Electrochemical synthesis of 6-amino-5-(3,4-dihydroxyphenyl) pyrimidine

Article abstract of DOI:10.1016/j.tetlet.2007.11.134

Electrochemical oxidation of several catechols is studied in the presence of 4(6)-aminouracil (3a) and 6-amino-1,3-dimethyl uracil (3b) as nucleophiles in aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results reveal th

Full text of DOI:10.1016/j.tetlet.2007.11.134

Available online at www.sciencedirect.com
Tetrahedron Letters 49 (2008) 710–714
Electrochemical synthesis of 6-amino-5-(3,4-dihydroxyphenyl)
pyrimidine
a,
a
a
*
Saied Saeed Hosseiny Davarani , Neda Sheijooni Fumani , Hamid Arvin-Nezhad ,
Farzaneh Moradi b
a Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113, Iran
b Department of Chemistry, Faculty of Science, Lorestan University, Khorram-Abad, Iran
Received 24 June 2007; revised 11 November 2007; accepted 21 November 2007
Abstract
Electrochemical oxidation of several catechols is studied in the presence of 4(6)-aminouracil (3a) and 6-amino-1,3-dimethyl uracil (3b)
as nucleophiles in aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results reveal that quinones
derived from catechols participate in Michael additions with 3a and 3b to give the corresponding catecholamine derivatives via an elec-
tron transfer followed by chemical reaction (EC) mechanistic pathway in good yields and purities.
Ó 2007 Published by Elsevier Ltd.
Keywords: Cyclic voltammetry; Electrochemical synthesis; Catechol; 4(6)-Amino uracil; Catecholamine; 6-Amino-1,3-dimethyl uracil
1. Introduction
ence of uracils 3a and 3b as nucleophiles. The present work
has led to the development of a facile and environmentally
friendly reagent-less electrochemical method for the syn-
thesis of catecholamine derivatives 5a–f under ambient
conditions and in a two-compartment cell using a graphite
electrode with high atomic economy.
The cyclic voltammogram of a 2 mM solution of cate-
chol 1a in 0.2 M sodium acetate solution as supporting
electrolyte shows an anodic (A1) and a corresponding
cathodic peak (C1), which correspond to the transforma-
tion of 1a to o-quinone 2a and vice versa within a quasi-
reversible two electron reaction (Fig. 1, curve a). A peak
current ratio ðICP1=IPA1Þ of nearly unity, particularly during
the repetitive recycling of potential, can be considered a
criterion for the stability of the o-quinones produced at
the surface of the electrode under the experimental condi-
tions. In other words, any hydroxylation13–20or dimeriza-
tion21–23 reaction is too slow to be observed on the cyclic
voltammetry time-scale.
Pyrimidines represent a broad class of compounds
which have received considerable attention due to their
wide range of biological activities.1–6 Several patents have
been reported on the preparation of these heterocycles,
derivatives of which are useful as bronchodilators,7,8 vaso-
dilators,3,4 antiallergic,7–9 antihypertensive,10 and anti can-
cer7,8 agents. Catecholamines have been found in many
plants and their synthesis is regulated by stress condi-
tions.11 They are widely used in pharmaceutical prepara-
tions. They can be oxidized chemically to o-quinone
derivatives, and in mammals they are known to function
as neurotransmitters with glycogen mobilizing ability.12
The importance of uracil derivatives and catecholamines
prompted us to synthesize a number of these compounds
from catechols and amino uracils. We have investigated
the electrochemical oxidation of catechols 1a–c in the pres-
The oxidation of catechol 1a in the presence of 6-amino-
1,3-dimethyluracil (3b) as nucleophile was studied in detail,
(Fig. 1, curve b). In this cyclic voltammogram, the cathodic
*
Corresponding author. Tel.: +98 21 22431667; fax: +98 21 22431663.
E-mail address: ss-hosseiny@cc.sbu.ac.ir (S.S.H. Davarani).
