,408 (NH), 1,701 (CO of lactone), 1,658 (CO of
1
ketone), 1,627 (CO of lactam), 1,597 (CN), 1,214 (C–O–C); H NMR (500 MHz,
CDCl3) d: 2.65 (s, 6H, CH3), 5.13 (s, 1H, CH), 6.61 (d, J = 4.0 Hz, 1H, Ar–H),
6.76 (dd, J = 4.0 Hz, J = 8.0 Hz, 1H, Ar–H), 6.87 (d, J = 8.0 Hz, 1H, Ar–H), 7.33
(d, J = 7.4 Hz, 2H, Ar–H), 7.44 (d, J = 7.4 Hz, 2H, Ar–H), 7.66–7.78 (m, 4H, Ar–
H), 8.39 (s, 1H, Coumarin H), 9.45 (s, 1H, NH), 9.59 (s, 1H, OH) ppm; 13C NMR
(125 MHz, CDCl3) d: 29.7, 43.9, 101.8, 104.8, 112.2, 117.8, 120.6, 124.0, 125.6,
126.7, 127.2, 127.8, 128.5, 128.8, 129.4, 131.0, 144.2, 146.4, 150.8, 155.7, 158.5,
162.0, 162.5, 164.0, 168.7 ppm; MS(ESI): m/z 480 (M?H)?; Anal. Calcd for
C28H21N3O5: C, 70.15; H, 4.38; N, 8.77 %. Found: C, 70.05; H, 4.33; N, 8.75 %.
Results and discussion
The synthetic pathways of the compounds 6a–j were achieved via 2-amino-3-
cyano-7-hydroxy-4-phenyl-4Hchromene derivatives (4a–j). 4H-Chromenes possess
potent biological activities like antitumor, antibacterial, antiviral, spasmolytic, and
anti-anaphylactic [25–30]. Therefore, various synthetic procedures have been
developed for the preparation of 4H-chromene derivatives [31–41]. However, these
methods often suffer from different drawbacks and most of them give moderate
yields even after prolonged reaction times. This clearly indicates that there is still
scope to develop an efficient and eco-sustainable method for the synthesis of 4H-
chromene derivatives. The 4H-chromene derivatives were obtained by the three-
component condensation of resorcinol, aldehydes, and malononitrile using DMAP
as catalyst in ethanol.
A diverse array of Lewis bases (e.g., tertiary phosphines, tertiary amines,
pyridines, and imidazoles) have been shown to serve as nucleophilic catalysts. The
acylation of alcohols by anhydrides, catalyzed by 4-(dimethylamino)pyridine
(DMAP), is perhaps the most frequently encountered example of nucleophilic
catalysis. In the presence of DMAP, acylations typically occur several orders of
magnitude more rapidly than in its absence [42].
The accelerating pace of reported applications for DMAP and the availability of
DMAP in commercial quantities, at modest prices, has continued to stimulate great
interest in its use as a catalyst in the fields of organic, polymer, analytical, and
biochemistry. Today, there are thousands of examples of the use of DMAP in far-
ranging fields of chemistry in both patents and the research literature. Many full-
scale production processes utilizing DMAP have been and are being operated.
Several pharmaceutical and agricultural products that rely on DMAP’s superior
123

M. Ghashang et al.
catalytic properties in their synthetic sequences have been produced for years. Since
1976 ,more than 11,000 US patents have been granted which mention DMAP or
dimethylaminopyridine [43]. Moreover, DMAP is non-hygroscopic, and is available
commercially. Also, it is easy to filter. However, to the best of our knowledge, there
is no report which utilizes DMAP as a basic catalyst in the synthesis of 2-amino-3-
cyano-7-hydroxy-4-substituted-4Hchromene derivatives.
To discover the suitable conditions for the reaction, a series of experiments were
performed with the standard reaction of resorcinol 1, benzaldehyde 2a, and
malononitrile 3 as a model reaction (Scheme 1).
