Synthesis of amide and ester derivatives of naphthopyrone carboxylic acid

Article abstract of DOI:10.1002/jhet.2136

The synthesis of various amide and ester derivatives of naphthopyrone-2-carboxylic acid has been carried out by reaction of 1-naphthol with dimethyl acetylenedicarboxylate, which gave a mixture of E and Z isomers of naphthoxy diester. The diester on hydrolysis with KOH gave corresponding diacid, which was a mixture of E and Z isomers. The E and Z isomers were difficult to separate, which were subjected to cyclization in sulfuric acid to get cyclized naphthopyrone carboxylic acid. This acid is converted into titled compounds.

Full text of DOI:10.1002/jhet.2136

July 2014
Synthesis of Amide and Ester Derivatives of Naphthopyrone
Carboxylic Acid
1185
*
J. N. Soni and S. S. Soman
Department of Chemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat 390002, India
*
E-mail: shubhangis@rediffmail.com
Received July 6, 2013
DOI 10.1002/jhet.2136
Published online 17 December 2013 in Wiley Online Library (wileyonlinelibrary.com).
The synthesis of various amide and ester derivatives of naphthopyrone-2-carboxylic acid has been carried
out by reaction of 1-naphthol with dimethyl acetylenedicarboxylate, which gave a mixture of E and Z isomers
of naphthoxy diester. The diester on hydrolysis with KOH gave corresponding diacid, which was a mixture of
E and Z isomers. The E and Z isomers were difficult to separate, which were subjected to cyclization in
sulfuric acid to get cyclized naphthopyrone carboxylic acid. This acid is converted into titled compounds.
J. Heterocyclic Chem., 51, 1185 (2014).
INTRODUCTION
expecting to show monoamine oxidase inhibition activity
and antiallergic activity. Synthesis of chromone-2-carboxylic
acid was reported from our laboratory earlier [13]. No one
has reported angular amide and ester derivatives of
naphthopyrone-2-carboxylic acid. Present investigation re-
ports synthesis of a new class of various amides using two dif-
ferent methods and ester derivatives of naphthopyrone-2-
carboxylic acid.
Chromones (benzopyran-4-ones) are one of the most abun-
dant groups of naturally occurring heterocyclic compounds [1].
Chromones have remarkable biological properties such as
antituberculosis [2,3]. Chromone scaffold has been recognized
as a pharmacophore of a number of bioactive molecules.
Disodium cromoglycate, the sodium salt of cromoglycic acid,
is a clinically useful antiallergic agent, particularly for bron-
chial asthma, and reported to inhibit the release of mediators
such as histamine, several kinins, and so on, of immediate
hypersensitivity reactions [4], which contain a chromone ring.
Heterocyclic analogues of ritonavir, HIV-1 protease inhibitor
are amide derivatives of chromone-2-carboxylic acid [5].
Chromone-3-carboxamide derivatives have been reported as
monoamine oxidase-B (MAO-B) inhibitors [6,7], whereas
chromone-2-carboxylic acid derivatives are reported as mela-
nin-concentrating hormone receptor 1 antagonists [8] or aden-
osine receptor ligands [9]. Photodimerization [10] reactions of
chromone-2-carboxylic esters and microwave-assisted synthe-
sis of various amide derivatives of chromone-2-carboxylic
acids [11] have been reported. Vercauteren et al. [12]
have reported the use of activated alkynes for condensing it
with tryptamine Pictel–Spengler synthesis of tertahydro-
β-carbolines, which involves acid-catalyzed ring closure.
Condensation [13] of 1-naphthol 1 with dimethyl
acetylenedicarboxylate (DMAD) in the presence of anhydrous
K2CO3 and dry acetone gave Z or cis and E or trans mixture of
dimethyl 2-(naphthalen-1-yloxy)maleate 2. It was not possible
to separate the Z and E mixture either by column chromatogra-
phy or by TLC method (Scheme 1). Earlier, S. S. Soman [13]
and J. K. Lynch [8] could not separate the Z and E isomer of
adducts obtained by the condensation of DMAD with couma-
rin and phenol, respectively. The IR spectrum of 2/2′ exhibited
band at 1735 cmÀ1 for ester group. In the 1H-NMR spectrum
of 2/2′, four singlets at δ 3.65, 3.68, 3.70, and 4.03 for methoxy
group clearly indicated that it is a Z and E mixture. The singlet
at δ 5.01 for one proton indicated Z or cis vinylic proton,
whereas the singlet at δ 6.72 indicated E or trans vinylic proton.
