Synthesis of 2-amino-4-aryl-5-oxo-4,5-dihydropyrano[3,2-c] chromene derivatives catalysed by KF-montmorillonite

Article abstract of DOI:10.3184/030823408X347585

A series of 2-amino-4-aryl-5-oxo-4,5-dihydropyrano[3,2-c]chromene derivatives has been synthesised by the reaction of 4-hydroxycoumarin and substituted cinnamonitriles catalysed by KF-montmorillonite. The structures were characterised by IR and ¹

Full text of DOI:10.3184/030823408X347585

542 RESEARCH PAPER
SEPTEMBER, 542–545
JOURNAL OF CHEMICAL RESEARCH 2008
Synthesis of 2-amino-4-aryl-5-oxo-4,5-dihydropyrano[3,2-c] chromene
derivatives catalysed by KF-montmorillonite
Da-Qing Shia,b*, Nan Wub and Qi-Ya Zhuangb
aCollege of Chemistry and Chemical Engineering, Key Laboratory of Organic Synthesis of Jiangsu Province, Suzhou University,
Suzhou 215123, P. R. China
bCollege of Chemistry and Chemical Engineering, Xuzhou Normal University, Xuzhou 221116, P. R. China
A series of 2-amino-4-aryl-5-oxo-4,5-dihydropyrano[3,2-c]chromene derivatives has been synthesised by the
reaction of 4-hydroxycoumarin and substituted cinnamonitriles catalysed by KF-montmorillonite. The structures
were characterised by IR and 1H NMR spectroscopic data and confirmed by X-ray diffraction analysis.
Keywords: dihydropyrano[3,2-c]chromene, KF-montmorillonite, coumarin
Coumarin (1-benzopyran-2-one) and its derivatives are
natural compounds and are important chemicals in perfume,
cosmetic and pharmaceutical industrial production.1 Some
coumarin derivatives have been reported to exhibit biological
properties.2-102-amino-4-aryl-5-oxo-4,5-dihydropyrano[3,2-c]
chromene derivatives are generally prepared by the reaction
of 4-hydroxycoumarin and substituted cinnamonitriles in an
organic solvent (e.g. ethanol) in the presence of an organic
base like piperidine11 or in aqueous media catalysed by
triethylbenzylammonium chloride.12
Smectite clays, especially montmorillonite, have been
used as heterogeneous catalyst in synthesis. Because of its
stability and ease of separation, montmorillonite has found
widespread use in a variety of heterogeneous reactions, such
as rearrangement,13-15 oxidation16 and addition17 reactions. In
previous reports, montmorillonite clays were used as the acidic
catalyst.18-20 Recently, we have reported that montmorillonite
coated with potassium fluoride (KF- montmorillonite) can be
used as an alkaline catalyst for organic synthesis.21-24 We now
report the efficient synthesis of 2-amino-4-aryl-5-oxo-4,5-
dihydropyrano[3,2-c]chromene derivatives catalysed by KF-
montmorillonite (Scheme 1).
Table 1shows that the reaction with DMF as solvent resulted
in a higher yield than those in other solvents. So DMF was
chosen as the solvent of this reaction.
To optimise the catalyst loading, 0.10 g, 0.15 g, 0.20 g, 0.25 g,
0.30 g, 0.35 g and 0.40 g of KF- montmorillonite was tested.
The results are summarised in Table 2 which shows that the
reaction catalysed by about 0.25 g KF-montmorillonite results in
the highest yield.
Under these optimised reaction conditions (15 ml DMF,
90°C, 0.25 g KF-montmorillonite), a series of 2-amino-4-
aryl-5-oxo-4,5-dihydropyrano[3,2-c]chromene derivatives (3)
were synthesised. The results are summarised in Table 3.
Structures of the products were established on the basis of
1
spectroscopic data, particularly H NMR analysis, and were
further confirmed by the X-ray crystal structure analysis of
the products 3e25 and 3s26 (Figs 1 and 2).
