3-Aryl- and 2,3-diaryl-4-oxo-4,5,6,7-tetrahydro-indazoles. 1. Reactions of phenyl- and tosyl-hydrazones of dimedone and cyclohexane-1,3-dione with substituted benzaldehydes

Article abstract of DOI:10.1007/s10593-006-0009-2

Sixteen 3-aryl-4-oxo-2-phenyl-4,5,6,7-tetrahydroindazoles were obtained from the reaction of the phenylhydrazones of dimedone and cyclohexane-1,3-dione with 3-bromo-, 4-bromo-, 4-chloro-, 4-fluoro-, 2-hydroxy-, 4-hydroxy-, 4-methoxy-, 2-nitro-, 3-nitro-,

Full text of DOI:10.1007/s10593-006-0009-2

Chemistry of Heterocyclic Compounds, Vol. 41, No. 11, 2005
3-ARYL- AND 2,3-DIARYL-4-OXO-4,5,6,7-TETRAHYDRO-
INDAZOLES. 1. REACTIONS OF PHENYL- AND TOSYL-
HYDRAZONES OF DIMEDONE AND CYCLOHEXANE-
1,3-DIONE WITH SUBSTITUTED BENZALDEHYDES
I. Strakova, A. Strakovs, and M. Petrova
Sixteen 3-aryl-4-oxo-2-phenyl-4,5,6,7-tetrahydroindazoles were obtained from the reaction of the
phenylhydrazones of dimedone and cyclohexane-1,3-dione with 3-bromo-, 4-bromo-, 4-chloro-,
4-fluoro-, 2-hydroxy-, 4-hydroxy-, 4-methoxy-, 2-nitro-, 3-nitro-, 4-nitro-, and 4-dimethylamino-
benzaldehydes. The interaction of the tosylhydrazones of dimedone and cyclohexane-1,3-dione with the
substituted benzaldehydes gave thirteen 3-aryl-4-oxo-4,5,6,7-tetrahydroindazoles.
Keywords: 3-aryl- and 2,3-diaryl-4-oxo-4,5,6,7-tetrahydroindazoles, substituted benzaldehydes, phenyl-
and tosylhydrazones of cyclohexane-1,3-diones.
In continuation of studies on the modification of hydrogenated indazoles and quinazolines, mainly in
their carbocyclic structural fragment [1-5], we have turned to the synthesis of 3-aryl-4-oxo-4,5,6,7-
tetrahydroindazoles. Two schemes are known for their synthesis. One is the interaction of enehydrazines,
obtained from cyclohexane-1,3-diones and benzenesulfonic acid hydrazide, with aromatic aldehydes [6], and the
other is the interaction of 2-benzoylcyclohexane-1,3-diones with hydrazines [7]. 2,3-Diaryl-4-oxo-4,5,6,7-
tetrahydroindazoles are obtained by the interaction of phenylhydrazones of cyclohexane-1,3-diones with
aromatic aldehydes [8] and by the reaction of 2,3-diphenyl-1,3,4-oxadiazolium perchlorate with dimedone [9].
We selected the reaction of 3-enehydrazino-2-cyclohexen-1-ones with aromatic aldehydes for the
synthesis of 3-aryl- and 2,3-diaryl-4-oxo-4,5,6,7-tetrahydroindazoles [6, 8]. Such a selection was made, in spite
of the extremely large number of known 2-aroylcyclohexane-1,3-diones [10-13] many of which are herbicides,
because of the simplicity of the synthesis and the availability of a wide selection of aldehydes.
In the present work 16 new 2,3-diaryl-4-oxo-4,5,6,7-tetrahydroindazoles 6 were synthesized by the
reaction of phenylhydrazones of dimedone 2,3A and cyclohexane-1,3-dione 2,3B with substituted
benzaldehydes 4.
It was shown previously [8] that on boiling the reactants in alcohol for 15 min pyrazolines of type 5 are
formed predominantly with only a little of their dehydrogenation products 6. However the procedure for
separating these compounds is complex, and in addition pyrazolines 5 are unstable. We selected more rigid
reaction conditions, heating a solution of equimolar quantities of reactants in DMSO at 100°C for 3-4 h, which
leads to the formation of compounds 6 exclusively (Table 1).
__________________________________________________________________________________________
Riga Technical University, Riga LV-1658, Latvia; e-mail: marina@osi.lv. Translated from Khimiya
Geterotsiklicheskikh Soedinenii, No. 11, pp. 1662-1668, November 2005. Original article submitted March 22,
2001; revision submitted September 10, 2003.
