A simple one-pot synthesis of 2,4-diaryl- 9H-pyrido[2,3-b]indoles under solvent-free conditions

Article abstract of DOI:10.1515/hc-2016-0222

A novel, simple, one-pot synthesis of 2,4-diaryl-9H-pyrido[2,3-b]indoles is described. Heating a mixture of chalcone, oxindole and ammonium acetate in the presence of potassium tert-butoxide under solvent-free conditions afforded the title compounds in good to excellent yields.

Full text of DOI:10.1515/hc-2016-0222

Heterocycl. Commun. 2017; aop
Mehdi Khoshneviszadeh, Aida Yahagh, Mehdi Soheilizad and Mohammad Mahdavi*
A simple one-pot synthesis of 2,4-diaryl-
9H-pyrido[2,3-b]indoles under solvent-free
conditions
DOI 10.1515/hc-2016-0222
enolate anion and subsequent cyclization of the adduct
in the presence of NH4OAc [9], reaction of 2-aminoin-
dole with 3,3-dimethoxy-2-formyl-propionitrile sodium
salt [10], reaction between 2-aminoindole and acetylenic
esters [11], condensation of 2-amidinylindole-3-carbalde-
hyde with acetophenone [12], cyclization of 1-methyl-3-(2-
carbomethoxyethyl)-2-iminoindoline [6], cross coupling
of ortho-pivaloylaminophenyl-ortho′-halopyridine [13],
Received November 28, 2016; accepted May 9, 2017
Abstract: A novel, simple, one-pot synthesis of 2,4-diaryl-
9H-pyrido[2,3-b]indoles is described. Heating a mixture of
chalcone, oxindole and ammonium acetate in the presence
of potassium tert-butoxide under solvent-free conditions
afforded the title compounds in good to excellent yields.
Keywords: ammonium acetate; chalcones; heterocycles; intramolecular [4ꢀ+ꢀ2] cycloaddition-elimination of
oxindoles; solvent-free; 9H-pyrido[2,3-b]indoles.
3-(2-ethynylphenylamino)-2(1H)-pyrazinone [14], intramo-
lecular hetero-Diels-Alder cycloaddition-aromatization
of ortho-vinyl C=C-conjugated arylcarbodiimide [15] and
pyrolysis of 1-benzylpyrazole with chloroform [16]. Several
of these multi-step methods have drawbacks such as not
Introduction
Pyrido[2,3-b]indoles (α-carbolines) have attracted consid- easily accessible starting materials, low overall yields,
erable attention due to their occurrence in carcinogenic harsh reaction conditions, long reaction times and use of
metabolites, biologically active compounds and natural toxic and hazardous starting materials, reagents and/or
products [1–3]. Some synthetic pyrido[2,3-b]indoles solvents.
including 1 are γ-aminobutyric acid (GABA) modulators
As part of our ongoing program to develop new facile
with potential as therapeutic agents for the treatment methods for the preparation of biologically active hetero-
of anxiety disorders [4]. Recently, some of related com- cyclic compounds from readily available building blocks
pounds have shown activity against Alzheimer’s disease, [17–20], we report herein a simple one-pot synthesis of
Parkinson’s disease, cerebrovascular accidents, amyo- 2,4-diaryl-9H-pyrido[2,3-b]indoles.
trophic lateral sclerosis, viral infections and autoimmune
diseases [5, 6]. Some compounds are antidepressant and
antineoplastic agents [7, 8].
Results and discussion
H2N
CO2Et
Heating a mixture of oxindole 2, chalcone 3 and ammo-
nium acetate in the presence of a catalytic amount of
Me
N
N
1
Me
potassium tert-butoxide under solvent-free conditions
produced the 2,4-diaryl-9H-pyrido[2,3-b]indole 4a–h in
82–90% yield (Scheme 1). The reaction was carried out by
mixing the oxindole and the chalcone, then adding a cata-
lytic amount of t-BuOK, stirring the mixture at 150°C for
5 min to form an oily mixture, followed by treatment with
an excess of NH4OAc and stirring at 200°C for an addi-
GABA modulator with anxiolytic activity
Pyrido[2,3-b]indoles can be synthesized by reaction
of α-oxoketene dithioacetal with 1-methyl-2-oxoindole
*Corresponding author: Mohammad Mahdavi, Drug Design and
Development Research Center, Tehran University of Medical
Sciences, P.O. Box 1417614411, Tehran, Iran,
1
tional 30 min. TLC and H NMR analyses of the resultant
yellowish liquid clearly indicated formation of pyrido[2,3-
b]indole 4a–h.
A possible reaction pathway for the formation
of 2,4-diaryl-9H-pyrido[2,3-b]indole 4 is suggested in
Scheme 2. The initial Michael addition reaction of the
e-mail: Mahdavi_chem@yahoo.com
Mehdi Khoshneviszadeh: Medicinal and Natural Products Chemistry
Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
Aida Yahagh and Mehdi Soheilizad: School of Chemistry, College of
Science, University of Tehran, Tehran, Iran
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2ꢀ
ꢀM. Khoshneviszadeh et al.: Synthesis of 2,4-diaryl-9H-pyrido[2,3-b]indoles
Ar
O
Ph
X
X
1) t-BuOK, 150°C, 5 min
N
O
Ar
Ph
N
2) NH4OAc, 200°C, 30 min
N
H
H
2
3
4a–h
4a: X = H; Ar = 4-Me-C6H4
4b: X = H; Ar = 3-Me-C6H4
4c: X = H; Ar = 4-MeO-C6H4
4d: X = H; Ar = 4-Cl-C6H4
4e: X = H; Ar = 2-furyl
4f: X = Br; Ar = 4-Me-C6H4
4g: X = Br; Ar = 3-Me-C6H4
4h: X = Br; Ar = 4-Cl-C6H4
Scheme 1ꢀ
O
Ar
O
Ar Ph
Ar
Ph
NH4OAc
Ph
3
NH
O
OH
t-BuOK
N
N
H
N
N
O
O
H
H
H
2
5
6
Ar
N
Ar
Ar
Ar Ph
Oxidation
NH2
N
N
N
H
N
Ph
Ph
Ph
N
N
7
8
4
O
H
H
H
H
Scheme 2ꢀ
C, H and N were performed using a Heraeus CHN-O-Rapid ana-
lyzer. Mass spectra were recorded on an Agilent Technologies HP
5973 mass spectrometer operating at an ionization potential of 20
oxindole 2 with chalcone 3 [21–25], leads to the forma-
tion of the intermediate product 5. Then, condensation
of ammonium acetate with this intermediate compound
followed by tautomerization generates the enamine 7.
Finally, intramolecular cyclization of 7 followed by tau-
tomerization and oxidation of 8 affords the product 4.
1
eV. H NMR (250.1 MHz) and 13C NMR (62.9) spectra were measured
with a Bruker DPX-250 spectrometer in CDCl3 with TMS as an inter-
nal standard. IR spectra were recorded in KBr pellets on a Shimadzu
IR-460 spectrometer.
General procedure for synthesis of 4a–h
Conclusion
A mixture of an oxindole (1.0 mmol), a chalcone (1.0 mmol) and
potassium tert-butoxide (0.034 g, 0.3 mmol) was stirred at 150°C for
5 min and the resultant oily mixture was then treated with ammo-
nium acetate (0.154 g, 2.0 mmol) over 4 min and stirred at 200°C for
A solvent-free reaction between oxindole 2, chalcone 3,
and ammonium acetate in the presence of potassium tert-
butoxide provides a simple one-pot approach to the syn-
thesis of a substituted pyrido[2,3-b]indole. Use of simple an additional 30 min. The resultant yellowish liquid solidified upon
cooling to room temperature and was crystallized from a mixture of
EtOAc/n-hexane (1:1).
starting materials, good atom economy, short reaction
time and good yield of the product are the main advan-
tages of this method.
2-Phenyl-4-(p-tolyl)-9H-pyrido[2,3-b]indole (4a)ꢁPale yellow
solid; yield 90%; mp 217–218°C; IR (cm−1): 3153, 1591, 1566, 1362, 1294,
1
1207, 1109, 997, 870, 820, 746, 696; H NMR: δ 2.55 (s, 3H), 6.47 (d,
Jꢀ=ꢀ7.8 Hz, 1H), 7.02 (dd, Jꢀ=ꢀ7.7, 7.4 Hz, 1H), 7.19 (t, Jꢀ=ꢀ7.5 Hz, 1H), 7.44
Experimental
(d, Jꢀ=ꢀ7.5 Hz, 2H), 7.50–7.60 (m, 3H), 7.62 (s, 1H), 7.71 (d, Jꢀ=ꢀ7.0 Hz, 2H),
7.73 (d, Jꢀ=ꢀ7.5 Hz, 1H), 8.28 (d, Jꢀ=ꢀ7.5 Hz, 2H), 12.36 (s, 1H); 13C NMR: δ
Oxindoles and potassium tert-butoxide were obtained from Merck 21.4, 111.4, 112.9, 114.4, 119.3, 120.6, 122.3, 126.2, 127.8, 128.6, 128.7, 129.1,
+
(Germany) and Sigma-Aldrich (USA). Chalcones were prepared 129.4, 136.3, 138.5, 139.4, 140.3, 146.3, 153.4, 154.2; MS: m/z 334 (M ).
according to the literature procedure [26]. Melting points were meas- Anal. Calcd for C24H18N2: C, 86.20; H, 5.43; N, 8.38. Found: C, 86.20;
ured on an Electrothermal 9100 apparatus. Elemental analyses for H, 5.42; N, 8.35.
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M. Khoshneviszadeh et al.: Synthesis of 2,4-diaryl-9H-pyrido[2,3-b]indolesꢂ
155.1; MS: m/z 414 (M+ 81Br), 412 (M+ 79Br). Anal. Calcd for C24H17BrN2: C,
69.74; H, 4.15; N, 6.78. Found: C, 69.68; H, 4.19; N, 6.80.
2-Phenyl-4-(m-tolyl)-9H-pyrido[2,3-b]indole (4b)ꢁPale yellow
solid; yield 85%; mp 187–188°C; IR (cm−1): 3329, 1583, 1566, 1485,
1
1450, 1385, 1292, 1211, 771, 740, 695; H NMR: δ 2.53 (s, 3H), 6.52 (d,
Jꢀ=ꢀ8.1 Hz, 1H), 7.02 (dd, Jꢀ=ꢀ7.6, 7.4 Hz, 1H), 7.20 (t, Jꢀ=ꢀ7.6 Hz, 1H), 7.40
(d, Jꢀ=ꢀ7.5 Hz, 1H), 7.51 (t, Jꢀ=ꢀ7.8 Hz, 1H), 7.55–7.62 (m, 6H), 7.69 (d,
Jꢀ=ꢀ7.8 Hz, 1H), 8.28 (d, Jꢀ=ꢀ7.5 Hz, 2H), 12.23 (s, 1H); 13C NMR: δ 21.5,
111.4, 112.9, 114.4, 119.4, 120.6, 122.3, 125.8, 126.2, 127.8, 128.6, 128.7,
129.1, 129.3, 129.4, 138.4, 139.2, 139.5, 140.2, 146.4, 153.4, 154.2; MS: m/z
6-Bromo-4-(4-chlorophenyl)-2-phenyl-9H-pyrido[2,3-b]indole
(4h)ꢁPale yellow solid; yield 84%; mp 264–266°C; IR (cm−1): 3240,
1
1586, 1559, 1517, 1483, 1452, 1350, 1290, 1205, 870, 815, 768, 695; H
NMR: δ 6.86 (d, Jꢀ=ꢀ8.5 Hz, 1H), 7.47 (dd, Jꢀ=ꢀ8.5, 7.4 Hz, 1H), 7.55–7.59
(m, 4H), 7.64 (d, Jꢀ=ꢀ8.3 Hz, 2H), 7.69 (d, Jꢀ=ꢀ8.3 Hz, 2H), 7.77 (s, 1H), 8.16
(d, Jꢀ=ꢀ7.1 Hz, 2H), 11.22 (s, 1H); 13C NMR: δ 112.6, 112.8, 114.7, 122.1, 124.7,
127.7, 129.1, 129.2, 129.3, 129.4, 129.9, 130.6, 135.2, 137.0, 137.8, 139.7, 145.3,
153.2, 155.3; MS: m/z 436 (M+ 81Br37Cl), 434 (M+ 79Br37Cl, M+ 81Br35Cl), 432
(M+ 79Br35Cl). Anal. Calcd for C23H14BrClN2: C, 63.69; H, 3.25; N, 6.46.
Found: C, 63.58; H, 3.38; N, 6.38.
+
334 (M ). Anal. Calcd for C24H18N2: C, 86.20; H, 5.43; N, 8.38. Found: C,
86.19; H, 5.50; N, 8.35.
4-(4-Methoxyphenyl)-2-phenyl-9H-pyrido[2,3-b]indole
(4c)ꢁPale yellow solid; yield 92%; mp 220–221°C; IR (cm−1): 3266,
1607, 1595, 1564, 1510, 1456, 1394, 1360, 1294, 1248, 1178, 1030, 837,
773, 742, 696; 1H NMR: δ 3.97 (s, 3H), 6.94 (dd, Jꢀ=ꢀ7.5, 1.0 Hz), 7.06 (dd,
Jꢀ=ꢀ7.6, 7.4 Hz), 7.15 (d, Jꢀ=ꢀ8.4 Hz, 2H), 7.30 (t, Jꢀ=ꢀ7.5 Hz, 1H), 7.47–7.59 (m,
4H), 7.74 (d, Jꢀ=ꢀ8.4 Hz, 2H), 7.75 (d, Jꢀ=ꢀ7.4 Hz, 1H), 8.20 (d, Jꢀ=ꢀ7.6 Hz,
2H), 10.99 (s, 1H); 13C NMR: δ 55.4, 111.3, 112.8, 114.2, 114.4, 119.4, 120.7,
122.3, 126.3, 127.7, 128.7, 129.1, 130.0, 131.5, 139.3, 140.2, 146.0, 153.3,
Acknowledgments: This study was supported by the
research council of Tehran University of Medical Sciences
(TUMS) and Iran National Science Foundation (INSF).
+
154.3, 160.1; MS: m/z 350 (M ). Anal. Calcd for C24H18N2O: C, 82.26; H,
5.18; N, 7.99. Found: C, 82.31; H, 5.23; N, 7.98.
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4-(4-Chlorophenyl)-2-phenyl-9H-pyrido[2,3-b]indole (4d)ꢁPale
yellow solid; yield 87%; mp 227–228°C; IR (cm−1): 3250, 1591, 1545,
1
1481, 1458, 1389, 1350, 1296, 1207, 1022, 773, 739, 698; H NMR: δ
7.05 (dd, Jꢀ=ꢀ8.5, 7.7 Hz, 1H), 7.41 (dd, Jꢀ=ꢀ8.5 Hz, Jꢀ=ꢀ7.1 Hz, 1H), 7.44
(d, Jꢀ=ꢀ7.1 Hz), 7.48–7.54 (m, 4 H), 7.66 (s, 1H), 7.68 (d, Jꢀ=ꢀ8.5 Hz, 2H),
7.79 (d, Jꢀ=ꢀ8.5 Hz, 2H), 8.22 (dd, Jꢀ=ꢀ7.1, 1.4 Hz, 2H), 12.11 (s, 1H); 13C
NMR: δ 111.3, 111.5, 112.9, 119.4, 119.6, 121.7, 126.6, 126.9, 128.8, 128.9,
+
128.9, 130.6, 133.6, 137.5, 139.2, 139.6, 143.7, 152.6, 153.1; MS: m/z 356 [M
37Cl], 354 (M+ 35Cl). Anal. Calcd for C23H15ClN2: C, 77.85; H, 4.26; N, 7.89.
Found: C, 77.83; H, 4.38; N, 7.88.
4-(Furan-2-yl)-2-phenyl-9H-pyrido[2,3-b]indole (4e)ꢁPale yellow
solid; yield 85%; mp 174–175°C; IR (cm−1): 3172, 1591, 1543, 1481, 1456,
1389, 1348, 1294, 1209, 1022, 771, 741, 694; 1H NMR: δ 6.59 (d, Jꢀ=ꢀ7.9 Hz,
1H), 6.72 (d, Jꢀ=ꢀ1.0 Hz, 1H), 7.15–7.29 (m, 3H), 7.52–7.62 (m, 3H), 7.82
(s, 2H), 8.22 (d, Jꢀ=ꢀ7.0 Hz, 2H), 8.49 (d, Jꢀ=ꢀ7.9 Hz, 1H), 11.75 (s, 1H); 13
C
NMR: δ 110.9, 111.0, 111.1, 111.3, 112.2, 120.1, 120.5, 123.7, 126.8, 127.5,
129.0, 129.1, 133.8, 139.3, 139.4, 143.6, 146.3, 152.3, 153.7; MS: m/z 310
+
(M ). Anal. Calcd for C21H14N2O: C, 81.27; H, 4.55; N, 9.03. Found: C,
81.19; H, 4.60; N, 8.99.
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yellow solid; yield 88%; mp 226–228°C; IR (cm−1): 3239, 1587, 1564,
1510, 1447, 1352, 1292, 1209, 872, 820, 770, 692; 1H NMR: δ 2.55 (s, 3H),
6.51 (d, J =8.6 Hz, 1H), 7.33 (d, Jꢀ=ꢀ8.6 Hz, 1H), 7.44 (d, Jꢀ=ꢀ7.5 Hz, 2H),
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2H), 11.84 (s, 1H); 13C NMR: δ 21.5, 112.0, 112.3, 112.8, 114.9, 122.3, 124.8,
127.9, 128.5, 129.0, 129.1, 129.2, 129.6, 135.7, 137.9, 139.1, 140.0, 146.9, 153.5,
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69.74; H, 4.15; N, 6.78. Found: C, 69.81; H, 4.18; N, 6.79.
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1
1481, 1446, 1381, 1352, 1292, 1211, 866, 800, 770, 696; H NMR: δ 2.53
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129.0, 129.1, 129.2, 129.3, 129.8, 137.8, 138.5, 138.7, 139.9, 146.9, 153.3,
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