Synthesis and reactions of 1-azo-2-azoniaallene salts derived from pyridine derivatives

Article abstract of DOI:10.1007/PL00010141

The 1-aza-2-azonia-allene salts prepared from 3-acetyl- or 3-benzoyl-pyridine via the corresponding hydrazone and α-chloroaryl-azo derivatives react with propionitrile to afford the corresponding 3-(3-pyridyl)-1,2,4-triazolium salts. The intramolecular cy

Full text of DOI:10.1007/PL00010141

Monatshefte fuÈr Chemie 129, 1293±1303 (1998)
Synthesis and Reactions of 1-Azo-2-azonia-
allene Salts Derived from Pyridine Derivatives
Atef M. Amer
Chemistry Department, Faculty of Science, Zagazig University, Zagazig, Egypt
Summary. The 1-aza-2-azonia-allene salts prepared from 3-acetyl- or 3-benzoyl-pyridine via the
corresponding hydrazone and ꢀ-chloroaryl-azo derivatives react with propionitrile to afford the
corresponding 3-(3-pyridyl)-1,2,4-triazolium salts. The intramolecular cyclization products could
be only isolated as the main products if the intermediate ꢀ-chlorophenyl-azo derivatives prepared
from 4-benzoyl pyridine were treated with SbCl5 in presence or absence of propionitrile. Also, only
3-methyl-1,2,3-triazolo[1,5-a]pyridinium salts were obtained by reaction of the cumulene prepared
from 2-acetyl-pyridine with or without propionitrile in good yields. Treatment of 3-pyridylinda-
zolium hexachloroantimonates and 3-methyl-1,2,3-triazolo[1,5-a]pyridinium salts with Na2CO3
gave 3-pyridylindazoles and 3-methyl-1,2,3-triazolo[1,5-a]pyridine.
Keywords. Cycloadditions; Hydrazones; Indazoles; Triazolium; Pyridines.
Synthese und Reaktionen von aus Pyridinderivaten abgleiteten 1-Azo-2-azoniumallensalzen
Zusammenfassung. Die 1-Aza-2-azoniasalze, die aus 3-Acetyl- oder 3-Benzoylpyridin uÈber die
entsprechenden Hydrazone und ꢀ-Chlorazoderivate dargestellt wurden, reagieren mit Propionitril zu
den entsprechenden 3-(3-Pyridyl)-1,2,4-triazoliumsalzen. Intramolekulare Cyklisierungsprodukte
È
konnten nur isoliert werden, wenn die intermediaren ꢀ-Chlorphenylazoderivate aus Benzoylpyridin
abgeleitet wurden und mit SbCl5 mit oder ohne Propionitril umgesetzt wurden. Ebenso wurden im
Fall der Reaktion des Cumulens aus 2-Acetylpyridin mit oder ohne Propionitril nur die 3-Methyl-
1,2,3-triazolo[1,5-a]pyridiniumsalze in guten Ausbeuten erhalten. Behandlung von 3-Pyridylinda-
zoliumhexachloroantimonaten mit Na2CO3 ergab 3-Pyridylindazole und 3-Methyl-1,2,3-tria-
zolo[1,5-a]pyridine.
Introduction
A series of studies have been directed towards the reaction of 1-aza-2-azonia-allene
salts with multiple bonds [1±5]. These compounds, prepared from hydrazones with
substituents such as methyl, phenyl, etc. have been postulated by Jochims as
intermediates in the cycloaddition to many types of multiple bonds [3±11]. It
seemed of interest to study the applicability of the cycloaddition protocol for
heterocumulenes derived from the three isomeric acetyl- and benzoyl-pyridines. In
the present study, the effect of the pyridyl ring in the heterocumulenes during the
cycloaddition of compounds 3a±i with nitriles will be investigated. The objective
of such a study was to elucidate the site selectivity of this procedure with respect to

1294
A. M. Amer
a synthetic method to obtain substituted triazolium and/or indazolium salts.
Recently, some indazole derivatives have been reported as inhibitors of
phosphodiesterase IV and tumor necrosis factor production [12]. This assessment
prompted us to prepare derivatives of 3-pyridylindazole from 3-pyridyl-indazolium
salts starting from azoazonia-allene salts to make them available for biological
testing.
Results and Discussion
The synthesis of 3,4-dimethyl-3-pyridyl-4-yl-1-(2,4,6-trichlorophenyl)-3H-[1,2,4]-
triazolium hexachloroantimonate from N-(1-pyridin-yl-ethylidene)-N0-(2,4,6-tri-
chlorophenyl)-hydrazine (1d) and acetonitrile in the presence of a Lewis acid has
been described previously [2]. The results of further experiments designed to
explore the scope and the limitations of this procedure as a synthetic method for the
formation of the pyridyl-triazolium salts 5a±b and 8d and the 3-pyridylindazoles 7
and 10e±g are the subject of the present investigation. For this purpose a series of
pyridyl hydrazones (1a±i) were synthesized by treatment of 2,4,6-trichlorophe-
nylhydrazine, ethyl carbazate, and phenyl hydrazine with the pyridyl ketones
3-acetyl-pyridine, 3-benzoyl-pyridine, 4-acetyl-pyridine, 4-benzoyl-pyridine, or
2-acetyl-pyridine. Oxidation of 1a±i by tert-butylhypochloride gave the geminal
chloropyridyl-azo compounds 2a±i in good yields (Scheme 1).
