5-Diazo-6,6-dimethyl-4-oxo-4,5,6,7-tetrahydroindazoles in [3+2] cycloaddition reactions

Article abstract of DOI:10.1007/s10593-007-0234-3

The [3+2] cycloaddition reactions of a series of 1,3-substituted 5-diazo-6,6-dimethyl-4-oxo-4,5,6,7-tetrahydroindazoles with maleic anhydride and dimethyl acetylenedicarboxylate gave 1′,3′-substituted 3-spiro[4,6-dioxo-4,6,3a,6a-tetrahydro-3H-furo[3,4-c]pyrazole] -5′-[6′,6′-dimethyl-4′-oxo-4′,5′,6′, 7′-tetrahydroindazoles] and 1′,3′-substituted 3-spiro[4,5-di(methoxycarbonyl)-3H-pyrazole]-5′-[6′, 6′-dimethyl-4′-oxo-4′,5′,6′,7′- tetrahydroindazoles] respectively. When heated the former eliminate nitrogen and are transformed into 1′,3′-substituted 6-spiro[2,4-dioxo-3- oxabicyclo[3.1.0]hexane]-5′-[6′,6′-dimethyl-4′-oxo- 4′,5′,6′,7′-tetrahydroindazoles].

Full text of DOI:10.1007/s10593-007-0234-3

Chemistry of Heterocyclic Compounds, Vol. 43, No. 12, 2007
5-DIAZO-6,6-DIMETHYL-4-OXO-
4,5,6,7-TETRAHYDROINDAZOLES
IN [3+2] CYCLOADDITION REACTIONS
I. Strakova1, A. Strakovs1, M. Petrova2, and S. Belyakov2
The [3+2] cycloaddition reactions of a series of 1,3-substituted 5-diazo-6,6-dimethyl-4-oxo-4,5,6,7-
tetrahydroindazoles with maleic anhydride and dimethyl acetylenedicarboxylate gave 1′,3′-substituted
3-spiro[4,6-dioxo-4,6,3a,6a-tetrahydro-3H-furo[3,4-c]pyrazole]-5′-[6′,6′-dimethyl-4′-oxo-4′,5′,6′,7′-
tetrahydroindazoles] and 1′,3′-substituted 3-spiro[4,5-di(methoxycarbonyl)-3H-pyrazole]-5′-[6′,6′-
dimethyl-4′-oxo-4′,5′,6′,7′-tetrahydroindazoles] respectively. When heated the former eliminate nitrogen
and are transformed into 1′,3′-substituted 6-spiro[2,4-dioxo-3-oxabicyclo[3.1.0]hexane]-5′-[6′,6′-
dimethyl-4′-oxo-4′,5′,6′,7′-tetrahydroindazoles].
Keywords: dimethyl acetylenedicarboxylate, 1,3- and 2,3-substituted 5-diazo-6,6-dimethyl-4-oxo-
4,5,6,7-tetrahydroindazoles, maleic anhydride, [3+2] cycloaddition.
In the last ten years the range of indazole derivatives with valuable biological activity has increased
substantially. Among them agonists of estrogen receptors [1] and dopamine D3 receptors [2], HIV protease
inhibitors [3], and new anti-inflammatory substances [4] have been discovered. In this connection in a
continuation of researches on the synthesis of 4,5-bifunctional 6,7-dihydro- and 4,5,6,7-tetrahydroindazoles
[5-10] we realized [3+2] cycloaddition reactions between 5-diazo-6,6-dimethyl-4-oxo-4,5,6,7-tetrahydro-
indazoles 1a-d and maleic anhydride.
The diazoindazoles 1a,b,d were obtained by the decomposition of the corresponding tosylhydrazones
2a,b,d in a water–ethanol solution of sodium hydroxide according to the procedure in [11, 12] that we used
earlier for the preparation of the diazoindazoles 1c and 3.
In the reaction of the diazoindazoles 1a-d with maleic anhydride by the classical methods [13, 14] the
corresponding 1',3'-substituted 6',6'-dimethyl-4,6,4'-trioxo-4,6,3a,6a,4',5',6',7'-octahydro-3H-spirofuro[3,4-c]-
pyrazole-3,5'-indazoles 4a-d are formed. The reactions were carried out by keeping equimolar amounts of the
reagents in methylene chloride for 15 days. The precipitated spiro compound 4 was filtered off and recrystallized
from ethyl acetate with minimal boiling.
