Synthesis of novel 7-(heteryl/aryl)chromones via Suzuki coupling reaction

Article abstract of DOI:10.1515/hc-2014-0004

A series of new 7-heteroaryl and arylchromones 6a-l were synthesized in moderate to good yields by the Suzuki reaction of the triflate (pseudo halide) 5 and a variety of heteroaryl and aryl boronic acids. The resulting products may be used as precursors for synthesis of potentially relevant compounds. The structures of all synthesized compounds were established based on IR, 1H NMR, ¹³C NMR, and DIPMS.

Full text of DOI:10.1515/hc-2014-0004

ꢁꢁꢁꢂ
ꢀHeterocycl. Commun. 2014; 20(2): 129–132
DOI 10.1515/hc-2014-0004ꢀ
NSayrendlatAhneithsa,iKs. Voenfugnoopavl Reedld7y*-a(nhd Ye. Jtaeyarpryakla/sah Rrayol)chromones via
Suzuki coupling reaction
Abstract: A series of new 7-heteroaryl and arylchromones groups present in substrates [15], and it proceeds well in
6a–l were synthesized in moderate to good yields by the the presence of water. In addition, the inorganic byprod-
Suzuki reaction of the triflate (pseudo halide) 5 and a uct of the reaction is non-toxic and easily removed from
variety of heteroaryl and aryl boronic acids. The resulting the mixture. This report presents synthesis of 7-heteryl/
products may be used as precursors for synthesis of poten- aryl-2,3-dimethylchromones starting from 7-hydroxy-
tially relevant compounds. The structures of all synthe- 2,3-dimethylchromones using the Suzuki coupling reac-
1
sized compounds were established based on IR, H NMR, tion. To the best of our knowledge, there are no reports
13C NMR, and DIPMS.
in the literature on C-C bond formation at C-7 position of
chromones.
Keywords: heteroaryl/arylboronic acids; heteroaryl/aryl-
chromones; pseudo halides; Suzuki coupling.
Results and discussion
*Corresponding author: K. Venugopal Reddy, Department of
Chemistry, Osmania University, Hyderabad 500007, Andhra
Pradesh, India, e-mail: kvgr1951@gmail.com
The aim of the present work was to develop a simple
and efficient procedure for the preparation of new chr-
omone derivatives bearing substituted heteroaryl and
aryl moieties by Suzuki cross coupling reactions. Aryl
triflates are good leaving groups that are more reactive
than aryl chlorides, bromides, and more stable to mois-
ture and air. The key intermediate chromenyl triflate 5
was prepared by a conventional method, which involves
treatment of the corresponding 7-hydroxy-2,3-dimethyl-
chromone 4 with triflic anhydride in the presence of
base triethylamine [16, 17]. Compound 4 [18, 19] was
prepared from resorcinol according to a procedure in
the literature (Scheme 1). The structure of chromenyl
triflate 5 was established by spectral analysis. The reac-
tion of the substrate 5 with boronic acids and esters in
the presence of Pd(PPh3)4, sodium carbonate in N,N-
dimethylformamide under mild conditions afforded the
corresponding heteroaryl and arylchromones 6a–l in
moderate to good yields (Scheme 2). Because aryl tri-
flates are sensitive to strong bases, sodium carbonate
was used to carry out the Suzuki reaction. The struc-
tures of compounds 6a–l were confirmed by spectral
analysis.
