Abstract: The title compound, 2-(4-fluoro-3-nitrophenyl)-6-(4-methoxyphenyl)imidazo[2,1-b]-1,3,4-thiadiazole (3) was obtained by the condensation of 5-(4-fluoro-3-nitrophenyl)-[1,3,4]thiadiazol-2-ylamine (1) with 4-methoxyphenacyl bromide (2). The newly prepared imidazo[2,1-b]-1,3,4-thiadiazole derivative (3) was characterized by IR, 1H-NMR, 13C-NMR and LCMS spectral data.
Molbank 2012, 2012(4), M778; doi:10.3390/M778
Short Note
2-(4-Fluoro-3-nitrophenyl)-6-(4-methoxyphenyl)imidazo[2,1-b]-1,3,4-thiadiazole
1 Research Department of Chemistry, P. A College of Engineering, Nadupadavu, Mangalore 574153, Karnataka, India
2 Department of Studies in Chemistry, Mangalore University, Mangalagangotri-574 199, Karnataka, India
bksaroj@yahoo.com
The IR spectrum of (2-(4-fluoro-3-nitrophenyl)-6-(4-methoxyphenyl)imidazo[2,1-b]-1,3,4-thiadiazole 3
showed strong absorption bands at 1599 cm−1
, 1485 cm−1
and 1324 cm−1
due to C–N, N–O and C–F
stretching of the nitro and fluoro group at the benzene ring. The absence of strong absorption bands at
3457 cm−1
and 3092.5 cm−1
due to the –NH2 group of the precursor thiazole amine 1 indicated the
formation of the product 3.
1
H-NMR was recorded in DMSO-d6 (400 MHz) and the spectrum showed
a signal at δ 3.78 ppm as a singlet which could be attributed to the methoxy group. The aromatic
protons of the methoxy-bearing phenyl ring appear as two doublets in the region δ 6.99 (d, J = 8.8 Hz,
2H) and 7.83 (d, J = 8.8 Hz, 2H) respectively.
The signals for three protons of the fluoro/nitro
substituted phenyl group appear at 8.33 (t, J = 8.2 Hz, 1H), 8.19 (dd, J = 1.7, 11.7 Hz, 1H) 8.00 (d,
J = 8.7 Hz, 1H). A singlet appears at δ 8.71 ppm which is due to the imidazole ring proton. The spinspin
coupling constant of 11.7 Hz, reflects the interaction between hydrogen and fluorine atom.
Further, the 13C-NMR spectrum was recorded in TFA because of the poor solubility of the compound
in DMSO and this spectrum shows peaks at 161.0, 143.5, 140.03, 133.9, 127.5, 123.0, 118.2, 117.2,
116.9, 115.5, 115.2, 112.7, 110.2, 109.9 and 54.9 which accounted for 17 carbon atoms with 2 sets of
equivalent carbons.
The mass spectrum shows the molecular ion peak at m/z 371.0 (M+
+1)
corresponding to the molecular formula of C17H11FN4O3S and elemental analysis gave satisfactory
results for the title compound.
A mixture of 5-(4-fluoro-3-nitrophenyl)-1,3,4-thiadiazol-2-ylamine (1) (5.0 g, 0.0208 mol) and
4-methoxyphenacyl bromide (2) (5.2 g, 0.0229 mol) in absolute ethanol (50 mL) was refluxed for 16 h.
The reaction mass was cooled to RT, the solid which precipitated was filtered and slurried with 10%
sodium bicarbonate (50 mL). The solid was collected by filtration, washed with water and dried under
suction to afford the title compound (6.2 g) as a brick-red solid with a yield of 80.5%.
Melting point: 228.2–229.5 °C.
LCMS: m/z = 371.0 (M+
+1).
IR (KBr): νmax (cm−1
), 1599, 1485 (N–O), 1324 (C–F).
1
H-NMR (400 MHz, DMSO-d6): δ ppm, 8.71 (s, 1H, ArH), 8.33 (t, J = 8.2 Hz, 1H, ArH), 8.19 (dd,
J = 1.7, 11.7 Hz, 1H, ArH), 8.00 (d, J = 8.7 Hz, 1H, ArH), 7.83 (d, J = 8.7 Hz, 2H, ArH), 6.99 (d,
J = 8.8 Hz, 2H, ArH), 3.78 (s, 3H, OCH3).
13C-NMR (100 MHz, TFA): δ ppm, 161.0, 143.5, 140.0, 133.9, 127.5, 123.0, 118.2, 117.2, 116.9,
115.5, 115.2, 112.7, 110.2, 109.9 and 54.9.
Elemental analysis: Calculated for C17H11FN4O3S., C, 55.13%; H, 2.99%; N, 15.13%; Found: C,
55.18%; H, 2.94%; N, 15.16%.
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