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C. Jin et al.
LETTER
(6) (a) Kurzer, F.; Hanks, D. R. Chem. Ind. (London, U.K.)
1966, 26, 1143. (b) Kurzer, F.; Wilkinson, M. J. Chem. Soc.
C. 1970, 19. (c) Kurzer, F.; Hanks, D. R. J. Chem. Soc. C.
1967, 746. (d) Kurzer, F.; Wilkinson, M. J. Chem. Soc. C
1970, 26. (e) Tilley, J. W.; Ramuz, H.; Levitan, P.; Blount,
J. F. Helv. Chim. Acta 1980, 63, 841.
(7) Su, W.; Liu, C.; Shan, W. Synlett 2008, 5, 725.
(8) Su, W.; Jin, C. Org. Lett. 2007, 9, 993.
(9) The thiazetidin-2-one ring system was reported only once
from dithiazolines with Ph3P, see: Tittelbach, F.; Seeboth, H.
Z. Chem. 1987, 27, 142.
compound 4f was obtained by flash chromatography under
N2.
2,6-Diisopropylphenyl Carbodiimide (4f)
Colorless oil. MS (EI): m/z (%) = 219 (100), 204 (74), 170
(32), 162 (39), 128 (43) 84 (29). Anal. Calcd for C25H34N2:
C, 82.82; H, 9.45; N, 7.73. Found: C, 82.83; H, 9.48; N, 7.70.
IR (KBr): nmax = 2965, 2069, 1461, 930cm–1. 1H NMR (500
MHz, CDCl3): δ = 1.25 (s, 12 H), 1.27 (s, 12 H), 3.21–3.28
(m, 4 H), 7.12 (d, 4 H, J = 7.5 Hz), 7.22 (dd, 2 H, J1 = 8.3Hz,
J2 = 7.5 Hz). 13C NMR (125 MHz, CDCl3): δ = 22.9, 29.8,
123.5 (2 × CH), 127.6 (2 × CH), 145.1.
(10) General Procedure for the Preparation of Compound 2
from 1
(12) One-Pot Preparation of Compound 3 from 1
To a mixture of EtOAc (25 mL), NaHCO3 (11.5 mmol, 0.97
g), and thioureas 1 (5 mmol), BTC (1.7 mmol, 0.5 g) was
added carefully in portions. The reaction mixture was stirred
at r.t. for 15 min. After completion (TLC), then N2H4·H2O
(10 mmol) was added to the mixture and stirred for 20 min
at 60 °C. The organic layer was washed with H2O (2 × 10
mml) and dried (MgSO4). The solvent was removed under
vacuum. The residual was purified by recrystallization in
PE–EtOAc to give 3 as a white crystal.
To a mixture of EtOAc (25 mL), NaHCO3 (11.5 mmol, 0.97
g), and thioureas 1 (5 mmol), BTC (1.7 mmol, 0.5 g) was
added carefully in portions. The reaction mixture was stirred
at r.t. for 15 min. After completion (TLC), CH2Cl2 (20 mL)
was added, the mixture was filtered, the organic solvent was
condensed, and the intermediate 2 was obtained as crystal
almost quantitatively.
3-p-Tolyl-4-(p-tolylimino)-1,3-thiazetidin-2-one (2b)
White needle crystals; mp 117.6–118.6 °C. MS (EI): m/z (%)
= 282 (100) [M+], 283 (17) [M+ + 1], 253 (45). Anal. Calcd
for C16H14N2OS: C, 68.06; H, 5.00; N, 9.92. Found: C,
68.08; H, 5.05; N, 9.91. IR (KBr): nmax = 1810, 1696, 1505,
1368 cm–1. 1H NMR (500 MHz, CDCl3): d = 2.33 (s, 3 H),
2.34 (s, 3 H), 6.99–7.01 (m, 2 H), 7.17 (d, 2 H, J = 8.0 Hz),
7.20 (d, 2 H, J = 8.0 Hz), 7.74–7.76 (m, 2 H). 13C NMR (125
MHz, CDCl3): d = 21.0, 21.1, 121.0, 121.3, 124.0, 130.0,
130.1, 132.7, 135.8, 136.4, 139.7, 157.9.
