Reactions of immonium and telluronium salts of 2-phenylbenzotellurazole

Article abstract of DOI:10.1007/s10593-007-0168-9

N-methyl-2-phenylbenzotellurazolinium iodide, like other N-methylbenzochalcogenazolium salts, readily undergoes reduction, hydrolysis, and recyclization with hydrazine hydrate and o-phenylene diamine. 1-Methyl-2-phenylbenzotelluronioazole perchlorate is an effective methylating agent in reactions with nucleophiles.

Full text of DOI:10.1007/s10593-007-0168-9

Chemistry of Heterocyclic Compounds, Vol. 43, No. 8, 2007
REACTIONS OF IMMONIUM
AND TELLURONIUM SALTS
OF 2-PHENYLBENZOTELLURAZOLE
G. M. Abakarov1, M.-Z. V. Vagabov1, V. A. Pantin1,
I. D. Sadekov2, and V. I. Minkin2
N-methyl-2-phenylbenzotellurazolinium iodide, like other N-methylbenzochalcogenazolium salts, readily
undergoes reduction, hydrolysis, and recyclization with hydrazine hydrate and o-phenylene diamine.
1-Methyl-2-phenylbenzotelluronioazole perchlorate is an effective methylating agent in reactions with
nucleophiles.
Keywords: N-methyl-2-phenylbenzotellurazolium iodide, 1-methyl-2-phenytelluronioazole perchlorate,
reduction, hydrolysis, recyclization.
We have established previously [1, 2] that, depending on the nature of the methylating agent, 2-phenyl-
benzotellurazole (1) is alkylated either at the nitrogen atom or the tellurium atom. N-methyl-2-phenyl-
benzotellurazolium iodide (2) was obtained in 90% yield when compound 1 was heated with an excess of
methyl iodide in a sealed ampule. On the other hand treatment of an acetonitrile solution of 2-phenyl-
benzotellurazole and methyl iodide with silver perchlorate (an equimolar ratio of the reagents) gave an almost
quantitative yield (95%) of 1-methyl-2-phenybenzotelluronioazole perchlorate (3). In this report we give an
account of the results of an investigation of some reactions of the salts 2 and 3.
Me
Me
–
I
+
N
N
NaBH4, MeOH
H
Ph
Ph
Te
Te
2
4
On treatment of a suspension of the immonium salt 2 in methanol with dry NaBH4 (A) reduction of the
C=N bond occurs to give 3-methyl-2-phenyl-2,3-dihydrobenzotellurazole (4) in greater than 70% yield, the
structure of which was confirmed by elemental analysis and 1H NMR spectroscopy. In the latter the signal of the
N-methyl group was observed at 2.60 ppm, whereas the analogous signal was observed at 3.81 ppm in the
spectrum of salt 2.
__________________________________________________________________________________________
1Dagestan State Technical University, Makhachkala 367015, Russia; e-mail: oksana1984@yandex.ru;
2Institute of Physical and Organic Chemistry, Rostov State University, Rostov-on-Don 344090, Russia; e-mail:
sadek@ipos.rsu.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, 1268-1272, August, 2007.
Original article submitted December 12, 2005.
1076
0009-3122/07/4308-1076©2007 Springer Science+Business Media, Inc.