0040-4039/$ - see front matter Ó 2007 Published by Elsevier Ltd.
doi:10.1016/j.tetlet.2007.11.134

S. S. H. Davarani et al. / Tetrahedron Letters 49 (2008) 710–714
711
ðICP1=IAP1Þ versus scan rate for a mixture of catechol (1a)
and 6-amino-1,3-dimethyluracil (3b) in 0.2 M sodium ace-
tate solution, confirms the reactivity of o-quinone (2a) with
6-amino-1,3-dimethyluracil (3b),24–27 appearing as an
increase in the height of the cathodic peak C1 at higher scan
rates (Fig. 3, curve g). A similar situation was observed
when 3b to 1a concentration was decreased. On the other
23
18
13
8
A1
b
a
c
3
hand, the peak current function for the A1 peak ðIAP1=m1=2
Þ
-2
decreased on increasing the scan rate (Fig. 3, curve h)
and such behavior is indicative of an electron transfer
followed by chemical reaction (EC) mechanism.15 Con-
trolled-potential coulometry was performed in 0.2 M
sodium acetate solution, containing 0.5 mmol of 1a and
0.5 mmol of 6-amino-1,3-dimethyluracil (3b) at 0.35 V
versus 3 M Ag/AgCl. The electrolysis progress was moni-
tored by cyclic voltammetry (Fig. 4). It was observed that,
proportional to the advancement of coulometry, the anodic
peak (A1) decreases. All anodic and cathodic peaks will dis-
appear when the consumption equals about 2eꢀ per mole-
cule of 1a. These observations allow us to propose the
pathways in Scheme 1 for the electro-oxidation of catechol
(1a) in the presence of 6-amino-1,3-dimethyluracil (3b).
Similar results were observed for the oxidation of 1b and
1c in the presence of 6-amino-1,3-dimethyluracil (3b), and
for 1a–c in the presence of 4(6)-aminouracil (3a). The suc-
cessful synthesis of the target materials (5a–f) was estab-
lished via IR, 1H NMR, 13C NMR, elemental analysis,
and MS spectroscopic methods, the results of which are
given in Section 2.
-7
-12
-17
C1
-0.7
-0.2
0.3
0.8
1.3
E/V vs. 3M Ag|AgCl
Fig. 1. Cyclic voltammogram of 2 mM catechol (1a): (a) in the absence of
6-amino-1,3-dimethyluracil (3b), (b) in the presence of 2 mM 6-amino-1,3-
dimethyluracil. (c) Cyclic voltammogram of 2 mM 6-amino-1,3-dimethyl-
uracil (3b) in the absence of catechol, at the glassy carbon electrode, in
0.2 M sodium acetate solution. Scan rate: 100 mV sꢀ1, T = ambient
temperature.
counterpart of the anodic peak A1 was decreased strongly
due to the reactivity of the formed o-quinone (2a) at the
surface of the electrode with 6-amino-1,3-dimethyluracil
(3b).24–27
An increase in the A1 peak current may be due to accu-
mulative current from catechol and the nucleophile. The
positive shift of the A1 peak and negative shift of the C1
peak in the presence of 6-amino-1,3-dimethyluracil are
probably due to the formation of a thin film of product
at the electrode surface, inhibiting to a certain extent, the
performance of the electrode process that was enhanced
during the repetitive cycling of the potential (Fig. 2).13,20,28
Furthermore, it can be seen that, the C1 peak current
increases proportionally to the augmentation of the poten-
tial scan rate. In other words, the peak current ratio
The presence of methyl and methoxy groups at C-3 of 1b
and 1c, respectively, probably causes the o-benzoquinone
derived from the oxidation of catechols 2b and 2c to be
attacked by 3a and 3b at C-4 or C-5 to yield two types of
80
0.7
0.65
0.6
A1
0.55
0.5
60
0.45
0.4
0.35
0.3
24
f
40
A1
0
500
1000
1500
2000
19
v (mV/sec)
20
0
(g)
a
14
(Second scan)
9
2.05
(First scan)
2
-20
-40
-60
4
1.95
1.9
-1
-6
1.85
1.8
0
500
1000
1500
2000
C1
-0.09
-0.59
0.41
0.91
v(mV/sec)
(h)
C1
E/V vs. 3M Ag|AgCl
-11
-0.7
-0.2
0.3
0.8
1.3
Fig. 3. Typical cyclic voltammograms of 2 mM catechol (1a) in the
presence of 2 mM 6-amino-1,3-dimethyluracil (3a), in 0.2 M sodium
acetate solution at the glassy carbon electrode (1.8 mm diameter) at
various scan rates. Scan rates from (a) to (f) are 50, 100, 200, 400, 800, and
E/V vs. 3M Ag|AgCl
Fig. 2. Cyclic voltammogram of 2 mM catechol: (a) in the presence of
2 mM 6-amino-1,3-dimethyluracil (first cycle), (b) in the presence of 2 mM
6-amino-1,3-dimethyluracil (second cycle), at the glassy carbon electrode,
in 0.2 M sodium acetate solution. Scan rate: 100 mV sꢀ1, T = ambient
temperature.
