Clean and convenient one-pot synthesis of 4-hydroxycoumarin and 4-hydroxy-2-quinolinone derivatives

Article abstract of DOI:10.1080/00397910903013713

A simple, efficient, and environmentally friendly procedure has been developed for the reaction of Meldrum's acid with phenol, substituted phenols, aniline, or substituted anilines with Eaton's reagent (phosphoric anhydride+methylsulfonic acid) as cyclization reagent. 4-Hydroxycoumarins and 4-hydroxy-2-quinolinones were synthesized in moderate yields by carrying out the reaction in solvent-free, convenient, and clean one-pot preparation.

Full text of DOI:10.1080/00397910903013713

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Clean and Convenient One-Pot Synthesis
of 4-Hydroxycoumarin and 4-Hydroxy-2-
quinolinone Derivatives
Wen-Tao Gao a , Wen-Duan Hou a , Mei-Ru Zheng a & Li-Jun Tang a
a College of Chemistry and Chemical Engineering, Bohai University,
Jinzhou, Liaoning, China
Version of record first published: 04 Feb 2010.
To cite this article: Wen-Tao Gao , Wen-Duan Hou , Mei-Ru Zheng & Li-Jun Tang (2010): Clean and
Convenient One-Pot Synthesis of 4-Hydroxycoumarin and 4-Hydroxy-2-quinolinone Derivatives,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 40:5, 732-738
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Synthetic Communications1, 40: 732–738, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910903013713
CLEAN AND CONVENIENT ONE-POT SYNTHESIS OF
4-HYDROXYCOUMARIN AND 4-HYDROXY-2-
QUINOLINONE DERIVATIVES
Wen-Tao Gao, Wen-Duan Hou, Mei-Ru Zheng, and Li-Jun Tang
College of Chemistry and Chemical Engineering, Bohai University, Jinzhou,
Liaoning, China
A simple, efficient, and environmentally friendly procedure has been developed for the reac-
tion of Meldrum’s acid with phenol, substituted phenols, aniline, or substituted anilines with
Eaton’s reagent (phosphoric anhydride þ methylsulfonic acid) as cyclization reagent.
4-Hydroxycoumarins and 4-hydroxy-2-quinolinones were synthesized in moderate yields
by carrying out the reaction in solvent-free, convenient, and clean one-pot preparation.
Keywords: Eaton’s reagent; 4-hydroxycoumarin; 4-hydroxy-2-quinolinone; one-pot
INTRODUCTION
4-Hydroxycoumarin and 4-hydroxy-2-quinolinone derivatives are naturally
occurring biologically active compounds[1,2] and are useful intermediates for many
industrial products such as dye stuffs,[3,4] herbicides,[5,6] and anticancer agents.[7]
In addition, recent reports showed 4-hydroxy-2-quinolinone derivatives, such as
4-hydroxy-3-arylquinolin-2(1H)-one and 4-hydroxy-3-nitro quinolin-2(1H)-one,
were selective glycine site antagonists related to several central nervous system
disorders including stroke, epilepsy, schizophrenia, Parkinson disease, and
Alzheimer disease.[8–13]
Many synthetic approaches to 4-hydroxycoumarin have been reported, mainly
using phenol,[14,15] acetosalicylic acid,[16,17] methyl salicylate,[18] or 20-
hydroxyacetophenone[19–21] as starting material. In 1960, Shah and coworkers[14]
developed a one-step method for the synthesis of 4-hydroxycoumarin in which phe-
nol was treated with malonic acid, zinc chloride, and phosphorus oxychloride at
approximately 65ꢀC to afford the corresponding 4-hydroxycoumarin. Since that
time, it has become an alternative and effective method for the preparation of
4-hydroxycoumarin derivatives.[22] However, this method still suffers from several
disadvantages such as long reaction time, tedious workup procedure, and poor yield.
Recently, acetosalicylic acid, methyl salicylate, or 20-hydroxyacetophenone has been
used for the synthesis of 4-hydroxycoumarin derivatives utilizing multiple steps or
Received September 8, 2008.
Address correspondence to Wen-Tao Gao, College of Chemistry and Chemical Engineering, Bohai
University, 19 Keji Road, Jinzhou, Liaoning 12100, China. E-mail: isfc@bhu.edu.cn
732

