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Helvetica Chimica Acta – Vol. 95 (2012)
isocyanides 1, carbodiimides 2, and trimethylsilyl azide (3). The ease of workup, high
yields, and fairly mild reaction conditions render this reaction a useful addition to
modern synthetic methodologies.
Experimental Part
General. Starting materials and solvents were obtained from Merck (Germany) and Fluka
(Switzerland) and were used without further purification. M.p.: Electrothermal 9100 apparatus;
uncorrected. IR Spectra: Jasco-FT-IR 6300 spectrometer; ˜n in cmꢀ1. 1H- and 13C-NMR Spectra: Bruker-
DRX-250-Avance spectrometer (250.0 and 62.5 MHz, resp.), in CDCl3; d in ppm rel. to Me4Si as internal
standard, J in Hz. EI-MS: HP 5937 (Agilent Technologies) mass selective detector; ionization potential
70 eV; in m/z. Elemental analyses: Heraeus-CHN-O-Rapid analyzer.
General Procedure. To a magnetically stirred soln. of isocyanide 1 (0.2 mmol) and carbodiimide 2
(0.2 mmol) in MeOH (3 ml) was added trimethylsilyl azide (3; 0.2 mmol). The mixture was stirred at r.t.
for 24 h. The solvent was evaporated to give the pure product.
1-(tert-Butyl)-N5,N’5-diisopropyl-1H-tetrazole-5-carboximidamide (4a): Yield 93%. White solid.
M.p. 105.4 – 107.98. IR (KBr): 3277 (NH), 2980, 1594, 1465, 1099. 1H-NMR: 1.16 (d, J ¼ 6.5, 1 Me2CH);
1.37 (d, J ¼ 6.5, 1 Me2CH); 1.61 (s, Me3C); 3.91 (m, J ¼ 6.5, 1 Me2CH); 4.44 (sept., J ¼ 6.5, 1 Me2CH); 5.14
(d, J ¼ 6, NH). 13C-NMR: 21.58; 22.64 (1 Me2CH); 29.60 (Me3C); 46.42, 48.27 (1 Me2CH); 59.72 (Me3C),
140.10; 154.11 (2 C¼N). EI-MS: 252 (Mþ, 2), 212 (27), 171 (12), 170 (100), 128 (10), 58 (8), 43 (26).
Anal. calc. for C12H24N6 (252.36): C 57.11, H 9.59, N 33.30; found: C 57.04, H 9.57, N 33.35.
N5,N’5-Diisopropyl-1-(1,1,3,3-tetramethylbutyl)-1H-tetrazole-5-carboximidamide (4b): Yield 98%.
White solid. M.p. 111.1 – 112.58. IR (KBr): 3268 (NH), 2979, 1598, 1467, 1147. 1H-NMR: 0.67 (s,
Me3C); 1.20 (d, J ¼ 6.25, 1 Me2CH); 1.41 (d, J ¼ 6.5, 1 Me2CH); 1.70 (s, Me2C); 1.98 (s, CH2); 3.93 (m, J ¼
7, 1 Me2CH); 4.44 (sept., J ¼ 6.5, 1 Me2CH); 5.11 (d, J ¼ 7.25, NH). 13C-NMR: 21.62; 22.69 (2 Me2CH);
29.80 (Me2C); 30.48 (Me3C); 31.44 (Me3C); 46.46, 48.31 (2 Me2CH); 54.12 (CH2); 62.93 (Me2C); 140.78;
154.13 (2 C¼N). EI-MS: 308 (Mþ, 1), 290 (5), 183 (58), 107 (52), 91 (100), 65 (23), 57 (13), 43 (14).
Anal. calc. for C16H32N6 (308.47): C 62.30, H 10.46, N 27.24; found: C 62.36, H 10.42, N 27.19.
1-Cyclohexyl-N5,N’5-diisopropyl-1H-tetrazole-5-carboximidamide (4c): Yield 82%. White solid. M.p.
