Formation of indazole derivatives from 2,4-disubstituted thiosemicarbazides and some chloro-p-quinones

Article abstract of DOI:10.3184/030823410X12797029344957

The reaction of 2,4-disubstituted thiosemicarbazides with 2,3,5,6-tetrachloro-1,4-benzo-quinone gave 2-aryl-5,6-dichloro-3-(substituted imino)-2,3-dihydro-1H -indazole-4,7-diones in 57-66% yield together with smaller amounts of 2-aryl-3-(substituted imino

Full text of DOI:10.3184/030823410X12797029344957

JOURNAL OF CHEMICAL RESEARCH 2010
RESEARCH PAPER 435
AUGUST, 435–439
Formation of indazole derivatives from 2,4-disubstituted
thiosemicarbazides and some chloro-p-quinones
Alaa A. Hassan*, Ashraf A. Aly and Mamdouh A. Mohamed
Chemistry Department, Faculty of Science, Minia University, 61519 El-Minia, Egypt
The reaction of 2,4-disubstituted thiosemicarbazides with 2,3,5,6-tetrachloro-1,4-benzo-quinone gave 2-aryl-
5,6-dichloro-3-(substituted imino)-2,3-dihydro-1H-indazole-4,7-diones in 57–66% yield together with smaller amounts
of 2-aryl-3-(substituted imino)-4,6,7-trichloro-2H-indazole-5(3H)-ones (21–25% yield). Reaction of 2,3-dichloro-1,4-
naphthoquinone with 2,4-disubstituted thiosemicarbazides provided 2-aryl-3-(substituted imino)-2,3-dihydro-1H-
benzo[f]-indazole-4,9-diones in 63–74% yield. Rationales for these transformations are presented.
Keywords: 2,4-disubstituted thiosemicarbazides, benzo- and naphthoquinones, indazole, derivatives
Compounds containing a p-quinone moiety show strong
biological activity due to their interference with metabolic
processes of both plant and animal cells.1,2 In another area
benzimidazole-quinones have been investigated for herbicidal
activity.3 The synthesis of indazole derivatives from the reac-
tion of diazoalkanes with some benzo- and naphthoquinones
have been investigated.3–6 Similarly, the analogous Michael
addition of N-2 substituted hydrazones, which can be regarded
as azaenamines, to 1,4-naphthoquinone, followed by ring
closure, gave indazole derivatives.7 Much less attention has
been given to the synthesis of indazole derivatives from
the reaction of thiosemicarbazides with benzoquinones.8–10
2,3,5,6-Tetrachloro-1,4-benzoquinone 2 and 2,3-dichloro-
1,4-naphthoquinone 3 undergo nucleophilic substitution of
one or two chlorine atoms by thioacetamide,11–13 thiourea,14,15
substituted thioureas,16 thiocarbazones,17 hydrazine-1,2-
dicarbothioamides,18 and thiosemicarbazides.9
We report here the results of our investigations on the
reaction of 2,4-disubstituted thiosemicarbazides 7a–d with
benzo- and naphthoquinones 2 and 3. These results are
compared with those obtained earlier.9
Addition of ethyl acetate solutions of 7a–d to a solution of
2 in the same solvent resulted in the appearance of a green
colour, which gradually changed into brown. When the reac-
tion mixture was monitored spectrophotometrically (at 10 °C),
an absorption maximum was observed in the visible region at
565–538 nm, that was assigned to the formation of an unstable
charge-transfer complex (CTC), since neither thiosemicarba-
zide derivatives 7a–d nor p-chloranil 2 alone absorb in this
region. After standing for 48 h at room temperature 5,6-
dichloro-2-aryl-3-(substituted imino)-2,3-dihydro-1H-inda-
zole-4,7-diones 8a–d (57–66%) and 3-(substituted imino)-
4,6,7-trichloro-2-aryl-2H-indazole-5(3H)-one 9a–d (21–25%)
were isolated by preparative thin layer chromatography
(Scheme 1). The structural assignment of the major products
8a–d is based on the following data: The IR spectrum of
3-(benzylimino)-5,6-dichloro-2-phenyl-2,3-dihydro-1H-
indazole-4,7-dione 8d showed broad bands at 3280 cm−1 for an
It has been reported that 4-substituted thiosemicarbazides
1a–c reacted with 2 and 3 in ethyl acetate with admission of air
to give compounds 4–6 (Fig. 1).9
Fig. 1
* Correspondent. E-mail: alaahassan2001@yahoo.com

436 JOURNAL OF CHEMICAL RESEARCH 2010
Scheme 1
NH group, with sharp bands at 1675 (CO) and at 1610 (C=N)
cm−1. The 1H NMR spectrum of 8d showed one broad singlet
at 11.18 ppm, due to the indazole-NH proton (11.14–11.21 for
compounds 8a–c). On the other hand, the alternative tautomer
14 was ruled out on the basis of δ values for the exocyclic-
NHR groups which are dependent on the nature of RNH
(ca 9.5 ppm when R = Ph, 7.8 ppm when R = benzyl).19 Also
present in the spectrum was another singlet at 4.57 ppm due
to the CH2-Ph group, as well as multiplets at 7.48–7.56 and
7.61–7.64 ppm, which are characteristic of phenyl protons.
