JOURNAL OF CHEMICAL RESEARCH 2007 703
C, 65.51; H, 3.53; N, 10.91; Found: C, 65.60; H, 3.47; N, 10.85%.
3-Methyl-10H-isoxazolo[5,4-a]carbazole (4e): White amorphous
powder (65%), m.p. 198–200°C. IR: νmax 3376, 2923, 1642, 1575,
1440 cm‑1. NMR: δH 8.70 (br s, 1H, N10‑H), 8.18–8.13 (d, 1H, C6‑
H, J = 7.84 Hz), 8.04–7.99 (d, 1H, C5‑H, J = 8.24 Hz), 7.62–7.58 (d,
1H, C9‑H, J = 8.08 Hz), 7.54–7.49 (m,1H, C8‑H), 7.44–7.41 (d, 1H,
C4‑H, J = 8.24 Hz), 7.36–7.32 (m,1H, C7‑H), 2.68 (s, 3H, C3‑CH3);
δC 157.2, 145.1, 135.0, 134.6, 130.3, 127.4, 121.6, 120.4, 117.9,
110.6, 108.3, 106.0, 105.1 (13 aromatic C), 21.4 (C3‑CH3). MS:
m/z (%) 222 (18). Anal. Calcd. for C14H10N2O: C, 75.66; H, 4.54; N,
12.60; Found: C, 75.76; H, 4.49; N, 12.64%.
C15H13N3: C, 76.57; H, 5.57; N, 17.86; Found: C, 76.59; H, 5.60; N,
17.9%.
3,7-Dimethyl-1,4,5,10-tetrahydropyrazolo[3,4-a]carbazole (6c):
White powder (15%), m.p. 187–189°C. IR: νmax 3253, 2923, 1628,
1574, 1445 cm‑1. NMR: δH 12.49 (br s, 1H, N1‑H),11.07 (br s, 1H,
N10‑H), 7.92 (s, 1H, C6‑H), 7.50–7.38 (d, 1 H, C9‑H, J = 8.48 Hz),
7.50–7.38 (d, 1H, C8‑H, J = 8.48 Hz), 2.79–2.61 (m, 2H, C5‑H2),
2.60–2.51 (m, 2H, C4‑H2), 2.45 (s, 3H, C7‑CH3), 2.05 (s, 3H, C3‑
CH3); δC 148.1, 144.0, 135.1, 132.6, 123.1, 122.8, 118.6, 118.1, 112.5,
109.4, 105.7 (11 aromatic C), 26.7 (C7‑CH3), 22.4 (C5), 20.9 (C4),
19.4 (C3‑CH3). MS: m/z (%) 237 (28). Anal. Calcd. for C15H15N3: C,
75.92; H, 6.37; N, 17.71; Found: C, 75.67; H, 6.29; N, 17.68%.
7-Chloro-1,10-dihydro-3-methylpyrazolo[3,4-a]carbazole (5d):
White powder (70%), m.p. 167–169°C. IR: νmax 3234, 2920, 1618,
1572, 1440 cm‑1. NMR: δH, 12.34 (br s, 1H, N1‑H), 11.56 (br s,
1H, N10‑H), 7.84–7.80 (d, 1H, C5‑H, J = 8.54 Hz), 7.68–7.64 (d,
1H, C4‑H, J = 8.54 Hz), 7.49–7.48 (d, 1H, C6‑H, Jmeta = 1.90 Hz),
7.32–7.28 (d, 1H, C9‑H, J = 8.52 Hz), 7.03–6.98 (dd, 1H, C8‑H,
Jortho = 8.52, Jmeta = 1.90 Hz), 2.20 (s, 3H, C3‑CH3); δC 143.9, 140.4,
138.2, 137.1, 128.4, 126.6, 123.7, 120.1, 118.9, 114.4, 112.6, 110.1,
109.1 (13 aromatic C), 23.7 (C3‑CH3). MS: m/z (%) 255 (26). Anal.
Calcd. for C14H10ClN3: C, 65.76; H, 3.94; N, 16.43; Found: C, 65.89;
H, 3.90; N, 16.40%.
