Walther reaction in the benzazoles series and preparation of their 2-deutero derivatives

Article abstract of DOI:10.1134/S107042800212014X

Reactions of 2-hydrazino-substituted 1-methylbenzimidazole, benzothiazole, and benzoxazole with azobenzene at 160-180°C resulted in hydrazino group elimination and formation of the corresponding 2-H-benzazoles. Under similar conditions the 2-deuterohydrazinobenzazoles prepared from 2-hydrazinobenzazoles and heavy water were converted into 2-deuterobenzazoles. Pleiades Publishing, Inc. 2006.

Full text of DOI:10.1134/S107042800212014X

ISSN 1070-4280 Russian Journal of Organic Chemistry, 2006, Vol. 42, No. 2, pp. 241-242. Ó Pleiades Publishing, Inc. 2006.
Original Russian Text Ó D.A. Lomov, Yu.M. Yutilov, N.N. Smolyar, 2006, published in Zhurnal Organicheskoi Khimii, 2006, Vol. 42, no. 2,
pp. 257-258.
Walther Reaction in the Benzazoles Series and Preparation
of Their 2-Deutero Derivatives
D.A. Lomov, Yu.M. Yutilov, and N.N. Smolyar
Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine,
Donetsk, 83114 Ukraine
e-mail: yutilov@skif.net
Received November 23, 2004
Abstract—Reactions of 2-hydrazino-substituted 1-methylbenzimidazole, benzothiazole, and benzoxazole with
azobenzene at 160–180°C resulted in hydrazino group elimination and formation of the corresponding 2-H-
benzazoles. Under similar conditions the 2-deuterohydrazinobenzazoles prepared from 2-hydrazinobenzazoles
and heavy water were converted into 2-deuterobenzazoles.
DOI: 10.1134/S107042800212014X
An elegant reaction between azobenzene and phenyl-
hydrazone that at 125–130°C led to elimination of the
hydrazino group and to formation of benzene, nitrogen,
and hydrazobenzene in nearly quantitative amounts was
discovered by R. Walther to the end of nineteen century
[1, 2]. This reaction was used in [3] in order to remove
a hydrazine group and to obtain the previously unknown
1,3-dimethylimidazo[4,5-C]pyridin-2-one. The reaction
also occurred with a quantitative yield of the target product
and hydrazobenzene.
of the deuterohydrazines were fused with azo-benzene
at 160–180°C. Azoles V and XII were isolated from the
reaction mixture by distillation, and 1-methyl-
benzimidazole (X) was eluted with benzene from sorbent
(aluminum oxide).
The composition and structure of compounds obtained
IV–XII were confirmed by elemental analysis (Table 1)
1
and H NMR spectra (Table 2). The chemical shift of
aromatic protons signals in the spectra of compounds IV
and VI are identical to the published data [4]. The signals
of aromatic protons of 2-deutero derivatives VII–XII are
observed in the stronger field with respect to those of the
unsubstituited benzazoles IV–VI (7.31–8.17 ppm).
We report here on the results of oxidation with azo-
benzene of 2-hydrazino derivatives of benzoxazole,
benzothiazole, and 1-methylbenzimidazole, and also of
their N-deutero derivatives aimed at conversion of these
hydrazines into the corresponding benzazoles. It turned
out that the reaction on azobenzene with 2- hydrazino
derivatives of 1-methylbenzimidazole (I), benzothiazole
(II), and benzoxazole (III) occurred under more stringent
conditions than with phenylhydrazine, and afforded the
expected benzazoles IV–VI in 88–97% yields (Table 1).
EXPERIMENTAL
1H NMR spectra of compounds synthesized were
registered on a spectrometer Gemini-200 at operating
frequency 200 MHz in CDCl3 for compounds IV–VI and
X–XII and in DMSO-d6 for compounds VII–IX. HMDS
was used as internal reference. The purity and homo-
geneity of compounds obtained was checked by TLC on
Silufol UV-254 plates (eluents ethanol or chloroform),
development under UV irradiation or in iodine vapor. The
syntheses of initial compounds I–III were described in
[8–10] respectively.