Our initial work started with the screening of solvent and catalyst so as to identify
optimal reaction conditions for the synthesis of chromene derivatives. To evaluate
the effect of the catalyst, we studied the reaction of benzaldehyde, resorcinol, and
malononitrile in different pyridine analogues, like DMAP, 4-carboxypyridine,
4-cyanopyridine, and pyridine, in ethanol. DMAP showed better catalytic activity
than 4-carboxypyridine, 4-cyanopyridine, and pyridine. The conversion of the
products increased in the order of 4-carboxy-pyridine\4-cyanopyridine\pyridine
\ DMAP. The electron-donating group-substituted pyridine exhibited higher
activity than the electron-withdrawing group-substituted pyridine.
Further, the reaction is carried out in methanol, water ,and under neat condition
in the presence of DMAP (10 mol %). Ethanol is proven to be the most suitable
solvent for this condensation in terms of yield and reaction time (Table 1, entry 4).
We also evaluated the amount of DMAP required for the reaction. The reaction was
significantly affected by decreasing the amount of DMAP from 10 to 5 mol%,
whereas no improvement could be observed upon increasing the catalyst loading to
15 mol% (Table 1, entries 11, 12). Thus, the best result was obtained with 10 mol%
of DMAP in ethanol at 60 °C (Table 1, entry 4). Encouraged by this successful
three-component reaction, the synthesis of diverse 2-amino-3-cyano-7-hydroxy-4-
phenyl-4Hchromene derivatives 4a–j was undertaken. The aromatic aldehydes
bearing electron-withdrawing and electron-donating groups were found to be
equally effective in producing 2-amino-3-cyano-7-hydroxy-4-phenyl-4Hchromene
derivatives 4a–j in very good yields (Table 2). The catalyst can be used at least four
times without a significant decrease in catalytic activity for the synthesis of
2-amino-3-cyano-7-hydroxy-4-phenyl-4Hchromene (Table 2, entry 1).
R
CHO
OH
CN
CN
DMAP (10 mol%)
EtOH, 60 oC
CN
R
HO
O
NH2
OH
1
2a-j
3
4a-j
Scheme 1 Synthesis of various 2-amino-3-cyano-7-hydroxy-4-phenyl-4Hchromene derivatives from
resorcinol, benzaldehydes, and malononitrile catalyzed by DMAP (10 mol %)
123

Synthesis and in vitro microbiological evaluation of novel series
Table 1 Optimization of the
Entry Solvent
Catalyst
Amount
(mol %)
Time Yield
(%)a
reaction conditions on the
synthesis of 2-amino-3-cyano-7-
hydroxy-4-phenyl-4Hchromene
(4a): solvent screening and
catalyst loading
(h)
1
2
EtOH
EtOH
4-Carboxy
pyridine
10
10
2
43
4-Cyano
pyridine
2
55
3
EtOH
EtOH
None
Pyridine
DMAP
DMAP
DMAP
DMAP
10
10
10
10
10
10
10
10
5
2
1
2
2
2
2
2
2
1
1
63
88
48
76
72
32
29
42
75
88
4
5
6
MeOH
Water
7
8
Dichlorometane DMAP
9
Cyclohexane
Acetonitrile
EtOH
DMAP
DMAP
DMAP
DMAP
Reaction conditions: resorcinol
(1 mmol), benzaldehyde
(1 mmol), malononitrile
(1 mmol) at 60 °C
10
11
12
EtOH
15
a
Isolated yield
Table 2 Synthesis of various
2-amino-3-cyano-7-hydroxy-4-
phenyl-4Hchromene derivatives
from resorcinol, benzaldehydes,
malononitrile catalysed by
DMAP (10 mol %)
Entry
R
Product Time Yield (%)a
(h)
Mp (°C)
1
2
H
4a
4b
4c
4d
4e
4f
1.0
1.0
1.0
1.0
1.5
1.5
1.0
1.5
1.5
1.5
88 (86, 84, 82)b 232–234
4-Cl
87
88
90
82
83
89
83
80
83
160–162
228–230
186–188
182–184
112–114
234–236
220–222
216–218
230–232
3
4-Br
4
4-F
5
4-CH3
4-OCH3
4-NO2
4-OH
3-OH
Reaction conditions: resorcinol
(1 mmol), benzaldehydes
(1 mmol), malononitrile
(1 mmol); DMAP 10 mol % in
ethanol at 60 °C
6
7
4g
4h
4i
8
9
a
Isolated yield
10
4-N(CH3)2 4j
b
Reusability of catalyst
After the synthesis of 2-amino-3-cyano-7-hydroxy-4-phenyl-4Hchromene, we
synthesized 8-hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-phenyl-3H-chromeno[2,3-
d]pyrimidin-4(5H)-one derivatives. Initially, the reaction between compound 4a
and coumarin-3-carboxylic acid was carried out under neat conditions at 60 °C
without and with different acid catalysts (sulfamic acid, silica perchloric acid,
xanthene sulfuric acid, melamine trisulfonic acid, SBPPSA; each 0.24 mmol) and
we observed maximum yield with SBPPSA (Table 3, entry 5).