Heating of the pyrazolines 4b,c for 1-2 min at the melting point or boiling in toluene led to the release of
nitrogen and transformation into the corresponding 1',3'-substituted 6',6'-dimethyl-2,4,4'-trioxo-4',5',6',7'-
tetrahydrospiro-3-oxabicyclo[3.1.0]hexane-6,5'-indazoles 5b,c.
__________________________________________________________________________________________
2
1Riga Technical University, Riga LV-1048, Latvia; e-mail: strakovs@latnet.lv. Latvian Institute of
Organic Synthesis, Riga LV-1006; e-mail: marina@osi.lv. Translated from Khimiya Geterotsiklicheskikh
Soedinenii, No. 12, pp. 1784-1791, December, 2007. Original article submitted March 17, 2006.
1512
0009-3122/07/4312-1512©2007 Springer Science+Business Media, Inc.

R
R
N
N
N
N
N2
p-MeC6H4O2SNHN
R1
R1
O
O
2a–d
1a–d
O
COOMe
MeOOC
O
R
N
O
O
N
R
O
3a
N
MeOOC
MeOOC
N
O
N
R1
6a
N
O
R1
N
N
4a–d
O
6c, d
–N2
R
R
N
N
O
R2
N
N
O
R1
R1
R3
O
O
O
8, 9
5b, c
N
N
MeOOC
MeOOC
N
R
N
R
N2
R1
N
N
R1
O
O
3a, b
7a, b
1, 2, 4 a R = Ph, R1 = H; b R = Ph, R1 = Me; c R = Py-2, R1 = Me; d R = C6H3(CF3)2-3,5,
R1 = Me; 3, 7 a R = 2- pyridyl, R1 = Ph; b R = Ph, R1 = C6H4OMe-4; 5 b R = Ph, R1 = Me;
c R = Py-2, R1 = Me; 6 c R = Py-2, R1 = Me; d R = C6H3(CF3)2-3,5, R1 = Me; 8 R = Ph,
R1 = Me, R2 = R3 = COOH; 9 R = 2- pyridyl, R1 = Me, R2 = COOH, R3 = CONHCH2Ph
Heating of the solution of the anhydride 5b in 5% aqueous sodium hydroxide solution to boiling
followed by acidification leads to the dicarboxylic acid 8. The benzylamide 9 is formed when a benzene solution
of equimolar amounts of the anhydride 5c and benzylamine is heated to boiling.
The reaction of the diazoindazoles 1b,c and 3a,b [12] with dimethyl acetylenedicarboxylate is carried
out by keeping equimolar amounts of the reagents in methylene chloride at 20°C for 4-5 days. In all cases the
corresponding 1',3'- or 2',3'-substituted 4,5-di(methoxycarbonyl)-6,6'-dimethyl-4'-oxo-4',5',6',7'-tetrahydro-
3H-spiropyrazole-3,5'-indazoles 6c,d and 7a,b were obtained.
1513

TABLE 1. The Characteristics of the Synthesized Compounds
Found, %
——————
Calculated, %
Com-
pound
Empirical
formula
mp, °C
Yield, %
С
Н
N
1a
1b
1d
2a
2b
2d
4a
4b
4c
4d
5b
5c
6c
6d
7a
7b
8
C15H14N4O
67.51
67.65
68.37
68.55
51.70
51.93
62.63
62.55
63.11
63.28
52.27
52.44
62.45
62.63
63.26
63.48
60.01
60.15
51.19
51.37
68.44
68.56
64.70
64.95
59.39
59.56
51.49
51.62
64.11
64.32
65.27
65.36
5.35
5.30
5.55
5.75
3.30
3.39
5.11
5.25
5.40
5.54
3.90
3.87
4.30
4.43
4.59
4.79
4.58
4.52
3.03
3.14
5.02
5.18
4.68
4.88
4.92
5.00
3.50
3.61
4.60
4.77
5.11
5.09
20.88
21.04
20.08
19.99
13.25
13.46
13.12
13.26
12.75
12.84
9.66
9.79
15.31
15.38
14.70
14.81
18.35
18.46
10.93
10.89
7.85
7.99
11.80
11.96
16.36
16.54
9.88
10.03
174-175
145-147
73
63
69
88
70
41
51
50
68
40
43
56
95
56
50
45
94
64
C16H16N4O
C18H14F6N4O
C22H22N4O3S
C23H24N4O3S
C25H22F6N4O3S
C19H16N4O4
C20H18N4O4
C19H17N5O4
C22H16F6N4O4
C20H18N2O4
C19H17N3O4
C21H21N5O5
C24H20F6N4O5
C26H23N5O5
C28H26N4O6
C20H20N2O5
C26H26N4O4
185-187
118-119
149-151
160-162
167-169 (dec.)