Salt 2 underwent hydrolysis under comparatively mild conditions (maintenance of a suspension in
aqueous NaOH (B) at 60-80°C) similarly to other N-methylbenzochalcogenium salts [3, 4]. However, in
difference from its thio- and selenoanalogs which gave on hydrolysis the corresponding thio- and selenophenols,
which are converted into the disulfides or diselenides by oxidizing agents [I2, K3Fe(CN)6], hydrolysis of salt 2
led directly to bis(2-N-methyl-N-benzoylaminophenyl)ditelluride (5). This ditelluride is evidently formed by
self-oxidation by aerial oxygen of the intermediate tellurophenol (6). We identified the ditelluride 5 in the form
of N-benzoyl-N-methyl-2-(methyltelluro)aniline 7 obtained by reduction of the ditelluride with sodium
borohydride and alkylation of the sodium tellurophenolate formed with dimethyl sulfate.
Me
N
O2
NaOH, H2O
– NaI
COPh
2
TeH
6
Me
N
Me
N
1. NaBH4
2. Me2SO4
COPh
COPh
Te
TeMe
2
7
5
In the 1H NMR spectrum there are, apart from the signals of the aromatic protons, singlets of the protons
of the NCH3 and TeCH3 groups at 3.30 and 2.08 ppm respectively.
One of the characteristic properties of N-methylbenzochalcogenazolium salts is their ability to undergo
recyclization with bifunctional compounds: hydrazine [5] and o-phenylenediamine [6]. Reaction of salt 2 with
hydrazine hydrate (C) gave di(2-N-methylaminophenyl)ditelluride (8) in greater than 50% yield and also
3,6-diphenyl-1,2-dihydro-1,2,4,5-tetrazine (9) (with a yield of about 40%).
NHMe
TeH
N
N
.
.
2 + H2NNH2 H2O
Ph
Ph
+
N
H
N
H
9
NHMe
O2
9
+
Te
2
8
Reaction of salt 2 with o-phenylenediamine (D) gave the ditelluride 8 (yield 43%) and 2-phenyl-
benzimidazole (10) (yield 39%).
H2N
N
DMF
8
Ph
2
+
+
N
H2N
H
10
1077

It is known that diphenylalkylsulfonium salts [7] and trimethylselenonium hydroxide [8] are effective
alkylating agents. In a series of telluro-organic compounds similar properties were observed for Te-methyl-
phenoxatelluronium iodide (11) [9]. The following equilibrium was established in a solution of this compound in
DMSO-d6.
O
O
–
+
(CD3)2S OMeI
(CD3)2SO
+
+
+
Te
Te
–
I
Me
11
Starting from this observation it might be expected that the telluronium salt 3 would have methylation
properties on reaction with nucleophilic reagents. On reaction with sodium hydroxide and phenol compound 1
2-phenylbenzotellurazolium perchlorate (12) were isolated in 70 and 85% yields respectively. Reaction of
compound 3 with triethylamine and pyridine gave methyltriethylammonium perchlorate (13) and
N-methylpyridinium perchlorate (14) in yields of 75 and 60% The yields of compound 1 were 73 and 65 %
respectively.
N
Ph
+
Te
–
ClO4
Me
3
NaOH
Ph
PhOH
– NaClO4
– PhOMe
–
ClO4
+
NH
N
Ph
+ MeOH
Te
Te
1
12
_
Et3N
N
+
+
1
+
3
Et3N MeClO4 + 1
_
ClO4
N
Me
13
14
EXPERIMENTAL
1H NMR spectra were recorded on a Varian Unity-300 (300 MHz) instrument with residual H of the
solvent as internal standard.
The salts 2 and 3 were synthesized by known methods [2].
Reactions of N-Methyl-2-phenylbenzotellurazolium Iodide (2). A. With NaBH4. 3-Methyl-
2-phenyl-2,3-dihydrobenzotellurazole (4). Dry sodium borohydride (1 g, 26 mmol) was added in small
portions with stirring to a suspension of compound 2 (2.25 g, 5 mmol) in methanol (100 ml) in an atmosphere of
argon. Stirring was continued for 1 h, then the product 4 was filtered off, dried, and recrystallized from
1
2-propanol to give orange plates, mp 141-143°C, yield 1.22 g (76%). H NMR spectrum (acetone-d6), δ, ppm:
6.15-7.28 (10H, m, H-2 and 9Harom); 2.60 (3H, s, NCH3). Found, %: C 51.90; H 3.89. C14H13NTe. Calculated, %:
C 52.08; H 4.07.
1078