1398
0009-3122/05/4111-1398©2005 Springer Science+Business Media, Inc.

H
N
R
R
R
R
OH
H2NNHPh
N
H
Ph
O
O
2
1
H2NNHTs
H
N
R
R
R
R
N
Ts
N
H
N
Ph
H
O
O
3
7
ArCHO
ArCHO
4
4
R
N
N
R
H
N
R
R
Ph
N
Ts
O
Ar
O
Ar
5
8
– HSO2C6H4Me
R
N
N
R
Ph
R
H
N
R
R
O
Ar
N
R
6
N
NH
O
Ar
O
Ar
9
10
1-10 A R = Me, B R =H; 4-6, 8, 9 a Ar = 3-BrC6H4, b Ar = 4-BrC6H4, c Ar = 4-C6H4Cl,
d Ar = 4-C6H4F, e Ar = 2-C6H4OH, f Ar = 4-C6H4OH, g Ar = 4-C6H4OMe,
h Ar = 2-C6H4NO2, i Ar = 3-C6H4NO2, j Ar = 4-C6H4NO2, k Ar = 4-C6H4NMe2
1
The structures of diarylindazoles 6 were confirmed by data of H NMR and IR spectra. The absorption
band of the carbonyl group of 4-oxo-4,5,6,7-tetrahydroindazoles 6 appeared at 1656-1671 cm-1. In the 1H NMR
spectra signals were detected for the protons of all the structural fragments of indazoles 6 (Table 2).
We also used the known reaction [6] of arylhydrazones with aldehydes for the synthesis of 3-aryl-4-oxo-
4,5,6,7-tetrahydroindazoles 9 unsubstituted at the nitrogen atom. We used enehydrazines 7, obtained from
cyclohexanediones 1 and the readily available tosylhydrazine. On heating enehydrazines 7 with aromatic
aldehydes in DMSO in the presence of piperidine acetate and an excess of piperidine, fission of toluenesulfonic
acid also occurs under the action of the latter and indazoles 9 are formed. We obtained 13 new 3-arylindazoles
by this procedure, for which a structure of both N(1)–H(9) and N(2)–H(10) derivatives is possible. In [6] a preference
was given for the 2H structure without material proof.
The spectroscopic data on indazoles 9 and 10 (νCO 1621-1632, νNH 3050-3150 cm-1, δNH 9.25-13.40 ppm)
do not permit rejection of either of the tautomeric forms 9 and 10. However the results of the alkylation and
acylation of this indazole [14-16], leading to a mixture of the N(1)- and N(2)-substituted derivatives, indicate only
the real existence of a tautomeric equilibrium.
1399

TABLE 1. Characteristics of the Synthesized Compounds
Found, %
Calculated, %
——————
Com-
pound
Empirical
formula
mp, °С
Yield, %
C
H
N
Hal, S
6Aa
6Ab
6Ac
6Ad
6Af
6Ag
6Ah
6Ai
6Aj
6Ak
6Bb
6Bc
6Bd
6Be
6Bg
6Bk
7A
C21H19BrN2O
C21H19BrN2O
C21H19ClN2O
C21H19FN2O
C21H20N2O2
C22H22N2O2
C21H19N3O3
C21H19N3O3
C21H19N3O3
C23H25N3O
63.60
63.81
63.66
63.81
71.66
71.89
75.20
75.43
75.95
75.88
76.05
76.27
69.90
69.79
69.71
69.79
69.58
69.79
77.11
77.28
62.01
62.14
70.52
70.70
74.40
74.49
74.77
74.98
75.22
75.45
76.17
76.10
4.70
4.84
4.77
4.84
5.25
5.46
5.63
5.73
6.00
6.07
6.39
6.40
5.22
5.30
5.21
5.30
5.26
5.30
6.33
6.49
4.10
4.12