In summary, we have developed a simple, convenient and
efficient synthetic protocol for the synthesis of 2-amino-4-
aryl-5-oxo-4,5-dihydropyrano[3,2-c]chromene derivatives in
good to excellent yields catalysed by KF-montmorillonite.
Compared to the standard methods,11,12 this method has the
advantages of good yields, mild reaction conditions, easy
work-up and inexpensive reagents.
To find the optimal solvent, the synthesis of 3a by the reaction
of 4-hydroxycoumarin (1) and 2-(4-bromobenzylidene)
malononitrile (2a) was carried out at 90°C catalysed by
KF-montmorillonite using EtOH, acetone, DMF, THF and
petroleum ether as solvents. The results are summarised in
Table 1.
Experimental
IR spectra were recorded on a Tensor 27 spectrometer in KBr. 1H NMR
spectra were determined on a Bruker DPX-400 MHz spectrometer
using DMSO-d6 solutions. Chemical shifts (d) are expressed in
ppm downfield from internal tetramethylsilane. Microanalyses were
carried out on a Perkin-Elmer 2400 II elemental analyser.
NH2
OH
R
O
CN
R
KF-Montmorillonite
+
ArHC C
Ar
DMF
O
O
O
O
1
2
3
Scheme 1
Table 1 Solvent optimisation for the synthesis of 3a*
Entry
Solvent
Reaction temperature/oC
Isolated yield/%
1
2
3
4
5
6
Acetone
50
80
80
70
90
60
54
75
78
85
94
26
95% EtOH
Anhydrous EtOH
THF
DMF
Petroleum ether
*1 (2 mmol), 2a (2 mmol) KF- montmorillonite (0.25 g), reaction time 6 h, in 15 ml solvent.
* Correspondent. E-mail: dqshi@263.net

JOURNAL OF CHEMICAL RESEARCH 2008 543
Fig. 1 The X-ray crystal structure of compound 3e.
Fig. 2 The X-ray crystal structure of compound 3s.
Table 2 The effect of amounts of KF-montmorillonite for the
synthesis of 3a*
Entry
Amounts of KF-montmorillonite/g
Isolated yield/%
1
2
3
4
5
6
7
0.10
0.15
0.20
0.25
0.30
0.35
0.40
42
47
86
94
94
86
86
*1 (2 mmol), 2a (2 mmol) in 15 ml DMF, 90°C, 6 h.
General procedure for the synthesis of 2-amino-4-aryl-4H,5H-pyrano
[3,2-c][1]benzopyran-5-one derivatives (4):
A
mixture of
4-hydroxycoumarin (2 mmol), substituted cinnamonitrile
1
2
(2 mmol) and KF-montmorillonite (0.25 g) in DMF (15 ml) was
stirred for 6–14 h at 90°C (monitored by TLC). Then the mixture
was cooled to room temperature, the solid material was filtered off
and was washed with DMF. The filtrate was poured into 200 ml
water. The white solid was filtered off, and then washed with water.
The crude solid was purified by recrystallisation from ethanol to give
pure 3.
2-Amino-4-(4-bromophenyl)-5-oxo-4,5-dihydropyrano[3,2-c]
chromene-3-carbonitrile (3a): M.p. 254–256°C. IR: ν/cm-1 3385,
3187, 2191, 1713, 1670, 1632, 1602, 1458, 1408, 1331, 1357, 1211,
1
1113, 1009, 956, 835, 774, 759. H NMR (DMSO-d6): d 4.48 (1H,
s, CH), 7.25 (2H, d, J = 8.4 Hz, ArH), 7.45 (2H, s, NH2), 7.47–7.48
(1H, m, ArH), 7.49–7.52 (3H, m, ArH), 7.70–7.75 (1H, m, ArH), 7.91
(1H, d, J = 7.4 Hz, ArH). Found: C, 57.89; H, 2.77; N, 7.15% Calcd
for C19H11BrN2O3: C, 57.74; H, 2.81; N, 7.09%.