7-Chloro-3-methyl-1,4,5,10-tetrahydropyrazolo[3,4-a]carbazole
(6d): White powder (12%), m.p. 172–174°C. IR: νmax KBr, 3218,
2923, 1627, 1579, 1440 cm‑1. NMR: δH 12.32 (br s, 1H, N1‑H),
11.57 (br s, 1H, N10‑H), 7.47 (s, 1H, C6‑H), 7.32–7.25 (d, 1H, C9‑H,
J = 8.48 Hz), 7.03–6.96 (d, 1H, C8‑H, J = 8.48 Hz), 2.90–2.83 (m,
2H, C5‑H2), 2.73–2.67 (m, 2H, C4‑H2), 2.19 (s, 3H, C3‑CH3); δC,
146.0, 141.9, 134.7, 130.9, 128.1, 120.6, 118.0, 115.1, 114.1, 112.9,
109.4 (11 aromatic C), 26.4 (C5), 22.3 (C4), 21.0 (C3‑CH3). MS:
m/z (%) 237 (28). Anal. Calcd. for C14H12ClN3: C, 65.25; H, 4.69; N,
16.30; Found: C, 65.05; H, 4.73; N, 16.39%.
Reaction of 2-acetyl-2,3,4,9-tetrahydro-1H-carbazol-1-ones (3a-e)
with hydrazine hydrate: General procedure
To the appropriate 2‑acetyl‑2,3,4,9‑tetrahydro‑1H‑carbazol‑1‑one
(3, 1 mmol) in glacial acetic acid (15 ml) was added hydrazine
hydrate (2 mmol) and the whole was refluxed on an oil bath for 1 h.
The reaction was monitored by TLC. After completion of the reaction
the mixture was poured onto crushed ice. The precipitate was
collected, washed with water, and dried. It was purified by column
chromatography over silica gel using petroleum ether/ethyl acetate
(successively 98:2 and 85:15) as eluant. The former fraction yielded
the respective 1,10‑dihydro‑3‑methylpyrazolo[3,4‑a]carbazole (5),
the latter the respective 3‑methyl‑1,4,5,10‑tetrahydropyrazolo[3,4‑
a]carbazole (6).
1,10-Dihydro-3,9-dimethylpyrazolo[3,4-a]carbazole (5a): White
powder (75%), m.p. 142–144°C. IR: νmax 3275, 2934, 1630, 1574,
1458 cm‑1. NMR: δH 12.00 (br s, H, N1‑H), 11.12 (br s, 1H, N10‑
H), 7.89–7.83 (d, 1H, C6‑H, J = 8.84 Hz), 7.73–7.66 (d, 1H, C5‑H,
J = 8.48 Hz), 7.36–7.29 (d, 1H, C4‑H, J = 8.48 Hz), 7.14–7.08 (d, 1H,
C8‑H, J = 7.00 Hz), 7.07–7.01 (m, 1H, C7‑H), 2.55 (s, 3H, C9‑CH3),
2.49 (s, 3H, C3‑CH3); δC 142.1, 139.4, 132.3, 129.9, 128.7, 127.6,
122.3, 120.1, 118.9, 117.8, 116.3, 111.3, 107.5 (13 aromatic C), 20.7
(C9‑CH3), 18.6 (C3‑CH3). MS: m/z (%) 235 (42). Anal. Calcd. for
C15H13N3: C, 76.57; H, 5.57; N, 17.86; Found: C, 76.60; H, 5.51; N,
17.82%.