In its 13C NMR spectrum, 8d displayed the characteristic
resonances for carbonyl groups in chlorinated benzoquinones
at 173.48 and 173.55 ppm.20 The decoupled carbon spectrum
of 8d showed signals at 119.18, 158.12 and 153.07 ppm,
assigned to C-3a, C-7a and C-3, respectively. In addition, a
signal for C-5 and C-6 was present at 140.28 ppm.
The presence of a benzyl methylene group was also evident
from the 13C DEPT NMR spectrum which exhibited a negative
signal at 51.38 ppm. The constitution of compounds 8a–d was
further confirmed by EI-mass spectrometry. The following
features of the fragmentation patterns provided additional
support for the assigned structures. The mass spectra were
characterised by loss of 28 a.m.u (dinitrogen or carbonyl
group), followed by loss of R–NC and Cl which were common
to the spectra of all of the compounds.
spectrum of 9b clearly indicated a methyl group singlet at
2.24 ppm, in addition to multiplets at 7.43–7.54 ppm, due to
the phenyl protons. In the 13C NMR spectrum of 9b, the signal
characteristic of a chlorinated benzoquinone carbonyl group
appeared at 174.26 ppm,20 whilst the other carbonyl carbon
was replaced by signal at 150.12 ppm (C-7a).20 In addition, the
indazole-C-3 carbon was observed at 156.57 ppm, and a methyl
signal resonated at 20.87 ppm. Other signals were observed
which clearly indicated the presence of Cl–C= and Cl–C=
C–Cl fragments at 140.07, 141.14 and 141.36 ppm, respec-
tively. The formation of 9b was further confirmed by mass
spectrometry; besides the molecular ion at 421/415, the frag-
ment ion patterns characteristic of substituted trichloro
compounds were observed.21
2,3-Dichloro-1,4-naphthoquinone 3 was chosen to compare
its reactivity towards 2,4-disubstituted thiosemicarbazides
7a–d with that of p-chloranil 2. It has been reported that 3
resembles 2 in most of its substitution reactions, especially
with nitrogen nucleophiles (amines, amino acids, pyrazoles,
imidazoles, etc.).22–30 From this point of view one might expect
that 7a–d should react with 3 in a similar manner to 2.
Mixing equimolar amounts of 7a–d and 3 in ethyl acetate
for 72 h led to the formation of benzo[f]indazol-4,9-dione
derivatives 10a–d (Scheme 1). In the IR spectra of 10a–d
one carbonyl band was seen in the range 1680–1675 cm−1, and
a band between 1620 and 1630 cm−1 was assigned to a C=N
vibration, besides a broad band between 3305 and 3295 cm−1
The structures of the minor products 9a–d (25–21 %) were
delineated from their spectroscopic properties and gross
compositions.
2-(4-Methylphenyl)-3-(phenylimino)-4,6,7-
1
due to an NH group. The H NMR spectra of compounds
trichloro-2H-indazol-5(3H)-one 9b was obtained as character-
istically reddish brown crystals. Its molecular structure is
supported by the following findings: The gross formula
C20H12Cl3N3O represents a product derived from one molecule
of 7b and one molecule of 2 with loss of sulfur, HCl and H2O.
