Amino- and hydrodefluorination of polyfluoroaromatic amines with aqueous ammonia in a steel autoclave. Synthesis of highly pure tetrafluorophenylenediamines

Article abstract of DOI:10.1007/s11172-009-0101-8

The action of aqueous ammonia on liexafhiorobenzene in a steel autoclave at 180-220 °C yields a mixture of isomeric tet rafluorophenylenediamines and 2,4,5-trifhioroplienylene-1,3-diamine. The content of the hydrodefluorination product significantly depends on the reaction temperature and time. Tetrafluorophenylene-1,3-diamine undergoes hydrodefluorination with aqueous ammonia in a steel autoclave at 200 °C to give 2,4,5-trifluorophenylene-1,3- diamine; when the additives of NH₄F and/or FeCl₃ are present, 2,5-difluorophenylene-1,3-diamine is additionally formed. The hydrodefluorination products are not formed during bis-aminodefluorination of hexafluorobenzene with aqueous ammonia in a glass reactor or with anhydrous ammonia (in a mixture with aprotic solvent) in a steel autoclave.

Full text of DOI:10.1007/s11172-009-0101-8

Russian Chemical Bulletin, International Edition, Vol. 58, No. 4, pp. 823—827, April, 2009
823
Aminoꢀ and hydrodefluorination of polyfluoroaromatic amines
with aqueous ammonia in a steel autoclave. Synthesis
of highly pure tetrafluorophenylenediamines
a
a
a
a
a,b
S. Z. Kusov, V. I. Rodionov, T. A. Vaganova, I. K. Shundrina, and E. V. Malykhin
aN. N. Vorozhtsov Institute of Organic Chemistry,
Siberian Branch of the Russian Academy of Sciences,
9
prosp. Akad. Lavrent'eva, 630090 Novosibirsk, Russian Federation.
Fax: +7 (383) 330 9752. Eꢀmail: malykhin@nioch.nsc.ru
b
Novosibirsk State University,
2
ul. Pirogova, 630090 Novosibirsk, Russian Federation
The action of aqueous ammonia on hexafluorobenzene in a steel autoclave at 180—220 °C
yields a mixture of isomeric tetrafluorophenylenediamines and 2,4,5ꢀtrifluorophenyleneꢀ1,3ꢀ
diamine. The content of the hydrodefluorination product significantly depends on the reaction
temperature and time. Tetrafluorophenyleneꢀ1,3ꢀdiamine undergoes hydrodefluorination with
aqueous ammonia in a steel autoclave at 200 °C to give 2,4,5ꢀtrifluorophenyleneꢀ1,3ꢀdiamine;
when the additives of NH F and/or FeCl are present, 2,5ꢀdifluorophenyleneꢀ1,3ꢀdiamine is
4
3
additionally formed. The hydrodefluorination products are not formed during bisꢀaminodefluꢀ
orination of hexafluorobenzene with aqueous ammonia in a glass reactor or with anhydrous
ammonia (in a mixture with aprotic solvent) in a steel autoclave.
Key words: polyfluoroarenes, hexafluorobenzene, amines, ammonia, aminodefluorination,
nucleophilic substitution, hydrodefluorination, organofluorine compounds.
Perfluoro(het)arenes and their derivatives with elecꢀ
tronꢀwithdrawing substituents readily undergo monoꢀ
and/or bisꢀhydrodefluorination under the action of susꢀ
exceed nonꢀfluorinated analogs in many physicoꢀchemiꢀ
1
2
cal characteristics. The use of polyimides in HiꢀTechꢀ
applications principally requires high purities of polyfluoꢀ
roarylenediamine monomers (the absence of partially fluꢀ
orinated analogs). For instance, one of two known by now
1
,2
pended Zn in aqueous solutions of KOH,
KH PO
2 4
(
see Ref. 3), and NH (see Ref. 4) or a Zn/Cu pair in
3
5
13
aqueous DMF at room temperature or on moderate heatꢀ
perfluorinated aromatic polyimides, obtained by the conꢀ
ing (up to 70 °C). Along with this, the hydrodefluorination
densation of compound 2 and dianhydride of 1,4ꢀbis(3,4ꢀ
dicarboxytrifluorophenoxy)tetrafluorobenzene, has proved
promising material for the opticoꢀcommunication techꢀ
(
up to 8% of all products) occured during bisꢀaminodefluꢀ
orination of octafluoronaphthalene upon the action of
6
14
aqueous ammonia, during which the polyfluoroarene has
nique due to the ability to form a film transparent in the
contacts with the steel surface of an autoclave and water at
visible and near IR regions (0.8—1.5 μm) including
absorption wavelengths of the overtones of the Carom—H
bond stretching vibrations.