In the same fashion the oxidation with azobenzene of
N-deuterohydrazino derivatives of azoles VII–IX afforded
2-D-benzazoles X–XII. Deuterated hydrazines VII–IX
were prepared by triple recrystallization from the heavy
water of bases I–III. After thorough drying the samples
3K1 13Kꢀ
3K1 13Kꢀ
ꢁꢂꢃ ꢁꢄꢃ &
1
;
1
1
1
' 2
ꢁꢂꢃ ꢁꢄꢃ &
1+1+
1'1'
'
;
;
;
, ,,,
9,, ,;
,9 9,
; ;,,
X = NMe (I, IV,VII, X), S (II, V,VIII, XI), O (III, VI, IX, XII).
241

LOMOV et al.
Table 1. Yields, melting (boiling) points, and elemental analyses of compounds IV–XII
242
)RXQGꢀꢁꢂꢁꢁ
+ꢁꢄ+ꢆ'ꢅꢁ
&DOFXODWHGꢀꢁꢂꢁ
+ꢁꢄ+ꢆ'ꢅꢁ
)RUPXODꢁꢁ
&RPSGꢃꢁQRꢃꢁ<LHOGꢀꢁꢂꢁ PSꢁꢄESꢅꢀꢁƒ&ꢁ
&ꢁ
1ꢁ
&ꢁ
1ꢁ
ꢁ
,9ꢀ
9ꢀ
ꢇꢈꢁ
ꢇꢌꢁ
ꢐꢐꢁ
ꢇꢊꢁ
ꢇꢍꢁ
ꢐꢈꢁ
ꢇꢈꢁ
ꢇꢈꢁ
ꢇꢊꢁ
ꢉꢊ±ꢉꢋꢁ
ꢄꢍꢍꢍ±ꢍꢍꢊꢅ ꢁ ꢉꢍꢃꢈꢊꢁ
ꢄꢎꢐꢈ±ꢎꢐꢍꢅ ꢁ ꢌꢈꢃꢊꢋꢁ
ꢎꢏꢈ±ꢎꢏꢍꢁ
ꢎꢇꢏ±ꢎꢇꢊꢁ
ꢎꢏꢇ±ꢎꢊꢈꢁ
ꢉꢍ±ꢉꢏꢁ
ꢌꢍꢃꢋꢎꢁꢁ
ꢉꢃꢈꢋꢁ
ꢏꢃꢉꢌꢁ
ꢊꢃꢎꢐꢁ
ꢌꢃꢐꢋꢁ
ꢋꢃꢇꢏꢁ
ꢉꢃꢋꢋꢁ
ꢉꢃꢌꢊꢁ
ꢊꢃꢏꢐꢁ
ꢊꢃꢇꢋꢁ
ꢍꢎꢃꢈꢏꢁ
ꢎꢈꢃꢎꢇꢁ
ꢎꢎꢃꢋꢐꢁ
ꢏꢏꢃꢌꢐꢁ
ꢍꢊꢃꢐꢊꢁ
ꢍꢌꢃꢊꢇꢁ
ꢍꢈꢃꢐꢌꢁ
ꢎꢈꢃꢎꢈꢁ
ꢎꢎꢃꢋꢈꢁ
& + 1 ꢁ
& + 16ꢁ
ꢌꢍꢃꢌꢈꢁꢁ
ꢉꢍꢃꢎꢇꢁ
ꢌꢈꢃꢋꢐꢁ
ꢋꢐꢃꢎꢐꢁ
ꢊꢇꢃꢇꢇꢁ
ꢋꢋꢃꢍꢌꢁ
ꢌꢍꢃꢎꢉꢁ
ꢉꢎꢃꢌꢊꢁ
ꢌꢈꢃꢈꢈꢁ
ꢉꢃꢎꢈꢁ
ꢏꢃꢌꢏꢁ
ꢊꢃꢍꢏꢁ
ꢌꢃꢇꢏꢁ
ꢋꢃꢇꢇꢁ
ꢉꢃꢉꢍꢁ
ꢉꢃꢐꢎꢁ
ꢊꢃꢊꢊꢁ
ꢋꢃꢈꢏꢁ
ꢍꢎꢃꢍꢈꢁ
ꢎꢈꢃꢏꢉꢁ
ꢎꢎꢃꢌꢉꢁ
ꢏꢏꢃꢇꢍꢁ
ꢍꢊꢃꢇꢐꢁ
ꢍꢌꢃꢉꢍꢁ
ꢍꢎꢃꢈꢊꢁ
ꢎꢈꢃꢍꢇꢁ
ꢎꢎꢃꢉꢉꢁ
9,ꢀ
9,,ꢀ
9,,,ꢀ
,;ꢀ
;ꢀ
;,ꢀ
;,,ꢀ
& + 12ꢁ
& + ' 1 ꢁ
& + ' 1 6ꢁ
& + ' 1 2ꢁ
& + '1 ꢁ
& + '16ꢁ
& + '12ꢁ
ꢋꢐꢃꢈꢍꢁ
ꢊꢇꢃꢐꢈꢁ
ꢋꢋꢃꢎꢎꢁ
ꢌꢍꢃꢈꢎꢁ
ꢉꢎꢃꢋꢊꢁ
ꢄꢍꢎꢇꢅꢁ
ꢄꢎꢌꢌ±ꢎꢌꢐꢅꢁ ꢉꢇꢃꢐꢐꢁ
ꢁa Publ.: bp 223–225°C [5]. b Publ.: bp 183°C [6], mp 66°C [7].