179–181 (dec.)
154-156 (dec.)
162-164 (dec.)
202-204
257-258
159-160
230-231
14.21
14.43
11.03
10.89
7.49
7.60
12.30
12.22
185-186
195-197
65.00
65.21
67.93
68.10
5.33
5.47
5.55
5.72
252-253
9
285-287
The structure of the synthesized compounds was confirmed by the data from the IR and 1H NMR spectra
(Table 2) and in the case of the spiro compound 4c also by X-ray crystallographic experiments (Table 1).
In the indazole derivatives 4 the methyl groups at C(6) and also each of the hydrogens of the C(7)
methylene group appear as separate signals. In compounds 5 there are six-proton singlets for the two C(6) methyl
groups and also singlets for the C(7) methylene groups. The signals of the methyl groups in compounds 5 were
1
3
assigned according to their 13C satellite signals in the H NMR spectra, which make it possible to record JHH
between the magnetically equivalent protons (4-5 Hz).
The signals for the protons of the furopyrazole structural fragments at the C(3a) and C(6a) atoms of
compounds 4 are found at δ 3.21-3.76 (3a) and 6.29-6.78 ppm (6a) and for the symmetrical spiro-substituting
groups of compounds 5 at δ 3.62-3.67 ppm.
For an objective assessment of the structure of compound 4c an X-ray crystallographic analysis of the
crystals of this compound was undertaken (Fig. 1, Tables 3-5).
1514

TABLE 2. The Spectra of the Synthesized Compounds
IR spectrum,
Com-
ν, cm-1
1Н NMR spectrum, δ, ppm. (SSCS, J, Hz)*
pound
(С=О, NH, OH)
1a
1b
1c
2а
2b
2d
4a
1630, 2095
1630, 2090
1640, 2095
1642, 3230
1650, 3260
1645, 3250
1.35 (6H, s, 2CH3); 2.96 (2H, s, CH2); 7.22-7.70 (5Н, m, C6H5);
8.06 (1Н, s, H-3)
1.26 (6H, s, 2CH3); 2.56 (3H, s, CH3); 3.40 (2H, s, CH2);
7.50-7.80 (5Н, m, C6H5)
1.44 (6H, s, 2CH3); 2.53 (3H, s, CH3); 3.06 (2H, s, CH2);
7.42 (3Н, br. s, C6H3)
1.21 (6H, s, 2CH3); 2.55 (3H, s, CH3); 3.35 (2H, s, CH2);
7.28-8.00 (10Н, m, C6H5, С6Н4, H-3); 12.50 (1H, br. s, NH)
1.30 (6H, s, 2CH3); 2.42 (3H, s, CH3); 2.60 (3H, s, CH3);
3.45 (2H, s, CH2); 7.25-7.80 (9Н, m, C6H5, С6Н4); 12.65 (1H, br. s, NH)
1.40 (6H, s, 2CH3); 2.45 (3H, s, CH3); 2.60 (3H, s, CH3);
3.50 (2H, s, CH2); 7.30-7.95 (7Н, m, C6H4, С6Н3); 12.65 (1H, br. s, NH)
1864, 1782,
1684
0.98 (3H, s, CH3); 1.04 (3H, s, CH3); 3.18 and 3.28 (2H, two d,
2J = 12.4, H-7); (1H, d, J = 12.4, H-7); 3.74 (1H, d, J = 9.6, H-3a);