1
20—140 °C. Consequently, metal components of the steel
(
Fe, Cr, Ni) can serve as reducing agents of polyfluoroareꢀ
2
nes. The same reason can presumably be responsible
for the side hydrodefluorination during the synthesis of
isomeric tetrafluorophenylenediamines (the ratio of metaꢀ
and paraꢀisomers is (85—87) : (10—13)) by bisꢀaminoꢀ
defluorination of hexafluorobenzene (1) with aqueous
Earlier, an original technique for the isolation of indiꢀ
vidual diamines 2 and 3 from the mixture of products of
direct bisꢀaminodefluorination of 1 has been suggested,
which is based on a selective complexation with 18ꢀcrownꢀ6.
This method exceeds preparative gas liquid chromatoꢀ
graphy (cf. Ref. 7a) in the efficiency of separation of diꢀ
amines 2 and 3, but did not allow us to completely sepaꢀ
rate them from partially fluorinated analogs.
7
a,8
ammonia (200—215 °C)
when it is run in a steel
autoclave.
A necessity to develop convenient methods for proꢀ
ducing 2,4,5,6ꢀtetrafluorophenyleneꢀ1,3ꢀdiamine (2) and
This reason sets a problem for the present work, which
consists in the study of competition of aminoꢀ and hydroꢀ
defluorination during the reaction of compound 1 with
2
,3,5,6ꢀtetrafluorophenyleneꢀ1,4ꢀdiamine (3) (cf. with the
9
10,11
multiꢀstep syntheses of compounds 2 and 3
) is due
7
a,8
to their use in the synthesis of aromatic polyimides, which
aqueous ammonia
in a steel autoclave, the largeꢀscale
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 806—810, April, 2009.
066ꢀ5285/09/5804ꢀ0823 © 2009 Springer Science+Business Media, Inc.
1

824
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 4, April, 2009
Kusov et al.
technological reactor, in order to find conditions for the
minimization of the side process and producing highly
pure target tetrafluorophenylenediamines.
Scheme 1
Results and Discussion
It was found that diamination of compound 1 with
aqueous ammonia (NH (aq)) in a steel autoclave is effiꢀ
3
cient in the temperature range 180—220 °C (Scheme 1).
Along with the target compounds 2 and 3, hydrodefluoriꢀ
nated compounds are indeed formed, primarily 2,4,5ꢀtriꢀ
fluorophenyleneꢀ1,3ꢀdiamine (5), the content of which in
the mixture of products depends on the process conditions
(
Table 1, see Scheme 1).
Contribution of the hydrodefluorination is already noꢀ
2
: metaꢀisomer, 3: paraꢀisomer
ticeable at the lower border (180 °C) of the temperature
range (see Table 1, entry 1) and increases with elevation of
the process temperature (entries 1, 3, 6, and 8) and inꢀ
crease in its time (entries 2, 4, 5, and 7). At the higher
border of the temperature range (220 °C), the content of
compound 5 is ~40% to the moment of entire consumpꢀ
i. NH /H O, 180—220 °C, steel autoclave.