3,9-Dimethyl-1,4,5,10-tetrahydropyrazolo[3,4-a]carbazole (6a):
White powder (15%), m.p. 168–170°C. IR: νmax 3253, 2923, 1624,
1576, 1446 cm‑1. NMR: δH 12.05 (br s, 1H, N1‑H),11.13 (br s, 1H,
N10‑H), 7.90–7.82 (d, 1H, C6‑H, J = 8.00 Hz), 7.19–7.01 (m, 2H,
C7, C8‑H), 3.00–2.89 (m, 2H, C5‑H2), 2.82–2.70 (m, 2H, C4‑H2),
2.57 (s, 3H, C9‑CH3), 2.23 (s, 3H, C3‑CH3); δC 142.8, 138.1, 130.7,
128.9, 124.1, 120.1, 119.0, 118.1, 114.3, 111.9, 108.4 (11 aromatic
C), 28.7 (C9‑CH3), 24.4 (C5), 21.8 (C4), 20.7 (C3‑CH3). MS: m/z
(%) 237 (40). Anal. Calcd. for C15H15N3: C, 75.92; H, 6.37; N, 17.71;
Found: C, 76.03; H, 6.32; N,17.76%.
1,10-Dihydro-3,8-dimethylpyrazolo[3,4-a]carbazole (5b): Pale
yellow powder (80%), m.p. 164–166°C. IR: νmax 3274, 2923, 1628,
1574, 1440 cm‑1. NMR: δH 12.43 (br s, 1H, N1‑H), 11.17 (br s, 1H,
N10‑H), 8.01–7.96 (d, 1H, C5‑H, J = 7.92 Hz), 7.77–7.72 (d, 1H,
C6‑H, J = 8.46 Hz), 7.45 (s, 1H, C9‑H), 7.40–7.35 (d, 1H, C7‑H,
J = 8.46 Hz), 7.05–7.00 (d, 1H, C4‑H, J = 7.92 Hz), 2.37 (s, 3H, C8‑
CH3), 2.20 (s, 3H, C3‑CH3); δC 144.3, 138.5, 136.1, 130.9, 129.0,
128.1, 124.4, 122.1, 120.9, 114.3, 112.3, 108.4, 107.0 (13 aromatic
C), 24.7 (C8‑CH3), 22.6 (C3‑CH3). MS: m/z (%) 235 (32). Anal.
Calcd. for C15H13N3: C, 76.57; H, 5.57; N, 17.86; Found: C, 76.67;
H, 5.63; N, 17.71%.
3,8-Dimethyl-1,4,5,10-tetrahydropyrazolo[3,4-a]carbazole (6b):
Pale yellow powder (10%), m.p. 150–152°C. IR: νmax 3250, 2919,
1630, 1576, 1440 cm‑1. NMR: δH 12.43 (br s, 1H, N1‑H), 11.29 (br s,
1H, N10‑H), 7.40 (s, 1H, C9‑H), 7.04–6.95 (m, 2H, C6, C7‑H),
2.61–2.51 (m, 4H, C4‑H2, C5‑H2), 2.40 (s, 3H, C8‑CH3), 2.20
(s, 3H, C3‑CH3); δC 146.4, 140.7, 135.1, 129.9, 122.8, 120.4, 118.0,
116.1, 113.3, 112.5, 106.9 (11 aromatic C), 28.0 (C8‑CH3), 25.7 (C5),
22.6 (C4), 19.7 (C3‑CH3). MS: m/z (%) 237 (28). Anal. Calcd. for
C15H15N3: C, 75.92; H, 6.37; N, 17.71; Found: C, 75.99; H, 6.31; N,
17.65%.
1,10-Dihydro-3,7-dimethylpyrazolo[3,4-a]carbazole (5c): Needles
(65%), m.p. 157–159°C. IR: νmax 3354, 2947, 1630, 1564, 1449 cm‑1.