When 2a±i were treated with the Lewis acid SbCl5 at ꢀ60ꢁC, they afforded the
highly reactive 1-aza-2-azonia allene salts 3a±i. It was found that it is possible to
trap 3a, b with nucleophiles such as propionitrile to obtain the triazolium salts 5
(Scheme 2). To rationalize the formation of 5a, b, one has to assume the formation
of intermediates 4a, b which undergo a 1,2-shift of the substituent R2. Treatment of
2b, c with SbCl5 in CH2Cl2 at ꢀ50ꢁC induced an intramolecular cyclization to
afford the 3-pyridyl-3-yl-1H-indazolium hexachloroantimonates 6b, c in good
yields. It is worth noting the complete regioselectivity of the cycloaddition, the
R1
R2
R3
1a±3a 3-pyridyl CH3 2,4,6-trichlorophenyl
1b±3b 3-pyridyl Ph 2,4,6-trichlorophenyl
1c±3c 3-pyridyl Ph COOC2H5
1d±3d 4-pyridyl CH3 2,4,6-trichlorophenyl
1e±3e 4-pyridyl Ph
1f±3f 4-pyridyl Ph
1g±3g 4-pyridyl Ph
2,4,6-trichlorophenyl
COOC2H5
Ph
1h±3h 2-pyridyl CH3 2,4,6-trichlorophenyl
1i±3i
2-pyridyl CH3 COOC2H5
Scheme 1

1-Azo-2-azonia-allene Salts
1295
Scheme 2
complete site selectivity of the rearrangement, and the exclusive migration of phenyl.
On the other hand, no condensation products from intramolecular cyclization at the
carbon pyridine could be observed (Scheme 2).
The reaction of the cumulene 3d with propionitrile afforded only the 3H-
triazolium salt 9d without migration of the methyl group from carbon to nitrogen
(Scheme 3). The triazolium derivatives 9d and 10d can easily be distinguished by
their 1H NMR methyl reasonances which appear in the range of 2.3 to 2.6 ppm for
9d and of 3.8 to 4.1 ppm for 10d. This is in contrast to the results for 3-acetyl-
Scheme 3

1296
A. M. Amer
Scheme 4
pyridine. Also, the reaction of the cumulenes 3e±g with or without propionitrile
afforded only the indazolium salts 11e±g via intramolecular cyclization. The
expected triazolium salts did not form in contrast to cumulene 3b prepared from
3-benzoyl-pyridine (Scheme 3).
Similarly, only the 3-methyl-1,2,3-triazolo[1,5]pyridinium salts 14h±i were
isolated when the cumulenes 3h±i were treated with or without propionitrile, and
no traces of the expected triazolium salts could be observed (Scheme 4).
In conclusion, only the cumulenes 3a, b derived from 3-acetyl- or 3-benzoyl-
pyridine show regioselectivity in the cycloaddition reaction with nitrile. This is in
contrast to the cumulenes 3e±i derived from 4-benzoyl- or 2-acetyl-pyridine.
Treatment of 3-pyridyl-indazolium salts 6b and 11e±g as well as the 3-methyl-
1,2,3-triazolo[1,5]pyridinium salt 14i with aqueous sodium carbonate yielded the
3-pyridyl-indazole derivatives 7b, 12e±g, and 3-methyl-1,2,3-triazolo[1,5]pyridine
15 in good yields. This method provides a possible starting point for the synthesis
of many new indazole derivatives. Furthermore, treatment of indazoles 7b or 12e
with picric acid afford the pure indazolium picrates 8b or 13e. The structures of all
novel compounds were con®rmed by their elemental and spectroscopic data.
Experimental
Melting points were measured on a Ko¯er hot stage microscope (Reichert, Vienna) and are
uncorrected. 1H and 13C NMR spectra were recorded on a Bruker DPX 200 spectrometer at 200 MHz
(1H) and 50 MHz (13C); chemical shifts are given in ꢁ units relative to internal TMS at 295 K. IR
spectra were obtained on a Biorad FT-IR-45 instrument. All experiments were carried out with
exclusion of moisture. For all new compounds satisfactory elemental analyses were obtained.
Preparation of hydrazones 1
A mixture of 100 mmol of ketone (3-acetyl-pyridine, 3-benzoyl-pyridine, 4-benzoyl-pyridine, or
2-acetyl-pyridine) and 100 mmol hydrazine in 70 ml methanol ‡ 1 ml acetic acid was heated under
re¯ux for 5 h. Evaporation of the solvent and crystallization of the residue afforded the pure
hydrazone. N-(1-pyridin-4-yl-ethylidene)-N0-(2,4,6-trichlorophenyl)-hydrazine (1d) was prepared
according to Ref. [2].
N-(1-Pyridin-3-yl-ethylidene)-N0-(2,4,6-trichlorophenyl)-hydrazine (1a; C13H10Cl3N3)
Prepared from 12.10 g 3-acetyl-pyridine (100 mmol) and 21.15 g 2,4,6-trichlorophenylhydrazine
(100 mmol); crystallization from petrol ether (50±70ꢁC) gave 29.85 g colourless ®ne crystals (95%);

1-Azo-2-azonia-allene Salts
1297
1
m.p.: 86±90ꢁC; IR (KBr): ꢂ ˆ 3350 br, 2950 br, 1610, 1480, 1450 cmꢀ1; H NMR (CDCl3): 2.37
(s, CH3), 7.38 (m, 3H, Hpy‡trichlorophenyl), 7.47 (s, NH), 8.13±8.19 (dd, 1Hpy), 8.56±8.59 (dd, 1Hpy),
8.97 (d, 1Hpy) ppm; 13C NMR (CDCl3): 21.38 (CH3), 133.45, 135.87, 137.63, 138.53, 144.02,
144.42, 146.90, 152.53, 154.91, 157.09 (aryl, C=N) ppm.
N-(Phenyl-pyridin-3-yl-methylene)-N0-(2,4,6-trichlorophenyl)-hydrazine (1b; C18H12Cl3N3)
Prepared from 18.32 g 3-benzoyl-pyridine (100 mmol) and 21.15 g 2,4,6-trichlorophenyl-hydrazine
(100 mmol); crystallization from methanol gave 3.48 g colourless ®ne crystals (89%); m.p.: 118±
1
120ꢁC; IR (KBr): ꢂ ˆ 3360 br, 3130, 1620, 1580, 1520, 1490 cmꢀ1; H NMR (CDCl3): 7.29 (m,
5Har), 7.47 (s, NH), 7.55±7.62 (m, 3Har), 7.79 (dd, 1Hpy), 8.73 (d, Hpy), 8.83 (s, 2Hpy) ppm; 13C
NMR (CDCl3): 133.96, 135.78, 136.05, 137.23, 138.03, 138.47, 138.63, 139.82, 146.42, 146.74,
154.85, 159.26, 160.41 (aryl, C=N) ppm.
