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1129, 1063, 1026, 752, 685 cmꢀ1
.
1H NMR (250 MHz, CDCl3)
d ¼ 6.72 (s, 1H, CH), 7.38–7.45 (m, 3H, Ph), 7.50–7.63 (m, 2H,
Ph), 8.00 (br, 1H, NH). 13C NMR (62.9 MHz, CDCl3) d ¼ 101.1,
125.6, 127.9, 129.2, 129.4, 143.2, 143.8, 145.2. MS (EI, 70 eV) m/z
(%): 213(M + 1, 4), 212(M+, 33), 77(62.4), 69(16.5), 50(31.6). Anal.
calcd for C10H7F3N2 (%): C, 56.61; H, 3.33; N, 13.20. Found: C,
56.73; H, 3.28; N, 13.08.
1-(2-Furoyl)-3,5-dimethyl-1H-pyrazole (3n). White solid,
(86%, 0.163 g), mp: 105–106 ꢁC. IR (KBr): 3125, 3100, 2990, 2930,
1680, 1585, 1565, 1460, 1375, 1350, 1275, 1025, 950, 875 cmꢀ1
.
1H NMR (400 MHz, CDCl3) d ¼ 2.10 (s, 3H, CH3), 2.58 (s, 3H,
CH3), 5.83 (s, 1H, CH), 6.39 (dd, 1H, CH), 7.52 (d, 1H, CH), 7.74
(d, 1H, J ¼ 3 Hz, CH). MS (EI, 70 eV) m/z (%): 191(M + 1, 8.7),
190(M+, 33.5), 161(100), 133(28.9), 108(24.5), 94(54). Anal. calcd
for C10H10N2O2 (%): C, 63.15; H, 5.30; N, 14.73. Found: C, 63.45;
H, 5.26; N, 15.18.
Fig. 2 Reusability of catalyst in condensation of pentane-2,4-dione
and PhNHNH2. Reaction time ¼ 4 min.
reaction activated by the catalyst CSA, which results in inter-
mediate 4. Intramolecular nucleophilic addition in 4 catalysed
by CSA gives 5. Finally, dehydration of 5 in the presence of the
catalyst produces the corresponding pyrazole 3 and releases the
catalyst for the next catalytic cycle.50
Recyclability of the catalyst was also examined. To this end,
the catalyst which was recovered from the reaction between
pentane-2,4-dione and PhNHNH2 by ltration was washed
three times with DCM and dried at 80 ꢁC for period of 6 h in a
vacuum oven. The recovered catalyst can be reused four times
in subsequent reactions without any signicant loss in its
activity. The results with the recyclable CSA are summarized
in Fig. 2.
5-Methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one (7a). White
solid, (92%, 0.160 g) mp: 127–128.5 ꢁC (Lit.46 127–129 ꢁC). IR
(KBr): 3050, 2920, 1750, 1585, 1490, 1440, 1380, 1350, 1170,
1140, 910, 810, 760, 750, 680, 640 cmꢀ1 1H NMR (250 MHz,
.
CDCl3) d ¼ 2.19 (s, 3H, CH3), 3.42 (s, 2H, CH2), 7.18 (m, 1H, Ph)
7.37 (m, 2H, Ph) 7.78 (m, 2H, Ph). 13C NMR (62.9 MHz, CDCl3)
d ¼ 17.1, 43.1, 118.9, 125.1, 128.8, 138.0, 156.4, 170.6. MS (EI, 70
eV) m/z (%): 175(M + 1, 4.8), 174(M+, 50), 149(4), 145(6), 142(2),
132(7), 105(26), 91(58), 77(100), 63(41), 50(65), 41(43). Anal.
calcd for C10H10N2O (%): C, 68.95; H, 5.79; N, 16.08. Found: C,
68.42; H, 5.42; N, 15.88.
3-Methyl-1H-pyrazol-5-ol (8a). White solid, (94%, 0.092 g)
mp: 220–222 ꢁC (220–224 ꢁC, CAS no. 108-26-9). IR (KBr): 2200–
3400, 1620, 1564, 1457, 1250, 1195, 985, 765 cmꢀ1. 1H NMR (250
MHz, DMSO) d ¼ 2.07 (s, 3H, CH3), 5.2 (s, 1H), 10.3 (br, 2H, NH
and OH). 13C NMR (62.9 MHz, DMSO) d ¼ 11.5, 89.4, 140.2,
161.6. MS (EI, 70 eV) (m/z, (%): 99(M + 1, 5), 98(M+, 100), 81(1),
69(15), 67(16), 56(12), 40(30). Anal. calcd for C4H6N2O (%): C,
48.97; H, 6.16; N, 28.56. Found: C, 49.09; H, 6.03; N, 28.38.