1600 mV sꢀ1, respectively. (g) Variation of peak current ratio (IpC1=IAP1
)
versus scan rate. (h) Variation of peak current function for the A1 peak
(IAP1=m1=2) versus scan rate. T = ambient temperature.

712
S. S. H. Davarani et al. / Tetrahedron Letters 49 (2008) 710–714
R1
OH
OH
57
47
37
27
60
40
Ip = -0.56C + 54.63
2
H2N
R
= 0.9999
n = 2.05
20
0
H
a
R1
R2
N
R2
N
O
O
0
50
100
150
OH
N
R3
O
NH2
Charge/C
+
N
R3
5b-5c and 5e-5f
OH
17
7
R3
N
H
H
O
O
f
1b-1c
O
HO
N
R2
R1
-3
-13
-23
HO
NH2
6b-6c and 6e-6f
Scheme 2.
-0.7 -0.5 -0.3 -0.1
0.1
0.3
0.5
0.7
0.9
1.1
1.3
1
E/V
in the H spectra. The ortho and meta hydrogens would
couple, which would result in a doublet with a coupling
constant ‘J’ of about 10 Hz. These results would be consis-
tent with the presence of two adjacent protons on the
catechol ring of 6b, 6c, 6e and 6f.29 Therefore, according
Fig. 4. Cyclic voltammograms of 0.5 mM catechol (1a) in the presence of
0.5 mM 6-amino-1,3-dimethyluracil (3b), at a glassy carbon electrode
during controlled-potential coulometry at 0.35 V versus 3 M Ag/AgCl.
After the consumption of: (a) 0, (b) 13.1, (c) 31, (d) 50, (e) 68, (f) 75 C.
Inset: Variation of peak current ðIAP1Þ versus charge consumed. Scan rate:
100 mV sꢀ1, T = ambient temperature.
1
to H NMR results we suggest that o-quinones 2b and 2c
are attacked at C-5 selectively by 3a and 3b, leading to
the formation of products 5b, 5c, 5d and 5f, respectively.
In conclusion, the results of this work show that
catechols are oxidized in solution to their respective
o-quinones. The quinones are then attacked by 4(6)-amino-
uracil (3a) or 6-amino-1,3-dimethyluracil (3b) to form
catecholamine derivatives (Table 1). The advantage of the
present work is the development of a one-pot electrolytic
method for the synthesis of catecholamine derivatives
5a–f in good yields and purities, with 2eꢀ consumption
per molecule of catechol.
R1
R1
OH
OH
R1
O
O
+
-2H 2 e
-
R1
2a-2c
1a-1c
O
R2
N
NH
O
NH2
+
R2
O
O
O
N
OH
N
R3
H
N
O
R3
O
2a-2c
3a-3b
4a-4f
R1
R1
2. Apparatus and reagents
OH
OH
O
NH2
NH
H
R2
Cyclic voltammetry was performed using a computer-
ized 747 Metrohm polarograph. The controlled-potential
(potenstiostat) coulometry and controlled-potential (poten-
tiostat) preparative electrolysis were carried out with a
Zahrner pp-200 Potentiostat/galvanostat. The working
electrode used in the voltammetry experiments was a glassy
carbon disc (2.5 mm2 area), and a platinum wire was used
as the counter electrode. The working electrode was used in
the controlled-potential coulometry and macro scale elec-
trolysis was an assembly of four graphite rods (25 cm2
R2
O
N
OH
N
H
O
N
N
O
O
R3
R3
4a-4f
5a-5f
R2 R3
R1
R2 R3
5
R1
1
3
a
a
H
H
H
a
H
H
H
H
H
H
b
c
Me
b
Me Me
b
c
d
e
f
Me
OMe
H
OMe
H
Me Me
Me Me
Me
OMe Me Me
Table 1
Scheme 1.
Electroanalytical and preparative data
Product
Applied potential (V) 3 M Ag/AgCl
Yield (%)
products in each case (Scheme 2). Spectroscopic character-
ization by H NMR revealed the presence of singlets, due
to the C-5 aromatic hydrogens (d = 6.36 and 6.47,
d = 6.25 and 6.28, d = 6.36 and 6.46, and d = 6.25 and
6.26 ppm for 5b, 5c, 5e, and 5f, respectively). Addition to
C-4 would lead to the generation of more complex features,
5a
5b
5c
5d
5e
5f
0.35
0.30
0.30
0.35
0.30
0.30
86
88
84
91
94
90
1

S. S. H. Davarani et al. / Tetrahedron Letters 49 (2008) 710–714
713
area) and a large surface platinum gauze constituted the
2.1.3. 6-Amino-5-(3,4-dihydroxy-5-methoxyphenyl)
counter electrode (graphite rods from Azar Electrode,
Urmieh, Iran and all other electrodes from Metrohm).
