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vessel was carefully monitored. After the irradiation, the reaction tube was cooled with high-pressure
air through an inbuilt system in the instrument until the temperature had fallen below 50 °C. The
mixtures were cooled and then poured into ice-water. The solids that formed were collected by using
filtration and crystallized from benzene to give compound 4 as a yellow powder (48%), mp 199 °C
1
(Lit. [16] mp 197–199 °C), IR (KBr): 3421, 3316 (NH2), 1684 (CO) cm−1. H-NMR (DMSO-d6):
δ = 6.86 (1H, s, 1-H); 7.17–7.21 (m, 2H, 7-H and 9-H), 7.32 (t, 1H, J = 8.0 Hz, 8-H),
7.79 (brs. 2H, NH2, D2O-exchangeable), 7.83 (d, 1H, J = 6.8 Hz, 6-H). 13C-NMR (DMSO-d6):
δ = 166.4 (C-3), 158.7 (C-2), 150.7, 130.7, 129.0, 124.1, 123.7, 117.8, 116.8, 97.8, 97.3. MS (EI)
m/z= 217 (M]+, 100), Anal. Calcd for C11H7NO2S: C, 60.83; H, 3.23; N, 6.45; S, 14.75. Found:
C, 60.88; H, 3.31; N, 6.45; S, 14.73.
3.2. Reaction of Compound 4 with Aromatic Diazonium Salts
A solution of each aryldiazonium chloride (10 mmol, prepared as described earlier [14]) at 0 °C was
added to a solution of 4 (10 mmol) in acetic acid (50 mL) containing sodium acetate (0.60 g). The
reaction mixture was stirred at room temperature for 1 h and the solid product was collected by
filtration and crystallized from DMF/ethanol (3:1).
3-Amino-1-(phenyldiazenyl)-4H-thieno[3,4-c]chromen-4-one (7a). Red crystals (79%), mp 239 °C
1
(Lit. [5] mp 238–239 °C), IR (KBr): 3310 and 3164 (NH2), 1674 (CO) cm−1. H-NMR (DMSO-d6):
δ = 7.02 (br s, 2H, NH2), 7.36–7.40 (m, 2H, arom-H), 7.44 (t, 1H, J = 8.4 Hz, arom-H), 7.50 (t, 2H,
J = 7.8 Hz, arom-H), 7.58 (t, 1H, J = 7.2 Hz, arom-H), 7.74 (d, 2H, J = 8.4 Hz, arom-H), 8.83 (d, 1H,
J = 9.0 Hz, arom-H). 13C-NMR (DMSO-d6): δ = 169.7 (CO), 158.7, 153.1, 152.5, 135.4, 133.5, 132.0,
129.9, 129.5, 129.3, 125.6, 122.2, 117.7, 117.5, 100.8. MS (EI) m/z= 321 (M]+, 100), UV/Vis at
λmax(DMF) = 490 nm. Anal. Calcd for C17H11N3O2S: C, 63.53; H, 3.45; N, 13.07; S, 9.97. Found: C,
63.22; H, 3.51; N, 12.86; S, 10.04.
3-Amino-1-(p-tolyldiazenyl)-4H-thieno[3,4-c]chromen-4-one (7b). Brown powder (75%), mp 293 °C
1
(Lit. [14] mp 290–292 °C), IR (KBr): 3386 and 3261 (NH2), 1683 (CO) cm−1; H-NMR (DMSO-d6):
δ = 2.37 (s, 3H, CH3), 6.96 (brs, 2H, NH2), 7.34–7.35 (m, 3H, arom-H), 7.41 (t, 1H, J = 8.4 Hz, arom-H),
7.55 (t, 1H, J = 7.2 Hz, arom-H), 7.62 (d, 2H, J = 8.4 Hz, p-tolyl-H), 8.80 (d, 1H, J = 7.8 Hz, arom-H).
13C-NMR (DMSO-d6): δ = 168.4 (CO), 158.7, 153.0, 150.5, 139.5, 134.5, 133.6, 131.8, 130.4,
129.2, 125.5, 122.2, 117.7, 117.6, 100.5, 21.4 (CH3). MS (EI) m/z= 335 (M]+, 100), UV/Vis
at λmax(DMF) = 319 nm. Anal. Calcd for C18H13N3O2S: C, 64.46; H, 3.90; N, 12.52; S, 9.56.
Found: C, 64.76; H, 3.99; N, 12.63; S, 9.32.
3-Amino-1-((4-methoxyphenyl)diazenyl)-4H-thieno[3,4-c]chromen-4-one (7c). Reddish brown crystals
(68%), mp 281–283 °C (Lit. [14] mp 280–281 °C), IR (KBr): 3380 and 3260 (NH2), 1681 (CO) cm−1.
1H-NMR (DMSO-d6): δ = 3.84 (s, 3H, OCH3), 6.96 (br s, 2H, NH2), 7.07 (d, 2H, J = 9 Hz,
p-methoxyphenyl-H), 7.32 (d, 1H, J = 8.4 Hz, arom-H), 7.39 (t, 1H, J = 7.8 Hz, arom-H), 7.53 (t, 1H,
J = 8.4 Hz, arom-H), 7.70 (d, 2H, J = 9 Hz, p-methoxyphenyl-H), 8.79 (d, 1H, J = 8.4 Hz, arom-H).
13C- NMR (DMSO-d6): δ = 168.0 (CO), 160.7, 158.8, 152.9, 146.6, 133.8, 133.3, 131.6, 129.1, 125.5,
123.9, 1117.7, 117.6, 115.2, 100.1, 55.9 (OCH3). MS (EI) m/z= 351 (M]+, 100), UV/Vis