3
2
tion of the intermediate pentafluoroaniline (4); in addiꢀ
tion, the product of deeper defluorination, viz., 2,5ꢀdifluꢀ
orophenyleneꢀ1,3ꢀdiamine (6), appears in the mixture (enꢀ
Table 1. The reaction of compound 1 with NH (aq) in a steel autoclave
3
a
Entry
Loading of reagents
Reaction conditions
Product
yields/g
Composition of the mixture (mol.%)
m(1)/g
V(NH (aq))/mL
T/°C
t/h
4
2 + 3
5
3
1
2
3
4
5
6
7
8
5.0
5.0
10
50
5.0
5.0
5.0
5.0
5.0
1.0
3.0
5.0
30
30
60
300
30
30
30
30
30
30
8g
180
180
200
200
210
210
220
220
200
220
200
160
200
220
6
24
6
8
5
6
4
6
6
12
6
6
30
30
4.9
4.8
8.6
45b
4.4
4.4
4.4
4.2
4.9
0.9f
2.3
4.8
9.5
42
20
8—10
12
19
16
9
—
7
—
54
72
72—77
75
61
52
60
44
92
83
2—3
7—8
13—16
13
18
30
27
44
—
—
c
d
e
9
1
1
1
1
1
0d
1
92
>98
19
8
<2
81
—
—
—
—
2
30
g,h
3
10
10
25
g,i
j
4
25
9.1
—
86
a
19
Data averaged over results of three—five experiments are given ( F NMR spectroscopy). The content of compounds 2—6 in the
product mixtures determined by the 19F NMR spectral data agree with the GCꢀMS data within ±7 rel.%. The F NMR spectra
19
(
acetoneꢀd , δ) of a mixture of products exhibit the following signals related to compounds 2—6: 2, –10.8 (2 F, F(4), F(6)), –6.8 (1 F,
6
F(5)), 3.5 (1 F, F(2)), cf. Ref. 15; 3, –0.2 (4 F, F(2), F(3), F(5), F(6)), cf. Ref. 15; 4, –14.2 (1 F, F(4)), –3.5 (2 F, F(3), F(5)), 0.4 (2 F,
F(2), F(6)), cf. Ref. 15; 5, –9.1 (1 F, F(6)), 3.2 (1 F, F(2)), 17.7 (1 F, F(5)), cf. Ref. 11; 6, –1.6 (1 F, F(2)), 43.6 (1 F, F(5)), cf. Ref. 16.
b
The yield of the mixture was 92 wt%; ratio of diamines 2 : 3 = 65 : 10.
The mixture contains 12% of compound 6; ratio of diamines 2 : 3 = 31 : 13.
The reaction was run in a glass tube.
Ratio of diamines 2 : 3 = 80 : 12.
The mixture of products presumably contains symmꢀtriaminotrifluorobenzene (~16%); M 177 (GCꢀMS data), 19F NMR spectrum
c
d
e
f
(
acetoneꢀd ), δ: –5.9 (s). Ratio of diamines 2 : 3 = 70 : 13.
Anhydrous ammonia was used.
Dioxane (50 mL) was used as a cosolvent.
Methyl tertꢀbutyl ether (MTBE) (50 mL) was used as a cosolvent.
The mixture of products contains symmꢀtriaminotrifluorobenzene (~14%).
6
g
h
i
j

Aminodefluorination of hexafluorobenzene
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 4, April, 2009
825
try 8). A comparison of these results with the experimental
results at 180—200 °C indicates the higher temperature
sensitivity of the hydrodefluorination process as compared
to the amination. The total fraction of the target products
efficiently7b at ~150–160 °C (see Table 1, entry 12) and
proceeds smoothly, i.e., without noticeable hydrodefluꢀ
orination. Only in the reaction of monoamine 4 with NH3
(aq) at 200 °C, a mixture of products of the same qualitative
composition as in the diamination of 1 is formed (Table 2,
entry 1). Proceeding from these results, compound 5 can
be formed by two possible ways (Scheme 2, cf. Ref. 11),
differing in the transformation of compound 4: amination
(a) or hydrodefluorination (b).
(
2 + 3) has the maximum of ~75% at 200 °C with the
content of compound 5 being 13—16% and of the interꢀ
mediate product 4, 8—12% (entries 3 and 4). The partially
hydrodefluorinated polyfluorophenyleneꢀ1,4ꢀdiamine was
not found in noticeable amounts in the mixtures.