The working electrode potentials were measured versus
3 M Ag/AgCl.
3-Methyl catechol was reagent grade material from
Acros. All other chemicals were reagent or pro-analysis
grade materials from Merck. These chemicals were used
without any further purification.
pyrimidine-2,4(1H,3H)-dione (5c, C11H11N3O5)
Mp >270 °C; IR (KBr) (mmax cmꢀ1): 3401, 1698, 1621,
1596, 1512, 1392, 1207, 1085. 1H NMR (300 MHz
DMSO-d6): d 3.70 (s, 3H, methoxy), 5.61 (s, 2H, NH2),
6.25 (s, 1H, aromatic), 6.28 (s, 1H, aromatic), 8.14 (s,
1H, OH), 8.79 (s, 1H, OH), 10.03 (s, 1H, NH), 10.32 (s,
1H, NH). 13C NMR (75.4 MHz DMSO-d6): d 56.09,
88.75, 106.76, 112.52, 122.92, 133.29, 145.94, 148.51,
150.44, 151.86, 163.49. Anal. Calcd for C11H11N3O5
(265.222): C, 49.81; H, 4.18; N, 15.84. Found: C, 49.77;
H, 4.15; N, 15.79. MS, m/z (%): 265 (M+, 100), 249 (15),
221 (5), 205 (25), 177 (20), 151 (10), 84 (15), 43 (89).
2.1. General procedure for the electro-organic synthesis of
5a–f
Sodium acetate (100 ml of 0.2 M) solution was pre elec-
trolyzed at the chosen potential (see Table 1) in a two-com-
partment cell. Next, 2 mmol of catechol 1a–c and
nucleophile 3a, 3b were added to the cell. Initially the cur-
rent density was 2 mA/cm2 and the electrolysis was termi-
nated when the decay of the current became more than
95%. The process was interrupted during electrolysis (due
to the formation of a thin film of product at the surface
of the electrode) and the graphite anode was washed in ace-
tone and polished to reactivate it. At the end of electrolysis,
a few drops of acetic acid were added to the solution and
the cell was placed in a refrigerator overnight. The precip-
itated solid was collected by filtration and after washing
with hot water and drying, the solid products were charac-
terized by IR, 1H NMR, 13C NMR, elemental analysis, and
MS.
2.1.4. 6-Amino-5-(3,4-dihydroxyphenyl)-1,3-dimethyl-
pyrimidine-2,4(1H,3H)-dione (5d, C12H13N3O4)
Mp >270 °C; IR (KBr) (mmax cmꢀ1): 3435, 3334, 3232,
1
1696, 1641, 1585, 1381, 1272, 1088, 780, 730. H NMR
(300 MHz DMSO-d6): d 3.12 (s, 3H, methyl), 3.32 (s, 3H,
methyl), 6.03 (s, 2H, NH2), 6.44 (d, J = 8 Hz, 1H, aro-
matic), 6.58 (s, 1H, aromatic), 6.72 (d, J = 8 Hz, 1H, aro-
matic) 8.81 (s, 1H, OH), 8.84 (s, 1H, OH). 13C NMR
(75.4 MHz DMSO-d6): d 28.05, 30.45, 89.30, 116.13,
119.50, 122.81, 124.78, 144.62, 145.55, 151.35, 152.24,
161.08. Anal. Calcd for C12H13N3O4 (263.249): C, 54.75;
H, 4.98; N, 15.96. Found: C, 54.81; H, 5.02; N, 15.99.
MS, m/z (%): 263 (M+, 100), 206 (25), 189 (25), 150 (60),
122 (25), 81 (10), 58 (75).