The IR spectrum of 9b showed a sharp absorption band
characteristic of a carbonyl group at 1675 cm−1 and the absence
of NH2 or NH groups. Also, upon transformation of 2 into 9b,
one of the benzoquinone-CO absorptions was replaced by
10a–d did reveal an indazole-NH signal between 11.28 and
11.20 ppm, whilst the aromatic protons resonated at 7.17 and
7.26 ppm, for the Ar3’,5’-H protons, two multiplets at 7.65–
7.83 for Ar6,7-H and at 8.09–8.27 for Ar5, 8-H. Furthermore,
multiplets were observed for Ar2`,6` and other phenyl protons
in the region 7.29–7.61 ppm. In the case of 10b, the 13C NMR
spectrum showed signals at 178.74 and 179.37 for (C-4 and
C-9), 156.83 (C-3), 151.06 (C-9a), 111.94 (C-3a) and 21.27
(CH3) ppm.
1
a new IR band at υmax 1630 cm−1 due to C=N. The H NMR

JOURNAL OF CHEMICAL RESEARCH 2010 437
Scheme 2
University, Egypt. The IR spectra were recorded with a Shimadzu 408
instrument using potassium bromide discs. Both 500 MHz H NMR
The benzo[f]indazole-4,9-diones 10a–d underwent mass
spectral fragmentation by loss of ArNC and ArN2 as well as
loss of mass 28 due to N2 or CO.
1
and 125 MHz 13C NMR spectra were recorded for DMSO-d6 solutions
on a Bruker Avance DRX 500 spectrometer. Chemical shifts are
expressed as δ [ppm] with reference to tetramethylsilane as an internal
standard, s = singlet, d = doublet, m = multiplet and br = broad. 13C
NMR assignments were made with the aid of distortionless enhance-
ment by polarisation transfer (DEPT) 135/90 spectra (qc = sp2 quater-
nary carbon atoms). Mass spectra were recorded on a Varian MAT
CH-7 instrument in EI mode at 70 eV ionisation energy. Preparative
layer chromatography (PLC) used air dried 1.0 mm thick layers of
slurry applied silica gel (Merck Pf254) on 48 cm wide and 20 cm high
glass plates using the solvents listed. Zones were detected by quench-
ing of indicator fluorescence upon exposure to 254 nm light and were
isolated by extraction with acetone.
The formation of indazole derivatives 8–10 may be ratio-
nalised as shown (Scheme 2). At first an unstable CTC is
formed followed by the formation of radicals (7a–d) and Q-H·.
The radicals (7a–d)· being a precursor to 11.8–10,17,31–33 The latter
reacts with the semiquinone Q-H˙ with elimination two mole-
cules of HCl to give the indazole derivatives 8a–d or 10a–d via
the intermediate 12. On the other hand, elimination of HCl and
H2O from the intermediate 13 affords the indazole derivatives
9a–d.
Conclusion
2,4-Disubstituted thiosemicarbazides 7a–d were synthesised by
reaction of the appropriate hydrazine hydrochloride with the appropri-
ate isothiocyanate derivative according to published procedures.34
2,3,5,6-Tetrachloro-1,4-benzoquinone (p-chloranil, 2) and 2,3-
dichloro-1,4 naphthoquinone 3 (Aldrich) were used as received.
The products obtained from the nucleophilic substitution
reactions of 2,4-disubstituted thiosemicarbazides 7a–d to
chlorinated benzo- and naphthoquinones 2 and 3 followed by
cyclisation are neither thiahetrocycles nor heterocyclic thiones,
but indazole derivatives. Whilst neither the S–C–N–N + C2 nor
the N–C(S)–N–N + C2 mode of reaction was found in this
study, a novel C–N–N + C2 addition mode was observed.
The reactivity of 2,4-disubstituted thiosemicarbazides 7a–d is
thus markedly different to that observed for the 4-substituted
thiosemicarbazides 1a–d.