The solvents played an important role in the synthesis of 8-hydroxy-2-(2-oxo-
2H-chromen-3-yl)-5-phenyl-3H-chromeno[2,3-d]pyrimidin-4(5H)-one derivatives.
Various reaction media were screened (ethanol, t-BuOH, acetonitrile, methanol,
THF, and 1,4-dioxane) using the model reaction (Table 4, entries 1–6). It was found
that the best results were obtained with 0.24 mmol of SBPPSA under solvent-free
123

M. Ghashang et al.
Amount of Time Yield
Table 3 Preparation of
Entry Catalyst
8-hydroxy-2-(2-oxo-2H-
chromen-3-yl)-5-phenyl-3H-
chromeno[2,3-d]pyrimidin-
4(5H)-one: catalyst screening
catalyst (mmol) (h)
(%)a
1
2
3
4
5
6
7
8
Sulfamic acid
0.24
0.24
0.24
4.0
4.0
4.0
4.0
3.0
4.0
3.0
3.0
68
Silica perchloric acid
Xanthene sulfuric acid
73
69
Melamine trisulfonic acid 0.24
58
SBPPSA
None
0.24
0
89
Reaction conditions: 4a
(1 mmol) and coumarin-3-
carboxylic acid (1 mmol) at
60 °C
Trace
89
SBPPSA
SBPPSA
0.30
0.18
76
a
Isolated yield
condition (Table 4, entry 7). The reaction was completed in 3 h and the expected
product was obtained in 90 % yield.
At these optimised conditions (solvent-free, 60 °C, 0.24 mmol of SBPPSA), we
synthesized various 8-hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-phenyl-3H-chro-
meno[2,3-d]pyrimidin-4(5H)-one derivatives 6a–j (Table 5) (Scheme 2). After
completion of the reaction, the catalyst was recovered by evaporating the aqueous
layer, which was washed with acetone, dried, and reused for four subsequent
reactions without significant loss of its activity (Table 5, entry 1; Fig. 1). All the
synthesized compounds were confirmed by their analytical and spectroscopic data.
Biological activity
All the compounds were screened for their antibacterial activity against Escherichia
coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Staphylococcus aureus,
and for antifungal activity against Aspergillus flavus, Rhizopus schipperae,
Aspergillus niger, and Candida albicans. Compounds 6b–j with various substituents
in the aromatic ring will be useful in understanding the influence of steric and
electronic effects on the biological activity.
Antibacterial activity
For evaluating antibacterial activity ,Ciprofloxacin was used as the standard drug.
Serial dilutions of the drug in Muller Hinton broth were placed in tubes and their pH
was adjusted to 5.0 using phosphate buffer. A standardized suspension of the test
bacterium was inoculated and incubated for 16–18 h at 37 °C. The minimum
inhibitory concentration (MIC) was noted by seeing the lowest concentration of the
drug at which there was no visible growth. The observed MIC are given in Table 6.