All aromatic protons appeared between δ 6.75 and 8.34
confirmed the formation of 2 as cis–trans mixture. The ratio
of E and Z isomer of 2 was found to be 57:43 from 1H-NMR.
Mild hydrolysis of 2/2′ in aqueous KOH (1%) at room
temperature gave a mixture of Z and E or cis and trans 2-
(naphthalen-1-yloxy)maleic acid 3/3′, which also could
not be separated into Z and E isomer. The IR spectrum of
RESULTS AND DISCUSSION
In view of these findings, we have synthesized various am-
ide and ester derivatives of naphthopyrone-2-carboxylic acid,
© 2013 HeteroCorporation

1186
J. N. Soni and S. S. Soman
Vol 51
Scheme 1. Condition: (i) 1-Naphthol, Dimethyl acetylenedicarboxylate, K2CO3, dry acetone, reflux, 8 h (ii) 1% aqueous KOH, RT, 12 h
(iii) H2SO4, 60–70°C, 2 h.
3/3′ showed bands at 1713 cmÀ1 and broad band at
2500–3053 cmÀ1 for > C═O and –OH of carboxylic acid.
Now, the absence of singlet for methoxy group in
1H-NMR spectrum of 3/3′ confirmed the hydrolysis of
esters. The presence of singlet for one proton each at δ
4.95 and 6.66 indicated cis and trans vinylic protons
confirming it as Z and E mixture. Compound 3/3′on
cyclization with concentrated sulfuric acid gave 4-
oxo-4H-benzo[h]chromene-2-carboxylic acid 4. The IR
spectrum of 4 showed bands at 1725 cmÀ1, and broad band
from 2500–3500 cmÀ1 indicated presence of carboxylic
acid group. The other sharp band at 1641 cmÀ1 indicated
presence of carbonyl group of chromone. In 1H-NMR
spectrum of 4 in DMSO-d6, the disappearance of two sin-
glets at δ 4.95 and 6.66 and the appearance of one singlet
at δ 7.07 indicated aromatic proton at C-3, thus confirmed
the cyclization. The multiplet from δ 7.81 to 8.53 for six
protons indicated remaining aromatic protons (Scheme 1).
This acid 4 is converted into corresponding amide 5 using
two different methods [14]. Formation of amide 5a–b using
1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochlo-
ride (EDC.HCl), 4, 4′-dimethylaminopyridine (DMAP) and
amine gave very low yield, hence, we have used
oxalylchloride and prepared acid chloride of 4 and then its
reaction with pyrrolidine gave 5c (Scheme 2).
Scheme 2. Condition: (iv) EDC.HCl, DMAP, Triethylamine, Amine, dry
THF, RT, 8 h (v) Oxalyl chloride, DMF, CH2Cl2, 2 h (vi) Amine, TEA,
CH2Cl2, 8 h (vii) Alcohol, Dry HCl gas, 2 h.
We have synthesized various esters [15] 6a–e of
naphthopyrone-2-carboxylic acid by using various alcohols
and passing dry HCl gas as shown in Scheme 2. The structures
obtained by reaction of 1-naphthol with DMAD was found
to be inseparable cis and trans mixture. From 1H-NMR, the
trans isomer was found to be a major product than cis iso-
mer. The corresponding diacid 3 obtained by hydrolysis of
diester 2 with aqueous KOH was found to be cis and trans
mixture. Here, also trans isomer was found to be a major
product. Hence, the yield of naphthopyrone-2-carboxylic
acid was found to be less. The cyclized naphthopyrone-
2-carboxylic acid was converted into corresponding
amides using EDC.HCl. Because the yields were very
1
of all compounds were confirmed by their IR, H-NMR,
13C-NMR, mass spectra, and elemental analyses.
CONCLUSION
We have synthesized naphthopyrone-2-carboxylic acid
from corresponding naphthyloxy diacid. The diester 2
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

July 2014
Naphthopyrone, Carboxylic Acid, Amide, Ester
1187
with plenty of water, and dried, which gave a yellow solid.
low, the naphthopyrone-2-carboxylic acid was converted
into the corresponding acid chloride and then treated with
amine to get the corresponding amide. Naphthopyrone-
2-carboxylates were prepared by using various alcohols
and passing dry HCl gas.