Reactions of 2,4-disubstituted thiosemicarbazides (7a–d) with
p-chloranil (2)
To a solution of 2 (246 mg, 1 mmol) in dry ethyl acetate (15 mL), was
added the appropriate 2,4-disubstituted thiosemicarbazides 7a–d
(1 mmol) in dry ethyl acetate (10 mL) dropwise with stirring at room
temperature. The colour of the reaction changed gradually from green
to brown. Stirring was contained for 48 h with admission of air to
complete the reaction. The reaction mixture was concentrated and the
residue was then separated by PLC using toluene/ethyl acetate (3:1)
as eluent, to give numerous zones, the two most intense of which
were removed and extracted. The faster migrating zone contained
Experimental
Melting points have been determined using open capillaries on a
Gallenkamp melting point apparatus and uncorrected. Elemental
analyses were determined by the Microanalytical Centre, Cairo

438 JOURNAL OF CHEMICAL RESEARCH 2010
2-aryl-5,6-dichloro-3-(substituted imino)-2,3-dihydro-1H-indazole-
4,7-diones 8a–d. The slowest migrating zone contained 2-aryl-3-
(substituted imino)-4,6,7-trichloro-2H-indazol-5(3H)-ones 9a–d. The
zones were extracted with acetone and recrystallisation from suitable
solvents afforded the pure compounds 8a–d and 9a–d.
5,6-Dichloro-2-phenyl-3-(phenylimino)-2,3-dihydro-1H-indazole-
4,7-dione (8a): Reddish brown crystals (0.242 g, 63 %), m.p. 279–
281 °C (acetonitrile). 1H NMR (DMSO-d6): δ = 11.21 (br, 1H,
indazole-NH), 7.52–7.62 (m, 10H, ArH). 13C NMR (DMSO-d6):
δ = 173.44, 173.52 (CO), 158.17 (C-7a), 152.98 (C-3), 146.84, 140.27
(C-5,6), 137.66 (ArC), 129.67, 129.55, 127.63, 127.45, 126.97, 126.84
(Ph-CH), 119.28 (C-3a). IR (KBr): ν (cm−1) 3285 (NH), 1680 (CO),
1615 (ArC=N), 1585 (ArC=C). MS: m/z (%) = 387/383 [M+] (46),
355 (31), 319 (28), 283 (23), 180 (42), 105 (54), 77 (100), 65 (57).
C19H11Cl2N3O2 (384.22): Calcd: C, 59.39; H, 2.89; Cl, 18.45; N, 10.94.
Found: C, 59.52; H, 3.02; Cl, 18.38; N, 11.12%.
ν (cm−1) 1680 (CO), 1630 (ArC=N), 1595 (ArC=C). MS: m/z (%) =
443/435 [M+] (29), 399 (32), 363 (27), 292 (41), 264 (28), 161 (33),
91 (62), 77 (100), 65 (81). C19H9Cl4N3O (437.11): Calcd: C, 52.21;
H, 2.08; Cl, 32.44; N, 9.61. Found: C, 51.98; H, 1.96; Cl, 32.57;
N, 9.75%.
3-(Benzylimino)-2-phenyl-4,6,7-trichloro-2H-indazole-5(3H)-one
(9d): Brown crystals (0.087 g, 21 %), m.p. 311–313 °C (acetonitrile).
1H NMR (DMSO-d6): δ = 7.61–7.64, 7.43–7.62, (m, 10H, ArH), 4.61
(s, 2H, CH2-Ph). 13C NMR (DMSO-d6): δ = 174.36 (CO), 156.29
(C-3), 150.16 (C-7a), 141.28, 141.15, 140.26 (C-4,6,7), 147.26,
137.71, 131.12 (ArC), 129.25, 129.18, 127.55, 127.17, 126,93, 126.85
(ArCH). IR (KBr): ν (cm−1), 1680 (CO), 1625 (ArC=N), 1590
(ArC=C) cm−1. MS: m/z (%) = 415/421 [M+] (36), 379 (25), 243 (29),
307 (25), 190 (27), 117 (54), 91 (100), 77 (74), 65 (65). C20H12Cl3N3O
(416.64): Calcd: C, 57.65; H, 2.90; Cl, 25.52; N, 10.08. Found:
C, 57.76; H, 3.02; Cl, 25.41; N, 9.93%.
5,6-Dichloro-2-(4-methylphenyl)-3-(phenylimino)-2,3-dihydro-
1H-indazole-4,7-dione (8b): Reddish brown crystals (0.263 g, 66 %),
m.p. 291–293 °C (methanol). 1H NMR (DMSO-d6): δ = 11.21 (br, 1H,
indazole-NH), 7.54–7.62, 7.46–7.50, (m, 9H, ArH), 2.23 (s, 3H, CH3).
