ꢀꢀꢀꢁ
4ꢀ ꢀJ. Khalafy et al.: Synthesis of imidazo[2,1-b][1,3,4]thiadiazol-7-ium hydroxides
After completion of the reaction, the residue of the product 4a–k 2-Ethyl-5-(2-hydroxy-4-oxoquinolin-3(4H)-ylidene)-6-(p-tol-
was filtered and washed with water.
yl)-5,6-dihydroimidazo[2,1-b][1,3,4]thiadiazol-7-ium
hydroxide
(4e)ꢁYield 89%; white solid; mp 215–216°C; reaction time 2 h; IR:
νmax 3320, 2948, 2845, 1650, 1608, 1538, 1503, 1440, 1387, 1273, 725 cm−1;
1H NMR: δ 11.20 (s, 1H, exchanged by D2O addition, OH), 9.02 (m, 1H,
exchanged by D2O addition, NH), 7.95 (d, Jꢀ=ꢀ7.5 Hz, 1H, Ar), 7.62 (d,
Jꢀ=ꢀ7.5 Hz, 2H, Ar), 7.46 (t, Jꢀ=ꢀ7.5 Hz, 1H, Ar), 7.20 (t, Jꢀ=ꢀ7.5 Hz, 4H, Ar),
6.27 (d, 1H, Jꢀ=ꢀ5.7 Hz exchanged to singlet by D2O addition, CH), 2.82
2-Ethyl-5-(2-hydroxy-4-oxoquinolin-3(4H)-ylidene)-6-phe-
nyl-5,6-dihydroimidazo[2,1-b][1,3,4]thiadiazol-7-ium hydrox-
ide (4a)ꢁYield 87%; white solid; mp 196–197°C; reaction time
3 h; IR: νmax 3297, 2940, 2845, 1690, 1648, 1606, 1508, 1441, 1390,
1
1272, 748 cm−1; H NMR: δ 11.24 (s, 1H, exchanged by D2O addition,
(q, Jꢀ=ꢀ7.5 Hz, 2H, CH2), 2.24 (s, 3H, CH3), 1.21 (t, Jꢀ=ꢀ7.5 Hz, 3H, CH3); 13
C
OH), 9.06 (bd, 1H, Jꢀ=ꢀ7 Hz, exchanged by D2O addition, NH), 7.96
(d, Jꢀ=ꢀ8 Hz, 1H, Ar), 7.72 (d, Jꢀ=ꢀ8 Hz, 2H, Ar), 7.46 (t, Jꢀ=ꢀ7 Hz, 2H, Ar),
7.35 (t, Jꢀ=ꢀ7.5 Hz, 2H, Ar), 7.17 (d, Jꢀ=ꢀ8 Hz, 1H, Ar), 7.13 (d, Jꢀ=ꢀ8 Hz,
1H, Ar), 6.32 (d, Jꢀ=ꢀ7 Hz, 1H, converted to a singlet by D2O addi-
tion, CH), 2.82 (q, Jꢀ=ꢀ7.5 Hz, 2H, CH2), 1.21 (t, Jꢀ=ꢀ7.5 Hz, 3H, CH3);
13C NMR: δ 194.2, 169.0, 162.3, 162.0, 161.2, 138.8, 136.0, 132.5, 129.5,
129.1, 127.57, 126.9, 125.3, 122.8, 121.0, 116.4, 111.0, 25.1, 23.5. Anal.
Calcd for C21H18N4O3S: C, 62.06; H, 4.46; N, 13.78. Found: C, 62.40;
H, 4.41; N, 14.13.
NMR: δ 193.7, 169.0, 162.3, 161.9, 143.2, 138.8, 133.3, 130.0, 129.2, 128.2,
127.0, 125.3, 122.8, 121.0, 116.5, 114.6, 111.2, 25.1, 23.5. Anal. Calcd for
C22H20N4O3S: C, 62.84; H, 4.79; N, 13.32. Found: C, 62.75; H, 4.83; N, 13.50.
2-Ethyl-6-(4-hydroxy-3-methoxyphenyl)-5-(2-hydroxy-4-oxo-
quinolin-3(4H)-ylidene)-5,6-dihydroimidazo[2,1-b][1,3,4]thiadi-
azol-7-ium hydroxide (4f)ꢁYield 94%; white solid; mp 221–222°C;
reaction time 3 h; IR: νmax 3074, 2946, 2932, 1634, 1605, 1511, 1399,
1
1289, 1183, 1029, 769 cm−1; H NMR: δ 11.26 (s, 1H, exchanged by D2O
addition, OH), 9.82 (bd, 1H, Jꢀ=ꢀ7 Hz exchanged by D2O addition, NH),
8.87 (s, 1H, exchanged by D2O addition, OH), 7.95 (d, Jꢀ=ꢀ8. Hz, 1H,
Ar), 7.48 (t, Jꢀ=ꢀ7.5 Hz, 1H, Ar), 7.34 (s, 1H, Ar), 7.26 (d, Jꢀ=ꢀ8 Hz, 1H, Ar),
7.19 (d, Jꢀ=ꢀ7.5 Hz, 2H, Ar) 6.70 (d, Jꢀ=ꢀ8 Hz, 1H, Ar), 6.26 (bd, Jꢀ=ꢀ7 Hz,
1H, converted to a singlet by D2O addition, CH), 3.79 (s, 3H, OCH3),
2.82 (q, Jꢀ=ꢀ7 Hz, 2H, CH2), 1.21 (t, Jꢀ=ꢀ7 Hz, 3H, CH3); 13C NMR: δ 192.2,
168.9, 165.8, 162.4, 161.5, 151.7, 147.3, 138.7, 132.7, 130.5, 127.0, 125.1,
123.5, 122.9, 121.5, 121.0, 116.4, 113.0, 111.4, 56.6, 25.0, 23.5. Anal. Calcd
for C22H20N4O5S: C, 58.40; H, 4.46; N, 12.38. Found: C, 58.23; H, 4.62;
N, 12.13.