2-Amino-4-(3,4-dichlorophenyl)-5-oxo-4,5-dihydropyrano[3,2-c]
chromene-3-carbonitrile (3b): M.p. 243–244°C (Lit.27 242–244°C).
IR: ν/cm-1 3382, 3176, 2192, 1715, 1682, 1615, 1493, 1469, 1375,
1273, 1208, 1178, 1098, 955, 894, 767. 1H NMR (DMSO-d6): d 4.56
(1H, s, CH), 7.29–7.33 (1H, m, ArH), 7.46–7.51 (2H, m, ArH), 7.57–
7.60 (2H, m, ArH), 7.71–7.76 (1H, m, ArH), 7.89–7.92 (1H, m, ArH),
7.96 (2H, s, NH2).
2-Amino-4-(3-nitrophenyl)-5-oxo-4,5-dihydropyrano[3,2-c]
chromene-3-carbonitrile (3c): M.p. 253–255°C (Lit.12 254–255°C).
IR: ν/cm-1 3382, 3194, 2206, 1697, 1675, 1607, 1495, 1472, 1381,
1256, 1209, 959, 760. 1H NMR (DMSO-d6): d 4.48 (1H, s, CH),
7.46–7.54 (4H, m, NH2 + ArH), 7.61–7.65 (1H, m, ArH), 7.72–7.75
(1H, m, ArH), 7.81 (1H, d, J = 8.4 Hz), 7.91–7.95 (2H, m, ArH), 8.12
(1H, d, J = 8.4 Hz ArH).
2-Amino-4-(4-fluorophenyl)-5-oxo-4,5-dihydropyrano[3,2-c]
chromene-3-carbonitrile (3d): M.p. 259–261°C (Lit.12 260–262°C).
IR: ν/cm-1 3394, 3328, 3198, 2960, 2874, 2199, 1682, 1603, 1469,
1414, 1368, 1330, 1251, 1214, 1159, 1141, 1037, 976, 750. 1H NMR
(DMSO-d6): d 4.49 (1H, s, CH), 7.11–7.15 (2H, m, ArH), 7.30–7.33
(2H, m, ArH), 7.41 (2H, s, NH2), 7.45–7.52 (2H, m, ArH), 7.70–7.74
(1H, m, ArH), 7.90 (1H, d, J = 7.2 Hz, ArH).
2-Amino-4-(4-methoxyphenyl)-5-oxo-4,5-dihydropyrano[3,2-c]
chromene-3-carbonitrile (3e): M.p. 229–230°C (Lit.11 227°C).
IR: ν/cm-1 3385, 3190, 3064, 2955, 2837, 2207, 1715, 1669, 1607,
1511, 1493, 1455, 1381, 1327, 1305, 1253, 1207, 1176, 1112, 1053,
1029, 957, 902, 837, 780, 752. 1H NMR (DMSO-d6): d 3.72 (3H, s,
CH3O), 4.39 (1H, s, CH), 6.86 (2H, d, J = 8.8 Hz, ArH), 7.17 (2H, d,
J = 8.8 Hz, ArH), 7.38 (2H, s, NH2), 7.45–7.52 (2H, m, ArH), 7.69–
7.73 (1H, m, ArH), 7.89 (1H, d, J = 7.6 Hz, ArH).