13C NMR (DMSO-d6): δ = 173.41, 173.47 (CO), 158.09 (C-7a),
153.11 (C-3), 140.16 (C-5, 6), 137.61, 133.12 (ArC), 129.62, 127.57,
127.41, 126.85, 126.79 (ArCH), 119.37 (C-3a), 20.71(CH3). IR (KBr):
ν (cm−1) 3300 (NH), 1680 (CO), 1610 (ArC=N), 1590 (ArC=C). MS:
m/z (%) = 401/397 [M+] (34), 382 (36), 354 (27), 283 (41), 180 (28),
91 (100), 77 (78), 76 (71), 65 (42). C20H13Cl2N3O2 (398.24): Calcd:
C, 60.32; H, 3.29; Cl, 17.80; N, 10.55. Found: C, 60.19; H, 3.38;
Cl, 17.94; N, 10.41%.
Reactions of 2,4-disubstituted thiosemicarbazides (7a–d) with 2,3-
dichloro-1,4-naphthoquinone (3)
A solution of 7a–d (1.0 mmol) in dry ethyl acetate (15 mL) was added
dropwise with stirring to a solution of 3 (1.0 mmol) in dry ethyl ace-
tate (15 mL). The reaction mixture was stirred for 72 h, during which
time it turned from orange into green and finally to brown in colour.
The reaction mixture was concentrated and subjected to PLC using
toluene/ethyl acetate (2:1) as eluent to give only one zone which
was removed and extracted to give the substituted imino-2-aryl-2,3-
dihydro-1H-benzo[f]indazole-4,9-diones 10a–d.
2-Phenyl-3-(phenylimino)-2,3-dihydro-1H-benzo[f]indazole-4,9-
dione (10a): Reddish brown crystals (0.259 g, 71 %), m.p.267–269 °C
(acetonitrile). 1H NMR (DMSO-d6): δ = 11.26 (br, 1H, indazole-NH),
δ = 8.09–8.25 (m, 2H, Ar5,8-H), 7.67–7.83 (m, 2H, Ar6,7-H), 7.33–
7.51 (m, 10 H, ArH). 13C NMR (DMSO-d6): δ = 179.34, 178.78 (CO),
156.87 (C-3), 150.93 (C-9a), 147.64, 137.57, 131.66, 130.84 (ArC),
129.68, 129.64, 127.93, 127.78, 127.67, 127.35, 126.89, 126.64
(ArCH), 112.22 (C-3a). IR (KBr): ν (cm−1) 3305 (NH), 1680 (CO),
1625 (ArC=N), 1600 (ArC=C). MS: m/z (%) = 365 [M+] (51), 262
(36), 157 (39), 129 (17), 105 (37), 103 (76), 77 (100), 65 (42).
C23H15N3O2 (365.38): Calcd: C, 75.60; H, 4.14; N, 11.50. Found:
C, 75.46; H, 4.02; N, 11.67%.
2-(4-Chlorophenyl)-5,6-dichloro-3-(phenylimino)-2,3-dihydro-1H-
indazole-4,7-dione (8c): Pale brown crystals (0.256 g, 61 %), m.p.
1
307–309 °C (acetonitrile). H NMR (DMSO-d6): δ = 11.14 (br, 1H,
indazole-NH), 7.58–7.71 (m, 9H, ArH). IR (KBr): ν (cm−1) 3290
(NH), 1675 (CO), 1615 (ArC=N), 1590 (ArC=C). MS: m/z (%) =
424/417 [M+] (44), 383 (32), 355 (21), 319 (25), 283 (17), 180 (24),
77 (100), 65 (49). C19H10Cl3N3O2 (418.66): Calcd: C, 54.51; H, 2.41;
Cl, 25.40; N, 10.04. Found: C, 54.31; H, 2.52; Cl, 25.50; N, 10.23%.