4-HYDROXYCOUMARINS AND 4-HYDROXY-2-QUINOLINONES
733
expensive reagents. The microwave-assisted means has also been used in the
synthesis of 4-hydroxy-2-quinolinone under the catalyst toluenesulfonic acid.[23]
RESULTS AND DISCUSSION
To contribute to the development of environmentally benign organic chemis-
try, we are focusing our research on the new, clean, and convenient one-pot prep-
aration of 4-hydroxycoumarin and 4-hydroxy-2-quinolinone derivatives without
using POCl3 and Lewis acids such as AlCl3. The procedure is depicted in Scheme 1.
In the envisaged annulation step, cyclization of malonic acid monoaryl ester to
form 4-hydroxycoumarin and 4-hydroxy-2-quinolinone derivatives is a convenient
procedure; the crucial problem to be solved is to reduce or eliminate the decarbox-
ylation of the intermediates. Thus, Eaton’s reagent was chosen as cyclization reagent
in mild reaction condition. Malonic acid monoaryl ester or amide can readily be
synthesized in good yield from the reaction of hydroxyl- or amino group–substituted
benzene with Meldrum’s acid.
Malonic acid monoester (3a) had been synthesized by the reaction of phenol
and Meldrum’s acid with the toluene as solvent.[24] Here, we successfully performed
the reaction under solvent-free conditions, which resulted in a good yield (90.2%).
Acetone, as a sole by-product and useful solvent, was collected in 90% yield by a
cooling tube apparatus in the reaction process. As a result, this process is very clean
and very atom efficient.
Even more convenient is that the obtained compound 3a needed no separation
and could immediately be treated with the cyclization reagent, thus making the
one-pot synthesis of 4-hydroxy-coumarin possible.
We first estimated the reactivity of the one-pot model reaction between phenol
1a (1 mmol) and Meldrum’s acid 2 (1 mmol) in solvent-free conditions at 100ꢀC: after
3 h, acetone was collected in 90.0% yield by a cooling tube apparatus in the reaction
process with the small remaining amount of acetone removed under vacuum. The
Scheme 1. One-pot synthesis of 4-hydroxycoumarin and 4-hydroxy-2-quinolinone.

734
W.-T. GAO ET AL.
residue was then immediately treated with Eaton’s reagent at 70ꢀC for 4 h, also
without adding solvent. Finally, 10 mL H2O were added to produce the corres-
ponding 4-hydroxycoumarin (4a) in 60.5% yield. The separation and purification
processes are very simple, because they involved only Buchner funnel filtration
and recrystallization by ethanol. This methodology was extended to the synthesis
of 4-hydroxy-2-quinolinone (4g) in 62.8% yield.
In a second series of experiments, we explored the general validity of the
present methodology; different 4-hydroxycomarin and 4-hydroxy-2-quinolinone
derivatives were synthesized in yields of 60.5–90.1% and 50.2–79.1%.
It must be emphasized that when R is an electron-withdrawing group, the
desired compound is given in relatively poor yield (see Table 1, 4i), whereas when
R is an electron-donating group, the corresponding product can be obtained in good
yield (Table 1, 4b).
The results in Table 1 indicate that the present 4-hydroxycoumarin preparation
has considerable facility, because a variety of substituted 4-hydroxycoumarins and
4-hydroxy-2-quinolinones have been obtained from inexpensive materials (i.e., sub-
stituted phenols, substituted anilines, Meldrum’s acid, Eaton’s reagent). Moreover,
the yields of the substituted 4-hydroxycoumarin and 4-hydroxy-2-quinolinone deri-
vatives in Table 1 ranged from 50.2% to 90.1%, which increases the attractiveness of
the approach. Finally, the reaction was very clean and avoided the use of POCl3 and
Lewis acids such as AlCl3. These considerations demonstrated that the present
method offers certain advantages when substituted 4-hydroxycoumarin and
4-hydroxy-2-quinolinone derivatives are desired.
Table 1. One-pot synthesis of 4-hydroxycoumarin and 4-hydroxy-2-quinolinone derivatives
Compound
X
R1
R2
R3
Yield (%)
4a
4b
4c
4d
4e
4f
O
O
H
But
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
But
Me
OMe
H
60.5
90.1
70.4
70.5
69.3
82.6
62.8
64.4
50.2
61.3
66.0
79.1
67.0
O
O
H
O
Me
H
O
But
H
4g
4h
4i
NH
NH
NH
NH
NH
NH
NH
H
H
Me
Br
H
4j
H
OMe
H
Et
4k
4l
Me
H
4m
Et
H

