Analytical Methods in Environmental Chemistry Journal Vol 1(2018) 39-46
Research Article, Issue 1
Analytical Methods in Environmental Chemistry Journal
AMECJ
A green approach to electrosynthesis of chromeno[3’,4’:5,6]
pyrano [2,3-d] pyrimidines by electrochemistry
Reyhaneh Kazemi Rada*
a Department of Chemistry, Rasht Branch, Islamic Azad University, Rasht, Iran
A R T I C L E I N F O:
A B S T R A C T
Eletrochemistry is a broad, useful, and selective technique method in many research
Received 27 Aug2018
fields. Among them, the investigation of performance of electrochemical methods in
Revised form 11 Nov 2018
determination, synthesis and selective reduction/oxidation of different elements and
Accepted 23 Nov 2018
molecules have attracted growing attention due their intrinsic advantages such as
selectivity, low cost, and high yield of synthesis. Moreover, electrocatalytic synthesis
Available online 26 Dec 2018
of organic molecules is known as a green and environmentally benign method. In
the present form, electrocatalytic multicomponent transformation of barbituric acid,
------------------------
aromatic aldehydes, and 4-hydroxycumarin was carried out. The electrocatalytic
transformation was done in alcohols in the presence of tetrabutylammounium flouride
as an electrolyte in an undivided cell containing an iron electrode as the cathode and a
Keywords:
Pt electrode as the anode at a constant current leads to substituted chromeno[3’,4’:5,6]
Analytical methods
pyrano[2,3-d] pyrimidines in good to high yields (54-92%) at room temperature.
The yield of reaction was obtained by gravimetric analysis and calculated upon
Characterization
theoretical conversion. The application of the effective electrocatalytic cascade
Electrocatalytic transformation
method to the formation of chromeno-pyrano-pyrimidines is also beneficial from the
Chromene
viewpoint of diversity-oriented large-scale processes and represents an example of
facile environmentally benign synthetic concept for electrocatalytic multicomponent
Multicomponent reaction
reactions. The products were characterized with proper analytical methods such as
Pyranopyrimidine
elemental analysis (CHN), FT-IR, 1H-NMR, and 13C-NMR spectrometry. Finally, the
obtained results showed that the desired products were synthesized.
1. Introduction
wide range of the diverse pharmacological action
Chromene derivatives have attracted great interest
such as antitumor, cardiotonic, hepatoprotective,
due to biological and pharmacological activities
antihypertensive, anticoagulant and antibronchitic
such as anti-coagulant, anti-cancer, spasmolytic,
activity
[7-12]. Moreover, pyranopyrimidine
diuretic, anti-anaphylatic, etc. Furthermore,
derivatives occur widely in the structures of various
the chromene derivatives are widely found in
natural products [13].
natural alkaloids, flavonoids, tocopherols, and
Thus, chromeno pyrano[2,3-d]pyrimidine system
anthocyanins [1-6].
appears to be of the interest because it incorporates
Pyrano[2,3-d]pyrimidines have also received
a chromene and a pyrano[2,3-d]pyrimidine
considerable attention over the past years due to their
heterocyclic ring, which are both promising with
respect to biological responses.
* E-mail: reyhanehkazemi83@gmail.com
40
Analytical Methods in Environmental Chemistry Journal; Vol. 1 (2018)
To the best of our knowledge, there are only a
2.3. Experimental characterisation data for
few reports on the three-component coupling
compounds 4a-g
of
4-hydroxycoumarin, aldehydes, and cyclic
7-phenyl-chromeno[3’,4’:5,6]pyrano[2,3-d]
1,3-dicarbonyl compounds [14,15].
pyrimidine-6,8,10(7H,9H,11H)-trione (4a):
Due to the extensive research on the electrochemistry
Yellow solid; mp (dec.) > 300oC. IR (KBr): νmax =
of organic compounds, electrosynthesis has become
3400, 3209, 3029, 2943, 1684, 1612, 1568, 1390,
a useful method in modern organic chemistry
1190 cm-1;
1H-NMR (400 MHz, DMSO-d6): δ
[16,19]. Electrochemical organosynthetic methods
= 6.11 (s, 1H), 7.04-7.08 (m, 2H), 7.13-7.16 (m,
have received significant attention because of their
3H), 7.25-7.29 (m, 2H), 7.51-7.55 (m, 1H), 7.78-
benefit to the environment. In these procedures,
7.81 (m, 1H), 9.93 (s, 1H, NH), 10.12 (s, 1H, NH);
electricity acts as a ‘green’ oxidative and reductive
13C-NMR (100 MHz, DMSO-d6): δ = 166.2, 165.9,
agent.
