344 JOURNAL OF CHEMICAL RESEARCH 2013
196.7 ppm. Anal. Calcd for C8H11NO3 (169.18): C, 56.80; H, 6.55; N,
8.28. Found: C, 56.61; H, 6.54; N, 8.25%.
5c: M.p. 138–140 °C; IR (KBr): υmax = 3455, 3057, 2962, 1793,
1676, 1603, 1536, 1484, 1218 cm−1, 1H NMR (500 MHz, d6-DMSO):
δ = 0.84–1.46 (7H, m, n-butyl), 1.23 (9H, s, t-butyl), 2.75 (2H, t,
J = 7.3 Hz), 5.51 and 7.99 (2 H, D2O-exchangeable OH and NH) ppm.
13C NMR (125 MHz, d6-DMSO): δ = 14.1, 19.7, 27.7, 29.5, 41.0,
51.4, 197.6 ppm. Anal. Calcd for C12H19NO2 (209.28): C, 68.87; H,
9.15; N, 6.69. Found: C, 69.01; H, 9.14; N, 6.72%.
4a: M.p. 170–172 °C; IR (KBr): υmax = 3430, 3050, 2938, 1796,
1742, 1669, 1529, 1470, 1240 cm−1, 1H NMR (500 MHz, DMSO-d6):
δ = 1.07–1.87 (20H, m, 10CH2 of cyclohexyl), 2.97 (2H, m, CH of
cyclohexyl), 7.94 (2H, D2O-exchangeable OH and NH) ppm. 13C
NMR (125 MHz, d6-DMSO): δ = 24.4, 25.2, 31.0, 49.7, 200.2 ppm.
Anal. Calcd for C16H24N2O2 (276.37): C, 69.53; H, 8.75; N, 10.14.
Found: C, 69.27; H, 8.69; N, 10.19%.
4b: M.p. 197–200 °C; IR (KBr): υmax = 3481, 3065, 2981, 1797,
1650, 1499, 1401, 1220 cm−1, 1H NMR (500 MHz, d6-DMSO):
δ = 1.24 (18H, s, t-butyl), 5.71 and 7.84 (2H, D2O-exchangeable OH
and NH) ppm. 13C NMR (125 MHz, d6-DMSO): δ = 27.9, 51.8, 197.3
ppm. Anal. Calcd for C12H20N2O2 (224.30): C, 64.26; H, 8.99; N,
12.49. Found: C, 63.97; H, 8.84; N, 12.60%.
4c: M.p. 151–153 °C; IR (KBr): υmax = 3195, 3059, 2956, 1800,
1676, 1611, 1537, 1484, 1220 cm−1, 1H NMR (500 MHz, d6-DMSO):
δ = 0.86 (6H, t, J = 7.3 Hz), 1.30 (4H, m), 1.51 (4H, m), 2.81 (4H, t,
J = 7.6 Hz), 8.30 (2 H, D2O-exchangeable OH and NH) ppm. 13C
NMR (125 MHz, d6-DMSO): δ = 14.1, 19.7, 29.7, 41.0, 198.7 ppm.
Anal. Calcd for C12H20N2O2 (224.30): C, 64.26; H, 8.99; N, 12.49.
Found: C, 64.17; H, 9.92; N, 12.55%.
Received 24 January 2013; accepted 24 March 2013
Paper 1301747 doi: 10.3184/174751913X13677757448841
Published online: 12 June 2013
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4
5
Synthesis of compounds 5a–c; general procedure
6
The alkyl isocyanide 2 (1 mmol) was added to a solution of squaramic
acid 3 (1 mmol) in ethanol (20 mL) at room temperature. The reaction
mixture was then stirred at room temperature for 3 hours. Upon com-
pletion, monitored by TLC, the solvent was removed under reduced
pressure and the resultant solid was washed and then purified by
recrystallisation from ethyl acetate to give the pure product.
5a: M.p. 158–160 °C; IR (KBr): υmax = 3437, 3050, 2932, 1802,
1740, 1669, 1535, 1478, 1237 cm−1, 1H NMR (500 MHz, d6-DMSO):
δ = 1.07–1.97 (10H, m, 5CH2 of cyclohexyl), 1.24 (9H, s, t-butyl),
2.96 (1H, m, CH of cyclohexyl), 7.73–7.77 (2H, D2O-exchangeable
OH and NH) ppm. 13C NMR (125 MHz, d6-DMSO): δ = 24.4, 25.2,
27.7, 31.0, 49.7, 51.1, 199.7 ppm.Anal. Calcd for C14H21NO2 (235.32):
C, 71.46; H, 8.99; N, 5.95. Found: C, 71.66; H, 9.03; N, 5.93%.
5b: M.p. 112–114 °C; IR (KBr): υmax = 3460, 3041, 2934, 1796,
1741, 1675, 1482, 1252 cm−1, 1H NMR (500 MHz, d6-DMSO):
δ = 0.81–1.83 (17H, m, 5CH2 of cyclohexyl, 7H n-butyl), 2.49–2.83
(3H, m, CH of cyclohexyl, CH2 n-butyl), 5.38 and 8.22 (2H, D2O-
exchangeable OH and NH) ppm. 13C NMR (125 MHz, d6-DMSO):
δ = 14.1, 19.7, 24.4, 25.2, 29.8, 31.0, 41.0, 49.7, 200.1 ppm. Anal.
Calcd for C14H21NO2 (235.32): C, 71.46; H, 8.99; N, 5.95. Found: C,
71.32; H, 8.95; N, 5.98%.
7
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