In general, all the synthesized compounds exerted a wide range of modest
antibacterial activity in vitro against the tested organisms. Compound 6a without
any substituent in the aryl moiety exhibits antibacterial activity in vitro at 75 lg/mL
against P. aeruginosa. It exhibits antibacterial activity against the other tested
organisms only at 150 lg/mL. However, 6b, in which the hydrogen at the para
position of the aryl moiety is replaced by chlorine, shows activity against all the
123

Synthesis and in vitro microbiological evaluation of novel series
Table 4 Preparation of 8-hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-phenyl-3H-chromeno[2,3-d]pyrimidin-
4(5H)-one: solvent screening
Entry
Solvent
Amount of
catalyst (mmol)
Time
(h)
Yield
(%)a
1
2
3
4
5
6
7
Ethanol
t-BuOH
Acetonitrile
Methanol
THF
0.24
0.24
0.24
0.24
0.24
0.24
0.24
4.0
4.0
4.0
4.0
4.0
4.0
3.0
77
29
41
69
46
57
90
1,4-Dioxane
None
Reaction conditions: 4a (1 mmol) and coumarin-3-carboxylic acid (1 mmol) in the presence of SBPPSA
(0.2 g, equal to 0.24 mmol of H?) at 60 °C
a
Isolated yields
Table 5 Preparation of various
Entry
R
Product Time Yield (%)a
(h)
Mp (°C)
8-hydroxy-2-(2-oxo-2H-
chromen-3-yl)-5-phenyl-3H-
chromeno[2,3-d]pyrimidin-
4(5H)-one derivatives
1
2
H
6a
6b
6c
6d
6e
6f
3.0
3.0
3.0
3.0
3.5
3.5
3.0
3.0
3.5
3.5
90 (88, 86, 85)b 218–220
4-Cl
86
88
87
85
84
91
93
90
81
226–228
242–244
202–204
208–210
246–248
234–236
220–222
214–216
230–232
3
4-Br
4
4-F
5
4-CH3
4-OCH3
4-NO2
4-OH
3-OH
Reaction conditions: 4a–j
(1 mmol) and coumarin-3-
carboxylic acid (1 mmol) in the
presence of SBPPSA
6
7
6g
6h
6i
8
(0.24 mmol) at 60 °C
9
a
Isolated yield
10
4-N(CH3)2 6j
b
Reusability of catalyst
R
R
O
SBPPSA
(0.24 mmol)
NH
O
HOOC
O
CN
HO
O
N
Solvent-free
60 oC
O
HO
O
NH2
O
4a-j
5
6a-j
O
SiO2
O
Si
N
O
N-SO3H
SBPPSA
Scheme 2 Synthesis of various 8-hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-phenyl-3H-chromeno[2,3-
d]pyrimidin-4(5H)-one derivatives from 4a–j and coumarin-3-carboxylic acid catalyzed by SBPPSA
123

M. Ghashang et al.
94
92
90
88
86
84
82
80
Reusability of the catalyst SBPPSA
90%
88%
86%
85%
1
2
3
4
Number of Runs
Fig. 1 Reusability of the catalyst SBPPSA for the synthesis of 8-hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-
phenyl-3H-chromeno[2,3-d]pyrimidin-4(5H)-one
Table 6 In vitro antibacterial
activity of compounds 6a–j
Compounds
Minimum inhibitory concentration (MIC) in lg/mL
E. coli P. aeruginosa K. pneumonia S. aureus
6a
6b
6c
6d
6e
6f
150
50
75
150
50
150
25
25
50
25
50
25
25
12.5
50
25
25
75
75
75
75
50
75
50
6g
6h
6i
12.5
75
12.5
50
12.5
75
12.5
50
50
25
50
25
6j
75
50
75
50
Ciprofloxacin 25
12.5
25
25
tested organisms in the range of 25–50 lg/mL. Compound 6c, which has the
bromine in the para position, has the same activity as 6b, which has the chlorine in
the para position. Indeed, the compounds 6b–j, bearing a substituent in the aryl
group, are more active than the parent compound 6a. Only 6g which has a nitro
group at the para position and 6d which has a fluorine group in the para position are
more active than the reference drug Ciprofloxacin.