165.4, 165.0, 152.6, 151.5, 143.8, 131.6, 128.0,
127.1, 125.1, 124.3, 123.6, 119.4, 116.0, 105.9,
2. Experimental Procedure
89.8, 34.0; Anal. Calcd for C20H12N2O5: C, 66.67;
2.1. Material and Methods
H, 3.36; N, 7.77. Found: C, 66.54; H, 3.24; N, 7.98.
All reagents were purchased from Merck and Fluka
and used without further purification. The melting
7-(3-nitrophenyl)-chromeno[3’,4’:5,6]
points were obtained in open capillary tubes and
pyrano[2,3-d]pyrimidine-6,8,10(7H,9H,11H)-
were measured on an Electrothermal IA 9100
trione (4b):
apparatus. IR spectra were recorded on KBr pellets
Yellow solid; mp
(dec.)
> 300oC. IR
(KBr):
with a Shimadzu FT-IR 8600 spectrophotometer.
νmax = 3400, 3211, 3072, 2980, 1684, 1612, 1570,
1H and 13C NMR spectra were determined with a
1525, 1351, 1282, 1183 cm-1; 1H-NMR (400 MHz,
Bruker DRX-400 Avance instrument at 400 and
DMSO-d6): δ = 6.22 (s, 1H), 7.25 (t, J = 7.6 Hz,
100 MHz. Elemental analysis were carried out on a
1H), 7.31 (d, J = 8.4 Hz, 1H), 7.46-7.58 (m, 3H),
Thermo Finnigan Flash EA 1112 series instrument.
7.80 (d, J = 7.6 Hz, 1H), 7.86 (s, 1H), 7.97 (d, J
= 7.6 Hz, 1H), 10.03 (s, 1H, NH), 10.17 (s, 1H,
2.2. General procedure for the synthesis of 4a-g
NH); 13C-NMR (100 MHz, DMSO-d6): δ = 166.2,
A mixture of barbituric acid 1 (2 mmol), aromatic
164.9, 164.7, 152.7, 151.4, 148.1, 146.9, 134.2,
aldehyde 2a-g (2 mmol), 4-hydroxycoumarin 3 (2
131.8, 129.7, 124.6, 124.4, 123.7, 123.6, 121.5,
mmol), and TBAF (0.04 g, 0.2 mmol) in n-PrOH/
120.6, 116.1, 104.9, 89.3, 34.2; Anal. Calcd for
H2O (15/5 mL) were electrolyzed in an undivided
C20H11N3O7: C, 59.27; H, 2.74; N, 10.37. Found: C,
cell equipped with a magnetic stirrer, a platinum
59.22; H, 2.74; N, 10.39.
anode and an iron cathode at room temperature under
a constant current density of 4 mA/cm2 (I = 20 mA,
7-(4-nitrophenyl)-chromeno[3’,4’:5,6]
electrodes square 5 cm2). Progress of the reaction
pyrano[2,3-d]pyrimidine-6,8,10(7H,9H,11H)-
was monitored by thin layer chromatography. After
trione (4c):
electrolysis was finished, the precipitation of the
Orange solid; mp (dec.) > 300oC. IR (KBr): νmax
products were obtained at pH = 7. In addition, filter
= 3415, 3213, 3055, 2962,
1686,
1610,
1569,
cakes were washed twice with hot ethanol to give
1512, 1379, 1346, 1183 cm-1; 1H-NMR (400 MHz,
pure target products 4a-g.