(0.2 g, 21.5%); mp: 148–150°C; IR (KBr): υ 3445 (OH), 3084,
2984, 1724 (>C═O), 1641 (>C═O) cmÀ1
;
1H-NMR
(400 MHz, DMSO-d6): δ 7.07 (1H, s, Ar H), 7.81–7.87 (2H, m
Ar H), 7.97 (2H, s, Ar H), 8.12–8.15 (1H, m, Ar H), 8.48–8.53
(1H, m, Ar H).
General method for 5a–5b.
In a solution of 4 (0.5g,
0.21mmol) in dry THF (50mL) EDC.HCl (0.4g, 0.21mmol),
DMAP (0.05 g, 10%), triethylamine (0.61 mL, 0.43 mmol), and
p-toluidine/morpholine (0.21 mmol) were added. The reaction
mass was stirred at room temperature for 8 h, and then poured
into ice and extracted with ethyl acetate. After removal of
solvent, it gave a brown liquid. The crude product was purified
by column chromatography using 5% ethyl acetate in
petroleum ether.
EXPERIMENTAL
Reagent grade chemicals and solvents were purchased from
a commercial supplier and used without purification. TLC was
performed on silica gel F254 plates (Merck, India). Acme’s
(India) silica gel (60–120 mesh) was used for column chromato-
graphic purification. Melting points are uncorrected and were
measured in open capillary tubes, using a Rolex melting point
apparatus (India). IR spectra were recorded as KBr pellets on
4-Oxo-N-p-tolyl-4H-benzo[h]chromene-2-carboxamide
(5a). This compound was obtained as a brown solid. (0.125 g, 14%);
mp: 205–210°C; IR (KBr): υ 3348 (NH), 3063, 2919, 2855, 1694
1
PerkinElmer RX 1 spectrometer. H-NMR and 13C-NMR spec-
(>C═O), 1651 (>C═O) cmÀ1 1H-NMR (400 MHz, CDCl3): δ
;
tral data were recorded on Bruker Advance 400 spectrometer
(400 MHz) (India) with TMS as internal standard. J values are
in hertz. Elemental analyses were recorded on Thermosinnigan
Flash 11-12 series EA. Mass spectra were determined by ESI/
MS, using a Shimadzu LCMS 2020 apparatus (India).
2.41 (3H, s, CH3), 7.27–7.29 (2H, d, J = 8 Hz, Ar H), 7.41 (1H, s,
Ar H), 7.66–7.68 (2H, d, J = 8.4 Hz, Ar H), 7.78–7.82 (2H, m, Ar
H), 7.85–7.88 (1H, d, J = 8.8 Hz, Ar H), 7.99–8.02 (1H, m, Ar H),
8.17–8.20 (1H, d, J = 8.4 Hz, Ar H), 8.46–8.48 (1H, dd, J = 3.6,
6.0 Hz, Ar H), 8.57 (1H, s, NH); 13C-NMR (400 MHz, CDCl3): δ
21.05, 113.90, 120.56, 120.78, 121.06, 121.70, 123.48, 126.44,
127.71, 128.68, 129.87, 129.91, 133.75, 135.73, 136.36, 152.62,
154.29, 156.97, 177.79; ms: m/z 330.0 [M + 1]+; Anal. Calcd for
C21H15NO3: C, 76.58; H, 4.59; N, 4.25. Found: C, 76.45; H,
Dimethyl 2-(naphthalen-1-yloxy)maleate (2/2′).
To the
solution of 1-naphthol 1 (5 g, 3.47 mmol) in dry acetone (50 mL),
anhydrous potassium carbonate (16.77 g, 12.13 mmol), a solution of
dimethyl acetylenedicarboxylate (4.26 mL, 3.47 mmol) in dry
acetone (100 mL), was added very slowly. The reaction mixture
was refluxed for 8 h in water bath. The reaction mass was poured in
crushed ice and extracted with ethyl acetate, which gave a viscous
liquid after the removal of ethyl acetate, which was purified by
column chromatography using 5% ethyl acetate in petroleum ether,
which gave a brown liquid. (7.2 g, 72.5%); IR (KBr): υ 3053, 2880,
1735 (>C═O) cmÀ1;1H-NMR (400 MHz, CDCl3): δ 3.65 (3H, s),
3.68 (3H, s), 3.70 (3H, s), 4.03 (3H, s), 5.01 (1H, s, cis vinylic
proton), 6.72 (1H, s, trans vinylic proton), 6.75–6.77 (1H, dd,
J=8.0Hz, Ar H), 7.26–7.29 (1H, m, Ar H), 7.31–7.35 (1H, t,
J = 7.6, 8.4 Hz, Ar H), 7.47–7.51 (1H, t, J = 7.6, 8.4 Hz, Ar H),
7.55–7.60 (5H, m, Ar H), 7.79–7.81 (1H, d, J=8.4Hz, Ar H),
7.84–7.87 (1H, m, Ar H), 7.91–7.93 (1H, m, Ar H), 8.00–8.04
4.69; N, 4.41.
