660
Medicinal Chemistry Research (2021) 30:655–663
chopped ice. A cold suspension of cyanogen bromide (0.1
moles, 10.5 g) in water (100 mL) was added over 5 min with
faster stirring. The reaction mixture was stimulated/stirred
for 1 h at room temperature, solid sodium bicarbonate (0.1
moles, 8.4 g) was also added in small portions over 1.5 h to
bring the pH in the range of 6.5–7.0. Constant stirring was
continued for the next 1 h. The solid compound obtained
was separated by filtering, it was washed with cold water,
and on recrystallization using ethyl alcohol, the yield of
95% and m.p of 128–132 °C [29] was recorded.
stretching), 1681.23 (C=O, stretching), 3109.23 (Ar C–H,
stretching), 3369.24, 3148.64 (NH, stretching); H NMR
1
(DMSO-d6, δ, ppm): 7.39–7.97 (8, 2H, Ar–H), 8.83 (s, 1H,
NHC=O, D2O exchangeble), 13.18 (bs, 1H, NHC=S, D2O
exchangeable); 13C NMR (DMSO-d6, δ, ppm): 110.6,
115.5, 123.8, 124.8, 127.5, 137.7, 128.9, 128.9, 130.1,
131.3, 143.6, 148.4, 152.6, 165.4, 177.5; Elemental analysis
for C15H10ClN3O2S: Cald. C: 54.30, H: 3.04, N: 12.67, S:
9.66; Found, C: 54.29, H: 3.01, N: 12.66, S: 9.68; Mass
spectra, (EI) m/z: 331.78 (M+ peak).
2/4-Substituted benzoyl isothiocyanates 2(a–g)
N-{(1,3-Benzo[d]oxazol-2-yl)carbamothioyl}-4-methyl-
benzamide 3c
Substituted benzoyl chloride (0.1 moles) was added drop-
wise to a solution of ammonium thiocyanate (0.1 moles,
7.6 g) in dry benzene (25 ml) with vigorous stirring. The
mixture was refluxed for 2 h. The resultant mixture was
cooled and filtered. The filtrate is separated as benzoyl
isothiocyanates 2(a–g) [30].
Beige powder; yield 91%; m.p.: 235 °C; IR (KBr, νmax
,
cm−1): 1097.18 (C=S, stretching), 1589.23 (Ar C=C,
stretching), 1576.70 (C=N, stretching), 1685.32 (C=O,
stretching), 3081.21 (Ar C–H, stretching), 3351.39, 3168.41
(NH, stretching), 1473 (CH3, bend), 2982 (C–H, stretch-
1
ing); H NMR (DMSO-d6, δ, ppm): 2.34 (s, 3H, CH3);
N-(benzo[d]oxazol-2-ylcarbamothioyl)-2/4-substituted
benzamides 3(a–g)
7.41–7.91 (m, 8H, Ar–H), 8.17 (s, 1H, NHC=O, D2O
exchangeble), 12.87 (bs, 1H, NHC=S, D2O exchangeable);
13C NMR (DMSO-d6, δ, ppm): 21.3, 110.6, 115.5, 123.8,
124.8, 127.4, 127.4, 129.1, 129.1, 130.2, 141.8, 143.6,
148.4, 152.6, 165.4, 177.5; Elemental analysis for
C16H13N3O2S: Cald. C: 61.72, H: 4.21, N: 13.50, S: 10.30;
Found, C: 61.71, H: 4.20, N: 13.51, S: 10.29; Mass spectra,
(EI) m/z: 311.07 (M+ peak).
The mixture of 2-aminobenzoxazole (0.01 mole) 1 and
benzoyl isothiocyanate (0.01 mole) 2(a–g) in dry acetone
(25 mL) was refluxed for 3 h, the obtained solid was filtered,
washed with benzene, dried, and recrystallized using ben-
zene. The spectral and elemental data are given below.
N-{(1,3-benzo[d]oxazol-2-yl)carbamothioyl} benzamide 3a
N-{(1,3-Benzo[d]oxazol-2-yl)carbamothioyl}-4-
methoxybenzamide 3d
Beige powder; yield 95%; m.p.:249 °C; IR (KBr, νmax
,
cm−1): 1071.63 (C=S, stretching), 1558.21 (Ar C=C,
stretching), 1614.32 (C=N, stretching), 1661.38 (C=O,
stretching), 3051 (Ar C–H, stretching), 3371, 3162 (NH,
stretching) (see Supplementary Material, Fig. S1); 1H NMR
(DMSO-d6, δ, ppm): 7.38–8.03 (m, 9H, Ar–H), 8.81 (s, 1H,
NHC=O, D2O exchangeble), 13.12 (bs, 1H, NHC=S, D2O
exchangeable) (see Supplementary Material, Fig. S2); 13C
NMR (DMSO-d6, δ, ppm): 110.6, 115.5, 123.8, 124.8,
127.5, 127.5, 128.8, 128.8, 132.1, 133.2, 143.6, 148.4,
152.6, 165.4, 177.5 (see Supplementary Material, Fig. S3);
Elemental analysis for C15H11N3O2S: Cald. C: 60.59, H:
3.73, N: 14.13, S: 10.78; Found, C: 60.58, H: 3.71, N:
14.15, S: 10.76; Mass spectra, (EI) m/z: 297.33 (M+ peak)
(see Supplementary Material, Fig. S4).
yellow powder; yield 90%; m.p.: 176 °C; IR (KBr, νmax, cm−1):
1143.81 (C=S, stretching), 1602.52 (C=N, stretching),
1685.18 (C=O, stretching), 1680.15 (Ar C=C, stretching),
2705.78 (O–CH3, stretching), 2950.34 (C–H Aliph, stretching),
3190.17 (Ar C–H, stretching), 3361.39, 3297.33 (NH,
stretching); 1H NMR (DMSO-d6, δ, ppm): 3.83 (s, 3H, OCH3);
7.17–7.93 (m, 8H, Ar–H), 8.20 (s, 1H, NHC=O, D2O
exchangeble), 12.59 (bs, 1H, NHC=S, D2O exchangeable);
13C NMR (DMSO-d6, δ, ppm): 55.8, 110.6, 114.4, 114.4,
115.5, 123.8, 124.3, 124.3, 124.8, 125.5, 143.6, 148.4, 152.6,
164.0, 165.4, 177.5; Elemental analysis for C16H13N3O3S:
Cald. C: 58.70, H: 4.00, N: 12.84, S: 9.80; Found, C: 58.69, H:
4.01, N: 12.83, S: 9.81; Mass spectra, (EI) m/z: 327.03
(M+ peak).
N-{(1,3-Benzo[d]oxazol-2-yl)carbamothioyl}-4-chloro-
benzamide 3b
N-{(1,3-Benzo[d]oxazol-2-yl)carbamothioyl}-4-
nitrobenzamide 3e
yellow powder; yield 93%; m.p.: 247 °C; IR (KBr, νmax
,
Dark yellow powder; yield 80%; m.p.: 268 °C; IR (KBr,
cm−1): 709.12 (C–Cl, stretching), 1057.12 (C=S, stretch-
ing), 1601.19 (Ar C=C, stretching), 1658.81 (C=N,
ν
max, cm−1): 1114.18 (C=S, stretching), 1331.82 (C–NO2,
stretching), 1589.06 (Ar C=C, stretching), 1632.54 (C=N,