2-Ethyl-5-(2-hydroxy-4-oxoquinolin-3(4H)-ylidene)-6-(4-
methoxyphenyl)-5,6-dihydroimidazo[2,1-b][1,3,4]thiadiazol-
7-ium hydroxide (4b)ꢁYield 91%; white solid; mp 210–211°C;
reaction time 2 h; IR: νmax 3310, 2942, 2842, 1664, 1606, 1545, 1505,
1
1442, 1391, 1252, 1171, 752 cm−1; H NMR: δ 11.22 (s, 1H, exchanged
by D2O addition, OH), 8.99 (d, 1H, Jꢀ=ꢀ5 Hz, exchanged by D2O addi-
tion, NH), 7.96 (d, Jꢀ=ꢀ7.5 Hz, 2H, Ar), 7.46 (t, Jꢀ=ꢀ9 Hz, 1H, Ar), 7.20–7.13
(m, 2H, Ar), 6.90 (d, Jꢀ=ꢀ9 Hz, 2H, Ar), 6.24 (d, Jꢀ=ꢀ5 Hz, converted to
a singlet by D2O addition, 1H, CH), 3.73 (s, 3H, OCH3), 2.82 (q, 3H,
Jꢀ=ꢀ7.5 Hz, 2H, CH2), 1.21 (t, Jꢀ=ꢀ7.5 Hz, 3H, CH3); 13C NMR: δ 192.5, 168.9,
163.1, 162.3, 161.9, 161.8, 138.8, 131.4, 129.1, 128.4, 125.3, 122.8, 120.9,
116.51, 114.8, 112.9, 111.3, 56.8, 25.0, 23.5. Anal. Calcd for C22H20N4O4S:
C, 60.54; H, 4.62; N, 12.84. Found: C, 60.76; H, 4.53; N, 12.75.
6-(4-Chlorophenyl)-2-ethyl-5-(2-hydroxy-4-oxoquinolin-3(4H)-
ylidene)-5,6-dihydroimidazo[2,1-b][1,3,4]thiadiazol-7-ium
hydroxide (4g)ꢁYield 89%; white solid; mp 217–218°C; reaction time
2 h; IR: νmax 3307, 2951, 2855, 1689, 1648, 1605, 1502, 1390, 1268, 1094,
754 cm−1; 1H NMR: δ 11.25 (s, 1H, exchanged by D2O addition, OH), 9.07
(m, 1H, Jꢀ=ꢀ6 Hz, exchanged by D2O addition, NH), 7.96 (d, Jꢀ=ꢀ8 Hz,
1H, Ar), 7.73–7.68 (m, 2H, Ar), 7.47–7.40 (m, 3H, Ar), 7.21–7.12 (m, 2H,
Ar), 6.32 (m, 1H, CH), 2.82 (q, Jꢀ=ꢀ7.5 Hz, 2H, CH2), 1.21 (t, Jꢀ=ꢀ7.5 Hz,
3H, CH3); 13C NMR: δ 193.4, 169.0, 162.3, 161.3, 138.8, 137.7, 134.8, 131.0,
129.8, 128.7, 127.7, 125.4, 122.9, 121.1, 116.5, 114.6, 110.8, 25.0, 23.5. Anal.
Calcd for C21H17ClN4O3S: C, 57.21; H, 3.89; N, 12.71. Found: C, 57.24; H,
3.85; N, 12.57.