DMSO-d6): δ = 6.21 (s, 1H), 7.25-7.32 (m, 4H),
7.54 (t, J = 8.4 Hz,1H), 7.79-7.80 (m, 1H), 8.06
Electrosynthesis of chromeno-pyrano-pyrimidines; Reyhaneh Kazemi-Rad
41
(d, J = 8.8 Hz, 2H), 9.97 (s, 1H, NH), 10.09 (s, 1H,
7-(3-bromophenyl)-chromeno[3’,4’:5,6]
NH); 13C-NMR (100 MHz, DMSO-d6): δ = 168.9,
pyrano[2,3-d]pyrimidine-6,8,10(7H,9H,11H)-
166.0, 153.4, 152.8, 151.4, 145.5, 143.6, 131.8,
trione (4f):
128.3, 124.6, 123.7, 123.5, 123.4, 119.3, 116.0,
White solid; mp (dec.) > 350oC. IR (KBr): νmax =
105.0, 89.8, 34.7; Anal. Calcd for C20H11N3O7: C,
3333, 3167, 3060, 2933, 1684, 1612, 1576, 1468,
59.27; H, 2.74; N, 10.37. Found: C, 59.12; H, 2.78;
1398, 1188 cm-1; 1H-NMR (400 MHz, DMSO-d6):
N, 10.50.
δ = 6.11 (s, 1H), 7.06-7.14 (m, 3H), 7.24-7.29 (m,
3H), 7.52-7.55 (m, 1H), 7.79 (s, 1H), 9.97-10.08
7-(2-chlorophenyl)-chromeno[3’,4’:5,6]
(brs, 2H, NH); 13C-NMR (100 MHz, DMSO-d6): δ
pyrano[2,3-d]pyrimidine-6,8,10(7H,9H,11H)-
= 166.1, 164.7, 152.7, 151.4, 147.4, 131.7, 130.3,
trione (4d):
129.7, 128.0, 127.1, 126.4, 126.0, 124.4, 123.7,
White solid; mp (dec.) > 300oC. IR (KBr): νmax =
121.7, 119.4, 116.0, 105.2, 89.4, 34.0; Anal. Calcd
3433, 3197, 3057, 2964, 1686, 1612, 1568, 1402,
for C20H11BrN2O5: C,
54.69; H,
2.52; N,
6.38.
1188 cm-1; 1H-NMR (400 MHz, DMSO-d6): δ =
Found: C, 54.35; H, 2.64; N, 6.63.
5.99 (s, 1H), 7.08-7.17 (m, 2H), 7.21-7.27 (m, 3H),
7.33 (d, J = 7.2 Hz, 1H) , 7.50 (t, J = 7.2 Hz, 1H),
7-(4-bromophenyl)-chromeno[3’,4’:5,6]
7.76 (d, J = 7.2 Hz, 1H), 9.86 (s, 1H, NH), 10.00
pyrano[2,3-d]pyrimidine-6,8,10(7H,9H,11H)-
(s, 1H, NH); 13C-NMR (100 MHz, DMSO-d6): δ
trione (4g):
= 168.4, 165.6, 165.4, 164.0, 152.5, 151.5, 141.8,
White solid; mp (dec.) > 300oC. IR (KBr): νmax =
133.2, 131.4, 130.7, 129.7, 127.2, 126.2, 124.2,
3400, 3210, 3084, 2930, 1684, 1612, 1568, 1377,
123.6, 119.5, 115.9, 106.0, 88.3, 34.1; Anal. Calcd
1184 cm-1; 1H-NMR (400 MHz, DMSO-d6): δ =
for C20H11ClN2O5: C,
60.85; H,
2.81; N,
7.10.
6.06 (s, 1H), 6.99 (d, J = 8.0 Hz, 2H), 7.23-7.29
Found: C, 60.74; H, 2.93; N, 7.13.
(m, 2H), 7.32 (d, J = 8.0 Hz, 2H), 7.51 (d, J =
7.6 Hz, 1H), 7.78 (t, J = 7.6 Hz, 1H), 9.88 (s, 1H,
7-(4-chlorophenyl)-chromeno[3’,4’:5,6]
NH), 10.06 (s, 1H, NH); 13C-NMR (100 MHz,
pyrano[2,3-d]pyrimidine-6,8,10(7H,9H,11H)-
DMSO-d6): δ = 168.0, 166.0, 152.5, 151.4, 148.4,
trione (4e):
143.7, 131.6, 130.8, 129.5, 124.4, 123.6, 120.3,
White solid; mp (dec.) > 350oC. IR (KBr): νmax =
119.4, 118.0, 116.0, 105.4, 89.8, 33.7; Anal. Calcd
3429, 3217, 3068, 2920, 1686, 1612, 1572, 1373,
for C20H11BrN2O5: C,
54.69; H,
2.52; N,
6.38.