4-(2,5-Dimethylphenyl)-5-(2,5-dimethylphenylamino)-
[1,2,4]triazol-3-one (3d)
White crystals; mp 194.1–195.3 °C. MS (EI): m/z (%) = 308
(100) [M+], 309 (22) [M+ + 1], 249 (13), 145 (25), 131 (22),
121 (42), 91 (15), 77 (30). Anal. Calcd for C18H20N4O: C,
70.11; H, 6.54; N, 18.17. Found: C, 70.10; H, 6.58; N, 18.14.
IR (KBr): nmax = 3188, 1716, 1557, 1372, 1036 cm–1. 1H
NMR (500 MHz, DMSO): d = 1.99 (s, 3 H), 2.12 (s, 3 H),
2.18 (s, 3 H), 2.26 (s, 3 H), 6.67 (t, 1 H, J = 1.0 Hz), 6.91 (d,
1 H, J = 8.0 Hz), 7.01 (d, 1 H, J = 1.0 Hz), 7.08 (s, 1 H), 7.14
(t, 2 H, J = 7.5 Hz), 7.20 (d, 1 H, J = 8.0 Hz), 11.13 (s, 1 H).
13C NMR (125 MHz, DMSO): d = 17.4, 17.5, 20.7, 21.1,
121.8, 123.9, 126.2, 129.8, 130.2, 130.5, 131.0, 133.7,
135.6, 136.4, 138.9, 145.0, 153.5.
3-(4-Methoxyphenyl)-4-(4-methoxyphenylimino)-1,3-
thiazetidin-2-one (2i)
White crystals; mp 88.5–90.1 °C. MS (EI): m/z (%) = 314
(100) [M+], 315 (18) [M+ + 1], 271 (16). Anal. Calcd for
C13H14N2O3S: C, 61.13; H, 4.49; N, 8.91. Found: C, 61.11;
H, 4.54; N, 8.94. IR (KBr): nmax = 1802, 1693, 1502,
1375cm–1. 1H NMR (500 MHz, CDCl3): d = 3.79 (S, 3 H),
3.80 (s, 3 H), 6.88–6.93 (m, 4 H), 7.04–7.07 (m, 2 H), 7.75
(dd, 2 H, J1 = 6.8 Hz, J2 = 2.5 Hz). 13C NMR (125 MHz,
CDCl3): d = 55.5 (2 × CH), 114.3, 114.7, 122.3, 123.4,
125.1, 128.1, 139.2, 139.3, 157.9, 158.0.
4-(4-Methoxyphenyl)-5-(4-methoxyphenylamino)-
[1,2,4]triazol-3-one (3i)
White crystals; mp 211.2–215.5 °C. MS (EI): m/z (%) = 312
(100), 313 (18) [M+ + 1], 297 (35), 134 (17), 122 (22), 77 (8).
Anal. Calcd for C16H16N4O3: C, 61.53; H, 5.16; N, 17.94;
Found: C, 61.51; H, 5.19; N, 17.98. IR (KBr): nmax = 3085,
1701, 1601, 1085 cm–1. 1H NMR (500 MHz, DMSO):
d = 3.68 (s, 3 H), 3.81 (s, 3 H), 6.78–6.82 (m, 2 H), 7.05–
7.08 (m, 2 H), 7.29–7.36 (m, 4 H), 7.85 (s, 1 H), 11.05 (s, 10
H). 13C NMR (125 MHz, DMSO): d = 55.6, 55.9, 114.2,
115.0 (2 ¥ CH), 119.6, 125.1, 129.7 (2 × CH), 134.3
(4 ¥ CH), 144.7, 153.7, 154.2, 159.6.
(11) Typical Procedure for the Preparation of Compound 4f
from 1
To a mixture of EtOAc (25 mL), NaHCO3 (11.5 mmol, 0.97
g), and thioureas 1f (5 mmol), BTC (1.7 mmol, 0.5 g) was
added carefully in portions. The reaction mixture was stirred
at r.t. for 15 min. After completion (TLC), the mixture was
filtered, the organic solvent was condensed and the
Synlett 2009, No. 4, 607–610 © Thieme Stuttgart · New York