111.9 – 113.48. IR (KBr): 3289, 2938, 1593, 1455, 1168. 1H-NMR: 1.20 (d, J ¼ 6.25, 1 Me2CH); 1.42 (d, J ¼
6.5, 1 Me2CH); 1.22 – 2.19 (m, 5 CH2 of Chx); 3.94 (m, 1 Me2CH); 4.33 – 4.54 (m, 1 Me2CH, CH of Chx);
4.99 (d, J ¼ 6.5, NH). 13C-NMR: 21.60, 22.71 (2 Me2CH); 24.73, 24.75, 32.96 (5 CH2 of Chx); 46.48; 48.35
(2 Me2CH); 58.80 (CH of Chx), 140.96, 154.07 (2 C¼N). Anal. calc. for C14H26N6 (278.40): C 60.40, H
9.41, N 30.19; found: C 60.34, H 9.39, N 30.22.
1-(tert-Butyl)-N5,N’5-dicyclohexyl-1H-tetrazole-5-carboximidamide (4d). Yield 93%. White solid.
1
M.p. 122.3 – 124.48. IR (KBr): 3313 (NH), 2926, 1594, 1444, 1102. H-NMR: 1.11 – 2.07 (m, 10 CH2 of
Chx); 1.67 (s, Me3C); 3.54 – 3.73 (m, CH of Chx); 3.84 – 4.01 (m, CH of Chx); 4.71 (d, J ¼ 5.5, NH).
13C-NMR: 24.87, 24.97, 25.05, 25.50, 31.83, 33.25 (10 CH2 of Chx); 29.70 (Me3C); 53.46, 55.34 (2 CH of
Chx); 59.69 (Me3C); 139.97, 153.96 (2 C¼N). EI-MS: 332 (Mþ, 2), 290, 249, 221, 168, 83, 55. Anal. calc.
for C18H32N6 (332.49): C 65.02, H 9.70, N 25.28; found: C 64.97, H 9.66, N 25.34.
N5,N’5-Dicyclohexyl-1-(1,1,3,3-tetramethylbutyl)-1H-tetrazole-5-carboximidamide (4e): Yield 97%.
1
White solid. M.p. 65.8 – 66.28. IR (KBr): 3313, 2926, 1594, 1445, 1100. H-NMR: 0.69 (s, Me3C); 1.07 –
2.04 (m, 10 CH2 of Chx); 1.71 (s, Me2C); 1.99 (s, CH2); 3.51 – 3.68 (m, CH of Chx); 3.93 – 4.08 (m, CH
of Chx); 5.15 (d, J ¼ 7.5, NH). 13C-NMR: 24.88, 24.98, 25.02, 25.47, 31.86, 33.14 (10 CH2 of Chx); 29.82
(Me2C); 30.50 (Me3C); 31.46 (Me3C); 53.52, 55.17 (2 CH of Chx); 54.11 (CH2); 62.90 (Me2C); 140.74,
154.11 (2 C¼N). Anal. calc. for C22H40N6 (388.59): C 68.00, H 10.38, N 21.63, found: C 68.07, H 10.34, N
21.60.
N5,N’5,1-Tricyclohexyl-1H-tetrazole-5-carboximidamide (4f): Yield 81%. White solid. M.p. 72.4 –
1
74.18. IR (KBr): 3313 (NH), 2926, 1594, 1444, 1101. H-NMR: 1.18 – 2.16 (m, 15 CH2 of Chx); 3.48 –
5.18 (4m, 3 CH of Chx, NH). 13C-NMR: 24.73, 24.84, 24.97, 25.06, 25.44, 31.82, 32.95, 32.99, 33.11 (15
CH2 of Chx); 53.62, 55.47, 58.76 (3 CH of Chx); 140.92, 153.98 (2 C¼N). Anal. calc. for C20H34N6 (358.52):
C 67.00, H 9.56, N 23.44; found: C 67.06, H 9.58, N 23.40.