N-Ethoxycarbonyl-N0-(phenyl-pyridin-3-yl-methylene)-hydrazine (1c; C15H15N3O2)
Prepared from 18.32 g 3-benzoyl-pyridine (100 mmol) and 10.41 g ethyl carbazate (100 mmol);
crystallization from petrol ether (50±70ꢁC) gave 4.18 g colourless ®ne crystals (90%); m.p.:
1
72±74ꢁC; IR (KBr): ꢂ ˆ 3350, 3046, 2985, 1738, 1690, 1600, 1580, 1585, 1568, 1522 cmꢀ1; H
NMR (CDCl3): 1.31 (t, J ˆ 7.1 Hz, CH3), 4.27 (q, J ˆ 7.1 Hz, CH2), 7.28±7.82 (m, 6Har), 8.05 (d,
1Hpy), 8.35 (br, NH), 8.60±8.76 (m, 2Hpy) ppm.
N-(Phenyl-pyridin-4-yl-methylene)-N0-(2,4,6-trichlorophenyl)-hydrazine (1e; C18H12Cl3N3)
Prepared from 18.32 g 4-benzoyl-pyridine (100 mmol) and 21.15 g 2,4,6-trichlorophenyl-hydrazine
(100 mmol); crystallization from ethanol gave 35.79 g colourless ®ne crystals (95%); m.p.: 140±
1
145ꢁC; IR (KBr): ꢂ ˆ 3360, 3135, 1620, 1580, 1568, 1520 cmꢀ1; H NMR (CDCl3): 7.31±7.66 (m,
9Har), 7.84 (s, NH), 8.55 (d, 2Hpy) ppm; 13C NMR (CDCl3): 129.99, 133.02, 135.42, 135.98, 137.25,
138.05, 138.21, 138.56, 139.60, 140.35, 145.87, 154.36, 154.98, 159.48, 161.03 (aryl, C=N) ppm.
N-Ethoxycarbonyl-N0-(phenyl-pyridin-4-yl-methylene)-hydrazine (1f; C15H15N3O2)
Prepared from 18.32 g 4-benzoyl-pyridine (100 mmol) and 10.41 g ethyl carbazate (100 mmol);
crystallization from ethanol gave 20.75 g colourless ®ne crystals (77%); m.p.: 180ꢁC; IR (KBr):
ꢂ ˆ 3346, 3133 br, 3046, 2986, 1739, 1689, 1599, 1585, 1522 cmꢀ1
;
1H NMR (CDCl3): 1.32
(t, J ˆ 7.1 Hz, CH3), 4.27 (q, J ˆ 7.1 Hz, CH2), 7.22 (d, 2Har), 7.36 (s, 3Har), 7.53 (d, 2Hpy), 7.66
(s, NH), 8.86 (d, 2Hpy) ppm; 13C NMR (CDCl3): 24.04 (CH3), 71.76 (CH2), 131.55, 132.68, 136.82,
137.83, 139.49, 145.21, 149.72, 156.54, 157.71, 160.92, 162.00 (aryl, C=N) ppm.
N-Phenyl-N0-(phenyl-pyridin-4-yl-methylene)-hydrazine (1g; C18H15N3)
Prepared from 18.32 g 4-benzoyl-pyridine (100 mmol) and 10.81 g phenylhydrazine (100 mmol)
after heating for 15 min; crystallization from CHCl3/MeOH gave 24.00 g yellowish white ®ne
1
crystals (88%); m.p.: 192±196ꢁC; IR (KBr): ꢂ ˆ 3352 br, 3133, 3040, 1620, 1580, 1518 cmꢀ1; H
NMR (CDCl3): 6.92 (t, 1Har), 7.10 (d, 2Har), 7.30 (m, 4Har), 7.48 (d, 2Hpy), 7.56 (m, 3Har), 7.84
(s, NH), 8.49 (d, 2Hpy) ppm; 13C NMR (CDCl3): 123.00, 130.01, 130.97, 138.65, 138.93, 139.52,
139.72, 140.41, 150.05, 153.03, 156.38, 157.73, 161.01 (aryl, C=N) ppm.
N-(1-Pyridin-2-yl-ethylidene)-N0-(2,4,6-trichlorophenyl)-hydrazine (1h; C13H10Cl3N3)
Prepared from 12.10 g 2-acetyl-pyridine (100 mmol) and 21.15 g 2,4,6-trichlorophenyl-hydrazine
(100 mmol); yellow orange oil which slowly solidi®es at ꢀ15ꢁC; crystallization from petrol ether

1298
A. M. Amer
(50±70ꢁC) gave 28.35 g ®ne crystals (90%); m.p.: 54ꢁC; IR (KBr): ꢂ ˆ 3350 br, 3135, 3040, 1618,
1
1579, 1567, 1490 cmꢀ1; H NMR (CDCl3): 2.50 (s, CH3), 7.23 (t, 1Hpy), 7.38 (s, 2Htrichlorophenyl),
7.63 (s, NH), 7.68 (t, 1Hpy), 8.15 (d, 1Hpy), 8.60 (d, 1Hpy) ppm; 13C NMR (CDCl3): 19.65
(CH3), 129.74, 132.18, 132.57, 135.50, 137.04, 138.51, 145.71, 147.06, 157.04, 157.93, 165.34
(aryl, C=N) ppm.