2-Ethyl-5-(2-hydroxy-4-oxoquinolin-3(4H)-ylidene)-6-(3-
methoxyphenyl)-5,6-dihydroimidazo[2,1-b][1,3,4]thiadiazol-
7-ium hydroxide (4c)ꢁYield 93%; white solid; mp 197–198°C;
reaction time 2.5 h; IR: νmax 3321, 2950, 2843, 1692, 1648, 1606, 1503,
1
1442, 1388, 1275, 1033, 754 cm−1; H NMR: δ 11.27 (s, 1H, exchanged
by D2O addition, OH), 8.98 (bd, 1H, Jꢀ=ꢀ5 Hz, exchanged by D2O addi-
tion, NH), 7.95 (d, Jꢀ=ꢀ8 Hz, 1H, Ar), 7.47 (t, Jꢀ=ꢀ8 Hz, 1H, Ar), 7.31–7.10
(m, 2H, Ar), 7.03 (d, Jꢀ=ꢀ8 Hz, 1H, Ar), 6.32 (d, Jꢀ=ꢀ5 Hz, 1H, CH), 3.73
(s, 3H, OCH3), 2.82 (q, Jꢀ=ꢀ7.5 Hz, 2H, CH2), 1.21 (t, Jꢀ=ꢀ7.5 Hz, 3H, CH3);
13C NMR: δ 193.9, 168.9, 162.4, 159.8, 143.6, 138.7, 137.6, 135.4, 131.2,
129.3, 125.3, 124.0, 122.9, 122.1, 121.3, 121.0, 116.4, 111.0, 104.1, 56.5, 25.1,
23.5. Anal. Calcd for C22H20N4O4S: C, 60.54; H, 4.62; N, 12.84. Found:
C, 60.34; H, 4.62; N, 12.56.
6-(4-Bromophenyl)-2-ethyl-5-(2-hydroxy-4-oxoquinolin-3(4H)-
ylidene)-5,6-dihydroimidazo[2,1-b][1,3,4]thiadiazol-7-ium
hydroxide (4h)ꢁYield 87%; white solid; mp 217–218°C; reaction
time 2.5 h; IR: νmax 3312, 2955, 2860, 1690, 1646, 1606, 1502, 1452,
1
1388, 1271, 1067, 756 cm−1; H NMR: δ 11.26 (s, 1H, exchanged by D2O
addition, OH), 9.09 (d, 1H, Jꢀ=ꢀ6 Hz exchanged by D2O addition, NH),
7.95 (d, Jꢀ=ꢀ8 Hz, 1H, Ar), 7.63 (d, Jꢀ=ꢀ8 Hz, 2H, Ar), 7.58 (d, Jꢀ=ꢀ8 Hz,
2H, Ar), 7.47 (t, Jꢀ=ꢀ7 Hz, 1H, Ar), 7.16 (t, Jꢀ=ꢀ8 Hz, 2H, Ar), 6.32 (m, 1H,
converted to a singlet by D2O addition, CH), 2.83 (q, Jꢀ=ꢀ7 Hz, 2H,
CH2), 1.21 (t, Jꢀ=ꢀ7.5 Hz, 3H, CH3); 13C NMR: δ 193.6, 169.0, 162.3, 143.5,
138.8, 135.1, 132.8, 131.0, 128.9, 126.8, 125.4, 124.0, 122.9, 121.0, 116.5,
110.7, 104.1, 25.0, 23.5. Anal. Calcd for C21H17BrN4O3S: C, 51.97; H, 3.53;
N, 11.54. Found: C, 52.05; H, 3.47; N, 11.32.
6-(3,4-Dimethoxyphenyl)-2-ethyl-5-(2-hydroxy-4-oxoquinolin-
3(4H)-ylidene)-5,6-dihydroimidazo[2,1-b][1,3,4]thiadiazol-7-ium
hydroxide (4d)ꢁYield 90%; white solid; mp 198–199°C; reaction time
2 h; IR: νmax 3343, 3283, 2962, 1691, 1630, 1512, 1453, 1407, 1260, 1161,
1
1018, 760 cm−1; H NMR: δ 11.26 (s, 1H, exchanged by D2O addition,
OH), 8.92 (bs, 1H, exchanged by D2O addition, NH), 7.96 (d, Jꢀ=ꢀ7.5 Hz,
1H, Ar), 7.47 (t, Jꢀ=ꢀ7.5 Hz, 1H, Ar), 7.35 (s, 2H, Ar), 7.30–7.23 (m, 2H, Ar),
6.92 (d, Jꢀ=ꢀ9 Hz, 1H, Ar), 6.29 (d, Jꢀ=ꢀ4 Hz,1H, CH), 3.73 (s, 3H, OCH3),
3.67 (s, 3H, OCH3), 2.82 (q, Jꢀ=ꢀ7 Hz, 2H, CH2), 1.21 (t, Jꢀ=ꢀ7 Hz, 3H, CH3);
13C NMR: δ 192.4, 168.9, 162.4, 161.7, 161.2, 153.0, 148.4, 138.8, 132.7,
130.5, 128.2, 128.1, 125.2, 125.2, 123.0, 122.9, 121.0, 116.4, 111.3, 57.5, 56.7,
25.1, 23.5. Anal. Calcd for C23H22N4O5S: C, 59.22; H, 4.75; N, 12.01. Found:
C, 59.36; H, 4.71; N, 12.11.
2-Ethyl-6-(4-fluorophenyl)-5-(2-hydroxy-4-oxoquinolin-
3(4H)-ylidene)-5,6-dihydroimidazo[2,1-b][1,3,4]thiadiazol-7-ium
hydroxide (4i)ꢁYield 91%; white solid; mp 197–198°C; reaction time
2 h; IR: νmax 3300, 2932, 2855, 1691, 1647, 1605, 1507, 1448, 1391, 1264,
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