Table 2. 1H NMR spectra of compounds IV–XII
&RPSGꢃQRꢃꢁ
&KHPLFDOꢁVKLIWꢀꢁGꢀꢁSSPꢁ
,9ꢀꢀ ꢏꢃꢐꢉꢁVꢁꢄꢏ+ꢀꢁ1&+ ꢅꢀꢁꢌꢃꢏꢎ±ꢌꢃꢊꢈꢁPꢁꢄꢏ+ꢀꢁ+ ꢀꢁ+ ꢀꢁ+ ꢅꢀꢁꢌꢃꢐꢏ±ꢌꢃꢐꢐꢁPꢁꢄꢎ+ꢀꢁ+ ꢅꢀꢁꢌꢃꢐꢇꢁVꢁꢄꢎ+ꢀꢁ+ ꢅꢁ
9ꢀꢀ
ꢌꢃꢊꢐꢁGꢁꢄꢎ+ꢀꢁ+ ꢀꢁ-ꢁꢌꢃꢐꢁ+]ꢅꢀꢁꢌꢃꢋꢏꢁGꢁꢄꢎ+ꢀꢁ+ ꢀꢁ-ꢁꢌꢃꢐꢁ+]ꢅꢀꢁꢌꢃꢇꢇꢁGꢁꢄꢁꢎ+ꢀꢁ+ ꢀꢁ-ꢁꢌꢃꢐꢁ+]ꢅꢀꢁꢐꢃꢎꢌꢁGꢁꢄꢎ+ꢀꢁ+ ꢀꢁ-ꢁꢌꢃꢐꢁ+]ꢅꢀꢁꢇꢃꢈꢍꢁVꢁ
ꢄꢎ+ꢀꢁ+ ꢅꢁ
9,ꢀ
ꢌꢃꢊꢍꢁTꢁꢄꢍ+ꢀꢁ+ ꢀꢁ+ ꢅꢀꢁꢌꢃꢉꢊꢁWꢁꢄꢎ+ꢀꢁ+ ꢅꢀꢁꢌꢃꢐꢊꢁWꢁꢄꢎ+ꢀꢁ+ ꢅꢀꢁꢐꢃꢎꢋꢁVꢁꢄꢎ+ꢀꢁ+ ꢅꢁ
9,,ꢀ ꢏꢃꢉꢈꢁVꢁꢄꢏ+ꢀꢁ1&+ ꢅꢀꢁꢉꢃꢐꢍ±ꢉꢃꢇꢊꢁPꢁꢄꢎ+ꢀꢁ+ ꢅꢀꢁꢉꢃꢇꢉ±ꢌꢃꢈꢋꢁPꢁꢄꢎ+ꢀꢁ+ ꢅꢀꢁꢌꢃꢎꢍꢁGꢁꢄꢎ+ꢀꢁ+ ꢀꢁ-ꢁꢌꢃꢈꢁ+]ꢅꢀꢁꢌꢃꢍꢍꢁGꢁꢄꢎ+ꢀꢁ+ ꢀꢁ
-ꢁꢌꢃꢈꢁ+]ꢅꢁ
9,,,ꢀ ꢌꢃꢈꢎꢁTꢁꢄꢎ+ꢀꢁ+ ꢅꢀꢁꢌꢃꢍꢍꢁTꢁꢄꢎ+ꢀꢁ+ ꢅꢀꢁꢌꢃꢏꢉꢁGꢁꢄꢎ+ꢀꢁ+ ꢀꢁ-ꢁꢌꢃꢇꢁ+]ꢅꢀꢁꢌꢃꢉꢎꢁGꢁꢄꢎ+ꢀꢁ+ ꢀꢁ-ꢁꢌꢃꢇꢁ+]ꢅꢁ
,;ꢀ
;ꢀ
;,ꢀ
ꢌꢃꢈꢋ±ꢌꢃꢏꢇꢁPꢁꢄꢊ+ꢀꢁ+ ꢀꢁ+ ꢀꢁ+ ꢀꢁ+ ꢅꢁ
ꢏꢃꢐꢋꢁVꢁꢄꢏ+ꢀꢁ1&+ ꢅꢀꢁꢌꢃꢏꢈ±ꢌꢃꢊꢊꢁPꢁꢄꢏ+ꢀꢁ+ ꢀꢁ+ ꢀꢁ+ ꢅꢀꢁꢌꢃꢐꢍ±ꢌꢃꢐꢉꢁPꢁꢄꢎ+ꢀꢁ+ ꢅꢁ
ꢉꢃꢌꢈꢁGꢁꢄꢎ+ꢀꢁ+ ꢀꢁ-ꢁꢌꢃꢌꢁ+]ꢅꢀꢁꢉꢃꢐꢈꢁGꢁꢄꢎ+ꢀꢁ+ ꢀꢁ-ꢁꢌꢃꢌꢁ+]ꢅꢀꢁꢌꢃꢎꢐꢁWꢁꢄꢍ+ꢀꢁ+ ꢀꢁ+ ꢅꢁ
;,,ꢀ ꢉꢃꢉꢊ±ꢉꢃꢐꢎꢁPꢁꢄꢍ+ꢀꢁ+ ꢀꢁ+ ꢅꢀꢁꢌꢃꢎꢍ±ꢌꢃꢍꢈꢁPꢁꢄꢍ+ꢀꢁ+ ꢀꢁ+ ꢅꢁ
ꢁ
Benzazoles IV–VI. A mixture of 10 mmol of an
and 10 mmol pf azobenzene was heated at 160–180°C
till the nitrogen liberation ceased. Reaction products XI
and XII were purified by vacuum distillation in a nitrogen
flow, and compound X was subjected to column chromato-
graphy on aluminum oxide, eluent benzene.
appropriate 2-hydrazinobenzazole I–III with an equimolar
amount of azobenzene was heated at 160–180°C till the
end of nitrogen liberation. Compounds V and VI were
isolated from the reaction mixture by simple distillation
at the atmospheric pressure in a nitrogen flow. Compound
IV was separated by column chromatography on