N-Ethoxycarbonyl-N0-(1-pyridin-2-yl-ethylidene)-hydrazine (1i; C10H13N3O2)
Prepared from 12.10 g 2-acetyl-pyridine (100 mmol) and 10.41 g ethyl carbazate (100 mmol);
crystallization from ethylacetate/petrol ether (50±70ꢁC) gave 24.18 g colourless ®ne crystals (90%);
1
m.p.: 110±112ꢁC; IR (KBr): ꢂ ˆ 3355, 3133, 2985, 2905, 1740, 1690, 1600, 1567, 1518 cmꢀ1; H
NMR (CDCl3): 1.34 (t, J ˆ 7.1 Hz, CH3), 2.38 (s, 3H, CH3), 4.33 (q, J ˆ 7.1 Hz, CH2), 7.22 (t, 1Hpy),
7.75 (t, 1Hpy), 8.10 (s, NH), 8.20 (d, 1Hpy), 8.64 (d, 1Hpy) ppm.
Preparation of ꢀ-chloroaryl-azo compounds 2
The reaction was carried out in the dark. 13.03 g tert-butylhypochlorite (120 mmol) were added
dropwise to a cold (ꢀ10ꢁC) solution of 100 mmol hydrazones 1a±i in 120 ml CHCl3. The mixture
was stirred for 3 h at 0ꢁC. Evaporation of the solvent afforded the orange-yellow compounds 2. In
most cases, the oil thus obtained was used without further puri®cation. 1-Chloro-1-pyridin-4-yl-
ethyl-(2,4,6-trichlorophenyl)-diazene (2d) was prepared according to Ref. [2].
1-Chloro-1-pyridin-4-yl-ethyl-(2,4,6-trichlorophenyl)-diazene (2a; C13H9Cl4N3)
1
Prepared from 3.14 g 1a (10 mmol); yield: 3.30 g (95%) as a yellow oil; H NMR (CDCl3): 2.38
(s, CH3), 7.44 (s, 2Htrichlorophenyl), 7.45 (m, 1Hpy), 8.06 (tt, 1Hpy), 8.66 (dd, 1Hpy), 8.97 (d, 1Hpy) ppm.
13C NMR (CDCl3): 39.31 (CH3), 103.47 (CCl), 133.29, 135.43, 136.70, 138.63, 143.84, 145.36,
146.34, 154.69, 156.58, 158.55 (aryl) ppm.
Chloro-phenyl-pyridin-3-yl-methyl-(2,4,6-trichlorophenyl)-diazene (2b; C18H11Cl4N3)
1
Prepared from 3.76 g 1b (10 mmol); yield: 4.00 g (98%) as an orange oil; H NMR (CDCl3): 7.27±
7.50 (m, 7Har), 8.07 (dd, 1Hpy), 8.65 (dd, 1Hpy), 8.95 (d, 2Hpy) ppm; 13C NMR (CDCl3): 105.30
(CCl), 136.38, 136.75, 137.15, 137.33, 137.44, 137.97, 138.24, 138.71, 139.61, 145.06, 146.83,
150.26, 150.77, 151.64, 154.87 (aryl) ppm.
Chloro-phenyl-pyridin-3-yl-methyl-ethoxycarbonyl-diazene (2c: C15H14ClN3O2)
Prepared from 2.69 g 1c (10 mmol); yield: 2.40 g (80%) as a reddish oil which solidi®ed at ꢀ15ꢁC;
IR (CCl4): ꢂ ˆ 3025, 2985, 1750, 1610, 1580, 1500 cmꢀ1
.
Chloro-phenyl-pyridin-4-yl-methyl-(2,4,6-trichlorophenyl)-diazene (2e; C18H11Cl4N3)
1
Prepared from 3.76 g 1e (10 mmol); yield: 4.05 g (99%) as a brown oil; H NMR (CDCl3): 7.40
(s, 5Hph), 7.56±7.59 (m, 4H, Hpy and Htrichlorophenyl), 8.69 (d, 2Hpy) ppm; 13C NMR (CDCl3): 108.37
(CCl), 132.57, 135.39, 136.89, 137.76, 138.20, 138.66, 138.59, 139.71, 143.99, 148.65, 154.86,
159.35, 159.88 (aryl) ppm.

1-Azo-2-azonia-allene Salts
1299
Chloro-phenyl-pyridin-4-yl-methyl-ethoxycarbonyl-diazene (2f; C15H14ClN3O2)
Prepared from 2.69 g 1f (10 mmol); yield: 2.50 g (83%) as a brown oil which solidi®ed at ꢀ15ꢁC; 1H
NMR (CDCl3): 1.44 (t, J ˆ 7.1 Hz, CH3), 4.48 (q, J ˆ 7.1 Hz, CH2), 7.38 (s, 5Har), 7.50 (d, 2Har),
7.55 (m, 2Har), 8.67 (d, 2Hpy) ppm.
Chloro-phenyl-pyridin-4-yl-methyl-phenyl-diazene (2g; C18H14ClN3)
Prepared from 2.73 g 1g (10 mmol); yield: 2.65 g (85%) as a orange red oil; 1H NMR (CDCl3): 7.36±
7.56 (m, 10Har), 7.81±7.91 (d, 2Hpy), 8.64 (d, 2Hpy) ppm; 13C NMR (CDCl3): 107.15 (CCl), 132.47,
132.57, 133.09, 134.38, 137.47, 138.20, 138.63, 138.88, 139.17, 144.78, 149.97, 158.57, 158.94
(aryl) ppm.
1-Chloro-1-pyridin-2-yl-ethyl-(2,4,6-trichlorophenyl)-diazene (2h; C13H9Cl4N3)
Prepared from 3.14 g 1h (10 mmol); yield: 3.47 g (100%) as a yellow oil which solidi®ed to give a
yellow powder; m.p.: 75ꢁC; 1H NMR (CDCl3): 2.46 (s, CH3), 7.29 (t, 1Hpy), 7.42 (s, 2Htrichlorophenyl),
7.72 (d, 1Hpy), 7.76 (t, 1Hpy), 8.70 (d, 1Hpy) ppm; 13C NMR (CDCl3): 37.31 (CH3), 105.75 (CCl),
132.26, 135.44, 136.58, 138.51, 140.07, 143.44, 146.49, 158.59, 167.24 (aryl) ppm.