2.1.5. 6-Amino-5-(3,4-dihydroxy-5-methylphenyl)-1,3-
dimethylpyrimidine-2,4(1H,3H)-dione (5e, C13H15N3O4)
Mp >270 °C; IR (KBr) (mmax cmꢀ1): 3476, 3416, 1693,
1648, 1596, 1314, 1200, 1017, 771, 608. 1H NMR
(300 MHz DMSO-d6): d 2.10 (s, 3H, methyl), 3.12 (s, 3H,
methyl), 3.37 (s, 3H, methyl), 6.02 (s, 2H, NH2), 6.36 (s,
1H, aromatic), 6.46 (s, 1H, aromatic), 8.12 (s, 1H, OH),
9.10 (s, 1H, OH). 13C NMR (75.4 MHz DMSO-d6): d
16.0, 27.5, 29.9, 89.03, 116.2, 123.4, 124.1, 142.2, 144.6,
150.8, 151.7, 160.5. Anal. Calcd for C13H15N3O4
(277.27): C, 56.31; H, 5.45; N, 15.15. Found: C, 56.29; H,
5.45; N, 15.17. MS, m/z (%): 277 (M+, 100), 220 (25),
203 (25), 191 (25), 164 (50), 136 (50), 77 (20), 57 (70), 30
(30).
2.1.1. 6-Amino-5-(3,4-dihydroxyphenyl)pyrimidine-
2,4(1H,3H)-dione (5a, C10H9N3O4)
Mp >270 °C; IR (KBr) (mmax cmꢀ1): 3496, 3441, 3248,
2882, 1724, 1592, 1550, 1446, 1372, 1113, 772, 708. 1H
NMR (300 MHz DMSO-d6): d 5.57 (s, 2H, NH2), 6.45
(d, J = 6 Hz, 1H, aromatic), 6.61 (s, 1H, aromatic), 6.70
(d, J = 6 Hz, 1H, aromatic), 8.78 (s, 1H, OH), 8.82 (s,
1H, OH), 10.07(s, 1H, NH), 10.33 (s, 1H, NH). 13C
NMR (75.4 MHz DMSO-d6): d 115, 119, 122, 123, 144,
145, 150, 151, 163. Anal. Calcd for C10H9N3O4 (235.196):
C, 51.07; H, 3.68; N, 17.87. Found: C, 51.18; H, 3.74; N,
17.89. MS, m/z (%): 235 (M+, 100), 189 (10), 147 (25),
122 (10), 103 (10), 63 (20), 43 (90).
2.1.2. 6-Amino–5-(3,4-dihydroxy-5-methylphenyl)-
pyrimidine-2,4(1H,3H)-dione (5b, C11H11N3O4)
2.1.6. 6-Amino-5-(3,4-dihydroxy-5-methoxyphenyl)-1,3-
dimethylpyrimidine-2,4(1H,3H)-dione (5f, C13H15N3O5)
Mp >270 °C; IR (KBr) (mmax cmꢀ1): 3419, 3336, 3248,
1693, 1638, 1587, 1519, 1332, 1213, 1095, 1031, 849, 778,
674. 1H NMR (300 MHz DMSO-d6): d 3.33 (s, 3H,
methyl), 3.38 (s, 3H, methyl), 3.70 (s, 3H, methoxy), 6.08
(s, 2H, NH2), 6.25 (s, 1H, aromatic), 6.26 (s, 1H, aromatic),
8.19 (s, 1H, OH), 8.82 (s, 1H, OH). 13C NMR (75.4 MHz
DMSO-d6): d 28.05, 30.44, 56.09, 89.66, 107.15, 112.81,
123.85, 133.56, 146.13, 148.78, 151.36, 152.26, 161.00.
Anal. Calcd for C13H15N3O5 (293.27): C, 53.24; H, 5.15;
N, 14.33. Found: C, 53.29; H, 5.18; N, 14.35. MS, m/z
Mp >270 °C; IR (KBr) (mmax cmꢀ1): 3458, 3353, 1721,
1634, 1389, 1579, 1313, 972, 752, 672, 592. 1H NMR
(300 MHz DMSO-d6): d 2.09 (s, 3H, methyl), 5.54 (s, 2H,
NH2), 6.36 (s, 1H, aromatic), 6.47 (s, 1H, aromatic), 8.09
(s, 1H, OH), 9.08 (s, 1H, OH), 10.02 (s, 1H, NH), 10.30
(s, 1H, NH). 13C NMR (75.4 MHz DMSO-d6): d 16.1,
88.63, 116.45, 123.01, 124.24, 124.44, 142.45, 144.93,
150.45, 151.81, 163.58. Anal. Calcd for C11H11N3O4
(249.223): C, 53.01; H, 4.45; N, 16.86. Found: C, 53.07;
H, 4.42; N, 16.91. MS, m/z (%): 249 (M+, 100), 231 (45),
205 (45), 188 (25), 163 (50), 117 (20), 77 (25), 43 (91).