2-(Morpholine-4-carbonyl)-4H-benzo[h]chromen-4-one
(5b). This compound was obtained as a brown solid. (0.09 g,
12%); mp: 96–100°C; IR (KBr): υ 3099, 2961, 2921, 2851, 1743
(>C═O), 1645 (>C═O) cmÀ1 1H-NMR (400 MHz, CDCl3): δ
;
2.03–2.06 (4H, m, -N- CH2), 3.67–3.70 (2H, t, -O- CH2), 4.51–4.54
(2H, t, -O- CH2), 7.30 (1H, s, Ar H), 7.73–7.80 (2H, m, Ar H),
7.84–7.86 (1H, d, J= 8.8 Hz, Ar H), 7.97–7.99 (1H, dd, J=1.6,
6.8 Hz, Ar H), 8.14–8.16 (1H, d, J= 8.8 Hz, Ar H), 8.64–8.66 (1H,
dd, J= 1.6, 7.6 Hz); Anal. Calcd for C18H15NO4: C, 69.89; H, 4.89;
N, 4.53. Found: C, 70.15; H, 4.63; N, 4.71.
2-(Pyrrolidine-1-carbonyl)-4H-benzo[h]chromen-4-one
(5c). Compound 4 (0.5 g, 0.21 mmol) dissolved in dichloromethane
(50 mL) and dimethylformamide (2 to 3 drops), oxalyl chloride
(0.79 mL, 0.83 mmol) was added slowly to the reaction flask and
stirred at room temperature for 2 h. the solvent was removed under
reduced pressure. The acid chloride obtained was dissolved in
dichloromethane (50 mL), triethylamine (0.56 mL, 0.40 mmol),
and pyrrolidine (0.17 mL, 0.21 mmol) were added and stirred at
room temperature for 8 h. The reaction mixture was poured into
water and extracted with dichloromethane (50 mL) thrice. The
solvent was removed under vacuum and the compound purified
by column chromatography using 5% ethyl acetate in
petroleum ether, which gave a yellow solid. (0.16 g, 23%); mp:
105–110°C; IR (KBr): υ 2963, 2919, 2875, 1629 (>C═O)
cmÀ1; 1H-NMR (400 MHz, CDCl3): δ 2.05–2.08 (4H, m, CH2),
3.74–3.77 (2H, t, CH2), 3.84–3.88 (2H, t, CH2), 6.95 (1H, s,
Ar H), 7.69–7.78 (2H, m, Ar H), 7.83–7.85 (1H, d, J = 8.4 Hz,
Ar H), 7.97–7.99 (1H, dd, J = 8.0 Hz, Ar H), 8.17–8.19 (1H, d,
J = 8.4 Hz, Ar H), 8.50–8.52 (1H, dd, J = 8.0 Hz, Ar H); Anal.
Calcd for C18H15NO3: C, 73.71; H, 5.15; N, 4.78. Found: C,
73.45; H, 5.33; N, 4.91.
(1H, m, Ar H), 8.34–8.36 (1H, m, Ar H).
2-(Naphthalen-1-yloxy)maleic acid (3/3′). The adduct 2/2′
(7.2g, 2.51 mmol) was stirred with 1% aqueous solution of KOH
(350mL) for 3 h and then left at room temperature for 12h. The
reaction mixture was extracted with dichloromethane (50 mL)
thrice, and the aqueous solution was acidified with concentrated
hydrochloric acid till pH 2; the solid obtained was filtered, the
crude product dissolved in saturated sodium bicarbonate, filtered,
and reprecipitated using concentrated hydrochloric acid to give a
yellow solid. (6g, 92.4%); mp: 165–170°C; IR (KBr): υ 3053,
2880, 1713 (>C═O) cmÀ1 1H-NMR (400 MHz, DMSO-d6): δ
;
4.95 (1H, s, cis vinylic proton), 6.66 (1H, s, trans vinylic proton),
6.76–0.678 (1H, d, J = 7.6 Hz, Ar H), 7.38–7.42 (2H, m, Ar H),
7.54–7.64 (6H, m, Ar H), 7.87–8.04 (4H, m, Ar H), 8.17–8.19
(1H, m, Ar H).