1-Chloro-1-pyridin-2-yl-ethyl-ethoxycarbonyl-diazene (2i; C10H12ClN3O2)
1
Prepared from 2.07 g 1i (10 mmol); yield: 1.90 g (79%) as a yellow oil; H NMR (CDCl3): 1.36
(t, J ˆ 7.1 Hz, CH3), 2.27 (s, CH3), 4.39 (q, J ˆ 7.1 Hz, CH2), 7.20 (t, 1Hpy), 7.32 (d, 1Hpy), 7.64
(t, 1Hpy), 8.59 (d, 2Hpy) ppm.
Reactions of the ꢀ-chloroarylazo compounds with propionitrile and formation of [1,2,4]triazolium
hexachloroantimonates 5a±b and 9b
A solution of 2.99 g SbCl5 (10 mmol) in 10 ml CH2Cl2 was added dropwise to a cold (ꢀ60ꢁC)
solution of 10 mmol of the ꢀ-chloroarylazo compound and 15 mmol nitrile in 25 ml CH2Cl2. The
mixture was stirred at ꢀ60ꢁC for 2 h, then at 0ꢁC for 1 h, and ®nally at room temperature for 15 min.
The solvent was evaporated under reduced pressure, and the remaining salt was puri®ed by
crystallization.
5-Ethyl-2-methyl-3-pyridyl-3-yl-1-(2,4,6-trichlorophenyl)-1H-[1,2,4]triazolium
hexachloroantimonate (5a; C16H14Cl9N4Sb)
Prepared from 3.49 g 2a (10 mmol), 2.99 g SbCl5 (10 mmol), and 0.83 g propionitrile (15 mmol); the
residue was crystallized at ꢀ20ꢁC from acetonitrile/ether to yield 5.73 g colourless ®ne crystals
(82%); m.p.: 188±193ꢁC; IR (KBr): ꢂ ˆ 3077, 2942, 1635, 1567, 1560, 1507, 1488, 1460, 1389,
1379 cmꢀ1
;
1H NMR (DMSO-d6): 1.30 (t, J ˆ 7.5 Hz, CH3), 2.84 (q, J ˆ 7.5 Hz, CH2), 4.05
(s, NCH3), 7.75 (dd, 1Hpy), 8.35 (s, 2Htrichlorophenyl), 8.50 (dd, 1Hpy), 8.94 (dd, 1Hpy), 9.25 (d, 1Hpy)
ppm; 13C NMR (DMSO-d6): 20.55 (CH3), 29.52 (CH2), 46.13 (NCH3), 130.46, 132.91, 134.19,
135.43, 140.80, 145.51, 147.96, 150.79, 159.99, 163.61, 167.40, 173.89 (aryl, C=N) ppm.
5-Ethyl-2-phenyl-3-pyridyl-3-yl-1-(2,4,6-trichlorophenyl)-1H-[1,2,4]triazolium
hexachloroantimonate (5b; C21H16Cl9N4Sb)
Prepared from 4.11 g 2b (10 mmol), 2.99 g SbCl5 (10 mmol), and 0.83 g propionitrile (15 mmol); the
residue was crystallized at ꢀ20ꢁC from acetonitrile/ether to yield 4.21 g colourless ®ne crystals

1300
A. M. Amer
(55%); m.p.: 206±208ꢁC; IR (KBr): ꢂ ˆ 3078, 2974, 1637, 1567, 1558, 1507, 1488, 1458, 1433,
1
1389, 1379 cmꢀ1; H NMR (DMSO-d6): 1.41 (t, CH3), 2.97 (q, CH2), 7.40±7.62 (m, 4Har), 7.66
(d, 2Har), 7.81 (dd, 1Har), 8.15 (s, 2Har), 8.79 (s, 2Har) ppm; 1H NMR (CD3CN): 1.46 (t, J ˆ 7.5 Hz,
CH3), 2.96 (q, J ˆ 7.5 Hz, CH2), 7.64±7.66 (s, 4Har), 7.76 (m, 1Har), 7.78 (s, 2Har), 8.20 (m, 1Har),
8.50 (d, 1Har), 8.96 (s, d, 2Har) ppm; 13C NMR (DMSO-d6): 20.59 (CH3), 29.73 (CH2), 130.23,
133.18, 133.50, 134.05, 137.25, 139.99, 140.33, 144.20, 145.60, 147.66, 150.70, 159.84, 163.66,
167.65, 174.97 (aryl, C=N) ppm.
5-Ethyl-3-methyl-3-pyridyl-4-yl-1-(2,4,6-trichlorophenyl)-1H-[1,2,4]triazolium
hexachloroantimonate (9d; C16H14Cl9N4Sb)
Prepared from 3.49 g 2d (10 mmol), 2.99 g SbCl5 (10 mmol), and 0.83 g propionitrile (15 mmol); the
residue was crystallized at ꢀ20ꢁC from acetonitrile and ether to yield 4.55 g faint yellow ®ne crystals
(65%); m.p.: 222ꢁC; IR (KBr): ꢂ ˆ 3077, 2972, 1615, 1560, 1550, 1531, 1485, 1450, 1390 cmꢀ1; 1H
NMR (DMSO-d6): 1.38 (t, J ˆ 7.5 Hz, CH3), 2.39 (s, CH3), 2.88 (q, J ˆ 7.5 Hz, CH2), 7.96 (d, 2Hpy),
8.35 (s, 2Htrichlorophenyl), 9.12 (d, 2Hpy) ppm.
General procedure for the preparation of 3-pyridyl-1H-indazolium salts 6b, c and 11e±g
A solution of 2.99 g SbCl5 (10 mmol) in 10 ml CH2Cl2 was added dropwise to a solution of 10 mmol
ꢀ-chlorophenyl-azo derivatives 2 in 25 ml CH2Cl2 at ꢀ50ꢁC. The mixture was stirred for 1 h at
ꢀ50ꢁC, then for 1 h at 0ꢁC, and for 15 min at room temperature. The solvent was evaporated and the
residue was crystallized to give the pure indazolium derivatives.
