JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Synthesis of Tetrahydrobenzo[b]pyrans and Pyrano[c]chromenes
Germany). All reagents and solvents were obtained
from Aldrich and Merck and used without further puri-
fication. Pectin was purchased from Sigma-Aldrich
(CAS No. 9000-69-5).
2-Amino-5,6,7,8-tetrahydro-4-(4-methyl)-7,7-dimethyl-
5-oxo-4H-chromene-3-carbonitrile (5h). M.p. 210–212 IR
(KBr) ν/cm−1 3465, 3320, 2955, 2190, 1676, 1247; 1H
NMR (400 MHz, DMSO-d6): δ 1.06 (s, 3H, CH3), 1.12 (s,
3H, CH3), 2.26 (dd, 2H, CH2, J 22.0, 16.4 2.30 (s, 3H), 2.46
(s, 2H, CH2), 4.38 (s, 1H, CH), 4.57 (s, 2H, NH2), 7.10 (d,
2H, Ar, J 8.0), 7.14 (d, 2H, Ar, J 8.0).
General procedure for the preparation of
tetrahydrobenzo[b]pyrans
Pectin 0.05 g was dissolved in H2O:EtOH (3:1),
and then aromatic aldehyde (1.0 mmol), malononitrile
(1.0 mmol), and dimedone (1.0 mmol) were added to
the mentioned solution at ambient condition. The prog-
ress of reaction was monitored by thin-layer chroma-
tography (TLC). After completion of reaction, the
products were isolated by filtration and washed with
water to remove pectin, and recrystallized from ethanol
(95%) to afford the pure products.
2-Amino-5,6,7,8-tetrahydro-4-(4-methoxyphe-
nyl)-7,7-dimethyl-5-oxo-4H-chromene-3-carbonitrile
(5i). M.p. 205–207 IR (KBr) ν/cm−1 3465, 3320,
2955, 2190, 1676, 1247; 1H NMR (300 MHz,
DMSO-d6): δ 0.95 (s, 3H,CH3), 1.04 (s, 3H,CH3),
2.09 (d, 1H, CH2, J 18.0), 2.25 (d, 1H, CH2,
J 18.0), 3.37 (s, 1H,CH2), 3.72 (s, 3H,OCH3), 4.13
(s, 1H,CH), 6.85 (d, 2H.Ar, J 8.0 Hz), 6.97 (br,
NH2), 7.06 (d, 2H, Ar, J 8.0 Hz).
2-Amino-5,6,7,8-tetrahydro-4-(4-hydroxyphenyl)-7,7-
dimethyl-5-oxo-4H-chromene-3-carbonitrile (5n). IR (KBr,
cm−1): 3285, 3160, 2960, 2185, 1675, 1209; 1H NMR
(400 MHz, CDCl3): δ (ppm): 1.05 (s,3H,CH3), 1.12 (s,3H,
CH3), 2.20–2.29 (dd, 2H, CH2, J 20.0, 16.0), 2.41–2.50
(dd, 2H, CH2, J 20.0, 16.0), 4.36 (s, 1H,CH), 4.53 (s, 2H,
NH2), 5.26 (s, 1H, OH), 6.71–7.28 (m, 4H, Ar).
General procedure for the synthesis of 3,4-dihidropyrano
[c]chromene derivatives
Pectin 0.05 was dissolved in EtOH (2.0 mL), and
then a mixture of an aromatic aldehyde (1.0 mmol),
malononitrile (1.0 mmol), and 4-hydroxycoumarine
(1.0 mmol) were added and stirred at ambient condi-
tions. The progress of the reaction was monitored by
TLC. After completion of the reaction, the mixture was
filtered and washed with water to remove the catalyst
from the reaction medium. The crude product was
recrystallized from ethanol to afford the pure 3,4-dihi-
dropyrano[c]chromene derivatives.
2-Amino-4,5-dihydro-4-(3-nitrophenyl)-5-oxopyrano
[3,2-c]chromene-3-carbonitrile (6b). M.p. 260–262 IR
(KBr) ν/cm−1 3402, 3322, 2202, 1703, 1670, 1606, 1538,
1
1380. H NMR (400 MHz, DMSO-d6): δ 4.75 (s, 1H,
CH), 7.48–8.16 (m, 9H, Ar, NH2).
2-Amino-4,5-dihydro-4-(2-fluorophenyl)-5-oxopyr-
ano[3,2-c]chromene-3-carbonitrile (6j). M.p. 220–223 IR
(KBr) ν/cm−1 3400, 3320, 2100, 1750, 1665, 1609, 1528,
1375.1H NMR (400 MHz, DMSO-d6): δ 4.75 (s,1H,
CH), 7.10–8.39 (m, 9H, Ar, NH2). 13C NMR
(100 MHz, DMSO-d6): δ 31.76 (CH), 56.83, 103.16,
113.33, 117.12 (CN), 119.50, 122.92, 125.14, 125.18,
125.24, 129.67, 130.22, 130.39, 133.55,152.64, 154.36,
158.64, 159.97, 162.33 (CO). MS m/z (%): 334 (M+,
29),313 (4),290 (6), 267 (8),239 (100), 222 (12),201
(2),183 (2),157 (3), 140 (5), 121 (20),92 (16),66
(12),44 (8).
2-Amino-4,5-dihydro-4-(thiophen-2-yl)-5-oxopyrano
[3,2-c]chromene-3-carbonitrile (6k). M.p. 250–252 IR
(KBr) ν/cm−1 3403, 3319, 2200, 1699, 1670, 1606, 1535,
1383.1H NMR (400 MHz, DMSO-d6): δ 4.61 (s,1H),
7.02–7.89 (m, 9H, Ar, NH2). 13C NMR (100 MHz,
DMSO-d6): δ 32.38 (CH), 58.29, 104.55, 113.32, 117.15
(CN), 119.57, 122.95, 125.29, 125.68, 127.56, 133.66,
Selected spectroscopic data of some products are
given below:
2-Amino-5,6,7,8-tetrahydro-7,7-dimethyl-5-oxo-4-
phenyl-4H-chromene-3-carbonitrile (5a). M.p. 230–232
IR (KBr) ν/cm−1 3390, 3245, 2960, 2190, 1676, 1209;
1H NMR (400 MHz, CDCl3) δ 1.07 (s, 3H, CH3),
1.14 (s, 3H, CH3), 2.23 (dd, 2H, CH2, J 22.0, 16.4),
2.48, (s, 2H, CH2), 4.43 (s, 1H, CH), 4.55 (s, 2H, NH2),
7.2, 7.3 (m, 5H, Ar).
2-Amino-5,6,7,8-tetrahydro-4-(4-nitrophenyl)-
7,7-dimethyl-5-oxo-4H-chromene-3-carbonitrile (5g).
M.p. 182–184 IR (KBr) ν/cm−1 3285, 3160, 2960,
1
2185, 1675, 1209; H NMR (300 MHz, DMSO-d6):
δ 0.95 (s, 3H, CH3), 1.027 (s, 3H, CH3), 2.12 (d,
1H, CH2, J 16.0,), 2.27 (d, 1H, CH2, J 16.0), 2.51
(d, 2H, CH2, J 12.0), 4.36 (s, 1H,CH), 7.19 (s,br,
NH2), 7.44 (d, 2H, Ar, J 8.0), 8.16 (d, 2H,
Ar, J 8.0).
J. Chin. Chem. Soc. 2016
© 2016 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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