In contrast to the reaction in a steel autoclave, the
diamination of 1 in a glass tube gave no product of hydroꢀ
defluorination 5 (see Table 1, entry 9). This confirms that
a contact of reagents with metals on the autoclave surface
is responsible for the hydrodefluorination of polyfluoroꢀ
arenes. An increase in temperature and time of the process
in a glass vessel leads to emergence of another product in
the mixture, which is presumably symmꢀtriaminotrifluoꢀ
robenzene (see Table 1, entry 10).
A principal possibility of hydrodefluorination of comꢀ
pound 2 (pathway a) is confirmed by the results of its
keeping at 200 °C in NH (aq) or in NH (aq) + MeOH
(on the influence of organic cosolvents on the rate of deꢀ
fluorination see Ref. 4) in autoclave, which led to the
formation of compound 5 (see Table 2, entries 2 and 3,
respectively). However, hydrodefluorination contributes
little in these experiments (cf. with the data in Table 1),
3
3
which can be due to the absence of NH F formed during
4
Special experiments have been performed to find out
compounds undergoing hydrodefluorination, as well as
conditions providing such a transformation.
the monoamination of compound 1 (on the influence of
inorganic electrolites on the rate of defluorination see
Ref. 20). In fact, the keeping of compound 2 in NH (aq)
3
The reaction of compound 1 with anhydrous NH * at
in the presence of FeCl (see Table 2, entry 4) and NH F +
3
3
4
1
00 (see Ref. 2) and 200 °C (see Table 1, entry 11) in
+ FeCl (entry 5) led to a considerable increase in the
3
a steel autoclave results in its amination to form monoamꢀ
ine 4. At 200 °C, the fraction of compounds corresponding
to diamination is ~8%. Products of defluorination were
not found. Their absence is an evidence that water, rather
than ammonia, is a source of hydrogen atom in the hydroꢀ
defluorination. The monoamination of compound 1 by
degree of its defluorination (compare with entries 2 and 3).
In this case, compound 5 undergoes defluorination, too;
a noticeable amount of compound 6 appears in the mixꢀ
ture of products (see Scheme 2). The results obtained conꢀ
firm that the inorganic products of the reaction, accumuꢀ
lated in the course of the transformation of compound 1
into 4 and further into the mixture 2 + 3, promote the
process of hydrodefluorination. In fact, phenylenediamine
2 is converted into 5 on simple keeping in the presence of
the action of NH (aq) to form monoamine 4 takes place
3
*
Critical parameters for NH : ρ 0.24 g cm–3, Tcr 132.6 °C,
3 cr
Pcr 112.5 atm (see Ref. 17).
FeCl in water at 220 °C (see Table 2, entry 6). This is also
3
Table 2. Hydrodefluorination of compounds 2 and 4
a
Entry
Loading of reagents
Reaction conditions Product The mixture composition (mol.%)
yields
Substrate
m/g)
Solvent
(V/mL)
Salt
(m/g)
T/°C
t/h
4
2
5
6
/
g
(
b
c
1
2
3
4 (5.0)
2 (5.0)
2 (5.0)
NH (aq) (30)
—
—
—
200
200
200
6
6
6
4.8
4.8
4.8
12
—
—
72
97
93
2.5
2.1
3.3
—
—
—
3
NH (aq) (30)
3
d
NH (aq) (30),
3
MeOH (10)
4
5
2 (2.0)
2 (5.0)
NH (aq) (30)
FeCl (1.2)
200
200
6
6
1.7
4.8
—
—
52
43
37
45
5.8
11
3
3
NH (aq) (30)
FeCl (3.0),
3
3
NH F (1.0)
4
6
7
2 (5.0)
4 (5.0)
H O (30)
FeCl (3.0)
220
250
15
15
4.7
4.9
—
84
80
—
18
—
<2
—
2
3
e
H O (30)
FeCl (3.0)
2
3
a
See Note a to Table 1.
b
c
d
e
The mixture of products contains compound 3 (12%).
The mixture of products contains symmꢀtriaminotrifluorobenzene (~1%).