2-Amino-4-(3-chlorophenyl)-5-oxo-4,5-dihydropyrano[3,2-c]
chromene-3-carbonitrile(3f):M.p.236–237°C(Lit.27235–236°C).IR:
ν/cm-1 3384, 3311, 3195, 3056, 2890, 2206, 1705, 1669, 1607, 1495,
1472, 1458, 1431, 1414, 1384, 1316, 1256, 1208, 1177, 1114, 1059,
1
997, 959, 902, 760, 714. H NMR (DMSO-d6): d 4.52 (1H, s, CH),
7.24–7.27 (1H, m, ArH), 7.30–7.38 (3H, m, ArH), 7.46 (2H, s, NH2),
Table 3 The synthesis of 3
Entry
Ar
R
Reaction times/h
Yield/%
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
4-BrC6H4
CN
6
7
11
8
8
7
12
10
10
11
9
10
7
8
6
14
6
94
86
91
93
86
84
90
84
80
80
85
80
90
85
86
84
87
86
80
70
3,4-Cl2C6H3
3-NO2C6H4
4-FC6H4
CN
CN
CN
4-CH3OC6H4
3-ClC6H4
CN
CN
3,4-OCH2OC6H3
3,4-(CH3O)2C6H3
4-CH3C6H4
3,4-(CH3)2C6H3
4-CH3OC6H4
4-CH3C6H4
4-FC6H4
C6H5
4-ClC6H4
3,4-OCH2OC6H3
4-BrC6H4
CN
CN
CN
CN
COOC2H5
COOC2H5
COOC2H5
COOC2H5
COOC2H5
COOC2H5
COOC2H5
COOC2H5
COOCH3
COOCH3
2,4-Cl2C6H3
4-ClC6H4
4-CH3C6H4
9
7
11
3s
3t

544 JOURNAL OF CHEMICAL RESEARCH 2008
7.48–7.53 (2H, m, ArH), 7.71–7.75 (1H, m, ArH), 7.90–7.92 (1H,
m, ArH).
3396, 3290, 3064, 2976, 2926, 1717, 1694, 1654, 1611, 1528,
1493, 1458, 1374, 1312, 1281, 1198, 1114, 1057, 1029, 951, 906,
896, 875, 820, 790, 759. 1H NMR (DMSO-d6): d 1.13 (3H, t,
J = 7.2 Hz, CH3), 4.01 (2H, q, J = 7.2 Hz, CH2O), 4.63 (1H,
s, CH), 5.94 (1H, s, OCH2O), 6.69 (1H, d, J = 8.4 Hz, ArH),
6.74–6.78 (2H, m, ArH), 7.44–7.51 (2H, m, ArH), 7.68–7.72
(1H, m, ArH), 7.80 (2H, s, NH2), 7.96 (1H, d, J = 7.2 Hz,
ArH). Found: C, 64.72; H, 4.19; N, 3.48. Calcd for C22H17NO7:
C 64.86, H 4.21, N 3.44%.
Ethyl 2-Amino-4-(4-bromophenyl)-5-oxo-4,5-dihydropyrano[3,2-c]
chromene-3-carboxylate (3q): M.p. 193–194°C. IR: ν/cm-1 3485,
3315, 3051, 2980, 1717, 1683, 1662, 1611, 1529, 1508, 1491, 1457,
1419, 1374, 1290, 1252, 1200, 1170, 1112, 1096, 1056, 954, 905, 844,
804, 785, 753, 726. 1H NMR (DMSO-d6): d 1.10 (3H, t, J = 7.2 Hz,
CH3), 4.00 (2H, q, J = 7.2 Hz, CH2O), 4.66 (1H, s, CH), 7.20 (2H, d,
J = 8.0 Hz, ArH), 7.35–7.54 (4H, m, ArH), 7.67–7.71 (1H, m, ArH),
7.90 (2H, s, NH2), 7.97 (1H, d, J = 7.6 Hz, ArH). Found: C, 57.15; H,
3.71; N, 3.06 Calcd for C21H16BrNO5: C 57.03; H. 3.65; N. 3.17%.
