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Z. Vafajoo et al. / C. R. Chimie 17 (2014) 301–304
Scheme 1.
shown that this method is capable of promoting organic
synthesis of pyrano [3,2-c]chromene derivatives in envir-
onmentally friendly conditions.
2.2.2. 2-Amino-5-oxo-4-o-tolyl-4,5-dihydropyrano[3,2-
c]chromene-3- carbonitrile (4n, Entry 14)
m.p.: 262–266 8C, 1H NMR (DMSO-d6, 500 MHz,
d
ppm): 2.48 (s, 3H, CH3), 4.73 (s, 1H, CH), 6.90–7.20 (m, 4H,
Ar), 7.34 (s, 2H, NH2), 7.41 (d, J = 8.3 Hz, 1H, Ar), 7.46 (t,
J = 7.6 Hz, 1H, Ar), 7.67 (t, J = 7.25, 1H, Ar), 7.89 (d, J = 7.8 Hz,
2. Experimental
2.1. Typical experimental procedure for electrocatalytic
synthesis of 2-amino-5-oxo-4,5-dihydropyrano[3,2-
c]chromene-3-carbonitrile derivatives
1H, Ar); 13C NMR (DMSO-d6,
d ppm125 MHz): 19.0, 57.9,
104.5, 122.8, 116.4, 119.1, 122.3, 124.6, 126.6, 123.6, 126.7,
127.8, 130.0, 132.7, 135.2, 142.2, 152.0, 153.4, 157.7,
159.5; IR (KBr, cmÀ1): 3400- 3283 (NH2), 3179 (CH
aromatic), 2202 (CꢀN), 1709 (C5O), MS (EI, 70 eV) m/z
(%) = 330 (M+, 18), 249 (24), 240 (17), 239 (100), 121 (21).
A mixture of aryl aldehyde (10 mmol), malononitrile
(12 mmol), 4-hydroxycoumarin (10 mmol), and NaBr
(0.1 g, 1 mmol) in EtOH (20 mL) was electrolyzed in an
undivided cell equipped with a magnetic stirrer, a graphite
anode, and an iron cathode at 25 8C under a constant
current density of 10 mA/cm2 [electrodes square 5 cm2],
until the catalytic quantity of 0.1 F/mol of electricity was
passed. After electrolysis was finished, the mixture was
filtered, then rinsed twice with an ice-cold ethanol/water
solution (9:1, 5 mL), and dried under reduced pressure.
3. Results and discussion
Our investigations of the electrocatalytic multicom-
ponent chain transformation of aryl aldehydes, 4-hydro-
xycoumarin and malononitrile into 2-amino-5-oxo-4,5-
dihydropyrano[3,2-c]chromene-3-carbonitrile
deriva-
tives under neutral and mild conditions by electrolysis
in an undivided cell began with the optimization of the
reaction conditions. The synthetic pathway is shown in
Scheme 1.
2.2. Analytical data for the selected compounds
2.2.1. 2-Amino-5-oxo-4-(2,5-dimethoxyphenyl)-4,5-
Table 1 lists the representative data obtained for the
synthesis of 2-amino-4-phenyl-4,5-dihydropyrano[3,2-
c]chromene-3-carbonitrile 4a from benzaldehyde 1a,
malononitrile 2 and 4-hydroxycoumarin 3 under various
experimental conditions. The reaction is performed
in alcoholic solvents in the presence of sodium bromide
as an electrolyte. The reaction mixture was stirred at
room temperature and the progress was monitored by
TLC.
Various current quantities were applied under the
mentioned conditions. Excellent conversions of the start-
ing materials were obtained under 10 mA/cm2 current
densities after 0.1 F/mol of electricity had passed. The
current density of 10 mA/cm2, I = 50 mA, electrode surface
dihydropyrano[3,2-c]chromene-3-carbonitrile (4l, Entry 12)
m.p.: 238–240 8C, 1H NMR (DMSO-d6, 500 MHz,
d
ppm): 3.63 (s, 3H, CH3), 3.64 (s, 3H, CH3), 4.64 (s, 1H, CH),
6.66 (d, J = 2.3 Hz, 1H, Ar), 6.76–6.79 (m, 1H, Ar), 6.90 (d,
J = 8.8 Hz, 1H, Ar), 7.25 (s, 2H, NH2), 7.43 (d, J = 8.25 Hz, 1H,
Ar), 7.46 (t, J = 7.5 Hz, 1H, Ar), 7.67 (t, J = 7.5 Hz, 1H, Ar), 7.89
(d, J = 7.7 Hz, 1H, Ar); 13C NMR (DMSO-d6, 125 MHz,
d
ppm): 55.2, 56.4, 56.8, 103.1, 112.2, 112.9, 113.1, 115.7,
116.4, 119.2, 122.2, 124.5,125, 131.9, 132.6, 151.5, 152.0,
153.1, 153.9, 158.5, and 159.4; IR (KBr, cmÀ1): 3403–
3322(NH2), 3192 (CH aromatic), 2195 (CꢀN), 1708(C5O),
MS (EI, 70 eV) m/z (%) =376 (M+, 23), 361 (14), 345 (42), 279
(100), 239 (26), 215 (13), and 121 (24) (Table 2).
Table 1
Optimization of reaction conditions for synthesis of 2-amino-4-phenyl-4,5-dihydropyrano[3,2-c]chromene-3-carbonitrile at room temperature.
Entry
I
Current density
(mA/cm2)
Time
Catalyst
Solvent
Electricity passed
(F/mol)
Yield
(%)
(mA)
(min)
1
2
3
4
5
6
7
8
5
1
375
190
87
–
EtOH
EtOH
EtOH
EtOH
EtOH
MeOH
n-PrOH
EtOH
0.1
0.1
0.1
0.1
0.1
0.1
0.1
–
62
70
82
92
80
80
83
0
10
20
50
75
50
50
–
2
–
4
–
10
15
10
10
–
35
–
25
–
35
–
35
–
35
Na