Ethyl-3-[(2,4-dinitrophenyl)hydrazono]butanoate (11a).
Conclusion
In summary, cellulose sulfuric acid, an efficient, non-toxic,
reusable and solidly supportive biodegradable acid catalyst,
has been prepared and utilized for the synthesis of pyrazole
derivatives by a one-pot coupling reaction of dicarbonyl
compounds and hydrazines/hydrazides. Moreover, the broad
scope, operational simplicity, practicability, and mild reaction
conditions render it an attractive approach for the generation of
different compounds with potential properties for use in
medicinal chemistry programmes.
Light orange solid, (90%, 0.279 g), mp: 88–89 C (Lit.47 88–90
ꢁ
ꢁC). IR (KBr): 3312, 3100, 2985, 1727, 1620, 1596, 1517, 1425,
1365, 1340, 1313, 1278, 1255, 1209, 1180, 1100, 1086, 1030, 920,
837, 743 cmꢀ1. 1H NMR (250 MHz, CDCl3) d ¼ 1.28 (t, 3H, CH3),
2.17 (s, 3H, CH3), 3.48 (s, 2H, CH2), 4.24 (q, 2H, CH2), 7.9 (d, 1H,
Ar), 8.28 (dd, 1H, Ar), 9.10 (d, 1H, Ar), 11.10 (s, 1H, NH). 13C
NMR (62.9 MHz, CDCl3) d ¼ 14.2, 16.2, 44.8, 61.5, 116.6, 123.4,
129.2, 130.0, 138.3, 145.0, 150.8, 169.3. MS (EI, 70 eV) m/z (%):
Selected experimental data
3,5-Dimethyl-1-phenyl-1H-pyrazole (3a). Orange colour 310(M+, 5), 279(2), 264(3), 237(5), 219(12), 196(7), 173(5.6),
liquid, yield 93%. IR (KBr): 3055, 2981, 2959, 2910, 2861, 1597, 167(8), 149(34), 131(14), 115(22), 103(25), 90(29), 76(46), 57(44),
1546, 1492, 1420, 1381, 1366, 1131, 1072, 1020, 977, 911, 779, 41(100). Anal. calcd for C12H14N4O6 (%): C, 46.45; H, 4.55; N,
755, 690 cmꢀ1
.
1H NMR (250 MHz, CDCl3): d ¼ 2.29 (s, 6H, 18.06. Found: C, 45.96; H, 4.39; N, 18.37.
2CH3), 5.99 (s, 1H, CH), 7.34 (m, 5H, Ph). 13C NMR (62.9 MHz,
Ethyl-3-(acetyl hydrazono)butanoate (14a). White solid,
CDCl3): d 12.4, 13.5, 106.9, 124.7, 127.2, 129.0, 139.4, 139.9, (88%, 0.164 g), mp: 88–90 ꢁC (Lit.48 89 ꢁC). IR (KBr): 3190, 2980,
148.9. MS (EI, 70 eV) m/z (%): 172(M+, 38), 130(20), 118(18), 2930, 1725, 1680, 1460, 1380, 1330, 1260, 1190, 1120, 1030, 870,
105(28), 91(18), 77(100), 65(25), 56(18), 51(48), 43(67). Anal. 730, 620 cmꢀ1 1HNMR (250 MHz, CDCl3) d ¼ 1.24 (t, J ¼ 7.3 Hz,
calcd for C11H12N2 (%): C, 76.71; H, 7.02; N, 16.27. Found: C, 3H, CH3), 1.92 (s, 3H, CH3), 2.20 (s, 3H, CH3), 3.26 (s, 2H, CH2),
76.58; H, 7.15; N, 16.32.
4.13 (q, 2H, J ¼ 7.3 Hz, CH2), 9.33 (s, 1H, NH). MS (EI, 70 eV) m/z
5-Phenyl-3-(triuoro methyl)-1H-pyrazole (3h). White solid, (%): 187(M + 1, 1), 186(M+, 10), 171(2), 144(9), 113(3), 98(100),
(93%, 0.197 g), mp: 121–122 ꢁC (Lit.49 120–121 ꢁC). IR (KBr): 70(28), 57(11.0), 54(11), 42(26). Anal. calcd for C8H14N2O3 (%):
3298, 3075, 2974, 1638, 1565, 1492, 1443, 1335, 1246, 1160, C, 51.60; H, 7.58; N, 15.04. Found: C, 51.64; H, 7.55; N, 15.09.
61198 | RSC Adv., 2014, 4, 61193–61199
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