796 Tejeswararao et al.
Asian J. Chem.
(ppm) on the delta (δ) scale. Melting points were measured
calcdd. (found) for C18H14N2S 291.0955 (291.0968) [M+H]+.
Anal. calcd. (found) for C18H14N2S: C, 74.45 (74.40); H, 4.86
(4.82); N, 9.65 (9.60); S, 11.04 (11.02).
on a micro melting apparatus and are uncorrected.
Synthesis of compounds 2a-j
5-(2,5-Dimethyl-1H-pyrrol-1-yl)-2-p-tolylbenzo[d]-
thiazole (2g): Pale yellow solid, m.p.: 91-93 ºC; 1H NMR (300
MHz, CDCl3): δ 2.07 (s, 6H, -CH3), 2.45 (s, 3H, Ar-CH3), 5.84
(s, 2H, pyrrole protons), 7.18-7.31 (m, 3H, Ar-H), 7.86-8.00
1-(2,4-Dichlorophenyl)-1H-pyrrole (2a): To a mixture
of 2,4-dichloro nitrobenzene (1 g, 5.20 mmol) in H2O (10 mL)
was added SnCl2·2H2O (3.51 g, 15.62 mmol) at room tempe-
rature and heated to 55 ºC for 30 min. After completion of the
reaction (monitored by TLC), basified the reaction mixture
slowly with saturated aqueous NaHCO3 at 0 °C and compound
was extracted with ethyl acetate (2 × 30 mL). The combined
organic phase was washed with brine (1 × 15 mL), dried over
anhydrous Na2SO4, removed solvent in vacuo and the crude
residue was purified by column chromatography on silica gel
(ethylacetate:hexane, 2:8) to afford compound 2a (0.93 g, 85
13
(m, 4H, Ar-H). C NMR (75 MHz, CDCl3): δ 21.55, 29.68,
110.67, 114.33, 118.33, 119.61, 122.24, 127.47, 129.77, 141.80.
HRMS (ESI) calcd. (found) for C20H18N2S 319.1268 (319.1283)
[M+H]+.Anal. calcd. (found) % for C20H18N2S: C, 75.44 (75.40);
H, 5.70 (5.72); N, 8.80 (8.85); S, 10.07 (10.04).
2-Chloro-5-(1H-pyrrol-1-yl)benzoic acid (2h): White
solid, m.p.: 123-125 °C (lit. [31] 125-128 °C); 1H NMR (300
MHz, CDCl3): δ 6.27 (t, 2H, J = 2.07 Hz, -pyrrole protons),
7.10 (t, 2H, J = 2.07 Hz, pyrrole protons), 7.46-7.57 (m, 2H,
Ar-H), 7.88 (s, 1H, Ar-H). 13C NMR (75 MHz, CDCl3): δ
110.99, 118.72, 121.70, 123.01, 128.79, 131.97, 131.78,
131.97, 138.59, 166.20. MS (ESI): m/z 222 (M+H)+. Anal.
calcd. (found) (%) for C11H8NO2Cl: C, 59.61 (59.64); H, 3.64
(3.62); Cl, 16.00 (19.98), N, 6.32 (6.30).
1
% yield) as white crystalline powder. H NMR (300 MHz,
CDCl3): δ 6. 25 (t, 2H, J = 2.26 Hz, pyrrole protons), 6.84 (t,
2H, J = 2.26 Hz, -pyrrole protons), 7.29-7.39 (m, 3H, Ar-H).
MS (ESI): m/z 213 (M+H)+, 214 (M+2).
1-(2,4-Difluorophenyl)-1H-pyrrole (2b): White solid,
1
m.p.: 50-52 °C; H NMR (300 MHz, CDCl3): δ 6.27 (t, 2H,
J = 2.26 Hz, -pyrrole protons), 6.85-7.01 (m, 4H, Ar-H), 7.28
2-Phenyl-7-(1H-pyrrol-1-yl)quinoxaline (2i): Pale brown
solid, decomposition point 191 ºC; 1H NMR (300 MHz, CDCl3):
δ 6.38 (t, 2H, J = 2.26 Hz, pyrrole protons), 7.25 (t, 2H, J =
2.26 Hz, -pyrrole protons), 7.48-7.59 (m, 3H, Ar-H), 7.86-
7.92 (dd, 1H, J(1,2) = 2.26 Hz, J(1,3) = 9.05 Hz, Ar-H), 8.03 (d,
1H, J = 3.02 Hz, Ar-H), 8.15-8.23 (m, 3H, Ar-H), 9.31 (s, 1H,
Ar-H). 13C NMR (75 MHz, CDCl3): δ 96.17, 111.85, 117.73,
119.21, 122.79, 127.59, 129.13, 130.35, 130.64, 139.66, 141.56,
142.54, 143.04. HRMS (ESI) calcd. for C18H13N3 272.1187
[M+H]+, found 272.1188.Anal. calcd. (%) for C18H13N3 calcd.
(found): C, 79.68 (79.64); H, 4.83 (4.82); N, 15.49 (15.45).
1-(2-Fluro-4-methylphenyl)-2,5-dimethyl-1H-pyrrole
(2j): 1H NMR (300 MHz, CDCl3): δ 1.99 (s, 6H, -CH3), 2.43
(s, 3H, Ar-CH3), 5.81 (s, 2H, -pyrrole protons), 6.97-7.13 (m,
(m, 1H, Ar-H). MS (EI): m/z (%) = 179 (M+, 100 %).