4.55
4.68
4.98
4.94
5.18
5.30
5.66
5.70
6.30
6.39
6.91
7.09
6.96
7.09
7.90
7.98
8.18
8.38
8.20
8.43
7.88
8.09
11.50
11.63
11.61
11.63
11.53
11.63
11.64
11.76
7.50
7.63
8.56
8.68
9.00
9.14
9.01
9.20
8.70
8.80
12.51
12.68
20.00
22.22
20.10
22.22
10.00
10.10
118-119
182-183
173
46
52
61
57
54
65
28
45
51
47
55
54
49
41
47
45
88
84
165
252-253
140-141
175-176
167-168
184-186
201-203
190-192
191-192
133-134
108-110
148-149
173-174
215-216
213-214
C19H15BrN2O
C19H15ClN2O
C19H15FN2O
C19H16N2O2
C20H18N2O2
C21H21N3O
21.50
21.76
10.80
10.98
C15H20N2O3S
C13H16N2O3S
58.18
58.42
55.46
55.70
6.60
6.54
5.60
5.75
8.87
9.08
10.11
9.99
10.20
10.40
11.20
11.44
7B
9Ab
9Ad
9Ae
9Af
9Ag
9Aj
9Ak
9Bb
9Bc
9Bd
9Bf
C15H15BrN2O
C15H15FN2O
C15H16N2O2
C15H16N2O2
C16H18N2O2
C15H15N3O3
C17H21N3O
56.20
56.44
69.61
69.75
70.10
70.29
70.33
70.29
71.20
71.09
62.96
63.15
71.81
72.05
53.50
53.63
63.10
63.29
67.61
67.81
68.21
68.41
69.17
69.40
4.66
4.74
5.80
5.85
6.13
6.29
6.20
6.29
6.70
6.71
5.11
5.30
7.37
7.47
3.73
3.81
4.42
4.50
4.70
4.82
5.17
5.30
5.72
5.82
8.59
8.78
10.66
10.84
10.88
10.93
10.85
10.93
10.19
10.36
14.55
14.73
14.70
14.83
9.49
9.62
11.11
11.35
11.98
12.17
12.09
12.27
11.35
11.56
24.80
25.04
244-245
198-199
246-247
254-256
198-200
280-282
216-218
260-262
252-254
210-212
264-265
216-217
253-255
78
76
78
61
75
75
81
77
72
70
78
63
70
C13H11BrN2O
C13H11ClN2O
C13H11FN2O
C13H12N2O2
C14H14N2O2
C15H17N3O
27.20
27.45
14.10
14.37
9Bg
9Bk
70.50
70.56
6.59
6.71
16.23
16.46
1400

TABLE 2. IR and 1H NMR Spectra of the Synthesized Compounds
IR spectrum,
Com-
pound
1Н NMR spectrum, δ, ppm (J, Hz)*
ν, cm-1
1
2
3
6Aa
6Ab
6Ac
6Ad
6Af
1670
1668
1.11 (6H, s, 2CH3); 2.40 (2H, s, CH2); 2.85 (2H, s, CH2);
7.18-7.56 (9H, m, C6H5, C6H4)
1.09 (6H, s, 2CH3); 2.41 (2H, s, CH2); 2.81 (2H, s, CH2);
7.01-7.16 (9H, m, C6H5, C6H4)
1665
1671
1.12 (6H, s, 2CH3); 2.41 (2H, s, CH2); 2.81 (2H, s, CH2);
7.30-7.32 (9H, m, C6H5, C6H4)
1.07 (6H, s, 2CH3); 2.42 (2H, s, CH2); 2.78 (2H, s, CH2);
6.99-7.41 (9H, m, C6H5, C6H4)
1.16 (6H, s, 2CH3); 2.36 (2H, s, CH2); 2.81 (2H, s, CH2);
6.78 (2H, m, 3J = 8, C6H4); 7.24-7.26 (5H, m, С6Н5);
7.25 (2H, m, 3J = 8, C6H4); 8.09 (1Н, br. s, ОН)
1665;
3400-3250
6Ag
1666
1.09 (6H, s, 2CH3); 2.41 (2H, s, CH2); 2.81 (2H, s, CH2);
3.78 (3H, s, OCH3); 6.82 (2H, m, 3J = 8, C6H4);
7.28-7.30 (7H, m, C6H4, С6Н5)
6Ah
6Ai
6Aj
1661
1656
1667
1.07 (6H, s, 2CH3); 2.31 (2H, s, CH2); 2.82 (2H, s, CH2);
7.25-8.15 (9H, m, C6H4, С6Н5)
1.16 (6H, s, 2CH3); 2.42 (2H, s, CH2); 2.86 (2H, s, CH2);
7.15-8.16 (9H, m, C6H4, С6Н5)