Naredla Anitha: Product Delivery Team, Integrated Product
Development, Innovation plaza, Dr. Reddy’s Laboratories Ltd.,
Baachupalli, Hyderabad 500072, Andhra Pradesh, India
Y. Jayaprakash Rao: Department of Chemistry, University College of
Science Saifabad, Osmania University, Hyderabad 5000007, Andhra
Pradesh, India
Introduction
Chromones (4H-1-benzopyran-4-ones) are naturally
occurring oxygen-containing heterocyclic compounds,
which perform important biological functions in nature
[1] and are a recognized pharmacophore of a large
number of bioactive molecules of either natural or syn-
thetic origin. Their derivatives are antibacterial, antican-
cer, antioxidant, estrogenic agents [2–4], and have been
considered as privileged structures in drug development
[5]. The Suzuki coupling reaction is the palladium cata-
lyzed C-C bond formation reaction of organoboran com-
pounds with organic halides or pseudo halides [6]. The
Suzuki reaction has recently gained much prominence
because it is suitable for large-scale synthesis includ-
ing the industrial synthesis of pharmaceuticals and fine
chemicals [7–9]. The key advantages of Suzuki coupling Conclusions
are mild reaction conditions and commercial availability
of a wide variety of heterocyclic and arylboronic acids A simple and efficient method of synthesis of heteryl- and
that are safer than other organometallic reagents [10–14]. aryl-substituted chromones 6a–l using the Suzuki cross
The Suzuki coupling process tolerates many functional coupling reaction was described.
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130ꢀ
ꢀN. Anitha et al.: 7-(Heteryl/aryl)chromones via Suzuki coupling reaction
Ac
2O
-CH -COOH
O
O
O
CH3
HO
OH
2
HO
OH
O
H
C
3COONa
ZnCl2
Heat
O
Heat
3
1
2
O
S
O
S
O
F
3C
F
C
3
O
H
O
O
O
F
3C
S
O
O
O
O
O
TEA
DCM
O
4
5
Scheme 1ꢀSynthesis of 2,3-dimethyl-4-oxo-4H-chromen-7-yl trifluoromethanesulfonate (5).
O
1
8
5
8a
4a
F
3C
Ar
S
O
O
O
O
2
ArB(OH)2, Na2CO3/H2O
Pd(PPh3)4 DMF
7
O
3
6
4
O
6a-l
5
6g: Ar = 2-methoxyphenyl
6h: Ar = 4-fluoro-3-methoxyphenyl
6i: Ar = 3-cyanophenyl
6a: Ar = 5-methyl-2-furyl
6b: Ar = 2,3-diflurophenyl
6c: Ar = 3-flurophenyl
6j: Ar = 2-trifluromethylphenyl
6k: Ar = 3-chloro-4-methylphenyl
6l: Ar = 3-chloro-4-flurophenyl
6d: Ar = 3,4-dimethylphenyl
6e: Ar = 2-thienyl
6f: Ar = 4-chloro-3-pyridyl
Scheme 2ꢀSynthesis of 7-(aryl/heteryl)-substituted chromones 6a–l.
3.0 Hz, H-4′), 2.40 (s, CH3-2), 2.39 (s, CH3-5′), 2.05 (s, CH3-3); 13C NMR:
δ 177.6 (Cꢀ= ꢀO), 166.9 (C-2′), 161.8 (C-2), 156.4 (C-8a), 156.2 (C-5′), 142.4
(C-7), 128.4 (C-4′), 124.8 (C-3′), 124.4 (C-4a), 123.5 (C-5), 121.4 (C-6), 116.7
(C-3), 115.1 (C-8), 20.2 (5′-CH3), 18.7 (2-CH3), 10.2 (3-CH3). HR-ESI-MS.
Calcd for C16H14O3+: m/z 254.0943, found: m/z 254.0938.
Experimental
Chromenyl triflate 5 [16, 17] and 7-hydroxy-2,3-dimethylchromone 4
[18, 19] were prepared by the reported procedures. Melting points were
obtained on a Polmon instrument, model MP 96, and were uncor-
rected. IR spectra were recorded in KBr pellets on a Fourier trans-
7-(2,3-Diflurophenyl)-2,3-dimethyl-4H-4-chromone (6b) Yield
70%; mp 136°C; IR: 1638.0 cm-1 (Cꢀ= ꢀO); 1H NMR: δ 8.28 (d, J ꢀ= ꢀ 8.0 Hz,
H-5), 7.61 (d, J ꢀ= ꢀ 1.2 Hz, H-8), 7.54 (dd, J ꢀ= ꢀ 8.0 Hz, J ꢀ= ꢀ 1.2 Hz, H-6),
7.29–7.20 (m, H-3′, H-4′, H-5′), 2.46 (s, CH3-2), 2.11 (s, CH3-3); 13C NMR:
δ 177.4 (Cꢀ= ꢀO), 162.2 (C-2), 155.6 (C-8a), 148.2 (C-2′), 142.7 (C-3′), 143.6
(C-5), 136.7 (C-7), 129.6 (C-1′), 127.3 (C-6′), 126.7 (C-5′), 123.3 (C-4a), 121.7
(C-4′), 117.3 (C-6), 117.1 (C-3), 115.4 (C-8), 18.6 (2-CH3), 10.1 (3-CH3). HR-
ESI-MS: Calcd for C17H12F2O2+: m/z 286.0805, found: m/z 286.0801.
form Perkin-Elmer model 337 instrument. H NMR (400 MHz) and 13C
1
NMR (100.6 MHz) spectra were recorded in CDCl3 solution on a Bruker
400 spectrometer using TMS as an internal standard. Mass spectral
data were obtained with an Agilent-6310 ion trap mass spectrometer.
General procedure for synthesis of 7-(aryl and
heteroaryl)-2,3-dimethyl-4-chromones 6a–l
7-(3-Fluorophenyl)-2,3-dimethyl-4H-4-chromone (6c) Yield 58%;
1
mp 107°C; IR: 1630.0 cm-1 (Cꢀ= ꢀO); H NMR: δ 8.25 (d, J ꢀ= ꢀ 8.0 Hz, H-5),
A mixture of chromenyl triflate 5 (0.8 mmol), a boronic acid (1.2
mmol), and aqueous Na2CO3 (1 mL, 2 m) in DMF was purged with
nitrogen with stirring for 30 min, and then treated with 4 mol% of
tetrakis(triphenylphosphine)palladium(0). The reaction mixture
was stirred at 60°C for 3–4 h. Afer completion of the reaction, the
mixture was cooled to room temperature, diluted with water (50 mL),
and extracted with diethyl ether (3 ꢀ× ꢀ 30 mL). The extract was dried
over Na2SO4 and concentrated under reduced pressure to give crude
compounds 6a–l, which were purified by column chromatography
on silica gel.
7.60 (d, J ꢀ= ꢀ 1.2 Hz, H-8), 7.56–7.49 (m, H-6, H-2′), 7.43–7.37 (m, H-5′),
7.28–7.23 (m, H-4′, H-6′), 2.45 (s, CH3-2), 2.10 (s, CH3-3); 13C NMR: δ
176.1 (Cꢀ= ꢀO), 161.5 (C-2), 155.5 (C-8a), 148.2 (C-3′), 142.7 (C-1′), 144.8
(C-5), 134.9 (C-7), 129.6 (C-2′), 127.3 (C-6′), 126.7 (C-5′), 123.4 (C-4a), 122.6
(C-4′), 118.1 (C-6), 117.4 (C-3), 115.6 (C-8), 18.6 (2-CH3), 10.1 (3-CH3). HR-
ESI-MS. Calcd for C17H12FO2+: m/z 268.0900, found: m/z 268.0903.
7-(3,4-Dimethylphenyl)-2,3-dimethyl-4H-4-chromone (6d) Yield
1
62%; mp 89°C; IR: 1628.0 cm-1 (Cꢀ= ꢀO); H NMR: δ 8.21 (d, J ꢀ= ꢀ 8.0 Hz,
H-5), 7.58 (d, J ꢀ= ꢀ 1.6 Hz, H-8), 7.56 (s, H-2′), 7.43–7.38 (m, H-6′, H-5′,
H-4′), 7.24 (d, J ꢀ= ꢀ 8.0 Hz, H-6), 2.43 (s, CH3-2), 2.35 (s, CH3-1′), 2.32 (s,
CH3-2′), 2.07 (s, CH3-3); 13C NMR: δ 177.8 (Cꢀ= ꢀO), 161.8 (C-2), 156.2 (C-8a),
146.1 (C-3′), 137.3 (C-4′), 137.2 (C-7), 136.9 (C-1′), 130.3 (C-2′), 128.5 (C-5′),
126.2 (C-6′), 124.7 (C-4a), 123.5 (C-5), 121.1 (C-6), 116.9 (C-3), 115.2 (C-8),
2,3-Dimethyl-7-(5-methyl-2-furyl)-4H-4-chromone (6a) Yield
60%; white solid; mp 123°C; IR: 1633.0 cm-1 (Cꢀ= ꢀO); 1H NMR: δ 8.14 (d,
J ꢀ= ꢀ 8.3 Hz, H-5), 7.60 (m, H-6, H-8), 6.71 (d, J ꢀ= ꢀ 3.0 Hz, H-3′), 6.10 (d, J ꢀ= ꢀ
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ꢀ131
19.9 (4′-CH3), 19.5 (3′-CH3), 18.6 (2-CH3), 10.1 (3-CH3). HR-ESI-MS. Calcd
for C19H18O2+: m/z 278.1307, found: m/z 278.1301.
Hz, H-4′), 7.71 (dd, J ꢀ= ꢀ 7.4 Hz, J ꢀ= ꢀ 7.6 Hz, H-5′), 7.58 (m, H-5, H-2′, H-6′),
2.45 (s, CH3-2), 2.09 (s, CH3-3); 13C NMR: δ 177.5 (Cꢀ= ꢀO), 162.2 (C-2), 156.1
(C-8a), 143.4 (C-7), 140.7 (C-1′), 131.8 (C-4′), 131.6 (C-2′), 130.9 (C-6′),
129.9 (C-5′), 126.9 (C-4a), 123.3 (C-5), 122.1 (C-6), 118.1 (CN), 117.4 (C-3),
116.0 (C-8), 113.3 (C-3′), 18.6 (2-CH3), 10.1 (3-CH3). HR-ESI-MS. Calcd for
C18H13NO2+: m/z 275.0946, found: m/z 275.0937.
2,3-Dimethyl-7-(2-thienyl)-4H-4-chromone (6e) Yield 56%; mp
112°C; IR: 1635.0 cm-1 (Cꢀ= ꢀO); 1H NMR: δ 8.15 (d, J ꢀ= ꢀ 8.0 Hz, H-5), 7.58–7.55
(m, H-6, H-8), 7.43 (d, J ꢀ= ꢀ 3.0 Hz, H-3′), 7.37 (dd, J ꢀ= ꢀ 3.0 Hz, J ꢀ= ꢀ 3.6 Hz,
H-4′), 7.11 (d, J ꢀ= ꢀ 3.6 Hz, H-5′), 2.40 (s, CH3-2), 2.05 (s, CH3-3); 13C NMR: δ
177.4 (Cꢀ= ꢀO), 161.9 (C-2), 156.2 (C-8a), 142.4 (C-7), 138.9 (C-2′), 128.4 (C-4′),
126.7 (C-5′), 126.5 (C-5′), 124.9 (C-3′), 124.7 (C-4a), 123.5 (C-5), 121.1 (C-6),
116.9 (C-3), 115.2 (C-8), 18.6 (2-CH3), 10.1 (3-CH3). HR-ESI-MS. Calcd for
C15H12O2S+: m/z 256.0558, found: m/z 256.0547.
7-(2-Trifluromethylphenyl)-2,3-dimethyl-4H-4-chromoneꢀ(6j)
1
Yield 70%; mp 128°C; IR: 1630.0 cm-1 (Cꢀ= ꢀO); H NMR: δ 8.21 (dd, J ꢀ= ꢀ
8.1 Hz, J ꢀ= ꢀ 0.2 Hz, H-6′), 7.78 (d, J ꢀ= ꢀ 7.8 Hz, H-5), 7.90 (dd, J ꢀ= ꢀ 8.4 Hz, J ꢀ= ꢀ
2.8 Hz, H-4′), 7.56 (d, J ꢀ= ꢀ 1.6 Hz, H-8), 7.52 (dd, J ꢀ= ꢀ 8.4 Hz, J ꢀ= ꢀ 1.6 Hz,
H-6), 7.45 (d, J ꢀ= ꢀ 8.4 Hz, H-3′), 2.44 (s, CH3-2), 2.08 (s, CH3-3); 13C NMR: δ
177.5 (Cꢀ= ꢀO), 162.2 (C-2), 156.1 (C-8a), 143.4 (C-1′), 140.7 (C-7), 134.4 (C-2′),
130.6 (C-5′), 129.7 (C-6′), 127.4 (C-3′), 126.7 (C-4a), 123.3 (C-5), 122.1 (C-6),
118.1 (CF3), 117.4 (C-3), 116.2 (C-8), 113.4 (C-3′), 18.4 (2-CH3), 10.1 (3-CH3).
HR-ESI-MS. Calcd for C18H13F3O2+: m/z 318.0869, found: m/z 318.0864.
2,3-Dimethyl-7-(4-chloro-3-pyridyl)-4H-4-chromone (6f) Yield
1
64%; mp 145°C; IR: 1632.0 cm-1 (Cꢀ= ꢀO); H NMR: δ 8.66 (s, H-6′), 8.28
(d, J ꢀ= ꢀ 8.4 Hz, H-5), 7.90 (dd, J ꢀ= ꢀ 8.4 Hz, J ꢀ= ꢀ 2.8 Hz, H-4′), 7.56 (d, J ꢀ= ꢀ
1.6 Hz, H-8), 7.52 (dd, J ꢀ= ꢀ 8.4 Hz, J ꢀ= ꢀ 1.6 Hz, H-6), 7.45 (d, J ꢀ= ꢀ 8.4 Hz,
H-3′), 2.44 (s, CH3-2), 2.08 (s, CH3-3); 13C NMR: δ 177.4 (Cꢀ= ꢀO), 162.2 (C-2),
156.1 (C-8a), 151.5 (C-2′) 148.1 (C-6′), 141.1 (C-5′), 137.3 (C-7), 134.0 (C-4′),
127.0 (C-6), 124.5 (C-4a), 123.2 (C-5), 122.1 (C-3′), 117.4 (C-3), 115.8 (C-8),
18.6 (2-CH3), 10.1 (3-CH3). HR-ESI-MS. Calcd for C16H1235ClNO2+: m/z
285.0557, found: m/z 285.0548.
7-(3-Chloro-4-methylphenyl)-2,3-dimethyl-4H-4-chromone (6k)
1
Yield 70%; mp 136°C; IR: 1632.0 cm-1 (Cꢀ= ꢀO); H NMR: δ 8.22 (dd, J ꢀ= ꢀ
8.2 Hz, J ꢀ= ꢀ 1.4 Hz, H-6), 7.46 (d, J ꢀ= ꢀ 1.4 Hz, H-8), 7.40 (d, J ꢀ= ꢀ 7.8 Hz,
H-5′), 7.33 (d, J ꢀ= ꢀ 7.8 Hz, H-6′), 7.46 (d, J ꢀ= ꢀ 8.2 Hz, H-5), 7.15 (s, H-2′), 2.43
(s, CH3-2), 2.39 (s, CH3), 2.08 (s, CH3-3); 13C NMR: δ 177.1 (Cꢀ= ꢀO), 162.0
(C-2), 155.5 (C-8a), 144.2 (C-1′), 139.8 (C-7), 135.9 (C-4′), 131.9 (C-3′), 130.9
(C-2′), 130.6 (C-5′), 127.9 (C-6′), 126.1 (C-4a), 125.5 (C-5), 121.5 (C-6), 118.4
(C-3), 117.1 (C-8), 20.9 (4′-CH3), 18.6 (2-CH3), 10.1 (3-CH3). HR-ESI-MS.
Calcd for C18H1535ClO2+: m/z 298.0761, found: m/z 298.0765.
2,3-Dimethyl-7-(2-methoxyphenyl)-4H-4-chromone (6g) Yield
60%; mp 92°C; IR: 1634.0 cm-1 (Cꢀ= ꢀO); 1H NMR: δ 8.19 (dd, J ꢀ= ꢀ 8.2 Hz,
J ꢀ= ꢀ 0.3 Hz, H-6), 7.57 (d, J ꢀ= ꢀ 0.3 Hz, H-8), 7.51 (dd, J ꢀ= ꢀ 8.1 Hz, J ꢀ= ꢀ 1.7 Hz,
H-6′), 7.38 (m, H-4′, H-3′), 7.05 (m, H-5′, H-5), 3.84 (s, OCH3), 2.43 (s,
CH3-2), 2.08 (s, CH3-3). 13C NMR: δ 177.9 (Cꢀ= ꢀO), 161.9 (C-2), 156.5 (C-2′),
155.7 (C-8a), 143.6 (C-7), 130.8 (C-6′), 129.7 (C-1′), 128.9 (C-4′), 126.2
(C-5), 125.2 (C-4a), 121.1 (C-6), 121.0 (C-5′), 118.2 (C-3), 116.9 (C-8), 111.4
(C-3′), 55.6 (OCH3), 18.6 (2-CH3), 10.1 (3-CH3). HR-ESI-MS. Calcd for
C18H16O3+: m/z 280.1099, found: m/z 280.1088.
7-(3-Chloro-4-fluoro-phenyl)-2,3-dimethyl-4H-4-chromone (6l)
Yield 67%; mp 140°C; IR: 1627.0 cm-1 (Cꢀ= ꢀO); 1H NMR: δ 8.24 (dd, J ꢀ= ꢀ 8.2
Hz, J ꢀ= ꢀ 1.4 Hz, H-6), 7.68 (d, J ꢀ= ꢀ 1.4 Hz, H-8), 7.52 (m, H-2′, H-5′, H-6′),
7.25 (d, J ꢀ= ꢀ 8.2 Hz, H-5), 2.44 (s, CH3-2), 2.08 (s, CH3-3); 13C NMR: δ 177.6
(Cꢀ= ꢀO), 162.1 (C-2), 159.6 (C-8a), 157.1 (C-7), 156.1 (C-1′), 143.6 (C-5), 136.7
(C-6′), 129.6 (C-2′), 127.1 (C-3′), 126.7 (C-5′), 123.3 (C-4a), 121.7 (C-4′), 117.3
(C-6), 117.0 (C-4a), 115.6 (C-8), 18.6 (2-CH3), 10.1 (3-CH3). HR-ESI-MS.
Calcd for C17H12F35ClO2+: m/z 302.0510, found: m/z 302.0506.
7-(4-Fluro-3-methoxyphenyl)-2,3-dimethyl-4H-4-chromone (6h)
Yield 71%; mp 118°C; IR: 1625.0 cm-1 (Cꢀ= ꢀO); 1H NMR: δ 8.23 (d, J ꢀ= ꢀ 8.2
Hz, H-6), 7.53 (m, H-8, H-5), 7.19 (m, H-2′, H-5′, H-6′), 3.98 (s, OCH3),
2.44 (s, CH3-2), 2.08 (s, CH3-3); 13C NMR: δ 177.1 (Cꢀ= ꢀO), 162.0 (C-2), 156.1
(C-8a), 151.6 (C-3′), 148.0 (C-4′), 145.2 (C-1′), 136.1 (C-7), 126.4 (C-5), 123.5
(C-6), 121.4 (C-6′), 120.0 (C-5′), 117.1 (C-4a), 116.4 (C-2′), 115.5 (C-3), 112.6
(C-8), 56.4 (OCH3), 18.6 (2-CH3), 10.1 (3-CH3). HR-ESI-MS. Calcd for
C18H15FO3+: m/z 298.1005, found: m/z 298.1001.
Acknowledgments: The authors are grateful to Dr. Red-
dy’s Laboratories Ltd. for providing facilities and analyti-
cal support.
7-(3-Cyanophenyl)-2,3-dimethyl-4H-4-chromone (6i) Yield 76%;
mp 96°C; IR: 1635.0 cm-1 (Cꢀ= ꢀO); 2212.0 cm-1 (CN); H NMR: δ 8.28 (d,
J ꢀ= ꢀ 8.2 Hz, H-6), 7.93 (d, J ꢀ= ꢀ 1.4 Hz, H-8), 7.87 (dd, J ꢀ= ꢀ 7.4 Hz, J ꢀ= ꢀ 1.3
1
Received December 29, 2013; accepted February 4, 2014
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