B. With NaOH. (N-Benzoyl-N-methyl)-2-methyltelluroaniline (7). A suspension of compound 2
(0.90 g, 2 mmol) in 1N aqueous NaOH (100 ml) was stirred for 1 h at 80-90°C. After cooling the reaction mass
the orange precipitate of ditelluride 5 was filtered off, dried, and suspended in methanol (20 ml) without further
purification. Dry sodium borohydride was added in small portions to the stirred suspension under argon until the
precipitate had completely dissolved to give a colorless solution. Dimethyl sulfate (0.5 g, 4 mmol) was added
rapidly to the colorless solution, the reaction mixture was stirred for 40 min with mild heating, cooled, poured
into water (100 ml), and extracted with chloroform (3×15 ml). The extract was dried over Na2SO4 and the
1
solvent evaporated to give a colorless crystalline product 7 (0.46 g, 65%), mp 145-147° (2-propanol). H NMR
spectrum (CDCl3), δ, ppm: 6.75-7.57 (9H, m, Harom); 3.30 (3H, s, NCH3); 2.08 (3H, s, TeCH3). Found, %:
C 50.91; H 4.07. C15H15NOTe. Calculated, %: C 51.04; H 4.29.
C. With NH2NH2·H2O. Di(2-N-methylaminophenyl)ditelluride (8). A suspension of compound 2
(2.25 g, 5 mmol) in hydrazine hydrate (10 ml) was stirred while boiling for 10 min. The red pasty mass was
separated by decanting the boiling liquid phase of the reaction mixture, dried and crystallized from 2-propanol to
1
give claret-red crystals of ditelluride 8 (0.6 g, 51%), mp 100-102°C. H NMR spectrum (CDCl3), δ, ppm:
6.30-7.80 (4H, m, Harom); 4.25 (1H, s, NH); 2.65 (3H, s, NCH3). Found, %: C 36.52; H 3.61. C14H16N2Te2.
Calculated, %: C 35.96; H 3.46.
The orange-yellow precipitate which formed on cooling the decanted liquid phase was filtered off, dried,
and recrystallized from ethanol to give orange-yellow crystals of compound 9 (0.28 g, 48%), mp 190-191°C (mp
191-192°C [5]).
D. With 1,2-(H2N)2C6H4. Compound 8. Compound 2 (2.25 g, 5 mmol) and o-phenylenediamine (0.55g,
5 mmol) were stirred in DMF (50 ml) with mild boiling for 3 h. The claret-red reaction mixture was cooled and
the unreacted salt 2 was filtered off. From the filtrate some of the solvent (40 ml) was evaporated under reduced
pressure, the residue was poured into water and extracted with benzene (2×20 ml). The extract was dried over
Na2SO4, the solvent was evaporated, and the residue was chromatographed on an Al2O3 column (eluent
chloroform). Fine shining claret-red crystals of compound 8 were obtained (0.51 g, 43%), mp 100-102°C
(2-propanol). The yellow residue which was not extracted by benzene was filtered off, dried, and recrystallized
from benzene to give fine colorless crystals of 2-phenylbenzimidazole 10 (0.38 g, 39%), mp 292-293°C (mp
294°C [6]).
Reactions of 1-Methyl-2-phenylbenzotelluronioazole Perchlorate (3). With NaOH.
2-Phenylbenzotellurazole (1). A suspension of salt 3 (0.42 g, 1 mmol) in 1 N alcoholic NaOH (50 ml) was
stirred with reflux for 1 h. The solution obtained was cooled, poured into water (100 ml), and extracted with
chloroform (3×15 ml). The extract was evaporated and the residue washed with hexane to give compound 1
(0.214 g, 70%) as large yellow crystals, mp 102-103°C (mp 102-103°C [10]).
With Phenol. 2-Phenylbenzotellurazolium Perchlorate (12). Phenol (0.21 g, 2 mmol) in acetonitrile
(10 ml) was added to a solution of salt 3 (0.84 g, 2 mmol) in acetonitrile (10 ml) and the reaction mixture was
boiled with stirring for 2 h. The solvent was partially evaporated and ether (20 ml) was added to the reaction
mixture. The precipitate formed was filtered off and dried to give product 12 as fine yellow crystals (0.69 g,
85%), mp 180-182°C (dec.). Found, %: C 38.70; H 2.30. C13H10ClNO4Te. Calculated, %: C 38.30; H 2.48.
The product 12 was identical to a sample of 12 prepared by the reaction of 2-phenylbenzotellurazole (1)
with perchloric acid in ethanol (no depression of the melting point in a mixed determination).
With Et3N. Methyltriethylammonium Perchlorate (13). Triethylamine (0.3 g, 3 mmol) was added
stepwise to a solution of salt 3 (0.84 g, 2 mmol) in acetonitrile (20 ml), the reaction mixture was stirred while
boiling for 1 h and then some solvent (10 ml) was evaporated. Ether (20 ml) was added to the remaining cooled
solution, the colorless precipitate was filtered off and recrystallized from ethanol to give fine colorless crystals of
1
the perchlorate 13 (0.321 g, 75%), mp 200-202°C. H NMR spectrum (DMSO-d6), δ, ppm: 3.55 (6H, q,
CH3CH2); 3.20 (3H, s, NCH3); 1.50 (9H, t, CH3CH2). Found, %: C 38.40; H 8.42. C7H18ClNO4. Calculated, %:
C 39.0; H 8.42. The solvent was evaporated from the filtrate and the residue recrystallized from hexane to give
large yellow crystals of compound 1 (0.445 g, 73%), mp 101-102°C.
1079

