Dechlorination of polychloroaromatic acids effected by reducing system NiCl2-2,2′-bipyridyl (or 1,10-phenanthroline)-Zn

Full text of DOI:10.1023/A:1020367927170

Russian Journal of Organic Chemistry, Vol. 38, No. 6, 2002, pp. 900 901. Translated from Zhurnal Organicheskoi Khimii, Vol. 38, No. 6, 2002,
pp. 942 943.
Original Russian Text Copyright
2002 by Trukhin, Adonin, Starichenko.
SHORT
COMMUNICATIONS
Dechlorination of Polychloroaromatic Acids Effected
by Reducing System NiCl 2,2 -bipyridyl
2
(
or 1,10-phenanthroline) Zn
D. V. Trukhin, N. Yu. Adonin, and V. F. Starichenko
Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Division,
Russian Academy of Sciences, Novosibirsk, 630090 Russia
Received July 11,2001
Partially chlorinated benzoic and phthalic acids,
phenanthroline) Zn (system A) with polyfluorochloro-
benzenes [6, 7] and with some polychloroarenes [7,
8] in aqueous dimethylformamide results in efficient
dechlorination of these substrates furnishing in the
former case fluorobenzenes and mixtures of partially
chlorinated arenes in the latter [6 8]. At the same
time we found that the catalytic system A under mild
conditions and with good yield transformed the penta-
fluorobenzoic acid into 2,3,4,5-tetrafluoro- and
3,4,5-trifluorobenzoic acids [9]. Taking into account
the above it seems feasible to study the reaction of
this system with polychloroaromatic acids, such as
pentachlorobenzoic and tetrachlorophthalic acid.
among them 3,4,5-trichlorobenzoic acid and 4,5-di-
chlorophthalic acid, are used in the synthesis of
phthalocyanine dyes and polymers [1], of pharma-
ceuticals [2] etc. The synthesis of 3,4,5-trichloro-
benzoic acid by oxidation of the corresponding benzo-
phenone is described in the literature [3]. This
procedure provides sufficiently high yield of the
target products, affords various halobenzoic acids,
but requires preliminary synthesis of initial benzo-
phenones [3]. The 3,4,5-trichlorobenzoic acid was
also obtained by hydrolysis of 3,4,5-trichlorobenzo-
trichloride that in its turn was prepared by trichlor-
omethylation of 1,2,3-trichlorobenzene [4]. This
procedure provides a possibility to obtain alongside
the 3,4,5-trichlorobenzoic acid quite a number of
various chlorobenzoic acids.; however the yields as a
rule are low [4].
We showed that reaction between pentachloro-
benzoic acid (I) and catalytic reducing system
NiCl 2,2 -bipyridyl (or 1,10-phenanthroline) Zn
2
(
A) resulted in hydrogenolysis of Carom Cl bonds in
positions 2 and 6 of the benzene ring. The reaction
gave rise to a mixture of 2,3,4,5-tetrachlorobenzoic
and 3,4,5-trichlorobenzoic acids within 1 2 h. At
prolonging the reaction to 4 h the only product was
acid II in 83 89% preparative yield. The reaction
The published data on preparation of 4,5-dichloro-
phthalic acid describe the chlorination of phthalic acid
catalyzed with iron chloride [5]. The arising mixture
of 3- and 4-chlorophthalic acids was separated by
rectification, and isomer with a chlorine in the fourth
position was subjected to further chlorination to
furnish a mixture of dichlorophthalic acids. Succes-
sive rectification provided the 4,5-dichlorophthalic
acid in about 10% yield [5]. The disadvantages of this
procedure include low yield of target products and
the necessity of rectification of the products. Another
described synthesis of the 4,5-dichlorophthalic acid
was carried out at 70 C in DMF H O.
2
(
sodium hydrogen salt) consists in reaction between
phthalic acid and chlorine in water solution of alkali
at 50 C [1]. The preparative yield of the target pro-
duct was 62%.
Dechlorination of tetrachlorophthalic acid (III)
under similar conditions also resulted in replacement
hydrogen for chlorine in positions neighboring to the
carboxy groups and in formation of a mixture contain-
ing 3,4,5-trichlorophthalic and 4,5-dichlorophthalic
It was shown before that reaction of catalytic
reducing system NiCl 2,2 -bipyridyl (or 1,10-
2
1
070-4280/01/3806-900$27.00 2002 MAIK Nauka/Interperiodica