NMR: δH 12.47 (br s, 1H, N1‑H), 11.04 (br s, 1H, N10‑H), 7.91
(s, 1H, C6‑H), 7.81–7.71 (d, 1H, C5‑H, J = 8.24 Hz), 7.61–7.51
(d, 1H, C4‑H, J = 8.24 Hz), 7.43–7.34 (d, 1H, C9‑H, J = 8.00 Hz),
7.24–7.15 (d, 1H, C8‑H, J = 8.00 Hz), 2.57 (s, 3H, C7‑CH3), 2.49
(s, 3H, C3‑CH3); δC 145.1, 138.6, 136.8, 131.5, 130.4, 127.6, 123.9,
120.4, 118.9, 116.9, 110.3, 108.4, 105.6 (thirteen aromatic C), 26.7
(C7‑CH3), 21.6 (C3‑CH3). MS: m/z (%) 235 (52). Anal. Calcd. for
1,10-Dihydro-3-methylpyrazolo[3,4-a]carbazole (5e): White
powder (68%), m.p. 150–152°C. IR: νmax 3216, 2923, 1627, 1580,
1444 cm‑1. NMR: δH 12.45 (br s, 1H, N1‑H), 11.32 (br s, 1H,
N10‑H), 8.14–8.08 (d, 1H, C5‑H, J = 7.92 Hz), 7.81–7.77(d, 1H, C9‑
H, J = 8.52 Hz), 7.67–7.62 (d, 1H C6‑H, J = 7.96 Hz), 7.32–7.28 (d,
1H, C4‑H, J = 7.92 Hz), 7.05–6.93 (m, 2H, C7, C8‑H), 2.20 (s, 3H,
C3‑CH3); δC 148.0, 144.2, 132.1, 131.9, 127.4, 127.3, 124.4, 124.1,
120.1, 118.9, 112.3, 110.4, 109.4 (13 aromatic C), 21.8 (C3‑CH3).
MS: m/z (%) 221 (46). Anal. Calcd. for C14H11N3: C, 76.00; H, 5.01;
N, 18.99; Found: C, 75.89; H, 5.01; N, 19.03%.
3-Methyl-1,4,5,10-tetrahydropyrazolo[3,4-a]carbazole
(6e):
White powder (15%), m.p. 190–192°C. IR: νmax 3218, 2923, 1627,
1579, 1440 cm‑1. NMR: δH 12.23 (br s, 1H, N1‑H), 11.33 (br s, 1H,
N10‑H), 7.45–7.40 (d, 1H, C9‑H, J = 7.60 Hz), 7.32–7.26 (d, 1H,
C6‑H, J = 7.88 Hz), 7.04–6.93 (m, 2H, C7, C8‑H), 2.92–2.84 (m, 2H,
C5‑H2), 2.73–2.67 (m, 2H, C4‑H2), 2.19 (s, 3H, C3‑CH3); δC 148.9,
144.3, 132.4, 129.9, 122.7, 120.1, 119.3, 118.0, 116.1, 111.9, 109.4
(11 aromatic C), 26.4 (C5), 24.3 (C4), 22.0 (C3‑CH3). MS: m/z (%)
223 (35). Anal. Calcd. for C14H13N3: C, 75.31; H, 5.87; N, 18.82;
Found: C, 75.51; H, 5.86; N, 18.88%.
Reaction of 2-acetyl-2,3,4,9-tetrahydro-1H-carbazol-1-ones (3a-e)
with semicarbazide hydrochloride: General procedure
To the appropriate 2‑acetyl‑2,3,4,9‑tetrahydro‑1H‑carbazol‑1‑one
(3, 1 mmol) in glacial acetic acid (15 ml) was added semicarbazide
hydrochloride (2 mmol) and the solution was refluxed on an oil bath
for 1 h. The reaction was monitored by TLC. After the completion
of the reaction it was poured onto crushed ice. The precipitate was
filtered off, washed with water and dried. It was purified by column
chromatography over silica gel using petroleum ether/ethyl acetate
(98:2 to get the respective 1,10‑dihydro‑3‑methylpyrazolo[3,4‑a]
carbazole (5).
1,10-Dihydro-3,9-dimethylpyrazolo[3,4-a]carbazole (5a): White
powder (80%).
1,10-Dihydro-3,8-dimethylpyrazolo[3,4-a]carbazole (5b): Pale
yellow powder (75%).
1,10-Dihydro-3,7-dimethylpyrazolo[3,4-a]carbazole (5c): Needles
(78%).
7-Chloro-1,10-dihydro-3-methylpyrazolo[3,4-a]carbazole (5d):
White powder (65%).
1,10-Dihydro-3-methylpyrazolo[3,4-a]carbazole (5e): White
powder (75%).
PAPER: 07/4859