172 Chermahini, Teimouri, Moaddeli
TABLE 4 Results Obtained from Catalyst Reuse Modified Montmorillonite K10 catalysts
Reused Cycle 1
Time (h)
Yielda
Reused Cycle 2
Reused Cycle 3
Reused Cycle 4
Catalyst
Time
Yield
Time
Yield
Time
Yield
Mont-K10-Cu
Mont-K10-Fe
Mont-K10-Zn
Mont-K10-Ni
4
6
8
6
65
75
66
70
4
6
8
8
68
70
60
65
5
6
8
8
65
74
64
60
5
6
8
8
60
65
63
67
aIsolated yields.
temperature then after grinding calcined for 3 h at
400◦C under airflow.
3-(1-H-Tetrazole-5-yl)pyridine (4b). White solid;
mp◦C = 238–240 (239–240 [15]); 1H NMR (DMSO-d6,
400 MHz): 9.1 (s, 1H), 8.8 (d, J = 3.8 Hz, 1H), 8.3(d,
J = 3.8 Hz, 1H), 7.6 (1H, m); 13C NMR (DMSO-d6,
100 MHz); 165, 153, 150, 136, 126, 123. IR (KBr) ν:
3080, 2950, 2890, 2850, 2761, 1480, 1200, cm−1.
General Procedure for Preparation of Tetrazoles
under Reflux Condition
The procedure for the synthesis of the tetrazole 1a
is a representative one. In a round-bottom flask,
benzonitrile (0.2 g, 2 mmol), sodium azide (0.4 g,
6 mmol), modified montmorillonite K-10 (5 mg),
and DMF (20 mL) were charged. Then the reac-
tion mixture was refluxed. The progress of reaction
was followed by TLC (75:25 ethylacetat:n-hexane).
After completion of the reaction, the reaction was
cooled to room temperature and insoluble material
was filtered and washed with doubly distilled water
and acetone to separate the catalyst. The solution
was acidified with HCl (2 mL, 12 M). The precip-
itate was collected, dried, and recrystallized from
water/ethanol to afford pure 5-phenyltetrazole as a
white powder, yield: 0.26 g, 85%. mp (◦C) = 214–216
(215–216 [15]). 1H NMR (DMSO-d6, 400 MHz): 7.6–
8.1 ppm (m, 5H); 13C NMR (DMSO-d6, 400 MHz);
124.5, 127.4, 129.9, 131.7. 155.8; MS (70 eV) m/z:
146, 118, 103, 91, 77, 63, 39; IR, (KBr), 3054, 2981,
2914, 2837, 2794, 2701, 2610, 1608, 726 cm−1
2-(1-H-Tetrazole-5-yl)pyridine (5b). White solid;
mp◦C = 208–210 (211 [16]); 1H NMR (DMSO-d6,
400 MHz): 7.4 (t, J = 6.4 Hz, 1H), 7.8 (t, J = 6.4 Hz,
1H) 8.0 (t, J = 8.0 Hz, 1H) 8.5 (d, J = 3.2 Hz, 1H)
ppm; 13C NMR (DMSO-d6, 100 MHz); 167, 158, 149,
137, 124, 121 ppm; MS (70 eV) m/z: 147, 119, 105,
91, 78, 51, IR (KBr)ν: 3278, 3181, 2929, 1662, 1578,
1390, 923 cm−1.
5-(4-Chlorophenyl)-1H-tetrazole
(6b). White
solid; mp◦C = 258–260 (263–264 [34]); 1H NMR
(acetone-d6, 400 MHz): 7.65 (d, J = 8.4 Hz, 2H), 8.15
(d, J = 8.4 Hz, 2H) 13C NMR (acetone-d6, 100 MHz);
136, 130, 128, 124 ppm; IR (KBr) ν: 3060, 2460,
1900, 1608, 1486, 1435, 1100 cm−1.
5-(Thiophen-2yl)-1H-tetrazole (7b). White solid;
1
mp◦C = 201–203 (210–213 [35], 205 [36]); H NMR
(DMSO-d6, 400 MHz): 7.1 (t, J = 4 Hz, 1H), 7.6 (d,
J = 4Hz, 1H), 7.7 (d, J = 4 Hz, 1H) ppm; 13C NMR
(DMSO-d6, 100 MHz); 149, 134, 130, 125 ppm; MS
(70 eV) m/z: 154, 152, 124, 109, 97, 69, 45; IR (KBr)
ν: 3108, 3093, 3076, 2952, 2890, 2789, 2685, 1505,
1434, 964 cm−1.
5-(4-Nitrophenyl)-1H-tetrazole
(2b). White
solid; mp◦C = 218–220 (219–220 [21]); 1H NMR
(DMSO-d6, 400 MHz): 8.1 (d, J = 8 Hz, 2H), 8.2 (d,
J = 8 Hz, 2H) ppm; 13C NMR (DMSO-d6, 100 MHz);
156, 130, 128, 124 ppm; MS (70 eV) m/z: 191, 163,
149, 134, 90, 63; IR (KBr) ν: 3103, 2914, 2853, 2752,
2621, 1605, 1526, 1487, 861 cm−1
4-(1H-Tetrazole-5-yl)benzaldehyde (8b). White
solid; mp◦C
=
180–182; 1H NMR (DMSO-d6,
400 MHz): 7.9 (d, J = 7.2 Hz, 2H), 8.0 (d, J = 7.2 Hz,
2H) 9.1 (s, 1H) ppm; 13C NMR (DMSO-d6, 100 MHz);
188, 156, 138, 131, 129, 128 ppm; MS (70 eV)/g/z:
174, 146, 130, 116, 102, 90, 57, 43 IR (KBr) ν: 3015,
2924, 2854, 2713, 2612, 1667, 1440, 776 cm−1.
4-(1-H-tetrazole-5-yl)pyridine (3b). White solid;
mp◦C = 254–256 (253–255 [33]); 1H NMR (DMSO-d6,
400 MHz): 8.0 (d, J = 7.8 Hz, 2H), 8.8 (d, J = 7.8 Hz,
2H) ppm; 13C NMR (DMSO-d6, 100 MHz); 165, 149,
134, 121 ppm; MS (70 eV) m/z: 147, 119, 92, 78, 62,
50. IR (KBr) ν: 3080, 3060, 3028, 2955, 2917, 2832,
2751, 2689, 1608, 1581, 1492, 1065, 784 cm−1.
4-(1H-Tetrazole-5-yl)benzonitrile
(9b). White
1
solid; mp◦C = 258–260 d (300 > d [37]); H NMR
(DMSO-d6, 400 MHz): 8.0 (d, J = 7.8 Hz, 2H),
Heteroatom Chemistry DOI 10.1002/hc