8
A. ASGHARI ET AL.
4.2. Procedure for electrochemical synthesis of acetaminophen derivatives (4a–c)
An estimated 0.4 mmol of thiouracil (3a) (or thiouracil derivatives) was dissolved in 16 mL
of DMF in an undivided cell, and then 64 mL of an acetate buffer solution (0.15 M, pH 5)
and 0.4 mmol of acetaminophen were added to the cell to give a final solution of 80 mL.
Finally, an electrolysis process was performed under a constant potential (0.55 V). The pro-
cess was terminated when the current decay became greater than 95%. It was interrupted
for several times to wash the carbon anode in acetone in order to reactivate it. The process
was monitored by cyclic voltammetry (CV). At the end of electrolysis, the cell was kept at
ambient temperature for 24 h to evaporate the solvent in order to reduce the volume of the
solution to half of its initial amount. Then each one of the precipitated solids were collected
by centrifugation and subsequently washed with water. After purification, the products
1
13
obtained were characterized using the FT-IR, H NMR, and C NMR spectroscopies, and
the elemental analysis technique.
4
.3. Characterization of products
4
.3.1. N-(4-hydroxy-3-((6-oxo-1,6-dihydropyrimidin-2-yl)thio)phenyl)acetamide (4a)
−
1
Yield: 76%. Mp: >260°C (decomposed). FT-IR (KBr, cm ): 3450 (broad, OH), 2975
1
(
broad, NH), 1660 (C=O, amide). H NMR (400 MHz, Dimethyl sulfoxide (DMSO)-d ):
6
δ (ppm) 2.04 (s, 3H, CH ), 5.96 (d, 1H, J = 6.8 Hz, aromatic), 6.77 (d, 1H, J = 9.2 Hz, aro-
3
matic), 7.46 (d, 1H, J = 6.4, aromatic), 7.66 (d, 1H, J = 8.4 Hz), 8.22 (s, 1H), 9.92 (broad,
1
3
1H, OH), 10.28 (broad, 1H, NH), 12.29 (broad, 1H, NH). C NMR (100 MHz, DMSO-
d6): δ 22.3, 76.7, 102.01, 111.4, 114.5, 126.5, 128.8, 132.9, 151.2, 158.0, 159.3, 168.8, 170.2.
Anal. Calcd. for C H N O S: C, 51.98; H, 4.00; N, 15.15. Found: C, 51.82.; H, 4.08; N,
1
2
11
3
3
1
5.06.
4.3.2. N-(4-hydroxy-3-((4-methyl-6-oxo-1,6-dihydropyrimidin-2-yl)thio)
phenyl)acetamide (4b)
−
1
Yield: 78%. Mp: >260°C (decomposed). FT-IR (KBr, cm ): 3300 (broad, OH), 3000
1
(
broad, NH), 1666 (C=O, amide). H NMR (400 MHz, DMSO-d ): δ (ppm) 1.98 (s, 3H,
6
CH ), 2.08 (s, 3H, CH ), 5.92 (s, 1H, aromatic), 6.57 (d, 1H, J = 6.8 Hz, aromatic), 7.53
3
3
(
d, 1H, J = 8.0, aromatic), 8.21 (s, 1H), 9.88 (broad, 1H, OH), 10.32 (broad, 1H, NH).
1
3
C NMR (100 MHz, DMSO-d ): δ 18.4, 28.9, 76.7, 101.4, 112.2, 115.3, 126.8, 128.6, 133.2,
6
1
50.2, 159.6, 160.2, 168.2, 178.7. Anal. Calcd. for C H N O S: C, 53.60; H, 4.50; N, 14.42.
13 13 3 3
Found: C, 53.72; H, 4.38; N, 14.36.
4.3.3. N-(4-hydroxy-3-((6-oxo-4-propyl-1,6-dihydropyrimidin-2-yl)
thio)phenyl)acetamide (4c)
−
1
Yield: 79%. Mp: >260°C (decomposed). FT-IR (KBr, cm ): 3200 (broad, OH), 2962
1
(
broad, NH), 1661 (C=O, amide). H NMR (400 MHz, DMSO-d ): δ (ppm) 0.85 (t, 3H,
6
CH ), 1.35 (m, 2H, CH ), 1.69 (t, 2H, CH ), 2.03 (s, 1H, CH ), 5.92 (s, 1H, aromatic), 6.61
3
2
2
3
(
d, 1H, J = 8.4 Hz, aromatic), 7.59 (d, 1H, J = 8.4, aromatic), 8.18 (s, 1H), 9.88 (broad, 1H,
13
OH), 10.20 (broad, 1H, NH), 12.23 (broad, 1H, NH). C NMR (100 MHz, DMSO-d ): δ
6
1
2.7, 24.4, 26.7, 38.6, 76.7, 101.0, 112.5, 113.6, 127.9, 129.4, 134.1, 150.6, 150.6, 161.2, 169.5,