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LETTER
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References and Notes
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(31) All pyrazoles exhibited satisfactory characterization data,
including 1H NMR, 13C NMR, IR, MS and HRMS.
(32) Qualitative NOESY effects were seen for 1,3-disubstituted
pyrazoles (Table 4, entries 1, 6 and 8) between the aryl
ortho-methine resonances and the pyrazole methine signals,
the latter of which were well separated (see ref. 3) in
chemical shift in the 1H NMR spectrum of both pyrazole
regioisomers. The 5-ethyl-trisubstituted pyrazole (entry 4)
showed NOESY effects between the aryl ortho-methine
resonances and the methylene protons.
(33) 1,3-Diphenylpyrazole (3): mp 81–83 °C (lit.35 mp 84–
85 °C); Rf = 0.61 (CH2Cl2). HRMS: m/z [MH+] calcd for
C15H13N2: 221.1073; found: 221.1074 [MH+]. IR (nujol):
nmax = 1598, 1526, 1504, 1360, 1264, 1114, 1061, 1046, 954,
755, 686 cm–1. UV (CH2Cl2): lmax (e) = 284 (17959), 224
(6189) nm. 1H NMR (400 MHz, CDCl3): d = 7.89 (1 H, d,
J = 2.5 Hz, 5-H), 7.85 (2 H, m, PhH), 7.71 (2 H, m, PhH),
7.38 (4 H, PhH), 7.24 (2 H, m, PhH), 6.71 (1 H, d, J = 2.5
Hz, 4-H) ppm. 13C NMR (100 MHz, CDCl3): d = 153.3 (C),
140.6 (C), 133.5 (C), 129.8 (CH), 129.1 (CH), 128.5 (CH),
128.4 (CH), 126.7 (CH), 126.2 (CH), 119.5 (CH), 105.4
(CH) ppm. MS (APCI): m/z (%) = 221 (100) [MH+], 194 (5),
118 (10).
(34) 1,5-Diphenylpyrazole (4): mp 52–55 °C (lit.35 mp 55–
56 °C); Rf = 0.18 (CH2Cl2). HRMS: m/z [MH+] calcd for
C15H13N2: 221.1073; found: 221.1072 [MH+]. IR (nujol):
nmax = 1596, 1541, 1502, 1450, 1385, 1224, 1158, 1130,
1068, 960, 761, 695 cm–1. UV (CH2Cl2): lmax (e) = 252
(14493). 1H NMR (400 MHz, CDCl3): d = 7.66 (1 H, d,
J = 1.5 Hz, 3-H), 7.28–7.22 (8 H, PhH), 7.19–7.15 (2 H, m,
PhH), 6.45 (1 H, d, J = 1.5 Hz, 4-H) ppm. 13C NMR (100
MHz, CDCl3): d = 143.0 (C), 140.3 (CH), 140.1 (C), 130.6
(CH), 128.9 (CH), 128.8 (CH), 128.5 (CH), 128.2 (CH),
127.4 (CH), 125.2 (CH), 107.9 (CH) ppm. MS (APCI):
m/z (%) = 221 (100) [MH+], 194 (10), 152 (5), 103 (5).
(35) Auwers, K. v.; Schmidt, W. Ber. Dtsch. Chem. Ges. 1925,
58, 528.
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(25) Engelmann, A.; Kirmse, W. Chem. Ber. 1973, 106, 3092.
(26) Coispeau, G.; Elguero, J. Bull. Soc. Chim. Fr. 1970, 2717.
Synlett 2007, No. 5, 704–708 © Thieme Stuttgart · New York