B. E. Blass et al. / Tetrahedron Letters 44 (2003) 3009–3011
3011
(3×100 mL). The combined extracts were dried over anhy-
drous Na2SO4. Removal of the solvent in vacuo gave the
desired product 2b (868 mg, 94%). The product obtained
could be carried to the next step without purification.
Spectral data for Table 1. Entry 2a (1H NMR, 300 MHz,
CDCl3): l 2.23 (s, 3H), 7.42–7.58 (m, 5H). (M+H) 189.
Entry 2b (1H NMR, 300 MHz, CDCl3): l 1.34 (s, 9H),
2.31 (s, 3H), 7.26–7.46 (m, 4H). (M+H) 245. Entry 2c (1H
NMR, 300 MHz, CDCl3): l 7.55–7.72 (m, 6H), 7.81 (d,
J=7.30 Hz, 2H), 7.98 (d, J=7.10 Hz, 2H). (M+H) 251.
Entry 2d (1H NMR, 300 MHz, CDCl3): l 3.63 (s, 3H),
7.27 (m, 2H), 7.37 (t, J=5.5 Hz, 1H), 7.68 (d, J=7.0 Hz,
2H). (M+H) 189. Entry 2e (1H NMR, 300 MHz, CDCl3):
l 2.21 (s, 3H), 3.71 (s, 3H). (M+H) 127.
J=5.5 Hz each, 2H), 3.71 (s, 3H), 4.65 (br s, 1H), 7.12 (d,
J=6.67 Hz, 2H), 7.38–7.50 (m, 8H). (M+H) 394. Entry 3d
(1H NMR, 300 MHz, CDCl3): d 0.95 (t, J=7.20 Hz, 3H),
1.29 (m, 2H), 1.45 (m, 2H), 2.23 (s, 3H), 3.17 (t, J=7.0
Hz, 2H), 7.50–7.62 (m, 5H). (M+H) 288. Entry 3e (1H
NMR, 300 MHz, CDCl3): l 1.11 (s, 9H), 2.21 (s, 3H), 3.71
(s, 3H), 3.84 (dd, J=3.0 Hz each, 2H), 4.52 (br s, 1H),
7.44–7.56 (m, 5H). (M+H) 390. Entry 3f (1H NMR, 300
MHz, CDCl3): l 1.28 (t, J=7.13 Hz, 3H), 2.09 (s, 3H),
2.21 (s, 3H), 2.54 (m, 2H), 2.73 (m, 2H), 4.15 (q, J=7.0
Hz, 2H), 4.49 (m, 1H), 7.34–7.53 (m, 5H). (M+H) 392.
Entry 3g (1H NMR, 300 MHz, CDCl3): l 1.13 (m, 3H),
1.23 (s, 9H), 1.92 (s, 3H), 1.98 (m, 2H), 2.26 (s, 3H), 2.37
(m, 2H), 4.06 (m, 2H), 4.45 (m, 1H), 7.10–7.30 (m, 4H).
(M+H) 448. Entry 3h (1H NMR, 300 MHz, MeOD): l 1.42
(s, 9H), 2.46 (s, 3H), 3.76 (s, 3H), 6.83–6.90 (m, 2H),
7.29–7.35 (m, 6H). (M+H) 394. Entry 3i (1H NMR, 300
MHz, MeOD): l 2.47 (s, 3H), 7.15–7.50 (m, 11H), 7.60 (d,
J=7.87 Hz, 1H), 7.68 (t, J=6.55 Hz, 1H), 7.90 (s, 1H).
(M+H) 412. Entry 3j (1H NMR, 300 MHz, MeOD): l 1.27
(t, J=7.13 Hz, 3H), 2.05 (s, 3H), 2.12 (m, 2H), 2.48 (m,
2H), 3.72 (s, 3H), 4.20 (q, J=7.12 Hz, 2H), 4.30 (t,
J=2.20 Hz, 1H), 7.36–7.53 (m, 5H). (M+H) 392. Entry 3k
(1H NMR, 300 MHz, MeOD): l 0.96 (t, J=7.30 Hz, 3H),
1.35 (m, 2H), 1.56 (m, 2H), 2.30 (s, 3H), 3.19 (t, J=7.0
Hz, 2H), 3.73 (s, 3H). (M+H) 226.
9. Typical procedure (3a): 4,5-Diamino-3-methyl-1-phenyl
pyrazole 2a (100 mg, 0.53 mmol) was dissolved in EtOH
(20 mL) followed by the addition of phenyl isocyanate
(63.13 mg, 0.53 mmol). The resulting reaction mixture was
stirred at room temperature for 2 hours. Solvent was
evaporated and the crude residue was purified over prepar-
ative HPLC affording 3a in 50% yield (Rf 0.30, 5%
MeOH-DCM). Spectral data for Table 2. Entry 3a (1H
NMR, 300 MHz, CDCl3): l 2.60 (s, 3H), 6.80–7.55 (m,
10H). (M+H) 308. Entry 3b (1H NMR, 300 MHz, CDCl3):
l 2.31 (s, 3H), 3.79 (s, 3H), 6.83 (d, J=8.5 Hz, 2H), 7.23
(d, J=8.5 Hz, 2H), 7.50–7.60 (m, 5H). (M+H) 338. Entry
3c (1H NMR, 300 MHz, CDCl3): l 2.10 (s, 3H), 3.13 (dd,