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Russ.Chem.Bull., Int.Ed., Vol. 54, No. 10, October, 2005
Shishkin et al.
1,2,3,5ꢀtetrabromobenzene,15 pentabromobenzene,16 hexaꢀ
bromobenzene,17 pentabromotoluene,18 pentabromofluoroꢀ
Reactions of substituted pentabromobenzenes with ButONa
in DMSO (general procedure). A mixture of DMSO (80 mL)
and C6Br5X (0.002 mol) was kept at constant temperature (60 °C)
under flow of argon until the polybromoarene dissolved comꢀ
pletely. Then 0.2 M ButONa (10 mL) in ButOH was added
to the reaction mixture at the above temperature under argon.
Samples were withdrawn at intervals from the reaction mixꢀ
ture and treated with 2% HCl; the precipitate that formed was
separated, washed to a neutral reaction, dried, and analyzed
by GLC and 1H NMR spectroscopy. The results are given in
Table 1.
benzene,19
pentabromochlorobenzene,20
pentabromoꢀ
nitrobenzene,21 pentabromoaniline,22 and 2,4,6ꢀtribromoꢀ3ꢀ
methylaniline23 were prepared according to described proceꢀ
dures.
1,2,3,4ꢀTetrabromoꢀ5ꢀchloroꢀ and 1,2,4,5ꢀtetrabromoꢀ3ꢀ
chlorobenzenes were synthesized by reductive deamination of
tetrabromochloroanilines prepared by reduction of the correꢀ
sponding tetrabromochloronitrobenzenes.21
Reduction of tetrabromonitrobenzenes (general procedure).
A
mixture of the corresponding polybromonitrobenzene
Debromination of pentabromotoluene with MeONa in
CH3OD—CD3COCD3. A mixture of pentabromotoluene (80 mg,
0.164 mmol), a solution of NaOMe (2 mL) in CH3OD (preꢀ
pared by dissolution of metallic Na in CH3OD; 0.1 mmol mL–1),
and CD3COCD3 (10 mL) was heated in a flow of argon under
reflux for 0.5 h. The reaction mixture was cooled and concenꢀ
trated to dryness; the residue was washed with 2% HCl and then
with water to a neutral reaction, dried, and analyzed by GLC
and 1H NMR spectroscopy. According to the data from 1H NMR
spectroscopy, a solution of the residue in CCl4 does not contain
even traces of protonꢀcontaining compounds. The GLC profile
fully agrees with that of a product obtained under analogous
conditions in nondeuterated solvents (the degree of conversion
of C6Br5Me was 90% (GLC); the contents of 2,3,4,5ꢀ, 2,3,4,6ꢀ,
and 2,3,5,6ꢀtetrabromotoluenes in the mixture were 5, 28,
and 67%, respectively (1H NMR)).
(0.022 mol) and reduced iron (15 g, 0.36 mol) in glacial aceꢀ
tic acid (200 mL) was refluxed for 2 h. The reaction mixꢀ
ture was cooled and diluted with water and the precipitate
that formed was separated, dried, and recrystallized from
benzene.
Deamination of tetrabromochloroanilines was carried out as
described for polybromomethoxyanilines.12 Compounds obꢀ
tained were purified by column chromatography on L 40/100
silica gel with light petroleum as an eluent (70—100 °C).
1,2,3,5ꢀTetrabromoꢀ4ꢀchlorobenzene, 1,2,3,5ꢀtetrabromoꢀ
4ꢀfluorobenzene, and 1,2,3,5ꢀtetrabromoꢀ4ꢀnitrobenzene were
obtained by the Sandmeyer substitution of bromine for the amino
group in the corresponding 3ꢀsubstituted 2,4,6ꢀtribromoanilines
as described for polybromomethoxyanilines.12 The products were
additionally purified by column chromatography on Al2O3 with
hexane as an eluent.
2,4,6ꢀTribromoꢀ3ꢀchloroaniline, 2,4,6ꢀtribromoꢀ3ꢀfluoroꢀ
aniline, and 2,4,6ꢀtribromoꢀ3ꢀnitroaniline were obtained by broꢀ
mination of the corresponding 3ꢀsubstituted anilines as described
for bromination of 3ꢀmethylaniline.23
References
1. V. N. Shishkin and K. P. Butin, Izv. Sib. Otd. Akad. Nauk
SSSR, Ser. Khim. Nauk, 1990, 84 [Izv. Sib. Otd. Akad. Nauk
SSSR, Ser. Khim. Nauk, 1990 (Engl. Transl.)].
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1,2,4,5ꢀTetrabromoꢀ3ꢀnitrobenzene.
A
mixture of
1,2,4,5ꢀtetrabromobenzene (3.7 g), NaNO3 (1.8 g), and
conc. H2SO4 (10 mL) was heated on a water bath with stirring
for 7 h. The reaction mixture was cooled, poured onto ice, and
neutralized with NaOH. The precipitate that formed was filꢀ
tered off, washed with water, dried, and recrystallized from
benzene.
1,2,3,4ꢀTetrabromoꢀ5ꢀnitrobenzene was obtained by oxidaꢀ
tion of 2,3,4,5ꢀtetrabromoaniline.24 A mixture of 2,3,4,5ꢀtetraꢀ
bromoaniline (2 g), AcOH (10 mL), 30% H2O2 (2.5 mL), and
conc. H2SO4 (0.2 mL) was heated on a water bath with stirring
for 6 h. The reaction mixture was cooled and diluted with water.
The precipitate that formed was filtered off, washed with 20%
H2SO4 and then with water to a neutral reaction, dried, and
recrystallized from benzene—light petroleum.
1,2,4,5ꢀTetrabromoꢀ3ꢀfluorobenzene was obtained by deꢀ
carboxylation of 2,3,5,6ꢀtetrabromoꢀ4ꢀfluorobenzoic acid preꢀ
pared as described for pentabromobenzoic acid.21 A mixture of
2,3,5,6ꢀtetrabromoꢀ4ꢀfluorobenzoic acid (0.5 g) and N,Nꢀdiꢀ
methylaniline (20 mL) was heated at 190 °C for 40 min. After
cooling, dilute HCl (1 : 1) (50 mL) was added. The precipitate
that formed was filtered off, washed with hot 5% Na2CO3 and
water, dried, and additionally purified by column chromatoꢀ
graphy on silica gel with light petroleum as an eluent.
The yields, melting points, spectroscopic characteristics, and
elemental analysis data for the polybromoarenes obtained are
given in Table 2.
8. G. E. Hall, R. Piccolini, and J. D. Roberts, J. Am. Chem.
Soc., 1955, 77, 4540.
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89, 6712.
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1978, 3319.
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Vestn. Mosk. Univ., Ser. 2: Khim., 1983, 24, 382 [Bull. Moscow
Univ., Div. Chem., 1983, 24 (Engl. Transl.)].
12. V. N. Shishkin, B. S. Tanaseichuk K. K. Lapin, A. A. Ivkina,
and K. P. Butin, Zh. Org. Khim., 1984, 20, 2588 [J. Org.
Chem. USSR, 1984, 20, 2357 (Engl. Transl.)].
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