Ethyl 2-Amino-4-(2,4-dichlorophenyl)-5-oxo-4,5-dihydropyrano
[3,2-c]chromene-3-carboxylate (3r): M.p. 200–201°C (Lit.12 197–
198°C). IR: ν/cm-1 3474, 3332, 2973, 2932, 2879, 1694, 1650, 1620,
1524, 1477, 1465, 1406, 1369, 1295, 1247, 1205, 1143, 1124, 1085,
1037,971,856,839,816.1HNMR(DMSO-d6):d1.06(3H,t,J=7.2Hz,
CH3), 3.96 (2H, q, J = 7.2 Hz, CH2O), 5.06 (1H, s, CH), 7.29–7.34
(2H, m, ArH), 7.44–7.52 (3H, m, ArH), 7.69–7.73 (1H, m, ArH),
7.94–7.98 (3H, m, NH2 + ArH).
2-Amino-4-(3,4-methylenedioxyphenyl)-5-oxo-4,5-dihydro-
pyrano[3,2-c]chromene-3-carbonitrile (3g): M.p. 245–247°C (Lit.12
244–246°C). IR: ν/cm-1 3395, 3317, 3189, 3024, 2906, 2190, 1699,
1661, 1608, 1496, 1442, 1383, 1325, 1312, 1250, 1235, 1205, 1176,
1113, 1095, 1066, 1035, 959, 919, 905, 860, 826, 810, 767, 706.
1H NMR (DMSO-d6): d 4.39 (1H, s, CH), 5.98 (2H, s, OCH2O),
6.72–6.74 (1H, m, ArH), 6.82–6.84 (2H, m, ArH), 7.36 (2H, s, NH2),
7.45–7.51 (2H, m, ArH), 7.69–7.73 (1H, m, ArH), 7.89 (1H, d,
J = 8.4 Hz, ArH).
2-Amino-4-(3,4-dimethoxyphenyl)-5-oxo-4,5-dihydropyrano[3,2-c]
chromene-3-carbonitrile (3h): M.p. 233–235°C (Lit.12 232–234°C).
IR: ν/cm-1 3399, 3321, 3186, 2944, 2836, 2189, 1725, 1672, 1607,
1506, 1456, 1412, 1377, 1295, 1255, 1208, 1178, 1161, 1110, 1032,
954, 936, 830, 764. 1H NMR (DMSO-d6): d 3.72 (6H, s, 2 × CH3O),
4.41 (1H, s, CH), 6.74 (1H, d, J = 8.4 Hz, ArH), 6.85–6.89 (2H, m,
ArH), 7.34 (2H, s, NH2), 7.45–7.51 (2H, m, ArH), 7.69–7.73 (1H, m,
ArH), 7.90 (1H, d, J = 7.2 Hz, ArH).
2-Amino-4-(4-methylphenyl)-5-oxo-4,5-dihydropyrano[3,2-c]
chromene-3-carbonitrile (3i): M.p. 252–254°C (Lit.11 255°C). IR:
ν/cm-1 3397, 3284, 3179, 2199, 1709, 1673, 1636, 1601, 1492, 1472,
1457, 1380, 1327, 1306, 1258, 1212, 1173, 1111, 1062, 957, 903,
1
755. H NMR (DMSO-d6): d 2.26 (3H, s, CH3), 4.40 (1H, s, CH),
7.12–7.15 (4H, m, ArH), 7.39 (2H, s, NH2), 7.45–7.52 (2H, m, ArH),
7.70–7.73 (1H, m, ArH), 7.90 (1H, d, J = 8.8 Hz, ArH).
Methyl 2-Amino-4-(4-chlorophenyl)-5-oxo-4,5-dihydropyrano[3,2-
c]chromene-3-carboxylate (3s): M.p. 227–229°C (Lit.12 227–229°C).