Antifungal activity
For evaluating antifungal activity, Amphotericin B was used as the standard drug.
Newly prepared compounds were also screened for their antifungal activity against
123

Synthesis and in vitro microbiological evaluation of novel series
Table 7 In vitro antifungal
activity of compounds 6a–j
Compounds
Minimum inhibitory concentration (MIC) in lg/
mL
A. flavus R. schipperae A. niger C. albicans
6a
6b
6c
6d
6e
6f
150
75
100
50
50
50
75
75
25
75
50
75
25
100
75
100
25
75
75
25
50
50
25
100
100
25
100
100
25
100
75
6 g
6h
6i
12.5
50
100
75
100
75
25
6j
75
100
50
50
Amphoterecin-
B
50
25
each fungal strain in DMSO by the serial plate dilution method. Sabourauds agar
media was prepared by dissolving peptone (1 g), D-glucose (4 g) and agar (2 g) in
distilled water (100 mL) and adjusting the pH to 5.7. Normal saline was used to
make a suspension of some of the fungal strains for lawning. A loopful of a
particular fungal strain was transferred to 3 mL saline to get a suspension of the
corresponding species. Twenty milliliters of agar media was poured into each Petri
dish. Excess of suspension was decanted and plates were dried by placing in an
incubator at 37 °C for 1 h. Using a punch, wells were made in these seeded agar
plates. The observed MIC are given in Table 7. It is seen that 6a shows antifungal
activity against all the tested fungi in the range of 100–150 lgmL-1. Compounds
6b–j which have substituents in the 4-aryl group are more active than the parent
compound 6a against all the tested fungi. The para-chloro compound 6b and the
para-bromo compound 6c have the same activity. Compounds 6d and 6g are more
active than the standard drug Amphotericin B against all the tested organisms.
Influence of aromatic substituents
The results suggest that the antibacterial and antifungal activities are markedly
influenced by the aromatic substituents. Thus, 6b, 6c, and 6g with electron-
withdrawing substituents in the aromatic ring show greater antibacterial activity
than the other compounds against all the tested organisms. Also, compounds 6d and
6g show greater antifungal activity than all the other compounds against all the
tested organisms. The aromatic substituents in 6b, 6c, and 6g have positive values
for the Hammett substituent constant rp [Cl (?0.23), Br (?0.23) and NO2 (?0.78)].
The aromatic substituents in 6e, 6f, and 6j have negative values for the Hammett
substituent constant rp [CH3 (-0.17), OCH3 (-0.27) and N(CH3)2 (-0.83)]. The
4-fluoro compound 6d is the most active compound, though the rp value of F
(?0.06) is less than that of the other substituents. Probably, the 4-fluoro compound
123

M. Ghashang et al.
is able to interact with the microorganisms more effectively due to some
intermolecular hydrogen bonding. Fluorine has the greatest ability to form hydrogen
bonding, and hence 6d is more active than the other compounds. The Hammett
substituent constant r for the aromatic substituents in 6h and 6i are rp OH (-0.37)
and rm OH (?0.12), respectively. Hence, 6i is more active than 6h.
Conclusions
In summary, we have developed a direct and efficient method for the preparation
of 8-hydroxy-2-(2-oxo-2H-chromen-3-yl)-5-phenyl-3H-chromeno[2,3-d]pyrimidin-
4(5H)-one derivatives by the condensation of 2-amino-3-cyano-7-hydroxy-4-
phenyl-4Hchromene derivatives with coumarin-3-carboxylic acid in the presence
of 0.24 mmol of SBPPSA as catalyst under solvent-free conditions. This method
tolerates most of the substrates, and the catalyst can be used at least four times
without significant loss of activity. All the compounds were screened for their
antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Klebsiella
pneumoniae, and S. aureus and antifungal activity against Aspergillus flavus,
Rhizopus schipperae, Aspergillus niger, and C. albicans.
Acknowledgment The author Mansoor is grateful to C. Abdul Hakeem College Management for the
facilities and support.
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