DECHLORINATION OF POLYCHLOROAROMATIC ACIDS
901
1
3
5
4
acids. Therewith in 4 h of the process the 3,4,5-tri-
chlorophthalic acid disappeared from the reaction
mixture, and acid IV could be isolated in preparative
yield 86 90%.
131.94 (C ), 134.86 (C , C ), 136.02 (C ), 164.69
(C ).
7
1H and 13C NMR spectra of reaction products were
registered on spectrometers Bruker WP200SY and
Bruker DRX500 respectively, internal reference
The comparison of the above discussed results
with the existing publications on preparation of
HMDS ( 0.04 ppm), solvent acetone-d . Elemental
6
composition was determined on Finnigan MAT 8200
instrument. Chromatographic analysis was carried
out on liquid chromatograph Milichrom-4-equipped
with a column 62 2 mm packed with a sorbent
Separon S-18, 5 . As detector served UV spectro-
photometer on wavelengths 230 and 254 nm. Eluent
aqueous acetonitrile, 60 and 70%.
3
,4,5-trichlorobenzoic and 4,5-dichlorophthalic acids
[
1, 3 5] shows the accessibility and efficiency of our
preparation method for these compounds by dechlorin-
ation of pentachlorobenzoic and tetrachlorophthalic
acids with the use of catalytic reducing system
NiCl 2,2 -bipyridyl (or 1,10-phenanthroline) Zn.
2
General procedure. From 0.065 g of nickel(II)
1
13
The melting point, H and NMR spectra of com-
pound IV were consistent with the published data [5].
chloride, 0.156 g of 2,2 -bipyridyl (or 0.196 g of
1
,10-phenanthroline) in 10 ml of aqueous DMF
(
volume ratio DMF : H O 9: 1) was prepared brightly
2
REFERENCES
colored complex, and then 5 g of zinc powder was
added thereto. After a darkly colored complex was
formed to the solution was added 10 mmol of the
initial acid (2.9 g of pentachlorobenzoic acid or 3 g of
tetrachlorophthalic acid), and the mixture was stirred
at 70 C in a flask equipped with a reflux condenser.
The reaction progress was monitored by HPLC. On
completion of the reaction the mixture was cooled,
quenched with 50 ml of 10% solution of hydrochloric
acid, and the reaction products were extracted into
ether (2 25 ml). The ether was removed on a rotary
evaporator. Synthesis of acid II: reaction time 4 h,
preparative yield 83 89%. Synthesis of acid IV: reac-
tion time 4 h, preparative yield 86 90%.
1
. Japan Patent 07109245, 1996. Chem. Abstr., 1996,
vol. 123, 82947j.
2. Europe Patent 459819, 1992; Chem. Abstr., 1992,
vol. 116, 214524m.
3. USPatent 5481032, 1996; Chem. Abstr., 1996, vol. 124,
145641y.
4. USPatent 3297771, 1967; Chem. Abstr., 1967, vol. 66,
65270v.
5
6
. Zweig, A. and Epstain, M., J. Org. Chem., 1978,
vol. 43, no. 19, pp. 3690 3692.
. Trukhin, D.V., Adonin, N.Yu., and Starichenko, V.F.,
Zh. Org. Khim., 2000, vol. 36, no. 1, pp. 143 144.
. RF Patent 2152921, 1998; Byull. Izobr., 2000, no. 20.
. Trukhin, D.V., Adonin, N.Yu., and Starichenko, V.F.,
Zh. Org. Khim., 2000, vol. 36, no. 8, pp. 2161 2162.
7
8
3
,4,5-Trichlorobenzic acid (II). mp 164 165 C
1
(
(
publ. 164 C [4]). H NMR spectrum, , ppm: 8.01
9. Adonin, N.Yu. and Starichenko, V.F., J. Fluorine
Chem., 2000, vol. 101, pp. 65 67.
2H). 13C NMR spectrum, , ppm: 130.39 (C , C ),
2
6
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 6 2002