1188 cm-1; 1H-NMR (400 MHz, DMSO-d6): δ =
Found: C, 54.62; H, 2.45; N, 6.50.
6.08 (s, 1H), 7.05 (d, J = 8.0 Hz, 1H), 7.07 (t, J =
8.0 Hz, 1H), 7.22 (d, J = 8.4 Hz, 2H), 7.27 (d, J =
3. Results and discussion
8.4 Hz, 2H), 7.51 (d, J = 7.2 Hz, 1H) , 7.78 (t, J =
Simple alcohols (methanol, ethanol, propanol) or
7.2 Hz, 1H), 9.90 (s, 1H, NH), 10.07 (s, 1H, NH);
alkanes
(heptane, hexane) are environmentally
13C-NMR (100 MHz, DMSO-d6): δ = 166.0, 164.8,
preferable solvents, whereas the use of
152.7, 151.4, 143.1, 131.6, 129.6, 129.0, 127.9,
dioxane, acetonitrile, acids, formaldehyde, and
124.4, 123.6, 119.4, 116.0, 105.5, 89.6, 33.7; Anal.
tetrahydrofuran is not recommendable from an
Calcd for C20H11ClN2O5: C, 60.85; H, 2.81; N, 7.10.
environmental perspective [20, 21]. In continuation
Found: C, 60.74; H, 2.93; N, 7.13.
of our work
[15,
22-24] on the development
of efficient and convenient procedures using
electrogenerated base, we were prompted to design
42
Analytical Methods in Environmental Chemistry Journal; Vol. 1 (2018)
R
O
CHO
OH
O
O
HN
HN
O
Electrolysis
+
+
PrOH, TBAF
O
N
O
O
O
O
N
O
H
R
H
1
2a-g
3
4a-g
Scheme 1. Synthesis of chromeno pyrano[2,3-d] pyrimidine.
Table 1. Electrocatalytic transformation of barbituric acid (1), 3-nitrobenzaldehyde (2b), and 4-hydroxycoumarin (3)
into 4ba.
Entry
Alcohol
I (mA)
Current density
Time
Electricity passed
Yield (%)
(mAcm-2)
(min)
(F mol-1)
1
MeOH
20
4
20
0.25
88
2
EtOH
20
4
20
0.25
90
3
PrOH
20
4
20
0.25
94
4
PrOH
10
2
40
0.25
80
5
PrOH
30
6
13.5
0.25
90
6
PrOH
50
10
8
0.25
87
a 3-nitrobenzaldeyde (2 mmol), barbituric acid (2 mmol), 4-hydroxycumarin (2 mmol), TBAF (0.2 mmol), alcohol/water (15/5 ml),
iron cathode (5 cm2), platinum anode (5 cm2), r.t.
a green and environmentally benign methodology
into corresponding chromeno-pyrano-pyrimidines
for the synthesis of chromeno pyrano[2,3-d]
4b in alcohol in an undivided cell containing
pyrimidine compounds based on electrochemically
an iron electrode as cathode and a Pt electrode
induced multicomponent reaction of barbituric
as anode at constant current in the presence of
acid, aromatic aldehydes and 4-hydroxycumarin in
tetrabutylammounium flouride as an electrolyte
an undivided cell containing an iron electrode as
was studied. Also, the effect of current and solvent
cathode and a Pt electrode as anode in the presence
was also examined (Table 1). As for alcohol used
of tetrabutylammounium flouride as electrolyte in
as solvent, PrOH is preferable to MeOH and EtOH
alcohols at room temprature.
for this electrocatalytic transformation at room
First, to evaluate the synthetic potential of
temperature.
the procedure proposed and to optimize the
As indicated in Table 1, excellent conversions of
electrolysis
conditions, the electrocatalytic
starting compounds were obtained after 0.25 F/mol
multicomponent transformation of barbituric acid 1,
of electricity. The current density 4 mA/cm2 (I =
3-nitrobenzaldehyde 2b, and 4-hydroxycoumarin 3
20 mA, electrodes surface 5 cm2) in n-PrOH at r.t.