1.11 (6H, s, 2CH3); 2.41 (2H, s, CH2); 2.81 (2H, s, CH2);
7.28-7.30 (5H, m, C6H5); 7.53 (2H, m, 3J = 8, C6H4);
8.14 (2H, m, 3J = 8, C6H4)
6Ak
1662
1.16 (6H, s, 2CH3); 2.44 (2H, s, CH2); 2.82 (2H, s, CH2);
2.89 (6H, s, N(CH3)2); 6.62 (2H, m, 3J = 8, C6H4);
7.28-7.30 (7H, m, C6H5, C6H4)
6Bb
6Bс
6Bd
6Be
6Bg
1660
1664
1667
2.16 (2H, m, CH2); 2.52 (2H, t, 3J = 7, CH2); 2.91 (2H, t, 3J = 7, CH2);
7.29-7.33 (9H, m, C6H5, C6H4)
2.15 (2H, m, CH2); 2.51 (2H, t, 3J = 7, CH2); 2.92 (2H, t, 3J = 7, CH2);
7.34-7.36 (9H, m, C6H5, C6H4)
2.15 (2H, m, CH2); 2.50 (2H, t, 3J = 6.5, CH2); 2.95 (2H, t, 3J = 6.5, CH2);
7.15-7.35 (9H, m, C6H5, C6H4)
2.17 (2H, m, CH2); 2.54 (2H, t, 3J = 6.5, CH2); 2.92 (2H, t, 3J = 6.5, CH2);
6.59-7.29 (9H, m, C6H5, C6H4); 8.45 (1H, br. s, OH)
1660;
3400-3250
1664
2.17 (2H, m, CH2); 2.52 (2H, t, 3J = 6.5, CH2); 2.92 (2H, t, 3J = 6.5, CH2);
3.73 (3H, s, OCH3); 6.89 (2H, m, 3J = 9, С6Н4);
7.24-7.26 (7Н, m, С6Н5, С6Н4)
6Bk
7A
1668
2.15 (2H, m, CH2); 2.53 (2H, t, 3J = 6.5, CH2); 2.89 (2H, t, 3J = 6.5, CH2);
2.90 (6H, s, N(CH3)2); 6.59 (2H, m, 3J = 9, С6Н4);
7.19 (2H, m, 3J = 9, С6Н4); 7.28-7.30 (5Н, m, С6Н5)
1600;
3250-3150
0.92 (6H, s, 2CH3); 1.90 (2H, s, CH2); 2.05 (2H, s, CH2);
2.37 (3H, s, CH3); 5.05 (1H, s, =CH-); 7.40 (2H, m, 3J = 6, С6Н4);
7.71 (2Н, m, 3J = 6, С6Н4); 8.62 (1H, br. s, NH); 9.74 (1H, br. s, NH)
7B
1595;
3250-3150
1.61-2.27 (6H, m, 3CH2); 2.41 (3H, s, CH3); 5.07 (1H, s, =CH-);
7.40 (2H, m, 3J = 6, С6Н4); 7.69 (2Н, m, 3J = 6, С6Н4);
8.59 (1H, br. s, NH); 9.70 (1H, br. s, NH)
9Ab
9Ad
9Ae
9Af
1626; 3100
1.01 (6H, s, 2CH3); 2.37 (2H, s, CH2); 2.81 (2H, s, CH2);
7.54 (2H, m, 3J = 8.5, С6Н4); 7.87 (2Н, m, 3J = 8.5, С6Н4);
9.25 (1H, br. s, NH)
1621;
3140-3080
1.03 (6H, s, 2CH3); 2.36 (2H, s, CH2); 2.49 (2H, s, CH2);
6.96-7.17 (2H, m, С6Н4); 7.86-8.06 (2Н, m, С6Н4);
11.16 (1H, br. s, NH)
1623;
3400, 3120
1.11 (6H, s, 2CH3); 2.45 (2H, s, CH2); 2.76 (2H, s, CH2);
6.83-7.34 (3H, m, С6Н4); 8.76-8.78 (1Н, m, С6Н4);
10.98 (2H, br. s, NH, OH)
1620;
3450, 3100
1.00 (6H, s, 2CH3); 2.34 (2H, s, CH2); 2.68 (2H, s, CH2);
6.78 (2H, m, 3J = 9, С6Н4); 7.93 (2Н, m, 3J = 9, С6Н4);
9.80 (1H, br. s, NH); 12.37 (1H, br. s, OH)
1401

TABLE 2 (continued)
1
2
3
9Ag
1630;
3150-3050
1.07 (6H, s, 2CH3); 2.34 (2H, s, CH2); 2.74 (2H, s, CH2);
3.82 (3H, s, OCH3); 6.92 (2H, m, 3J = 8.5, С6Н4);
8.04 (2Н, m, 3J = 8.5, С6Н4); 10.80 (1H, br. s, NH)
9Aj
1625;
1.05 (6H, s, 2CH3); 2.38 (2H, s, CH2); 2.75 (2H, s, CH2);
3130-3050
8.31-8.33 (4Н, m, С6Н4); 11.7 (1H, br. s, NH)
9Ak
1626;
3150-3050