714
S. S. H. Davarani et al. / Tetrahedron Letters 49 (2008) 710–714
(%): 293 (M+, 100), 207 (20), 180 (50), 151 (20), 136 (10), 78
(10), 58 (85), 32 (50).
12. Afkhami, A.; Nematollahi, D.; Madrakian, T.; Khalafi, L. Electro-
chim. Acta 2005, 50, 5633–5640.
13. Nematollahi, D.; Rafiee, M. J. Electroanal. Chem. 2004, 566, 31–
37.
Acknowledgment
14. Papouchado, L.; Petrie, G.; Adams, R. N. J. Electroanal. Chem. 1972,
38, 389–395.
15. Papouchado, L.; Petrie, G.; Sharp, J. H.; Adams, R. N. J. Am. Chem.
Soc. 1968, 90, 5620–5621.
16. Sioda, R. E. J. Phys. Chem. 1968, 72, 2322–2330.
Financial support from the Research Affairs of Shahid
Beheshti University is gratefully acknowledged.
17. Sioda, R. E.; Frankowska, B. J. Electroanal. Chem. 2004, 568, 365–
References and notes
370.
18. Sioda, R. E.; Frankowska, B. Tetrahedron Lett. 2005, 46, 2747–
1. Castle, R. N.; Philips, S. D. In Katritzky, A., Rees, C., Eds.;
Comprehensive Heterocyclic Chemistry; Boulton, A. J., McKillop,
A., Eds.; Pergamon: Oxford, 1984; Vol. 3, p 329ff.
2. Melik-Ogan Zhanyan, R. G.; Khachatryan, V. E.; Gapoyan, A. S.
Russ. Chem. Rev. 1985, 54, 262–268.
2749.
19. Young, T. E.; Griswold, J. R.; Hulbert, M. H. J. Org. Chem. 1974, 39,
1980–1982.
20. Nematollahi, D.; Habibi, D.; Rahmati, M.; Rafiee, M. J. Org. Chem.
2004, 69, 2637–2640.
3. Taylor, E. C.; Knopf, R. J.; Meyer, R. F.; Holmes, A.; Hoefle, M. L.
J. Am. Chem. Soc. 1960, 82, 5711–5718.
21. Nematollahi, D.; Rafiee, M.; Samadi-Maybodi, A. Electrochim. Acta
2004, 49, 2495–2502.
4. Figueroa-Villar, J. D.; Carneiro, C. L.; Cruz, E. R. Heterocycles 1992,
34, 891–894.
22. Rayn, M. D.; Yueh, A.; Wen-Yu, C. Electrochem. Soc. 1980, 127,
1489–1495.
5. Campaigne, E.; Eliss, R. L.; Bradford, M.; Ho, J. J. Med. Chem. 1969,
12, 339–342.
6. Blume, F.; Arndt, F.; Ress, R. Ger. Patent 3712782, 1988; Chem.
Abstr. 1989, 110, 154312e.
7. Coates, W. J. Eur. Patent 351058, 1990; Chem Abstr. 1990, 113,
40711.
23. Davarani, S. S. H.; Nematollahi, D.; Shamsipur, M.; Mashkouri
Najafi, N.; Masoumi, L.; Ramyar, S. J. Org. Chem. 2006, 71, 2139–
2142.
24. Nematollahi, D.; Tammari, E. Electrochim. Acta 2005, 50, 3648–
3654.
25. Bernier, J. L.; Henichart, J. P. J. Org. Chem. 1981, 46, 4197–4198.
8. Ramsey, A. A. U.S. Patent 3830812, 1974, FMC Corp.; Chem. Abstr.
1974, 81, 13617.
9. Kitamura, N.; Onishi, A. Eur. Patent 163599, 1984; Chem Abstr.
1984, 104, 18639.
10. Raddatz, P.; Bergmann, R. Ger. Patent 360731, 1988; Chem Abstr.
1988, 109, 54786.
11. Kulma, A.; Szopa J. Plant Sci. 2007, 172, 433–440.
26. Dotzauer, B.; Troschutz, R. Synlett 2004, 1039–1043.
27. Alizadeh, A.; Nematollahi, D.; Habibi, D.; Hesari, M. Synthesis 2007,
1513–1517.
28. Nematollahi, D.; Goodarzi, H. J. Electroanal. Chem. 2001, 510, 108–
114.
29. Silverstein, R. M.; Webster, F. M. Spectrometric Identification of
Organic Compounds, 6th ed.; Wiley: New York, 1998; p 212.
¨