Electrosynthesis of chromeno-pyrano-pyrimidines; Reyhaneh Kazemi-Rad
43
Table 2. Electrocatalytic transformation of barbituric acid(1), aromatic aldehydes (2a-g) and 4-hydroxycoumarin (3)
into chromeno-pyrano-pyrimidines 4a-g.
Product
Ar
Current density
Time Electricity passed Yield (%) Mp (ºC)
Mp (ºC)
(mAcm-2)
(min)
(F mol-1)
(lit. [14])
4a
C6H5
4
45
0.56
54
> 300 dec.
> 300 dec.
4b
3-NO2 C6H4
4
20
0.25
92
> 300 dec.
> 300 dec.
4c
4-NO2 C6H4
4
10
0.12
82
> 300 dec.
> 300 dec.
4d
2-Cl C6H4
4
25
0.16
88
> 300 dec.
> 300 dec.
4e
4-Cl C6H4
4
30
0.37
90
> 350 dec.
> 350 dec.
4f
3-BrC6H4
4
30
0.37
62
> 350 dec.
> 350 dec.
4g
4-BrC6H4
4
30
0.37
72
> 300 dec.
> 300 dec.
aReaction conditions: barbituric acid (2 mmol), aromatic aldehyde (2 mmol), 4-hydroxycoumarin (2 mmol), TBAF(0.2 mmol),
n-PrOH/H2O (15/5 mL), iron cathode (5 cm2), platinum anode (5 cm2), current density 4 mA/cm2, room temperature.
Cathode:
PrOH
+ e-
PrO
+
1/2H2
5
in solution:
O
O
O-
-
HN
HN
HN
+
PrO
O
N
O
O
N
O
O
N
O
H
H
H
6
1
-OPr
ArCHO
H
-OH-
O
2a-g
-OPr
Ar
O
O
Ar
O
H
H
NH
O
NH
O
O
3
Micheal
O
N
O
N
O
O O
Addition
H
H
7
-H2O
PrO
O
Ar
O
O Ar
O
H
O
NH
O
NH
-H2O
O
N
O
O
N
O
H
OH
H
4a-g
Scheme 2. A proposed mechanism for the electrocatalytic transformation of barbituric acid, aromatic aldehydes and
4-hydroxycumarin into chromeno-pyrano-pyrimidines 4a-g
44
Analytical Methods in Environmental Chemistry Journal; Vol. 1 (2018)
was found to be optimum for the electrochemically
in an undivided cell gives rise to the corresponding
induced chain process and allowed for the highest
chromeno-pyrano-pyrimidines in comparison
yield (92%) of chromeno-pyrano-pyrimidines 4b.
with conventional methods has advantages such
The increase in the current density up to 10 mA/
as (i) in situ generation of base and avoidance of
cm2 (I = 50 mA) results in a slight decrease of
polluting or hazardous chemicals or the addition
the reaction yield, which may be connected with
of base or probase, (ii) a fast one pot reaction in
the activation of undesired direct electrochemical
good to excellent yields at room temperature (iii).
processes possible under these conditions and
The procedure utilizes inexpensive reagents, green
leading to oligomerization of starting material.
solvents, simple equipment, and an undivided cell
Under the optimal conditions (current density 4
(v). Moreover, it is easily carried out and is fully
mA/cm2, 0.25 F/mol passed, n-PrOH as a solvent),
beneficial from the viewpoint of ecological organic
the electrolysis of barbituric acid
1, aromatic
synthesis and large-scale processes. Furthermore,
aldehydes 2a-g, and 4-hydroxycumarin 3 in an
this method can potentially used for determination
undivided cell gives rise to the corresponding
of such molecules.
chromeno-pyrano-pyrimidines 4a-g with 54-92 %
yield at r.t. (Scheme 1, Table 2).
5. Acknowledgements
Taking into consideration the above results, the
Financial support for this work by the research
following mechanism for the electrocatalytic
council of Islamic Azad University, Rasht Branch
chain transformation of barbituric acid 1, aromatic
is gratefully acknowledged.
aldehydes
2a-g, and
4-hydroxycumarin
3 into
corresponding chromeno-pyrano-pyrimidines 4a-g
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