4-Oxo-4H-benzo[h]chromene-2-carboxylic acid (4).
A
mixture of 3/3′ (1 g, 0.38 mmol) and concentrated sulfuric acid
(10 mL) was heated at 60–70C for 2 h. The reaction mixture
was poured into ice. The solid product was filtered, washed
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

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J. N. Soni and S. S. Soman
Vol 51
General procedure for 6a–6e.
Compound
4
(0.1 g,
Butyl 4-oxo-4H-benzo[h]chromene-2-carboxylate (6e). This
compound was obtained as a yellow solid. (0.04 g, 32%); mp:
84–86°C; IR (KBr): υ 3099, 3056, 2959, 2872, 1744 (>C═O),
0.04 mmol) dissolved in different alcohols and dry HCl gas was
purged for 2 h. Different alcohols were removed under vacuum,
poured into ice, and then extracted with dichloromethane; after
removal of the solvent, it gave a brown liquid. The crude
compound was purified by column chromatography using 5%
ethyl acetate in petroleum ether to obtain corresponding ester
derivatives.
1
1651 (>C═O) cmÀ1; H-NMR (400 MHz, CDCl3): δ 1.02–1.06
(3H, t, CH3), 1.52–1.57 (2H, q, CH2), 1.83–1.86 (2H, m, CH2),
4.46–4.49 (2H, t, ÀOCH2), 7.26 (1H, s, Ar H), 7.71–7.75
(2H, m, Ar H), 7.77–7.81 (1H, d, J = 8.8 Hz, Ar H), 7.92–7.95
(1H, dd, J = 1.2, 8.8 Hz, Ar H), 8.09–8.11 (1H, d, J = 8.8 Hz,
Ar H), 8.59–8.62 (1H, dd, J = 1.2, 8.8 Hz, Ar H); 13C-NMR
(400 MHz, CDCl3): δ 13.73, 19.17, 30.50, 66.76, 116.06,
120.33, 121.02, 122.86, 124.03, 126.20, 127.53, 128.11,
129.91, 136.23, 151.64, 153.65, 160.52, 178.19; ms: m/z
296.9 [M + 1]+; Anal. Calcd for C18H16O4: C, 72.96; H, 5.44.
Found: C, 72.67; H, 5.61.
Ethyl 4-oxo-4H-benzo[h]chromene-2-carboxylate (6a). This
compound was obtained as a yellow solid. (0.03g, 27%); mp: 126–
128°C; IR (KBr): υ 2994, 2904, 1739 (>C═O), 1651 (>C═O)
cmÀ1 1H-NMR (400 MHz, CDCl3): δ 1.49–1.53 (3H, t, CH3),
;
4.53–4.55 (2H, q, CH2), 7.29 (1H, s, Ar H), 7.73–7.77 (2H, m, Ar
H), 7.81–7.83 (1H, d, J = 8.8Hz, Ar H), 7.94–7.97 (1H, dd,
J = 1.6, 7.2 Hz, Ar H), 8.12–8.14 (1H, d, J = 8.4 Hz, Ar H), 8.63–
8.65 (1H, dd, J = 1.6, 7.6 Hz, Ar H); 13C-NMR (400 MHz,
CDCl3): δ 14.18, 63.02, 116.09, 120.34, 121.03, 122.89, 124.04,
126.20, 127.53, 128.11, 129.92, 136.23, 151.65, 153.65, 160.49,
178.18; ms: m/z 269.0 [M+ 1]+; Anal. Calcd for C16H12O4: C,
71.64; H, 4.51. Found: C, 71.35; H, 4.72.
Acknowledgments. The authors are thankful to the Head,
Department of Chemistry, Faculty of Science, The M. S. University
of Baroda for providing laboratory facility. One of the authors
(J. N. S) is thankful to UGC New Delhi (RFSMS) for their
financial support.
Methyl 4-oxo-4H-benzo[h]chromene-2-carboxylate (6b).