1.03 (6H, s, 2CH3); 2.28 (2H, s, CH2); 2.65 (2H, s, CH2);
2.97 (6H, s, 2CH3); 6.77 (2H, m, 3J = 8, С6Н4);
7.99 (2Н, m, 3J = 8, С6Н4); 13.1 (1H, br. s, NH)
9Bb
1630; 3100
2.08 (2H, m, CH2); 2.47 (2H, t, 3J = 6.5, CH2);
2.89 (2H, t, 3J = 6.5, CH2); 7.49 (2H, m, 3J = 8, C6H4);
8.09 (2H, m, 3J = 8, С6Н4); 13.27 (1H, br. s, NH)
9Bс
1632;
3120-3070
1.93-2.97 (6H, m, 3CH2); 7.47 (2H, m, 3J = 8, C6H4);
8.11 (2H, m, 3J = 8, C6H4); 13.4 (1H, br. s, NH)
9Bd
1626;
3100-3050
2.16 (2H, m, CH2); 2.50 (2H, t, 3J = 6.5, CH2);
2.87 (2H, t, 3J = 6.5, CH2); 7.02-7.21 (2H, m, C6H4);
8.01-8.17 (2H, m, С6Н4); 12.51 (1H, br. s, NH)
9Bf
1634;
3400-3100
1.99-2.32 (6H, m, 3CH2); 6.80 (2H, m, 3J = 8.5, C6H4);
7.91 (2H, m, 3J = 8.5, C6H4); 9.66 (1H, br. s, ОН);
13.16 (1H, br. s, NH)
9Bg
1630; 3100
2.11 (2H, m, CH2); 2.52 (2H, t, 3J = 6.5, CH2);
2.89 (2H, t, 3J = 6.5, CH2); 3.75 (3H, s, OCH3);
6.94 (2H, m, 3J = 9, C6H4); 8.02 (2H, m, 3J = 9, C6H4);
12.7 (1H, br. s, NH)
9Bk
1630;
3120-3070
2.11 (2H, m, CH2); 2.51 (2H, t, 3J = 6.5, CH2);
2.92 (2H, t, 3J = 6.5, CH2); 2.98 (6H, s, N(CH3)2);
6.77 (2H, m, 3J = 9, C6H4); 7.97 (2H, m, 3J = 9, C6H4);
12.51 (1H, br. s, NH)
_______
* Spectra were taken in CDCl3 (compounds 6Aa-Ak, Bb-Be, Bg, Bk, 9Ab,
Ad, Ae, Ag, Bd), DMSO-d6 (compounds 7A,B, 9Af, Aj, Ak, Bb, Bc, Bf),
and CDCl3 + DMSO-d6 (compounds 9Bg, Bk).
EXPERIMENTAL
The IR spectra were taken on a Specord 75-IR instrument for suspensions of substances in nujol
(1500-1800 cm-1) and in hexachlorobutadiene (2000-3600 cm-1). Only the absorption bands of the carbonyl
group are given in the 1500-1800 cm-1 region. The absorption bands of the stretching vibrations of C–H bonds in
the 2800-3050 cm-1 region are not given. The 1H NMR spectra were recorded on a Bruker WH/90DS (90 MHz)
instrument in CDCl3 and DMSO-d6, internal standard was TMS.
3-(3-Bromophenyl)-
(6Aa),
3-(4-Bromophenyl)-
(6Ab),
3-(4-Chlorophenyl)-
(6Ac),
3-(4-Fluorophenyl)- (6Ad), 3-(4-Hydroxyphenyl)- (6Af), 3-(4-Methoxyphenyl)- (6Ag), 3-(2-Nitrophenyl)-
(6Ah), 3-(3-Nitrophenyl)- (6Ai), 3-(4-Nitrophenyl)- (6Aj), and 3-(4-Dimethylaminophenyl)-6,6-dimethyl-4-
oxo-2-phenyl-4,5,6,7-tetrahydroindazoles (6Ak) (General Procedure). A mixture of phenylhydrazone 3A (4
mmol) and the appropriate aldehyde 4 (4 mmol) in DMSO (5 ml) with added glacial AcOH (0.2 ml) and
piperidine (0.8 ml) was heated on a boiling water bath for 3 h. After cooling, the reaction mixture was diluted
with water (30-40 ml) with stirring, the precipitated solid was triturated, filtered off, and recrystallized from
ethanol.