IR: ν/cm-1 3402, 3287, 3048, 2984, 2939, 1705, 1683, 1640, 1611,
1532, 1479, 1456, 1440, 1405, 1370, 1289, 1242, 1195, 1089, 1054,
1008, 951, 903, 843, 832, 785, 757. 1H NMR (DMSO-d6): d 3.64
(3H, s, CH3O), 4.90 (1H, s, CH), 6.48 (2H, s, NH2), 7.21 (2H, d,
J = 8.4 Hz, ArH), 7.27 (2H, d, J = 8.4 Hz, ArH), 7.31–7.35 (2H, m,
ArH), 7.54–7.58 (1H, m, ArH), 7.82 (1H, dd, J1 = 1.6 Hz, J2 = 8.0 Hz,
ArH).
2-Amino-4-(3,4-dimethylphenyl)-5-oxo-4,5-dihydropyrano[3,2-c]
chromene-3-carbonitrile (3j): M.p. 231–232°C (Lit.27 226–228°C).
IR: ν/cm-1 3381, 3324, 3176, 3056, 2192, 1493, 1711, 1680, 1608,
1469, 1456, 1407, 1376, 1312, 1253, 1208, 1178, 1114, 1098, 1040,
1021, 956, 905, 767. 1H NMR (DMSO-d6): d 2.17 (3H, s, CH3), 2.18
(3H, s, CH3), 4.37 (1H, s, CH), 6.95–6.97 (1H, m, ArH), 7.70–7.71
(1H, m, ArH), 7.06 (1H, d, J = 8.0 Hz, ArH), 7.35 (2H, s, NH2),
7.45–7.52 (2H, m, ArH), 7.69–7.74 (1H, m, ArH), 7.90–7.92 (1H, m,
ArH).
Methyl 2-Amino-4-(4-methylphenyl)-5-oxo-4,5-dihydropyrano[3,2-c]
chromene-3-carboxylate (3t): M.p. 204–205°C (Lit.12 204–206°C).
IR: ν/cm-1 3393, 3285, 3084, 2984, 2951, 1705, 1689, 1613, 1532,
1485, 1455, 1400, 1378, 1323, 1289, 1239, 1196, 1110, 1076, 1054,
1008, 951, 904, 840, 786, 762. 1H NMR (DMSO-d6): d 2.27 (3H, s,
CH3), 3.64 (3H, s, CH3O), 4.91 (1H, s, CH), 6.42 (2H, s, NH2), 7.05
(2H, d, J = 8.0 Hz, ArH), 7.25 (2H, d, J = 8.0 Hz, ArH), 7.29–7.34
(2H, m, ArH), 7.52~7.56 (1H, m, ArH), 7.82 (1H, dd, J1 = 1.6 Hz,
J2 = 8.0 Hz, ArH).
Ethyl 2-Amino-4-(4-methoxyphenyl)-5-oxo-4,5-dihydropyrano[3,2-c]
chromene-3-carboxylate (3k): M.p. 160–162°C (Lit.11 160°C). IR:
ν/cm-1 3403, 3289, 3048, 2984, 2944, 1713, 1670, 1611, 1532, 1485,
1456, 1426, 1397, 1378, 1290, 1235, 1196, 1080, 1053, 951, 903,
843, 785, 757. 1H NMR (DMSO-d6): d 1.10 (3H, t, J = 7.2 Hz, CH3),
3.67 (3H, s, CH3O), 3.99 (2H, q, J = 7.2 Hz, CH2O), 4.64 (1H, s,
CH), 6.79 (2H, d, J = 8.4 Hz, ArH), 7.13 (2H, d, J = 8.4 Hz, ArH),
7.44–7.51 (2H, m, ArH), 7.68–7.72 (1H, m, ArH), 7.80 (2H, s, NH2),
7.96 (1H, d, J = 8.8 Hz, ArH).
Ethyl 2-Amino-4-(4-methylphenyl)-5-oxo-4,5-dihydropyrano[3,2-c]
chromene-3-carboxylate (3l): M.p. 189–190°C (Lit.11 190°C). IR:
ν/cm-1 3407, 3293, 2980, 2889, 1692, 1683, 1622, 1522, 1471, 1402,
1366, 1288, 1226, 1198, 1158, 1140, 1081, 1033, 973, 846, 793.