Methyl 5-methoxy-4-(prop-2-ynloxy)-2-(1H-pyrrol-1-
yl)benzoate (2c): White solid, m.p.: 94-96 °C; 1H NMR (300
MHz, CDCl3): δ2.50 (t, 1H, J= 2.26 Hz, 1H), 3.64 (s, 3H, -OCH3),
3.94 (s, 3H, -CO2CH3), 4.78 (d, 2H, J = 2.26 Hz, -OCH2), 6.20
(t, 2H, J = 2.26 Hz, pyrrole protons), 6.68 (t, 2H, J = 2.26 Hz,
pyrrole protons), 6.95 (s, 1H, Ar-H), 7.32 (s, 1H, Ar-H). 13C
NMR (75 MHz, CDCl3): δ 52.39, 56.44, 56.87, 75.81, 77.58,
109.21, 112.79, 113.28, 122.48, 134.98, 148.31, 149.58, 171.55.
HRMS (ESI) calcd. (found) for C16H15NO4 286.1079 (286.1090)
[M+H]+.Anal. calcd. (found) % for C16H15NO4: C, 67.36 (67.41);
H, 5.30 (5.26); N, 4.91 (4.90); O, 22.43 (22.40).
Methyl 7-methoxy-2-methyl-4-(1H-pyrrol-1-yl)benzo-
furan-5-carboxylate (2d): Pale brown solid, m.p.: 127-129
ºC; 1H NMR (300 MHz, CDCl3): δ 2.46 (s, 3H, C2-CH3), 3.65
(s, 3H, -OCH3), 4.06 (s, 3H, -CO2CH3), 6.22 (t, 2H, J = 2.08 Hz,
pyrrole protons), 6.29 (s, 1H, -C3-H), 6.71 (t, 2H, J = 2.08 Hz,
pyrrole protons), 7.19 (s, 1H,Ar-H);13C NMR (75 MHz, CDCl3):
δ13.99, 52.29, 56.36, 101.78, 104.14, 107.10, 108.82, 122.48,
129.12, 143.60. HRMS (ESI) calcd. (found) for C16H15NO4
286.1079 (286.1068) [M+H]+. Anal. calcd. (found) % for
C16H15NO4: C, 67.36 (67.40); H, 5.30 (5.28); N, 4.91 (4.90);
O, 22.43 (22.42).
5-(1H-Pyrrol-1-yl)-2-p-anisole[d]thiazole (2e): Yellow
thick liquid; 1H NMR (300 MHz, CDCl3): δ3.89 (s, 3H, -OCH3),
6.32 (t, 2H, J = 2.07 Hz, pyrrole protons), 6.98 (d, 2H, J = 8.87
Hz, Ar-H), 7.12 (t, 2H, J = 2.07 Hz, -pyrrole protons), 7.38-7.43
(dd, 1H, J(1,2) = 2.26 Hz, J(1,3) = 8.68 Hz,Ar-H), 7.86 (d, 1H, J= 8.68
Hz, Ar-H), 7.98-8.05 (m, 3H, Ar-H). MS (ESI): m/z 307 (M+H)+.
5-(1H-Pyrrol-1-yl)-2-p-tolylbenzo[d]thiazole (2f): Pale
yellow solid, m.p.: 98-100 ºC; 1H NMR (300 MHz, CDCl3): δ
2.44 (s, 3H,Ar-CH3), 6.32 (t, 2H, J = 2.26 Hz, pyrrole protons),
7.12 (t, 2H, J = 2.26 Hz, pyrrole protons), 7.24-7.45 (m, 3H,
Ar-H), 7.84-8.10 (m, 4H, Ar-H). 13C NMR (75 MHz, CDCl3):
δ 29.73, 109.76, 111.36, 110.69, 114.35, 118.34, 119.64, 122.30,
129.08, 129.81, 130.74, 139.70, 141.82, 155.06. HRMS (ESI)
13
3H, Ar-H). C NMR (MHz, CDCl3): 12.41, 21.14, 105.80,
116.86, 117.12, 125.06, 129.11, 130.04, 140.42, 159.71. MS
(ESI): m/z 204 (M+H)+, 226 (M+Na).
2-(2,5-Dimethyl-1H-pyrrol-1-yl)benzenamine (3a): 1H
NMR (300 MHz, CDCl3): δ 1.96 (s, 6H, -CH3), 3.37-3.46 (bs,
2H, -NH2), 5.83 (s, 2H, -pyrrole protons), 6.75 (t, 1H, J = 7.70
Hz, Ar-H), 7.02 (d, 1H, J = 6.98 Hz, Ar-H), 7.15 (t, 1H, J =
7.70 Hz, Ar-H). MS (EI): m/z (%) 186 (M+, 100 %).
1
4-(1H-Pyrrol-1-yl)benzenamine (3c): H NMR (300
MHz, CDCl3): δ 3.40-3.75 (bs, 2H, -NH2), 6.20 (t, 2H, J =
2.07 Hz, -pyrrole protons), 6.65 (d, 2H, J = 8.49 Hz, Ar-H),
6.88 (t, 2H, J = 2.07 Hz, pyrrole protons), 7.13 (d, 2H, J =
8.49 Hz, Ar-H). MS (EI): m/z (%) 158 (M+, 100 %).
Synthesis of pyrroles from o-nitro aniline (4a-d): To a
mixture of 2-nitroaniline (1 g, 5.20 mmol and 2,5-hexanedione
(1.1g, 5.22 mmol) in H2O (10 mL) was added SnCl2·2H2O
(3.51 g, 15.62 mmol) at room temperature and heated to 55 ºC
for 30 min. After completion of the reaction (monitored by
TLC), basified the reaction mixture slowly with saturated
aqueous NaHCO3 at 0 ºC and compound was extracted with
ethyl acetate (2 × 30 mL). The combined organic phase was
washed with brine (1 × 15 ml), dried over anhydrous Na2SO4,
removed solvent in vacuo and the crude residue was purified