3-(Benzylimino)-5,6-dichloro-2-phenyl-2,3-dihydro-1H-indazole-
4,7-dione (8d): Brown crystals (0.229 g, 57 %), m.p. 286–288 °C
(acetonitrile). 1H NMR (DMSO-d6): δ = 11.18 (br, 1H, indazole-NH),
7.61–7.64, 7.48–7.56 (m, 10H, ArH), 4.57 (s, 2H, CH2-Ph). 13C NMR
(DMSO-d6): δ = 173.48, 173.55 (CO), 158.12 (C-7a), 153.07 (C-3),
140.28 (C-5,6), 137.61, 135.82, 133.15 (ArC), 129.66, 129.36, 128.86,
127.89, 127.46, 127.27 (ArC), 119.18 (C-3a), 51.38 (CH2Ph). IR
(KBr): ν (cm−1) 3280 (NH), 1675 (CO), 1610 (ArC=N), 1590 (ArC=C).
MS: m/z (%) = 401/397 [M+] (39), 369 (22), 298 (18), 180 (25),
91 (100), 77 (81), 65 (66). C20H13Cl2N3O2 (398.24): Calcd: C, 60.32;
H, 3.29; Cl, 17.80; N, 10.55. Found: C, 60.19; H, 3.36; Cl, 17.97;
N, 10.46%.
2-(4-Methylphenyl)-3-(phenylimino)-2,3-dihydro-1H-benzo[f]
indazole-4,9-dione (10b): Reddish brown crystals (0.280 g, 74 %),
1
m.p. 278–280 °C (acetonitrile). H NMR (DMSO-d6): δ = 11.22 (br,
1H, indazole-NH), 8.13–8.27 (m, 2H, Ar5,8-H), 7.65–7.79 56 (m, 2H,
Ar6,7-H), 7.17 (d, 2H, Ar3`,5`-H), 7.38–7.56 (m, 7H, ArH), 13C NMR
(DMSO-d6): δ = 179.37, 178.74, (CO), 156.83 (C-3), 151.06 (C-9a),
147.59, 137.64, 131.83, 130.79 (ArC), 129.60, 129.55, 127.89,
127.68, 127.41, 126.86, 126.61 (ArCH), 111.94 (C-3a), 21.27 (CH3).
IR (KBr): ν (cm−1) 3295 (NH), 1680 (CO), 1630 (ArC=N), 1595
(ArC=C). MS: m/z (%) = 379 [M+, 44], 364 (37), 261 (43), 156 (16),
128 (8), 103 (47), 91 (100), 77 (64), 65(54). C24H17N3O2 (379.41):
Calcd: C, 75.97; H, 4.52; N, 11.08. Found: C, 76.11; H, 4.43;
N, 10.95%.
2-(4-Chlorophenyl)-3-(phenylimino)-2,3-dihydro-1H-benzo[f]
indazol-4,9-dione (10c): Brown crystals (0.271 g, 68 %), m.p. 293–
295 °C (methanol). 1H NMR (DMSO-d6): δ = 11.28 (br, 1H, indazole-
NH), 8.10–8.22 (m, 2H, Ar5,8-H), 7.68–7.83 (m, 2H, Ar6,7-H), 7.43–
7.61 (m, 7H, ArH), 7.26 (d, 2H, Ar3p,5p-H). 13C NMR (DMSO-d6):
δ = 179.41, 178.69, (CO), 156.78 (C-3), 150.94 (C-9a), 147.65,
137.59, 132.78, 131.59, 130.66 (ArC), 129.68, 129.62, 127.93,
127.55, 127.38, 126.82, 126.75 (ArCH), 112.16 (C-3a). IR (KBr):
ν (cm−1) 3300 (NH), 1675 (CO), 1630 (ArC=N), 1590 (ArC=C). MS:
m/z (%) = 399/401 [M+, 32], 363 (54), 260 (29), 155 (13), 103 (49),
77 (100), 65 (57). C23H14ClN3O2 (399.83): Calcd: C, 69.09; H, 3.53;
Cl, 8.87; N, 10.51. Found: C, 68.94; H, 3.45; Cl, 9.02; N, 10.66%.