3-(4-Bromophenyl)-
(6Bb),
3-(4-Chlorophenyl)-
(6Bc),
3-(4-Fluorophenyl)-
(6Bd),
3-(2-Hydroxyphenyl)- (6Be), 3-(4-Methoxyphenyl)- (6Bg), 3-(4-Dimethylaminophenyl)-4-oxo-2-phenyl-
4,5,6,7-tetrahydroindazoles ( 6Bk) (General Procedure). A mixture of phenylhydrazone 3B (4 mmol) and the
1402

appropriate aldehyde 4 (4 mmol) in DMSO (5 ml) with added glacial AcOH (0.2 ml) and piperidine (0.8 ml) was
heated on a boiling water bath for 2 h. Water (30-40 ml) was then added with stirring to the reaction mixture, the
solid was triturated, and filtered off. Indazoles 6Bb,e were recrystallized from ethanol, and indazoles 6Bc,d,g,k
from an ethanol–water, 2:1 mixture.
5,5-Dimethyl-3-tosylhydrazinocyclohex-2-en-1-one (7A). Solutions of dimedone (2.80 g, 20 mmol) in
glacial AcOH (20 ml) and tosylhydrazine (3.72 g, 20 mmol) in glacial AcOH (20 ml) were prepared separately,
then mixed, and the mixture heated for 10 min on a boiling water bath. Water (20 ml) was added to the hot
mixture. The mixture was cooled, the solid enehydrazine 7A was filtered off, and recrystallized from ethanol.
3-Tosylhydrazinocyclohex-2-en-1-one (7B). Solutions of cyclohexane-1,3-dione (2.24 g, 20 mmol) in
water (20 ml) and tosylhydrazine (3.72 g, 20 mmol) in 80% AcOH (20 ml) were prepared separately, then
mixed, and the mixture heated for 3-5 min on a boiling water bath. Further water (25 ml) was added to the hot
reaction mixture, which was then cooled. The solid enehydrazine 7B was filtered off, and recrystallized from
ethanol.
3-(4-Bromophenyl)-
3-(4-Hydroxyphenyl)- (9Af),
(9Ab),
3-(4-Fluorophenyl)-
3-(4-Methoxyphenyl)-
(9Ad),
(9Ag),
3-(2-Hydroxyphenyl)-
3-(4-Nitrophenyl)-
(9Ae),
(9Aj),
3-(4-Dimethylaminophenyl)-6,6-dimethyl-4-oxo-4,5,6,7-tetrahydroindazoles (9Ak) (General Procedure).
Enehydrazine 7A (4 mmol) was dissolved with heating in DMSO (5 ml), glacial AcOH (0.2-0.3 ml) was added,
then the appropriate aldehyde (4 mmol) (the solid substance was previously dissolved in the minimum quantity
of DMSO), and finally piperidine (0.8 ml) was added. The reaction mixture was heated for 2 h on a boiling water
bath, on cooling water (50-60 ml) was added with stirring, the precipitated solid was triturated, then filtered off,
and recrystallized from 80% ethanol.
3-(4-Bromophenyl)-
(9Bb),
3-(4-Chlorophenyl)-
(9Bc),
3-(4-Fluorophenyl)-
(9Bd),
3-(4-Hydroxyphenyl)- (9Bf), 3-(4-Methoxyphenyl)- (9Bg), and 3-(4-Dimethylaminophenyl)-4-oxo-4,5,6,7-
tetrahydroindazole (9Bk) (General Procedure). Enehydrazine 7B (4 mmol) was dissolved with heating in
DMSO (5 ml), glacial AcOH (0.2 ml) was added, then the appropriate aldehyde (4 mmol) or a solution of it in
DMSO was added dropwise, and finally piperidine (0.8 ml) was added. The reaction mixture was heated on a
boiling water bath for 1.5-2 h, after cooling, water (50-60 ml) was added with stirring, the precipitated solid was
triturated, filtered off, and recrystallized from ethanol.
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