6.77 (1H, d, J = 9.6, H-6a); 7.53−7.78 (5Н, m, Ar); 8.27 (1Н, s, H-3a)
4b
4c
4d
1860, 1775,
1670
0.96 (3H, s, CH3); 1.27 (3H, s, CH3); 2.51 (3H, s, CH3); 2.95 (1H, d,
2J = 16.8, H-7); 3.28 (1H, d, J = 10.0, H-3a); 3.76 (1H, d,
2J = 16.8, H-3a); 6.29 (1H, d, J = 10.0, H-6a); 7.54 (5Н, m, Ar)
1867, 1779,
1671
1.03 (3H, s, CH3); 1.09 (3H, s, CH3); 2.39 (3H, s, CH3);
3.21 (3H, m, CH2, СН); 6.75 (1H, d, J = 10.0, H-6a); 7.48 (1H, m, Py);
7.95-8.13 (2Н, m, Py); 8.58 (1Н, m, J = 5.0, Py)
1862, 1775,
1670
0.98 (3H, s, CH3); 1.04 (3H, s, CH3); 2.41 (3H, s, CH3);
3.28 (2H, br. s, CH2); 3.74 (1H, d, J = 10.0, H-3a);
6.78 (1H, d, J = 10.0, H-6a); 8.29 (1H, br. s, Ar); 8.42 (1Н, br. s, Ar)
5b
1850, 1772,
1658
0.98 (6H, s, 2CH3); 2.37 (3H, s, CH3); 3.11 (2H, br. s, H-7);
3.62 (2H, s, H-3a, H-6a); 7.48-7.62 (5H, m, Ar)
5с
1845, 1776,
1658
1.03 (6H, s, 2CH3); 2.38 (3H, s, CH3); 3.47 (2H, s, H-7);
3.67 (2H, s, H-3a, H-6a); 7.45 (1H, dd, J = 5.0, J = 8.0, Ar); 7.92 (1Н, d,
J = 8.0, Ar); 8.05 (1Н, dt, J = 8.0, J = 2.0, Ar); 8.56 (1Н, d, J = 5.0, Ar)
6с
1740, 1720,
1660
1.48 (6H, s, 2CH3); 2.66 (3H, s, CH3); 3.65 (2H, s, CH2);
3.92 (3H, s, ОCH3); 3.94 (3Н, s, ОСН3); 7.33 (1H, m, Ar);
7.89-7.92 (2Н, m, Ar); 8.47 (1Н, m, Ar)
6d
7a
1745, 1730,
1662
1.44 (6H, s, 2CH3); 2.65 (3H, s, CH3); 3.10 (2H, s, CH2);
3.92 (6H, s, 2ОCH3); 7.91 (2Н, br. s, Ar); 7.99 (1Н, s, Ar)
1740, 1730,
1660
1.53 (6H, s, 2CH3); 3.26 (2H, s, CH2); 3.89 (3H, s, OCH3);
3.94 (3H, s, ОCH3); 7.23-7.35 (7Н, m, Ar);
7.67 (1Н, dt, J = 8.0, J = 2.5, Ar); 8.46 (1Н, m, Ar)
7b
8
1732, 1726,
1701
1.51 (6H, s, 2CH3); 3.20 (2H, s, CH2); 3.80 (3H, s, OCH3);
3.89 (3H, s, ОCH3); 3.93 (3H, s, OCH3); 6.82 (2H, m, Ar);
7.22-7.32 (7Н, m, Ar)
1865, 1711,
1677;
2640-2580
0.92 (6H, s, 2CH3); 2.36 (5H, s, CH2, CH3); 2.98 (2H, s, H-3a, H-6a);
7.38-7.62 (5Н, m, Ar); 12.25 (1Н, br. s, CООH);
13.12 (1Н, br. s, СООН)
9
1760, 1715,
1661; 3180,
2660-2600
0.99 (3H, s, CH3); 1.06 (3H, s, CH3); 2.37 (3H, s, CH3); 2.47 (1H, d,
J = 9.0, СН); 2.58 (1H, d, J = 9.0, CH); 3.43 (1H, d, J = 18.0, CH);
3.58 (1H, d, J = 18.0, CH); 4.12 (1H, dd, J = 15.0, J = 5.0, CH);
4.37 (1H, dd, J = 15.0, J = 5.0, CH); 7.01-7.21 (5Н, m, Ar);
7.41 (1Н, m, Ar); 8.02 (1Н, d, J = 8.0, Ar); 8.04 (1H, dt, J = 8.0,
J = 2.0, Ar); 8.51 (1Н, m, Ar); 9.15 (1Н, t, J = 5.0, NH);
13.94 (1Н, br. s, CООH).