4-HYDROXYCOUMARINS AND 4-HYDROXY-2-QUINOLINONES
735
CONCLUSION
In summary, a clean and convenient one-pot synthesis of 4-hydroxycoumarin
and 4-hydroxy-2-quinolinone derivatives has been developed. The procedure offers
several advantages including mild reaction conditions as well as simple experimental
and product isolation procedures, thus making this a useful and attractive
methodology.
EXPERIMENTAL
Melting points were measured on an X-6 micromelting-point apparatus and
are uncorrected. NMR spectra were recorded using a Varian Inova 500 NMR spec-
trometer at 500 MHz (1H NMR), and chemical shifts are expressed in Parts per
million (ppm) relative to tetramethylsilane (TMS), used as an internal standard.
Infrared (IR) spectra were measured as KBr pellets with a Fourier transform
(FT)=IR-430 spectrophotometer. Elemental analyses were carried out on an EA
1110 instrument.
Synthesis of 4-Hydroxycoumarin Derivatives (4a–4f)
A mixture of phenol (0.094 g, 1.0 mmol) and Meldrum’s acid (0.144 g,
1.0 mmol) was stirred at 100ꢀC for 3 h (monitored by thin-layer chromatography,
TLC). Afterward, the small remaining amount of acetone was removed by vacuum.
Eaton’s reagent (3 mL) was added to the mixture at 70ꢀC for 4 h. Then water was
added to this mixture while stirring vigorously. The precipitate was filtered by
suction, washed with H2O, and air dried to give a solid. It was recrystallized from
ethanol to afford 4a–4f.
Selected Data
4-Hydroxycoumarin (4a). Yellow powder; mp 213.0–214.3ꢀC (lit.[19]
211–213ꢀC);1H NMR (CDCl3) d: 12.53 (br s, 1H, OH), 7.22–7.93 (m, 4H, ArH),
ꢁ1
=
5.55 (s, 1H, ¼CH); IR (KBr) n: 3394 (OH), 1694 (C O) cm
.
6,8-Di-tert-butyl-4-hydroxycoumarin (4b). White solid; mp 262.2–263.5ꢀC;
1H NMR (CDCl3) d: 10.88 (br s, 1H, OH), 7.85 (d, J ¼ 2.35 Hz, 1H, ArH), 7.61 (d,
J ¼ 2.35 Hz, 1H, ArH), 6.02 (s, 1H, ¼CH), 1.52 [s, 9H, C(CH3)3], 1.43 [s, 9H,
C(CH3)3]; IR (KBr) n: 3247 (OH), 1680 (C O) cmꢁ1; Anal. calcd. for C17H22O3:
=
C, 74.42; H, 8.08; Found: C, 74.35; H, 8.11.
4-Hydroxy-6-methyl-coumarin (4c). Pale white powder; mp 261.0–261.2ꢀC
(lit.[22] 257–258ꢀC); 1H NMR (DMSO) d: 12.40 (br s, 1H, OH), 7.63 (d, J ¼ 8.55 Hz,
1H, ArH), 7.41–7.43 (m, 1H, ArH), 7.25 (d, J ¼ 1.25 Hz, 1H, ArH), 5.55 (s, 1H,
¼CH), 2.35 (s, 3H, ArCH3); IR (KBr) n: 3446 (OH), 1693
ꢁ1
=
(C O) cm
.
4-Hydroxy-6-methoxy-coumarin (4d). Pale red solid; mp 254.4–254.7ꢀC;
1H NMR (CDCl3) d: 12.30 (br s, 1H, OH), 7.72 (d, J ¼ 8.50 Hz, 1H, ArH),
6.89–6.92 (m, 2H, ArH), 5.42 (s, 1H, ¼CH), 3.85 (s, 3H, OCH3); IR (KBr) n:

736
W.-T. GAO ET AL.
3423 (OH), 1699 (C O) cmꢁ1. Anal. calcd. for C10H8O4: C, 62.50, H, 4.20; Found:
C, 62.47, H, 4.13.
=
4-Hydroxy-8-methyl-coumarin (4e). Yellow powder; mp 231.1–233.4ꢀC;
1H NMR (CDCl3) d: 12.39 (br s, 1H, OH), 7.65 (d, J ¼ 7.85 Hz, 1H, ArH), 7.52
(d, J ¼ 7.35 Hz, 1H, ArH), 7.18–7.21 (m, 1H, ArH), 5.55 (s, 1H, ¼CH), 2.35 (s,
3H, ArCH3); IR (KBr) n: 3438 (OH), 1694 (C O) cmꢁ1. Anal. calcd. for
=
C10H8O3: C, 68.18; H, 4.58. Found: C, 68.15; H, 4.52.
6-tert-Butyl-4-hydroxycoumarin (4f). Pale red crystal; mp 200.0–202.2ꢀC
(lit.[22] 199–201ꢀC); 1H NMR (DMSO-d6) d: 12.16 (br s, 1H, OH), 7.92 (d, J ¼ 2.60 Hz,
1H, ArH), 7.71 (d, J ¼ 8.50 Hz, 1H, ArH), 7.21–7.24 (m, 1H, ArH), 5.70 (s, 1H, ¼CH),
ꢁ1
=
1.48 [s, 3H, C(CH3)3]; IR (KBr) n: 3380 (OH), 1660 (C O) cm
.
Synthesis of 4-Hydroxy-2-quinolinone Derivatives (4g–4m)
A mixture of aniline (0.093 g, 1.0 mmol) and Meldrum’s acid (0.144 g,
1.0 mmol) was stirred at 80ꢀC for 1 h (monitored by TLC). Afterward, the small
remaining amount of acetone was removed by vacuum. Eaton’s reagent (3 mL)
was added to the mixture at 70ꢀC for 2 h. Then water was added to this mixture while
stirring vigorously. The precipitate was filtered by suction, washed with H2O, and air
dried to give a solid. It was recrystallized from ethanol to afford 4g–4m.
Selected Data
4-Hydroxy-quinolin-2-one
1
(4g). Pale
pink
crystal;
mp > 300ꢀC
(lit.[25] > 300ꢀC); H NMR (DMSO-d6): d 11.8 (br s, 1H, OH), 11.18 (s, 1H, NH),
7.77 (d, J ¼ 7.80 Hz, 1H, ArH), 7.48 (t, J ¼ 7.80 Hz, 1H, ArH), 7.25 (d, J ¼ 8.10 Hz,
1H, ArH), 7.13 (t, J ¼ 7.80 Hz, 1H, ArH), 5.73 (s, 1H, CH ¼); IR (KBr) n:
ꢁ1
=
3504–2900, 1662 (C O) cm
.
4-Hydroxy-6-methyl-1H-quinolin-2-one (4h). White farina; mp > 300ꢀC
1
(lit.[26] > 300ꢀC); H NMR (DMSO): d 11.19 (br s, 1H, OH), 11.09 (1H, s, NH),
7.55 (1H, s, ArH), 7.25–7.27 (1H, m, ArH), 7.15 (1H, d, J ¼ 8.35 Hz, ArH), 5.78
ꢁ1
=
(1H, s, CH¼), 2.35 (3H, s, CH3); IR (KBr) n: 3554–2890, 1662 (C O) cm
.
6-Bromo-4-hydroxy-1H-quinolin-2-one (4i). White crystal; >300ꢀC; 1H
NMR (DMSO): d 11.26 (br s, 1H, OH), 11.30 (s, 1H, NH), 7.85 (d, J ¼ 2.25 Hz,
1H, ArH), 7.63–7.65 (m, 1H, ArH), 7.21 (d, J ¼ 8.75 Hz, 1H, ArH), 5.75 (s, 1H,
CH¼); IR (KBr) n: 3471–2950, 1593 (C O) cmꢁ1. Anal. calcd. for C9H6BrO2N:
=
C, 45.03; H, 2.52; N, 5.83. Found: C, 45.13; H, 2.44; N, 5.65.
4-Hydroxy-6-methoxy-1H-quinolin-2-one (4j). White crystal; mp > 300ꢀC
(lit.[25] 298–300ꢀC); 1H NMR (DMSO): d 11.24 (br s, 1H, OH), 11.05 (s, 1H,
NH), 7.20–7.22 (m, 2H, ArH), 7.12–7.15 (m, 1H, ArH), 5.75 (s, 1H, CH¼), 3.79
(s, 3H, CH3); IR (KBr) n: 3552–2910, 1622 (C O) cmꢁ1. Anal. calcd. for
=
C10H9NO3: C, 62.82, H, 4.74; N, 7.33. Found: C, 63.00; H, 3.75; N, 7.35.
4-Hydroxy-8-methyl-1H-quinolin-2-one (4k). White solid; mp > 300ꢀC;
1H NMR (DMSO): d 11.27 (br s, 1H, OH), 10.26 (br s, 1H, NH), 7.65 (d, J ¼ 7.55 Hz,