With Pyridine. N-Methylpyridinium Perchlorate (14). Pyridine (0.47 g, 6 mmol) was added to a
solution of salt 3 (1.26 g, 3 mmol) in acetone (15 ml) and the mixture was stirred with boiling for 1 h. The
colorless precipitate was filtered off and recrystallized from ethanol to give perchlorate 14 (0.35 g, 60%) as
1
colorless crystals, mp 260°C (dec.). H NMR spectrum (acetone-d6), δ, ppm: 9.10-8.15 (5H, HHet); 4.75 (3H, s,
NCH3). Found, %: C 37.0; H 3.90. C6H8ClNO4. Calculated, %: C 37.2; H 4.17.
The filtrate was evaporated to dryness and the residue recrystallized from hexane to give compound 1 as
large yellow crystals (0.6 g, 65%), mp 101-102°C.
REFERENCES
1.
2
I. D. Sadekov, G. M. Abakarov, A. A. Schneider, and V. I. Minkin, Khim. Geterotsikl. Soedin., 136
(1988). [Chem. Heterocycl. Comp., 24, 116 (1988)].
I. D. Sadekov, G. M. Abakarov, A. A. Schneider, and V. I. Minkin, Khim. Geterotsikl. Soedin., 989
(1989). [Chem. Heterocycl. Comp., 25, 829 (1989)].
3.
J. V. Metzger, in: A. R. Katrizky (editor), Comprehensive Heterocyclic Chemistry, Pergamon Press, New
York, Toronto, Sydney, Paris, Frankfurt (1984). Vol. 6, p. 236.
4.
5.
J. Develotte. Ann. Chim.(Fr.), 5, 215 (1950).
O. P. Shvaika and V. I. Fomenko, Khim. Geterotsikl. Soedin., 635 (1976). [Chem. Heterocycl. Comp.,
12, 533 (1976)].
6.
7.
8.
H. Singh, R. Sarin, and K. Singh, Indian J. Chem., 27B, 132 (1988).
B. Badet, M. Julia, and C. Lefebvre, Bull. Soc. Chim. Fr., 431 (1984).
Y. Kiyoshi, N. Kazue, and K. Masayoshi, Tetrahedron Lett., 20, 1787 (1979).
D. Rainville and R. A. Zingaro, Inorg. Chim. Acta, 86, L33 (1984).
9.
10.
I. D. Sadekov, G. M. Abakarov, A. A. Schneider, S. G. Kuren, A. G. Starikov, A. D. Garnovskii, and
V. I. Minkin, Khim. Geterotsikl. Soedin., 120 (1989). [Chem. Heterocycl. Comp., 25, 103 (1989)].
1080