_______
1
* The H NMR spectra were recorded in CDCl3 (compounds 1a-c, 2a,b,d,
4b, 6c,d, 7a,b) and DMSO-d6 (compounds 4a,c,d, 5b,c, 8, 9).
1515

Fig. 1. Three-dimensional model of the molecule 4c with the numbers
of the atoms and the thermal vibration ellipsoids.
TABLE 3. The Crystallographic Data of Compound 4c
Empirical formula
Mr
C19H17N5O4
379.38
Crystal system
Space group
Monoclinic
C 2/c
Unit cell parameters:
a, Å
b, Å
c, Å
β, deg.
23.1182(5)
9.8210(3)
19.2573(4)
114.909(2)
V, Å3
3965.4(2)
8
Molecular multiplicity, Z
Density of crystals, d, g/cm3
Absorption coefficient, µ, mm−1
1.271
0.092
Number
5031
3411
265
of independent reflections
reflections with I > 2σ(I)
refined parameters
0.0874
Final R factor
SIR97 [1], SHELXL97 [2]
Employed programs
TABLE 4. The Principal Bond Lengths (l) in the Molecule of Compound 4c
Bond
N(1)–N(2)
l, Å
Bond
C(7)–C(8)
l, Å
1.375(4)
1.352(4)
1.432(4)
1.320(4)
1.556(4)
1.434(4)
1.217(4)
1.539(4)
1.515(4)
1.555(4)
1.554(4)
1.489(4)
1.379(5)
1.234(4)
1.491(4)
1.502(5)
1.196(4)
1.514(4)
1.360(5)
1.405(4)
1.181(4)
1.508(5)
N(1)–C(8)
N(1)–C(10)
N(2)–C(3)
C(4)–C(5)
C(4)–C(9)
C(4)–O(17)
C(5)–C(6)
C(5)–N(18)
C(5)–C(26)
C(6)–C(7)
C(8)–C(9)
N(18)–N(19)
N(19)–C(20)
C(20)–C(21)
C(21)–O(22)
C(20)–C(26)
C(21)–O(23)
O(23)–C(24)
C(24)–O(25)
C(24)–C(26)
1516

TABLE 5. The Principal Valence (ω) and Torsion (τ) Angles in the
Molecule of compound 4c
Angle
(2)−N(1)−C(8)
ω, deg
Angle
C(9)−C(4)−C(5)−C(6)
τ, deg
N
111.6(3)
106.2(2)
113.8(2)
111.7(3)
110.8(3)
32.3(3)
113.5(3)
128.2(3)
N(1)−N(2)−C(3)
C(5)−C(26)−C(20)−C(21)
N(19)−C(20)−C(26)−C(24)
C(5)−N(18)−N(19)
N(18)−N(19)−C(20)
C(21)−O(23)−C(24)
EXPERIMENTAL
The IR spectra were obtained on a Specord IR-75 instrument for suspensions in vaseline oil
(1800-1500 cm−1) and hexachlorobutadiene (3600-2000 cm−1). The frequencies of the stretching vibrations of the
1
C–H bonds in the region of 3050-2800 cm−1 are not given. The H NMR spectra were recorded on a Varian
Mercury BB spectrometer (200 MHz) with TMS as internal standard.
5-Diazo-6,6-dimethyl-1-phenyl (1a), 5-Diazo-3,6,6-trimethyl-1-phenyl- (1b), and 1-[(3,5-Bistri-
fluoromethyl)phenyl]-5-diazo-3,6,6-trimethyl-4-oxo-4,5,6,7-tetrahydroindazoles (1d). The corresponding
tosylhydrazone 2a,b,d (2 mmol) was suspended in aqueous solution (40 ml) sodium hydroxide (0.4 g). The
mixture was heated at 80-90°C with stirring for 1 h, and ethanol (15 ml) was added. The precipitate was filtered
off, compounds 1a,b were recrystallized from benzene–hexane and 1d from ethyl acetate–hexane.
6,6-Dimethyl-4-oxo-1-phenyl-5-tosylhydrazono- (2a), 3,6,6-Trimethyl-4-oxo-1-phenyl-5-tosyl-
hydrazono- (2b), and 1-[(3,5-Bistrifluoromethyl)phenyl]-3,6,6-trimethyl-4-oxo-5-tosylhydrazono-4,5,6,7-
tetrahydroindazoles (2d). A solution of the corresponding 4,5-dioxo derivative (5 mmol) [10, 15] and
tosylhydrazone (5 mmol) in ethanol (30 ml) was boiled for 2 h, cooled, and in the case of 2d diluted with an
equal quantity of water. The tosylhydrazone was filtered off and recrystallized from ethanol.
1',3'-Substituted
6',6'-Dimethyl-4,6,4'-trioxo-4,6,3a,6a,4',5',6',7'-octahydrospiro[3H-furo[3,4-c]-
pyrazole-3,5′-indazoles] 4a-d. A solution of the corresponding diazoindazole 1a-d (3 mmol) and maleic
anhydride (3 mmol) in methylene chloride (30 ml) was left at 20°C for 15 days. The precipitate was filtered off,
washed on the filter with methylene chloride, and recrystallized from ethyl acetate by briefly boiling.
1',3'-Substituted 6',6'-Dimethyl-2,4,4'-trioxo-4',5',6',7'-tetrahydrospiro[3-oxabicyclo[3.1.0]hexane-
6,5'-indazoles] 5b,c. The pyrazolines 4b,c in a wide test tube were immersed in an oil bath at 150°C for 2-3 min.
Bubbles of nitrogen were released. The residue was recrystallized from ethanol.
The same compounds 5b,c were obtained by boiling of the pyrazolines 4b,c (5 mmol) in toluene (30 ml)
for 2 h. The mixture was cooled, and the product was filtered off and recrystallized from ethanol.
2,3-Dicarboxy-5',3',6',6'-trimethyl-4'-oxo-1'-phenyl-4',5',6',7'-tetrahydrospiro[cyclopropane-
1,5'-indazole] (8). The indazole spiro derivative 5b (3 mmol) in 2% aqueous sodium hydroxide (3 ml) solution
was heated to boiling, cooled, and acidified to pH 3-4 with hydrochloric acid. The precipitated dicarboxylic acid
was filtered off and recrystallized from a solution of 1:1 ethanol–water.
3-Benzylaminocarbonyl-2-carboxy-5',3',6',6'-tetramethyl-4'-oxo-1'-(2-pyridyl)-4',5',6',7'-tetrahydro-
spiro[cyclopropane-1,5′-indazole] (9). To a solution of the anhydride 5c (3 mmol) in dry benzene (30 ml) we
added benzylamine (3.5 mmol). The mixture was boiled for 2-3 min and cooled. After 24 h the precipitated
compound 9 was filtered off and recrystallized from acetic acid.
4,5-Dimethoxycarbonyl-3'-(4-methoxyphenyl)-3′,6′,6′-trimethyl-4'-oxo-1'-(2-pyridyl)-
(6c)
and
1'-[(3,5-Bistrifluoromethyl)phenyl]-4,5-dimethoxycarbonyl-3'-(4-methoxyphenyl)-3',6',6'-trimethyl-4'-oxo-
(6d), 4,5-Dimethoxycarbonyl-3'-(4-methoxyphenyl)-6',6'-dimethyl-4'-oxo-3-phenyl-2'-(2-pyridyl)- (7a)
1517

and 4,5-Dimethoxycarbonyl-3'-(4-methoxyphenyl)-6′,6′-dimethyl-4′-oxo-2'-phenyl-4',5',6',7'-tetrahydro-
spiro[3H-pyrazole-3,5'-indazole] (7b). A solution of the corresponding diazoindazole 1c,d or 3a,b (3 mmol)
and dimethyl acetylenedicarboxylate (3 mmol) in methylene chloride (30 ml) was left at 20°C for four days.
Hexane (60 ml) was added, and the precipitated pyrazoles 6c,d and 7a,b were recrystallized from ethanol.
X-ray Crystallographic Investigations (Tables 3-5). For X-ray crystallographic analysis the diffraction
pattern of a single crystal of compound 4c, measuring 0.05×0.26×0.33 mm, was recorded on an automatic
Nonius KappaCCD diffractometer up to 2θmax = 57° (λMo = 0.71073 Å).
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