The mixture of products contains symmꢀtriaminotrifluorobenzene (2%).
The mixture of products contains 12% of compound 7 and 3.5% pentafluorophenylhydroxylamine. The 19F NMR spectrum of
19
compound 7 (acetoneꢀd ), δ: 1.0 (2 F, F(2), F(6)); 20.6 (2 F, F(3), F(5)) (cf. Ref. 18). The F NMR spectrum of pentafluorophenylꢀ
6
hydroxylamine (acetoneꢀd ), δ: –2.6 (1 F, F(4)); –2.2 (2 F, F(2), F(6)); 9.1 (2 F, F(3), F(5)) (cf. Ref. 19).
6

826
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 4, April, 2009
Kusov et al.
Scheme 2
confirmed by the fact that prolongation of the process
gives higher relative (to the sum 2 + 3) fraction of the
hydrodefluorination products already at the lower border
of the temperature range (180 °C) (see Table 1, cf. enꢀ
tries 1 and 2).
containing no hydrodefluorination products. The highly
pure target compounds can be easy isolated from this mixꢀ
ture by selective complexation with 18ꢀcrownꢀ6.
2
Experimental
Whether the pathway b is realized under the reaction
conditions cannot be confirmed due to the fact that aniline
19F NMR spectra were recorded on a Bruker AVꢀ300 specꢀ
trometer, the signals of C F were used as the reference. Identiꢀ
4
itself and the product of its hydrodefluorination 7 underꢀ
6
6
2
fication of components by GCꢀMS was performed using the
HPꢀG1081A complex consisting of a HР 5890 series II chroꢀ
matograph and a HРꢀ5971 mass selective detector (ionization
energy of electrons, 70 eV; an HРꢀ5 30 m×0.25 mm×0.25 μm
column (5% of biphenylsiloxane, 95% of dimethylsiloxane); heꢀ
go amination upon the action of NH (aq) at 200 °C to
3
give 2 and 5, respectively. This is the reason that the prinꢀ
cipal possibility to hydrodefluorinate aniline 4 was deꢀ
monstrated in the absence of ammonia: in water with the
FeCl additives at 250 °C, aniline 4 is converted into aniline
–1
3
lium was a carrier gas at 1 mL min ). Temperature conditions
7
(see Table 2, entry 7). To sum up, phenylenediamine 5,
the side product of bisꢀaminodefluorination of compound
upon the action of NH (aq) in a steel autoclave, can be
for the column: 2 min at 50 °C, further, heating at the rate of
–1
1
0 °C min , 5 min at 280 °C; the injector temperature was 280 °C;
1
the source of ions temperature was 173 °C. Data were collected
at the rate of 1.2 scans s– in the region of 30—650 at. mass units.
Stainless steel (Cr 18%, Ni 10%, Ti 1.5 %) autoclaves of
3
1
formed from both phenylenediamine 2 and aniline 4.
From all the results, it follows that a noticeable contriꢀ
bution of hydrodefluorination is due to the simultaneous
presence of a) the contact of the reaction mixture with the
reducing agent (metals on the autoclave surface); b) the
source of hydrogen atoms (water); c) the promoters of the
reaction (inorganic products), as well as to the high temꢀ
0
.05, 0.1, or 0.5 L in volume were used for the experiments, as
well as the following commercial reactants: 28% aq. ammonia
1
(
(
d = 0.9 g mL– ), rectified MTBE (99%), NH F and FeCl •6H O
4 3 2
pure grade). Hexafluorobenzene (1) (>99%) was obtained in
the Experimental Chemical Production of NIOKh SB RAS based
7c
on the procedure technological documents with subsequent
perature. When the process is run in NH (aq) in a steel
purification by freezing out. Pentafluoroaniline (4) (>99%) and
2,4,5,6ꢀtetrafluorophenyleneꢀ1,3ꢀdiamine (2) (>97%) were obꢀ
tained according to procedures described earlier.