This
compound was obtained as a yellow solid. (0.025 g, 24%); mp:
148–150°C; IR (KBr): υ 3072, 2956, 2922, 2853, 1746
(>C═O), 1655 (>C═O) cmÀ1; 1H-NMR (400 MHz, CDCl3): δ
4.01 (3H, s, CH3), 7.29 (1H, d, J = 1.2 Hz, Ar H), 7.72–7.79
(2H, m, Ar H), 7.82–7.84 (1H, d, J = 8.8 Hz, Ar H), 7.95–7.98
(1H, dd, J = 1.6, 7.2Hz, Ar H), 8.13–8.15 (1H, d, J = 8.8 Hz,
Ar H), 8.64–8.65 (1H, s, Ar H); 13C-NMR (400 MHz,
CDCl3): δ 53.60, 116.21, 120.30, 121.00, 122.85, 123.95,
126.17, 127.52, 128.09, 129.92, 136.20, 151.34, 153.57,
160.98, 178.02; Anal. Calcd for C15H10O4: C, 70.86; H,
3.96. Found: C, 70.55; H, 4.29.
REFERENCES AND NOTES
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H., Eds; Chapman and Hall: London, 1975; pp 971–1055.
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ton, B. D.; Falls, D.; Ogiela, C.; Reilly, R. M.; Campbell, T. J.;
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Med Chem 2012, 54, 914.
Isopropyl 4-oxo-4H-benzo[h]chromene-2-carboxylate (6c). This
compound was obtained as a yellow solid. (0.026 g, 23%); mp:
122–124°C; IR (KBr): υ 3059, 2885, 2834, 1732 (>C═O),
1
1683 (>C═O) cmÀ1; H-NMR (400 MHz, CDCl3): δ 1.48 (3H, s,
CH3), 1.49 (3H, s, CH3), 5.32–5.40 (1H, m, CH), 7.73 (1H, s, Ar
H), 7.74–7.78 (2H, m, Ar H), 7.83–7.85 (1H, d, Ar H), 7.96–7.99
(1H, dd, J= 1.6, 8.8 Hz, Ar H), 8.14–8.16 (1H, d, J=8.8Hz, Ar H),
8.65–8.74 (1H, d, J=7.6Hz, Ar H); 13C-NMR (400 MHz, CDCl3):
δ 21.79, 29.72, 71.24, 115.96, 120.36, 121.03, 122.91, 124.08,
126.18, 127.52, 128.11, 129.91, 136.25, 151.95, 153.69, 159.98,
178.30; ms: m/z 282.9 [M + 1]+; Anal. Calcd for C17H14O4: C,
72.76; H, 4.51. Found: C, 72.33; H, 5.00.
Allyl 4-oxo-4H-benzo[h]chromene-2-carboxylate (6d). This
compound was obtained as a yellow solid. (0.04 g, 34%); mp:
96–98°C; IR (KBr): υ 3059, 2885, 2829, 1732 (>C═O), 1683
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2011, 52, 6446.
[12] Vercauteren, J.; Lavand, C.; Levy, J.; Massiot, G. J Org Chem
1984, 49, 2278.
(>C═O) cmÀ1 1H-NMR (400 MHz, CDCl3): δ 4.96–4.97 (2H,
;
t,ÀOCH2), 5.41–5.44 (1H, dd, vinylic terminal proton), 5.51–5.56
(1H, m, vinylic terminal proton), 6.02–6.13 (1H, m, vinylic proton),
7.30 (1H, s, Ar H), 7.72–7.76 (2H, m, Ar H), 7.80–7.82 (1H, d,
J = 8.8 Hz, Ar H), 7.94–7.96 (1H, d, J = 7.6 Hz, Ar H), 8.11–8.13
(1H, d, J = 8.8Hz, Ar H), 8.61–8.63 (1H, dd, J = 1.6, 7.6Hz, Ar
H); 13C-NMR (400 MHz, CDCl3): δ 67.26, 116.29, 119.86,
120.33, 121.05, 122.86, 124.00, 126.25, 127.56, 128.12, 129.95,
130.80, 136.24, 151.40, 153.64, 160.20, 178.08; ms: m/z 281.0
[M + 1]+; Anal. Calcd for C17H12O4: C, 72.85; H, 4.32.
Found: C, 72.63; H, 4.50.
[13] Soman, S. S. Ind J Chem 1999, 38B, 542.
[14] Guillon, C. D.; Koppel, G. A.; Brownstein, M. J.; Chaney,
M. O.; Ferris, C. F.; Lu, S.; Fabio, K. M.; Miller, M. J.; Heindel, N. D.;
Hunden, D. C.; Cooper, R. D. G.; Kaldor, S. W.; Skelton, J. J.; Dressman,
B. A.; Clay, M. P.; Steinberg, M. I.; Brunsf, R. F.; Simon, N. G. Bioorg
Med Chem 2007, 15, 2054.
[15] Singh, S.; Basmadjian, G. P.; Avor, K. S.; Pouw, B.; Seale,
T. W. J Med Chem 1997, 40, 2474.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet