Efficient synthesis of polysubstituted pyridine under solvent-free conditions without using any catalysts

Article abstract of DOI:10.1080/00397910801991184

A convenient and environmentally friendly solvent-free procedure has been developed for the synthesis of polysubsituted pyridine derivatives. Compared with the classical reaction condition, this new synthetic method has the advantage of excellent yields,

Full text of DOI:10.1080/00397910801991184

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Efficient Synthesis of Polysubstituted
Pyridine under Solvent‐free Conditions
without Using Any Catalysts
Liangce Rong a , Hongxia Han a , Suhui Wang a & Qiya Zhuang a
a College of Chemistry and Chemical Engineering, Xuzhou Normal University,
Xuzhou, Jiangsu, China
Published online: 09 May 2008.
To cite this article: Liangce Rong , Hongxia Han , Suhui Wang & Qiya Zhuang (2008): Efficient Synthesis
of Polysubstituted Pyridine under Solvent‐free Conditions without Using Any Catalysts, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 38:11,
1808-1814
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Synthetic Communicationsw, 38: 1808–1814, 2008
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910801991184
Efficient Synthesis of Polysubstituted
Pyridine under Solvent-free Conditions
without Using Any Catalysts
Liangce Rong, Hongxia Han, Suhui Wang, and Qiya Zhuang
College of Chemistry and Chemical Engineering, Xuzhou Normal
University, Xuzhou, Jiangsu, China
Abstract: A convenient and environmentally friendly solvent-free procedure has been
developed for the synthesis of polysubsituted pyridine derivatives. Compared with the
classical reaction condition, this new synthetic method has the advantage of excellent
yields, easy setup, and mild reaction conditions.
Keywords: 2,3-Dihydroinden-1-one, cyclopentanone, pyridine, solvent-free condition
In recent years, solvent-free organic reactions[1] have generated great interest,
because of their many advantages such as high efficiency and selectivity, easy
separation and purification, mild reaction conditions, reduction in waste
produced, and benefit to industry as well as environment. Many articles
about solvent-free reactions have been reported, such as Grignard
reaction,[2] Reformatsky reaction,[3] aldol condensations,[4] Dieckmann con-
densations,[5] phenol coupling reaction,[6] reduction reaction,[7] and another
reactions.[8]
The pyridine ring system is found in a large number of naturally occurring
alkaloids and synthetic products of biological interest.[9] Therefore, new and
improved synthetic studies are important in the field of drug design. Many
Received July 16, 2007
Address correspondence to Liangce Rong, College of Chemistry and Chemical
Engineering, Xuzhou Normal University, Xuzhou, Jiangsu 221116, China. E-mail:
lcrong2005@yahoo.com
1808

Synthesis of Polysubstituted Pyridine
1809
articles[10] have been reported on design of new pyridine derivatives for use in
medicine. In continuation of our ongoing endeavor for solvent-free conditions
for the synthesis of organic compounds,[11] herein we report a practical and
simple method to prepare polysubsitutedpyridine derivatives by heating
starting material under dry conditions (Scheme 1).
The mixture of aromatic aldehyde, 2,3-dihydroinden-1-one, and NH4OAc
blended uniformly was put into a reaction flask at 70 8C for about 10 min, and
the reaction was completed with high yields. The results of reaction are listed
in Table 1. As shown in Table 1, the reaction time was quite short, and the
yields of products were very high (.90%). Furthermore, were catalysts not
needed and a series of aldehydes bearing either electron-withdrawing or
electron-donating groups could perform well in this reaction. Recently, Tu
et al.[12a] have reported the use of microwave irradiation for synthesis of
similar compounds, but it has limitations in that it can be only carried out
in the laboratory and is difficult to apply in industrial processes until now.
To examine the efficiency and the applicability of this method, we chose
cyclopentanone, cyclohexanone, and 3,4-dihydronaphthalen-1(2H)-one to
react with different aldehydes and NH4OAc (Scheme 2). However, we
found the reaction did not carry out as successfully as 2,3-dihydroinden-1-
one did. The cyclohexanone and 3,4-dihydronaphthalen-1(2H)-one did not
react with aldehydes and NH4OAc at all under the same reaction conditions,
and the cyclopentanone could react with aromatic aldehyde and NH4OAc to
give compound 6, but the yields were very low (,60%) and the reaction
needed a longer time. Only four compounds were gained (Table 2). At the
same time, to further investigate this reaction, the aliphatic aldehydes, such
as formaldehyde and acetaldehyde, were chosen to react with cyclopentanone
and NH4OAc, but no products were obtained. Cyclohexanone, 3,4-dihydro-
naphthalen-1(2H)-one, and aliphatic aldehydes did not fit this reaction.
In conclusion, we have developed a new process for the synthesis of
1-aryldiindeno[1,2-b:20,10-e]pyridine derivatives 4 via the reaction of
different aromatic aldehydes, 2,3-dihydroinden-1-one, and NH4OAc under
solvent-free conditions. At the same time, the 3,4-diarylidene-1,2,3,4,5,6-
hexahydro-7-aryldicyclopenta[b,e]pyridine 6 was gained when cyclopenta-
none was chosen to react with aromatic aldehydes and NH4OAc under same
conditions. On the basis of results of the reaction, we could conclude that
2,3-dihydroinden-1-one was the best fit for this reaction. Furthermore,
Scheme 1.

1810
L. Rong et al.
Table 1. Reaction time, yields, and melting point of product 4
Entry
Ar
Time (min) Yield (%)
Mp (8C)
4a
4b
4c
4d
4e
4f
4-FC6H4
4-ClC6H4
10
10
10
10
10
10
10
10
92
90
93
95
92
94
93
90
.300 (.300)[12c]
.300 (.300)[12b]
.300 (.300)[12b]
.300 (.300)[12c]
256–258 (251.8–252.2)[12a]
276–278 (.300)[12c]
.300 (.300)[12b]
252–254
4-BrC6H4
4-CH3C6H5
4-CH3OC6H4
2,4-Cl2C6H3
3,4-OCH2OC6H3
3,4-(CH3O)2C6H3
4g
4h
because it avoided use of a toxic organic solvent, this new protocol has the
advantages of good yield, lower cost, reduced environmental impact, and con-
venient procedure.
EXPERIMENTAL
Melting points were determined on an XT-5 microscopic melting-point
apparatus and were uncorrected. IR spectra were recorded on a FT IR-8101
1
spectrometer. H NMR spectra were obtained from solution in DMSO-d6
with Me4Si as internal standard using a Bruker-400 spectrometer. Microana-
lyses were carried out using a Perkin-Elmer 2400 II analyzer.
General Procedure for the Synthesis of Polysubsitutedpyridine
(4 and 6)
Aromatic aldehyde 1 (1 mmol or 3 mmol), 2,3-dihydroinden-1-one 2 (or
cyclopentanone 5) (2 mmol), and NH4OAc 3 (4 mmol) were blended
uniformly and put into a reaction flask at 70 8C. The reaction could be
completed within 10 min (or 80 min). Then the reaction mixture was poured
into water. The product was filtered, dried, and recrystallized from 95%
ethanol.
Scheme 2.

Synthesis of Polysubstituted Pyridine
1811
Table 2. Reaction time, yields, and melting point of product 6
Entry
Ar
Time (min)
Yields (%)
Mp (8C)
6a
6b
6c
6d
4-CH3C6H4
4-CH3OC6H4
4-ClC6H4
80
80
80
80
53
59
56
50
237–238
184–186
192–194
230–232
3-ClC6H4
Spectral Data
Compound 4a. IR (KBr) 3043, 2898, 1608, 1594, 1564, 1514, 1466, 1439,
1399, 1366, 1314, 1286, 1227, 1203, 1182, 1163, 1094, 1017, 948, 862,
1
852, 835, 792, 741, 704, 688, 652, 614, 576 cm21; H NMR (400 MHz,
DMSO-d6) 8.12 (d, J ¼ 8.0 Hz, 2H, 5,6-H), 7.85 (d, J ¼ 8.0 Hz, 2H, ArH),
7.67 (d, J ¼ 7.2 Hz, 2H, 2,9-H), 7.63 (t, J ¼ 7.2 Hz, 2H, 3,8-H), 7.53
(t, J ¼ 7.2 Hz, 2H, 4,7-H), 7.47 (d, J ¼ 8.0 Hz, 2H, ArH), 3.97 (s, 4H, 1,10-
H). Anal. calcd. for C25H16FN: C, 85.94; H, 4.62; N, 4.01. Found: C, 85.89;
H, 4.56; N, 4.10.
Compound 4b. IR (KBr) 3047, 2896, 1601, 1572, 1557, 1491, 1466, 1440,
1396, 1364, 1314, 1284, 1202, 1182, 1149, 1085, 1017, 852, 832, 704, 647,
1
613 cm21; H NMR (400 MHz, DMSO-d6) 8.13 (d, J ¼ 7.6 Hz, 2H, 5,6-H),
7.86 (d, J ¼ 8.0 Hz, 2H, ArH), 7.66 (d, J ¼ 7.2 Hz, 2H, 2,9-H), 7.64
(t, J ¼ 7.2 Hz, 2H, 3,8-H), 7.52 (t, J ¼ 7.2 Hz, 2H, 4,7-H), 7.46
(d, J ¼ 8.0 Hz, 2H, ArH), 3.97 (s, 4H, 1,10-H). Anal. calcd. for C25H16ClN:
C, 82.07; H, 4.41; N, 3.83. Found: C, 82.10; H, 4.38; N, 3.79.
Compound 4c. IR (KBr) 3045, 2894, 1595, 1570, 1556, 1502, 1489, 1466,
1440, 1397, 1364, 1314, 1202, 1282, 1181, 1149, 1094, 1067, 1011, 975,
960, 946, 850, 830, 742 703, 690, 645, 613, 574 cm21;1H NMR (400 MHz,
DMSO-d6) 8.12 (d, J ¼ 7.2 Hz, 2H, 5,6-H), 7.82 (d, J ¼ 8.0 Hz, 2H, ArH),
7.78 (d, J ¼ 7.2 Hz, 2H, 2,9-H), 7.73 (t, J ¼ 7.2 Hz, 2H, 3,8-H), 7.64
(t, J ¼ 7.2 Hz, 2H, 4,7-H), 7.50 (d, J ¼ 8.0 Hz, 2H, ArH), 3.96 (s, 4H,
1,10-H). Anal. calcd. for C25H16BrN: C, 73.18; H, 3.93; N, 3.41. Found: C,
73.25; H, 3.89; N, 3.35.
Compound 4d. IR (KBr) 3050, 2892, 1600, 1562, 1519, 1504, 1489, 1463,
1440, 1390, 1314, 1290, 1202, 1180, 1090, 850, 770 cm21 1H NMR
;
(400 MHz, DMSO-d6) 8.17 (d, J ¼ 8.0 Hz, 2H, 5,6-H), 8.12 (d, J ¼ 8.0 Hz,
2H, ArH), 7.85 (d, J ¼ 7.2 Hz, 2H, 2,9-H), 7.66 (t, J ¼ 7.2 Hz, 2H, 3,8-H),
7.64 (t, J ¼ 7.2 Hz, 2H, 4,7-H), 7.50 (d, J ¼ 8.0 Hz, 2H, ArH), 3.97 (s, 4H,
1,10-H), 2.35 (s, 3H, CH3). Anal. calcd. for C26H19N: C, 90.40; H, 5.54; N,
4.05. Found: C, 90.46; H, 5.48; N, 4.10.

1812
L. Rong et al.
Compound 4e. IR (KBr) 3051, 2893, 1612, 1561, 1517, 1464, 1440, 1288,
1025, 859, 831, 776 cm21 1H NMR (400 MHz, DMSO-d6) 8.11
;
(d, J ¼ 7.2 Hz, 2H, 5,6-H), 7.76 (d, J ¼ 8.0 Hz, 2H, ArH), 7.63 (d, J ¼ 7.2
Hz, 2H, 2,9-H), 7.51 (t, J ¼ 7.2 Hz, 2H, 3,8-H), 7.45 (t, J ¼ 7.2 Hz, 2H,
4,7-H), 7.14 (d, J ¼ 8.0 Hz, 2H, ArH), 3.95 (s, 4H, 1,10-H), 3.87 (s, 3H,
OCH3). Anal. calcd. for C26H19NO: C, 86.40; H, 5.30; N, 3.88. Found: C,
86.57; H, 5.26; N, 3.94.
Compound 4f. IR (KBr) 3050, 2891, 1592, 1566, 1504, 1476, 1439, 1367,
1314, 1282, 1202, 1181, 1149, 1097, 1061, 1027, 948, 862, 825, 776, 745,
1
704, 673, 651, 612 cm21; H NMR (400 MHz, DMSO-d6) 8.13 (d, J ¼ 8.0
Hz, 2H, 5,6-H), 7.97 (d, J ¼ 8.0 Hz, 2H, ArH), 7.82 (d, J ¼ 7.2 Hz, 2H,
2,9-H), 7.73 (d, J ¼ 7.2 Hz, 2H, 3,8-H), 7.67 (d, J ¼ 8.0 Hz, 2H, 4,7-H),
7.60 (d, J ¼ 8.0 Hz, 1H, ArH), 4.12 (s, 4H, 1,10-H). Anal. calcd. for
C25H15Cl2N: C, 75.01; H, 3.78; N, 3.50. Found: C, 75.10; H, 3.86; N, 3.60.
Compound 4g. IR (KBr) 3053, 2896, 1601, 1563, 1488, 1443, 1397, 1367,
1332, 1314, 1285, 1237, 1202, 1181, 1150, 1124, 1092, 1037, 938, 921,
1
908, 860, 824, 800, 746, 719, 706, 615, 575 cm21; H NMR (400 MHz,
DMSO-d6) 8.11 (d, J ¼ 7.6 Hz, 2H, 5,6-H), 7.78 (d, J ¼ 7.6 Hz, 2H, ArH),
7.71 (d, J ¼ 8.0 Hz, 2H, 2,9-H), 7.65 (d, J ¼ 7.2 Hz, 2H, 3,8-H), 7.50
(t, J ¼ 7.2 Hz, 2H, 4,7-H), 7.12 (s, 1H, ArH), 6.15 (d, J ¼ 6.4 Hz, 2H,
CH2), 3.98 (s, 4H, 1,10-H). Anal. calcd. for C26H17NO2: C, 83.18; H, 4.56;
N, 3.73. Found: C, 83.25; H, 4.45; N, 3.68.
Compound 4h. IR (KBr) 3050, 2892, 1609, 1588, 1559, 1520, 1466, 1444,
1416, 1397, 1364, 1315, 1299, 1283, 1224, 1180, 1147, 1101, 1050, 1023,
;
948, 887, 823, 750, 712 cm21 1H NMR (400 MHz, DMSO-d6) 8.12
(d, J ¼ 7.6 Hz, 2H, 5,6-H), 7.80 (d, J ¼ 7.6 Hz, 2H, ArH), 7.71
(d, J ¼ 8.0 Hz, 2H, 2,9-H), 7.65 (d, J ¼ 7.2 Hz, 2H, 3,8-H), 7.50
(t, J ¼ 7.2 Hz, 2H, 4,7-H), 7.32 (s, 1H, ArH), 6.15 (d, J ¼ 6.4 Hz, 2H,
CH2), 3.97 (s, 4H, 1,10-H), 3.82 (s, 3H, OCH3), 3.79 (s, 3H, OCH3). Anal.
calcd. for C27H21NO2: C, 82.84; H, 5.41; N, 3.58. Found: C, 82.79; H, 5.49;
N, 3.64.
Compound 6a. IR (KBr) 3016, 2918, 2871, 1569, 1558, 1541, 1510, 1457,
1
1426, 1363, 1297, 1270, 1240, 1183, 896, 807 cm21; H NMR (DMSO-d6)
7.51 (dd, J ¼ 4.0 Hz, J ¼ 4.0 Hz, 6H, ArH, 2 ꢀ ArCH55), 7.40
(d, J ¼ 8.0 Hz, 2H, ArH), 7.33 (d, J ¼ 8.0 Hz, 2H, ArH), 7.25
(d, J ¼ 8.0 Hz, 4H, ArH)), 3.10-3.11 (br, 4H, 1,6-H), 2.96-2.98 (br, 4H, 2,5-
H), 2.39 (s, 3H, CH3), 2.34 (s, 6H, 2 ꢀ CH3), Anal. calcd. for C34H31N: C,
90.02; H, 6.89; N, 3.09. Found: C, 90.16; H, 7.00; N 2.98.
Compound 6b. IR (KBr) 3035, 2914, 2835, 1605, 1561, 1532, 1510, 1455,
1440, 1417, 1359, 1291, 1251, 1203, 1175, 1229, 1034, 950, 930, 893, 872,

Synthesis of Polysubstituted Pyridine
1813
857, 821, 806, 757, 682, 645, 589 cm21
;
1H NMR (DMSO-d6) 7.55
(d, J ¼ 8.8 Hz, 4H, ArH), 7.46 (t, J ¼ 8.4 Hz, 4H, ArH), 7.06
(d, J ¼ 8.4 Hz, 2H, 2 ꢀ ArCH55), 7.01 (d, J ¼ 8.4 Hz, 4H, ArH)), 3.82
(s, 3H, CH3O), 3.80 (s, 3H, CH3O), 3.07–3.08 (br, 4H, 1,6-H), 2.96–2.98
(br, 4H, 2,5-H), Anal. calcd. for C34H31NO3: C, 81.41; H, 6.23; N, 2.79.
Found: C, 81.62; H, 6.18; N, 2.86.
Compound 6c. IR (KBr) 3028, 2933, 2843, 1595, 1490, 1460, 1405, 1361,
1
1296, 1262, 1223, 1134, 1091, 1013, 825, 734 cm21; H NMR (DMSO-d6)
7.66 (dd, J ¼ 6.4 Hz, J ¼ 6.4 Hz, 4H, ArH), 7.59 (t, J ¼ 5.6 Hz, 4H, ArH),
7.37 (dd, J ¼ 2.0 Hz, J ¼ 2.0 Hz, 2H, 2 ꢀ ArCH55), 7.27 (t, J ¼ 4.2 Hz,
4H, ArH)) 3.07–3.08 (br, 4H, 1,6-H), 2.96–2.98 (br, 4H, 2,5-H), Anal.
calcd. for C31H22Cl3N: C, 72.32; H, 4.31; N, 2.72. Found: C, 72.59; H,
4.27; N, 2.80.
Compound 6d. IR (KBr) 3045, 2921, 2851, 1589, 1561, 1542, 1479, 1458,
1419, 1360, 1299, 1284, 1264, 1238, 1200, 1137, 1098, 1080, 996, 911,
1
860, 787, 773, 751, 677 cm21; H NMR (DMSO-d6) 7.63 (dd, J ¼ 4.8 Hz,
J ¼ 4.8 Hz, 4H, ArH), 7.59 (d J ¼ 8.4 Hz, 3H, ArH), 7.55 (m, 2H,
2 ꢀ ArCH55), 7.46–7.51 (m, 5H, ArH,)), 3.15–3.18 (br, 4H, 1,6-H), 3.00–
3.02 (br, 4H, 2,5-H), Anal. calcd. for C31H22Cl3N: C, 72.32; H, 4.31; N,
2.72. Found: C, 72.61; H, 4.23; N, 2.84.
ACKNOWLEDGMENT
We are grateful to Peiyu Foundation (07PYL06) of Xuzhou Normal Univer-
sity and Natural Science Foundation (06XLA09) of Xuzhou Normal Univer-
sity for financial support.
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