1H NMR (DMSO-d6): d 1.12 (3H, t, J = 7.2 Hz, CH3), 2.21 (3H, s,
CH3), 3.99 (2H, q, J = 7.2 Hz, CH2O), 4.66 (1H, s, CH), 7.03 (2H,
d, J = 8.0 Hz, ArH), 7.11 (2H, d, J = 8.0 Hz, ArH), 7.43–7.51 (2H,
m, ArH), 7.68–7.71 (1H, m, ArH), 7.80 (2H, s, NH2), 7.97 (1H, d,
J = 8.4 Hz, ArH).
Ethyl 2-Amino-4-(4-fluorophenyl)-5-oxo-4,5-dihydropyrano[3,2-c]
chromene-3-carboxylate (3m): M.p. 223–225°C (Lit.12 222–224°C).
IR: ν/cm-1 3419, 3302, 2975, 2907, 1717, 1691, 1678, 1610, 1471,
1457, 1522, 1375, 1279, 1250, 1196, 1084, 1047, 953, 904, 860, 758,
744, 723. 1H NMR (DMSO-d6): d 1.10 (3H, t, J = 7.2 Hz, CH3), 3.99
(2H, q, J = 7.2 Hz, CH2O), 4.69 (1H, s, CH), 7.03–7.08 (2H, m, ArH),
7.24–7.28 (2H, m, ArH), 7.44–7.52 (2H, m, ArH), 7.69–7.72 (1H, m,
ArH), 7.86 (2H, s, NH2), 7.97 (1H, d, J = 7.6 Hz, ArH).
Ethyl 2-Amino-4-phenyl-5-oxo-4,5-dihydropyrano[3,2-c]chromene-
3-carboxylate (3n): M.p. 197–199°C (Lit.11 196°C). IR: ν/cm-1 3416,
3309, 3083, 2975, 1711, 1685, 1610, 1544, 1493, 1477, 1456, 1376,
1278, 1250, 1192, 1112, 1084, 1023, 954, 913, 843, 822, 768, 739,
703. 1H NMR (DMSO-d6): d 1.11 (3H, t, J = 7.2 Hz, CH3), 3.99 (2H,
q, J = 7.2 Hz, CH2O), 4.70 (1H, s, CH), 7.13–7.16 (1H, m, ArH),
7.23–7.24 (4H, m, ArH), 7.44–7.51 (2H, m, ArH), 7.68–7.72 (1H, m,
ArH), 7.82 (2H, s, NH2), 7.98 (1H, d, J = 8.4 Hz, ArH).
Ethyl 2-Amino-4-(4-chlorophenyl)-5-oxo-4,5-dihydropyrano[3,2-c]
chromene-3-carboxylate (3o): M.p. 191–193°C (Lit.11 192°C). IR:
ν/cm-1 3412, 3303, 2958, 2837, 1690, 1675, 1621, 1584, 1527, 1508,
1467, 1445, 1367, 1288, 1250, 1233, 1200, 1162, 1142, 1085, 1035,
972, 825, 848, 795, 763. 1H NMR (DMSO-d6): d 1.10 (3H, t, J = 7.2 Hz,
CH3), 3.99 (2H, q, J = 7.2 Hz, CH2O), 4.68 (1H, s, CH), 7.24–7.31
(4H, m, ArH), 7.45–7.52 (2H, m, ArH), 7.69–7.73 (1H, m, ArH), 7.88
(2H, s, NH2), 7.97 (1H, d, J = 8.8 Hz, ArH).
We are grateful to the “Surpassing Project” Foundation of
Jiangsu Province and the Foundation of the Key Laboratory
of Biotechnology on Medical Plants of Jiangsu Province for
financial support.
Received 7 June 2008; accepted 14 July 2008
Paper 08/5316 doi: 10.3184/030823408X347585
Published online: 8 September 2008
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