3-Pyridyl-3-yl-1-(2,4,6-trichlorophenyl)-1H-indazolium hexachloroantimonate
(6b; C18H11Cl9N3Sb)
Prepared from 4.11 g 2b (10 mmol) and 2.99 g SbCl5 (10 mmol); the residue was crystallized at
ꢀ20ꢁC from acetonitrile/ether to yield ®ne crystals (4.40 g, 62%); m.p.: 217±220ꢁC; IR (KBr):
ꢂ ˆ 3278, 3168, 3083, 1631, 1598, 1574, 1553, 1525, 1511, 1488, 1453 cmꢀ1; 1H NMR (DMSO-d6):
7.40±7.59 (m, 3Har), 8.05 (d, 1Har), 8.09 (s, 2Htrichlorophenyl), 8.31 (d, 1Har), 8.88 (d, 1Har), 8.99
(d, 1Har), 9.46 (s, 1Har), 11.50 (br, NH) ppm; 1H NMR (CD3CN): 7.37 (d, 1Har), 7.52±7.66 (m, 2Har),
7.85 (s, 2Htrichlorophenyl), 8.22 (d, 2Har), 8.75 (t, 1Har), 9.24±9.35 (m, 2Har), 13.50 (br, NH) ppm; 13
C
NMR (DMSO-d6): 120.94, 130.74, 131.21, 133.45, 136.87, 138.66, 139.46, 140.53, 142.48, 145.22,
146.33, 151.02, 151.11, 151.75, 152.26, 153.80 (aryl, C=N) ppm; 13C NMR (CD3CN): 120.22,
130.05, 130.57, 133.55, 137.78, 138.39, 139.06, 141.82, 142.74, 145.18, 146.58, 149.05, 149.48,
150.02, 151.83, 154.46 (aryl, C=N) ppm.
1-Ethoxycarbonyl-3-pyridyl-3-yl-1H-indazolium hexachloroantimonate (6c; C15H14Cl6N3O2Sb)
Prepared from 3.03 g 2c (10 mmol) and 2.99 g SbCl5 (10 mmol); the residue was crystallized at
ꢀ20ꢁC from acetonitrile/ether to yield 2.10 g ®ne crystals (35%); m.p.: 94±97ꢁC; IR (KBr):
ꢂ ˆ 3246, 3088, 3062, 2983, 1740, 1671, 1654, 1635, 1599, 1577, 1559, 1541, 1497 cmꢀ1; 1H NMR
(CD3CN): 1.23 (t, J ˆ 7.1 Hz, CH3), 4.18 (q, J ˆ 7.1 Hz, CH2), 7.34±7.87 (m, 5Har), 8.65±9.03
(m, 3Har), 12.78 (br, NH) ppm.
3-Pyridyl-4-yl-1-(2,4,6-trichlorophenyl)-1H-indazolium hexachloroantimonate
(11e; C18H11Cl9N3Sb)
Prepared from 4.11 g 2e (10 mmol), with or without propionitrile (15 mmol), and 2.99 g SbCl5
(10 mmol); the residue was crystallized at ꢀ20ꢁC from acetonitrile to yield 5.00 g ®ne crystals

1-Azo-2-azonia-allene Salts
1301
(71%); m.p.: 217±222ꢁC; IR (KBr): ꢂ ˆ 3277, 3166, 3083, 1632, 1598, 1574, 1553, 1525, 1511,
1487 cmꢀ1; 1H NMR (DMSO-d6): 7.47±7.60 (m, 3Har), 8.11 (s, 2Htrichlorophenyl), 8.43 (d, 1Har), 8.65
1
(d, 2Har), 8.96±9.00 (d, 2Har), 11.50 (br, NH) ppm; H NMR (CD3CN): 7.20 (d, 1Har), 7.40±7.69
(m, 2Har), 7.86 (s, 2Htrichlorophenyl), 8.34±8.38 (d, 1Har), 8.69±8.83 (m, 4Har), 13.00 (br, NH) ppm; 13
C
NMR (CD3CN): 120.53, 130.36, 131.23, 133.68, 134.37, 135.44, 138.52, 139.12, 142.10, 145.01,
146.79, 150.00, 151.32, 152.19, 161.01 (aryl, C=N) ppm.
1-Ethoxycarbonyl-3-pyridyl-4-yl-1H-indazolium hexachloroantimonate (11f; C15H14Cl6N3O2Sb)
Prepared from 3.03 g 2f (10 mmol) and 2.99 g SbCl5 (10 mmol); the residue was crystallized
at ꢀ20ꢁC from acetonitrile/ether to yield 2.30 g ®ne crystals (38%); m.p.: 203ꢁC; IR (KBr):
1
ꢂ ˆ 3126, 3062, 2984, 1740, 1642, 1605, 1579, 1541, 1510, 1489 cmꢀ1; H NMR (CD3CN): 1.29
(t, J ˆ 7.1 Hz, CH3), 4.24 (q, J ˆ 7.1 Hz, CH2), 7.35±7.69 (m, 4Har), 8.03 (d, 2Har), 8.57 (t, 2Har),
12.80 (br, NH) ppm.
1-Phenyl-3-pyridyl-4-yl-1H-indazolium hexachloroantimonate (11g; C18H14Cl6N3Sb)
From 3.07 g 2g (10 mmol), with or without propionitrile (15 mmol), and 2.99 g SbCl5 (10 mmol); the
residue was crystallized at ꢀ20ꢁC from acetonitrile and ether to yield 3.00 g greenish yellow ®ne
crystals (48%); m.p.: 215±220ꢁC; IR (KBr): ꢂ ˆ 3196, 3096, 3080, 2923, 2255 (w), 1635, 1595,
1560, 1525, 1507, 1497 cmꢀ1 1H NMR (DMSO-d6): 7.54±7.92 (m, 8Har), 8.45 (d, 1Har), 8.67
;
(d, 2Har), 8.96 (d, 2Har) ppm; 13C NMR (DMSO-d6): 121.84, 127.59, 131.09, 132.41, 134.10,
134.41, 134.50, 135.01, 138.31, 138.53, 139.13, 139.96, 148.62, 150.44, 158.10 (aryl, C=N) ppm.