aluminum oxide, eluent benzene.
REFERENCES
1. Walther, R., J. Prakt. Chem., 1895, vol. 52, p. 141.
2. Walther, R., J. Prakt. Chem., 1896, vol. 53, p. 433.
3. Yutilov, Yu.M. and Svertilova, I.A., Khim. Geterotsikl.
Soedin., 1994, p. 1071.
4. Aldrich Libray of NMR Spectra Edition, 1983, vol. 2,
p. 558.
5. Mills, B., J. Chem. Soc., 1922, vol. 121, p. 460.
6. Bamberger, K., Ber., 1903, vol. 36, p. 2051.
7. Fischer, O., Ber., 1905, vol. 38, p. 322.
8. Bednyagina, N.P. and Postovskii, I.Ya., Zh. Org. Khim.,
1960, vol. 30, p. 1431.
2-Deuterohydrazinobenzazoles VII–IX. A mixture
of 10 mmol of an appropriate 2-hydrazinobenzazole I–
III and 10 ml of D2O was heated to boiling for 2 h. On
cooling the water layer was decanted, 10 ml of D2O was
added, and the mixture was boiled for 2 h. These opera-
tions were thrice repeated. Then the solution was cooled,
the reaction product was filtered off, dried in a desiccator
over P2O5, and used for further transformations without
additional purification. When required, 2-deutero-
hydrazinobenzazoles VII–IX were purified by recrystal-
lization from anhydrous benzene.
9. Efros, L.S. and Davidenkov, L.R., Zh. Org. Khim., 1951, vol.
21, p. 2046.
2-Deuterobenzazoles X–XII. Amixture of 10 mmol
of an appropriate 2-deuterohydrazinobenzazole VII–IX
10. Sycheva, T.P., Pankina, Z.A., Kiseleva, I.D., and Shchuki-
na, M.N., Khim. Geterotsikl. Soedin., 1966, p. 506.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 42 No. 2 2006