3-(Benzylimino)-2-phenyl-2,3-dihydro-1H-benzo[f]indazol-4,9-
dione (10d): Brown crystals (0.239 g, 63 %), m.p. 273–275 °C
(acetonitrile). 1H NMR (DMSO-d6): δ = 11.20 (br, 1H, indazole-NH),
8.13–8.26 (m, 2H, Ar5,8-H), 7.65–7.80 (m, 2H, Ar6,7-H), 7.29–7.48
(m, 10H, ArH), 4.62 (s, 2H, CH2Ph). 13C NMR (DMSO-d6): δ =
179.41, 178.73 (CO), 156.78 (C-3), 151.09 (C-9a), 147.59, 137.62,
131.73, 130.76 (ArC), 129.64, 129.57, 128.12, 127.84, 127.73,
127.41, 126.92, 126.61 (ArCH), 111.88 (C-3a), 52.64 (CH2-Ph). IR
(KBr): ν (cm−1) 3295 (NH), 1680 (CO), 1620 (ArC=N), 1585 (ArC=C).
MS: m/z (%) = 379 [M+, 24], 262 (32), 157 (26), 129 (19), 117 (63),
91 (100), 77 (58), 65 (46). C24H17N3O2 (379.41): Calcd: C, 75.97;
H, 4.52; N, 11.08. Found: C, 76.12; H, 4.63; N, 10.99%.
2-Phenyl-3-(phenylimino)-4,6,7-trichloro-2H-indazole-5(3H)-one
(9a): Brown crystals (0.092 g, 23 %), m.p. 294–296 °C (methanol). 1H
NMR (DMSO-d6): δ = 7.49–7.58 (m, 10H, ArH). 13C NMR (DMSO-
d6): δ = 174.31 (CO), 156.49 (C-3), 150.26 (C-7a), 141.42, 141.19,
140.12 (C-4,6,7), 147.17, 137.55, 131.22 (ArC), 129.35, 129.26,
127.85, 127.41, 126.93, 126.79 (ArCH). IR (KBr): ν (cm−1) 1680
(CO), 1625 (ArC=N), 1600 (ArC=C). MS: m/z (%) = 407/401 [M+]
(39), 365 (27), 329 (21), 293 (41), 190 (35), 167 (15), 91 (83), 77
(100), 65 (46). C19H10Cl3N3O (402.66): Calcd: C, 56.67; H, 2.50;
Cl, 26.41; N, 10.44. Found: C, 56.81; H, 2.42; Cl, 26.54; N, 10.61%.
2-(4-Methylphenyl)-3-(phenylimino)-4,6,7-trichloro-2H-indazole-
5(3H)-one (9b). Reddish brown crystals (0.091 g, 22 %), m.p. 316–
1
318 °C (methanol). H NMR (DMSO-d6): δ = 7.43–7.54 (m, 9H,
ArH), 2.24 (s, 3H, CH3), 13C NMR (DMSO-d6): δ = 174.26 (CO),
156.57 (C-3), 150.12 (C-7a), 141.36, 141.14, 140.07 (C-4,6,7),
147.22, 137.61, 131.86, 131.42 (ArC), 129.41, 127.74, 127.36,
127.01, 126.86 (ArCH), 20.87 (CH3). IR (KBr): ν (cm−1) 1675 (CO),
1630 (ArC=N), 1600 (ArC=C). MS: m/z (%) = 421/415 [M+] (37),
400 (28), 364 (25), 328 (29), 292 (18), 189 (27), 161 (17), 103 (61),
91(100), 77 (86), 65 (43). C20H12Cl3N3O (416.69): Calcd: C, 57.65;
H, 2.90; Cl, 25.52; N, 10.08. Found: C, 57.81; H, 3.01; Cl, 25.41;
N, 9.94%.
2-(4-Chlorophenyl)-3-(phenylimino)-4,6,7-trichloro-2H-indazole-
5(3H)-one (9c): Pale brown crystals (0.109 g, 25 %), m.p. 333–335 °C
(methanol). 1H NMR (DMSO-d6): δ = 7.52–7.69 (m, 9H, ArH),
13C NMR (DMSO-d6): δ = 174.15 (CO), 156.44 (C-3), 150.23 (C-7a),
141.35, 141.26, 140.16 (C-4,6,7), 147.11, 137.67, 131.55, 130.86
(ArC), 129.36, 127.65, 127.26, 126.97, 126.81 (ArCH). IR (KBr):

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Received 1 April 2010; accepted 23 June 2010
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