3-Methyl-1-(2,4,6-trichlorophenyl)-1,2,3-triazolo[1,5-a]pyridinium hexachloroantimonate
(14h; C13H9Cl9N3Sb)
Prepared from 3.49 g 2h (10 mmol), with or without propionitrile (15 mmol), and 2.99 g SbCl5
(10 mmol) as described for 6b; the residue was crystallized from acetonitrile to yield 6.00 g faint
yellow prisms (91%); m.p.: 185±188ꢁC; IR (KBr): ꢂ ˆ 3095, 3030, 1625, 1576, 1556, 1485, 1432,
1378 cmꢀ1; 1H NMR (CD3CN): 2.89 (s, CH3), 7.95 (s, 2Htrichlorophenyl), 8.07 (t, 1Hpy), 8.39 (t, 1Hpy),
8.59 (d, 1Hpy), 8.81 (d, 1Hpy) ppm; 13C NMR (CD3CN): 20.12 (CH3), 131.33, 134.20, 134.92,
135.48, 140.18, 145.77, 146.25, 150.70, 153.94 (aryl, C=N) ppm; 13C NMR (CH2Cl2): 21.34 (CH3),
131.41, 134.49, 135.89, 140.45, 145.09, 146.33, 146.44, 152.02, 153.14 (aryl, C=N) ppm.
1-Ethoxycarbonyl-3-methyl-1,2,3-triazolo[1,5-a]pyridinium hexachloroantimonate
(14i; C10H12Cl6N3O2Sb)
Prepared from 2.41 g 2i (10 mmol), with or without propionitrile (15 mmol), and 2.99 g SbCl5
(10 mmol) as described for 6b; the residue was crystallized from acetonitrile and ether to yield 3.90 g
faint brown crystals (72%); m.p.: 80±82ꢁC; IR (KBr): ꢂ ˆ 3092, 3030, 2942, 1809 (w), 1709, 1620,
1
1607, 1528, 1460, 1376 cmꢀ1; H NMR (DMSO-d6): 1.57 (t, J ˆ 7.1 Hz, CH3), 2.59 (s, 3H, CH3),
4.95 (q, J ˆ 7.1 Hz, CH2), 6.71 (t, 1Hpy), 6.79 (t, 1Hpy), 7.24 (d, 1Hpy), 7.49 (d, 1Hpy) ppm.
General procedure for the hydrolysis of 6 and 14 and the formation
of 1H-indazole derivatives 7b and 12e±g
A solution of 4.0 g Na2CO3 in 15 ml water was added dropwise at room temperature to a solution of
10 mmol indazolium salts 6b or 11e±g in 15 ml CHCl3. The mixture was stirred for 30 min and then
extracted with 2Â20 ml CHCl3. The combined organic extracts were dried over anhydrous Na2SO4

1302
A. M. Amer
and the solvent was evaporated. The residue was puri®ed by column chromatography on silica using
a mixture of CHCl3/CH3OH ˆ 20/1 as eluent, the solvent was evaporated, and the residue was
crystallized to give pure indazole derivatives 7b and 12e±g.
3-Pyridyl-3-yl-1-(2,4,6-trichlorophenyl)-1H-indazole (7b; C18H10Cl3N3)
Prepared from 7.10 g 6b (10 mmol); yield: 2.63 g (71%) as brownish oil which solidi®ed at ꢀ20ꢁC
and crystallized from aqueous ethanol to give faint ®ne crystals; m.p.: 138±142ꢁC; IR (KBr):
ꢂ ˆ 3075, 3032, 1631, 1601, 1573, 1552, 1523, 1510, 1491 cmꢀ1; 1H NMR (CDCl3): 7.10 (d, 1Har),
7.28±7.46 (m, 3Har), 7.53 (s, 2Htrichlorophenyl), 8.04 (d, 1Har), 8.32 (tt, 1Har), 9.34 (d, 1Har), 9.60
(s, 1Har) ppm; 13C NMR (CDCl3): 119.61, 130.62, 131.27, 132.31, 133.57, 137.43, 137.83, 138.59,
138.92, 142.80, 144.97, 145.85, 145.98, 151.46, 157.65, 158.47 (aryl, C=N) ppm.
3-Pyridyl-4-yl-1-(2,4,6-trichlorophenyl)-1H-indazole (12e; C18H10Cl3N3)
From 7.10 g 11e (10 mmol); yield: 2.85 g (76%) as brownish solid which crystallized from aqueous
ethanol to give ®ne crystals; m.p.: 154±156ꢁC; IR (KBr): ꢂ ˆ 3076, 3030, 1632, 1601, 1573, 1552,
1524, 1510, 1491 cmꢀ1
;
1H NMR (CDCl3): 7.17 (d, 1Har), 7.38±7.57 (m, 2Har), 7.60
(s, 2Htrichlorophenyl), 8.05 (d, 2Hpy), 8.15 (d, 1Har), 8.79 (d, 2Hpy) ppm; 13C NMR (CDCl3): 119.80,
130.53, 131.33, 131.63, 132.69, 137.52, 138.22, 138.62, 139.70, 142.68, 145.77, 146.20, 151.15,
151.65, 153.40, 158.80 (aryl, C=N) ppm.
1-Ethoxycarbonyl-3-pyridyl-4-yl-1H-indazole (12f; C15H13N3O2)
Prepared from 6.03 g 11f (10 mmol); yield: 0.80 g (30%) as brownish solid which crystallized from
ethanol to give yellowish white crystals; m.p.: 150±158ꢁC; IR (KBr): ꢂ ˆ 3126, 3062, 2984, 1740,
1642, 1602, 1578, 1512, 1486 cmꢀ1; 1H NMR (CDCl3): 1.32 (t, J ˆ 7.1 Hz, CH3), 4.27 (q, J ˆ 7.1 Hz,
CH2), 7.23±8.01 (m, 6Har), 8.56 (d, 2Hpy) ppm.