4-HYDROXYCOUMARINS AND 4-HYDROXY-2-QUINOLINONES
737
1H, ArH), 7.32 (d, J ¼ 7.20 Hz, 1H, ArH), 7.05 (t, J ¼ 7.60 Hz, 1H, ArH), 5.75 (1H, s,
CH¼), 2.41 (s, 3H, CH3); IR (KBr) n: 3508–2900, 1688 (C O) cmꢁ1. Anal. calcd. for
=
C10H9NO2: C, 68.56; H, 5.18; N, 8.00. Found: C, 68.50; H, 5.22; N, 8.07.
1
6-Ethyl-4-hydroxy-1H-quinolin-2-one (4l). White crystal; mp > 300ꢀC; H
NMR (DMSO): d 11.23 (br s, 1H, OH), 11.03 (s, 1H, NH), 7.54 (d, 1H, J ¼ 1.00 Hz,
ArH), 7.34–7.36 (m, 1H, ArH), 7.15 (d, 1H, J ¼ 8.40 Hz, ArH), 5.70 (s, 1H, CH¼),
2.62–2.66 (m, 2H, CH2), 1.20 (t, J ¼ 7.55 Hz, 3H, CH3); IR (KBr) n: 3500–2920, 1670
(C O) cmꢁ1. Anal. calcd. for C11H11NO2: C, 69.83; H, 5.86; N, 7.40. Found: C,
=
69.77; H, 5.82; N, 7.47.
8-Ethyl-4-hydroxy-1H-quinolin-2-one (4m). White crystal; mp > 300ꢀC; 1H
NMR (DMSO): d 11.41 (br s, 1H, OH), 10.09 (s, 1H, NH), 7.43–7.45 (m, 1H, ArH),
7.41–7.43 (m, 1H, ArH), 7.15–7.18 (m, 1H, ArH), 5.68 (s, 1H, CH¼), 2.73–2.74 (m,
2H, CH2), 1.32 (t, 3H, CH3); IR (KBr) n: 3540–2900, 1680 (C O) cmꢁ1. Anal. calcd.
=
for C11H11NO2: C, 69.83; H, 5.86; N, 7.40. Found: C, 69.79; H, 5.88; N, 7.36.
ACKNOWLEDGMENT
The financial support provided by Science Foundation of Liaoning Province of
China (No. 202, 142, 037) is sincerely acknowledged.
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