1-Phenyl-3-pyridyl-4-yl-1H-indazole (12g; C18H13N3)
Prepared from 6.07 g 11g (10 mmol); yield: 1.35 g (50%) as brownish solid which crystallized from
aqueous ethanol to give ®ne crystals; m.p.: 72±75ꢁC; IR (KBr): ꢂ ˆ 3152, 3075, 3032, 1630, 1600,
1574, 1552, 1524, 1490 cmꢀ1; 1H NMR (CDCl3): 7.36±7.60 (m, 5Har), 7.78 (m, 3Har), 7.98 (d, 2Har),
7.98 (d, 1Har), 8.76 (d, 2Hpy) ppm; 13C NMR (CDCl3): 120.43, 120.67, 130.58, 130.72, 131.33,
132.32, 132.46, 132.83, 137.02, 137.30, 139.16, 139.30, 150.13, 159.82 (aryl, C=N) ppm.
3-Methyl-1,2,3-triazolo[1,5-a]pyridine (15; C7H7N3)
Prepared from 5.41 g 14i (10 mmol) as described for 7b; the residue was crystallized from benzene
and petrol ether (50±70ꢁC) to yield 1.10 g colourless needles (82%); m.p.: 83±85ꢁC [13]; faint deep
blue ¯uorescence under ultraviolet light; 1H NMR (CDCl3): 2.64 (s, CH3), 6.91 (t, 1Hpy), 7.15
(t, 1Hpy), 7.61 (d, 1Hpy), 8.64 (d, 1Hpy) ppm; 13C NMR (CDCl3): 19.47 (CH3), 126.24, 127.50,
134.32, 134.94, 135.45, 143.18 (pyridyl, C=C) ppm.
Formation of the 1H-indazolium picrates 8b and 13e
A solution of 0.28 g picric acid (1.2 mmol) in 3 ml ethanol was added dropwise to a solution of
3-pyridyl-indazole derivatives 7b and 12e (1 mmol) in 3 ml ethanol at room temperature. Yellow

1-Azo-2-azonia-allene Salts
1303
crystals precipitated at once; ®ltering afforded a yellow powder which was recrystallized from
ethanol.
3-Pyridyl-3-yl-1-(2,4,6-trichlorophenyl)-1H-indazolium picrate (8b; C24H13Cl3N6O7)
Prepared from 0.37 g 7b (1 mmol); yield: 0.54 g (90%) as yellow ®ne crystals; m.p.: 182±198ꢁC; 1H
NMR (CDCl3): 7.21 (d, 1Har), 7.52 (m, 2Har), 7.63 (s, 2Htrichlorophenyl), 8.04 (t, 1Har), 8.15 (d, 1Har),
8.89 (d, 1Har), 9.01 (d, 1Har), 9.02 (s, 2Htrinitrophenyl), 9.58 (s, 1Hpy) ppm.
3-Pyridyl-4-yl-1-(2,4,6-trichlorophenyl)-1H-indazolium picrate (13e; C24H13Cl3N6O7)
Prepared from 0.37 g 12e (1 mmol); yield: 0.56 g (92%) as yellow ®ne crystals; m.p.: 188±194ꢁC; 1H
NMR (CDCl3): 7.25 (d, 1Har), 7.56 (m, 2Har), 7.65 (s, 2Htrichlorophenyl), 8.19 (d, 1Har), 8.61 (d, 2Har),
8.95 (d, 2Har), 8.99 (s, 2Htrinitrophenyl) ppm; 13C NMR (CDCl3): 110.99, 120.19, 121.69, 132.60,
142.86, 126.62, 128.78, 129.22, 129.25, 132.36, 135.81, 137.45, 140.37, 141.45, 142.55, 149.90,
161.44 (aryl, C=N) ppm.
Acknowledgements
È È
È
The author thanks Prof. J. C. Jochims, Fakultat fur Chemie der Universitat Konstanz, for helpful
È
discussions. He is also indebted to his colleagues in the Institut fur Chemie, Johannes Kepler
È
Universitat Linz, for their kind assistance during a fellowship sponsored by the Austrian Academic
Exchange Service, Vienna, Austria.
References
[1] Amer AM, Mostafa MA, Amer MS (1997) A®nidad 470: 305
[2] Amer AM (1995) Monatsh Chem 126: 431
[3] Wang Q, Amer A, Troll C, Fisher H, Jochims JC (1993) Chem Ber 126: 2519
[4] Wang Q, Amer A, Mohr S, Ertel E, Jochims JC (1993) Tetrahedron 49: 9973
[5] Al-Masoudi N, Hassan NA, Al-Soud YA, Schmidt P, Gaafar AM, Weng M, Marino S, Schoch A,
Amer A, Jochims JC (1998) J Chem Soc Perkin Trans 1, 947
È
[6] Wang Q, Jochims JC, Kohlbrandt S, Dahlenburg L, Al-Talib M, Hamed A, Ismail AE (1992)
Synthesis 710
[7] Wang Q, Al-Talib M, Jochims JC (1994) Chem Ber 127: 541
[8] Wang Q, Mohr S, Jochims JC (1994) Chem Ber 127: 974
[9] Guo Y, Wang Q, Jochims JC (1996) Synthesis 274
[10] Wirschun W, Jochims JC (1997) Synthesis 233
[11] Wirschun W, Maier GM, Jochims JC (1997) Tetrahedron 53: 5755
[12] Anthony M PCT Int. Appl. WO 98 09, 961 (Cl. C07D401/2) 12 Mar 1998; (1988) Chem Abstr
128: 217368
[13] Bower JD, Ramage GR (1957) J Chem Soc 4506
Received July 3, 1998. Accepted July 13, 1998