3
autoclave, it is possible to minimize contribution of the
hydrodefluorination if refuse the oneꢀpot bisꢀaminodefluꢀ
orination of compound 1, thereby excluding the inorganic
saltsꢀpromoters, which are formed in the amination step
of compound 1. The use of nonꢀmetallic reactors (see, for
example, Table 1, entries 9 and 10) or anhydrous aminaꢀ
ting systems allowed us to completely avoid the hydrodeꢀ
fluorination. Thus, compound 1 upon the action of anhyꢀ
2
Reaction of polyfluoroarenes with NH (aq) or water in a steel
3
autoclave (general procedure). Polyfluoroarene was placed into
autoclave, the capacity of which was 1.6 times larger than a total
volume of the reagents used, then, NH3 (aq) or water and,
if necessary by the experimental conditions, NH F and/or
4
FeCl •6H O were added. The autoclave was hermetically sealed,
3
2
heated with stirring to the necessary temperature, and kept for
the time required. After the reaction was over and the autoclave
was cooled, the reaction mixture was removed quantitatively
drous NH in dioxane (entry 13) or MTBE (entry 14) in
3
a steel autoclave gives rise to a mixture of diamines 2 and 3

Aminodefluorination of hexafluorobenzene
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 4, April, 2009
827
(
thoroughly washing the autoclave walls and cap with MTBE).
7. Sintezy ftororganicheskikh soedinenii [Synthesis of Organoꢀ
fluorine Compounds], Eds I. L. Knunyants, G. G. Yakobson,
Khimiya, Moscow, 1973, (a) p. 194; (b) p. 190; (c) p. 130
(in Russian).
8. G. M. Brooke, J. Burdon, M. Stacey, J. C. Tatlow, J. Chem.
Soc., 1960, 1768; G. G. Yakobson, V. D. Shteingarts, G. G.
Furin, N. N. Vorozhtsov, Jr., Zh. Obshch. Khim., 1964, 34,
3514 [J. Gen. Chem. USSR (Engl. Transl.), 1964, 34, 3560].
9. A. M. Doyle, A. E. Pedler, J. Chem. Soc. C, 1971, 282;
P. Robson, J. Roylans, R. Stephens, J. C. Tatlow, R. E.
Wortchington, J. Chem. Soc., 1964, 5748.
The aqueous layer was extracted with MTBE, the combined
washings and extracts were dried with MgSO , MTBE was evapꢀ
4
19
orated to obtain a dry residue, which was analyzed by F NMR
and GCꢀMS. The loading of reagents, the reaction conditions,
and the product yields are given in Tables 1 and 2.
To run the process in a glass reactor (see Table 1, entry 9),
a sealed tube with reagents was placed into an autoclave, before
sealing, the 2/3 of the free space was filled with NH (aq) to
equalize the pressure arising in the tube and autoclave on heating.
3
Reaction of polyfluoroarenes with anhydrous NH in a steel
3
autoclave. Polyfluoroarene was placed into autoclave followed
by addition of an aprotic solvent, if required by the experimental
10. US Pat. 3461135; Chem. Abstrs, 1969, 71, 80989.
11. G. A. Selivanova, L. M. Pokrovskii, V. D. Shteingarts,
Zh. Org. Khim., 2001, 37, 429 [Russ. J. Org. Chem. (Engl. Transl.),
2001, 37, 404].
12. Yu. N. Sazanov, Zh. Prikl. Khim., 2001, 74, 1217 [Russ. J.
Appl. Chem. (Engl. Transl.), 2001, 74, 1253].
conditions. Liquid NH was added using a dropping funnel with
3
pressureꢀequalization arm. The autoclave was hermetically
sealed, heated with stirring to the necessary temperature, and
kept for the time required. After the reaction was over and the
autoclave was cooled, gaseous NH was slowly released through
13. S. Ando, T. Matsuura, S. Sasaki, in Fluoropolymers 2: Propꢀ
erties, 1999, Ed. G. Hougham, Kluwer Academic—Plenum
Publishers, New York, 1999, 277; S. Ando, T. Matsuura,
S. Sasaki, Macromolecules, 1992, 25, 5858.
14. EP Pat. 1275679; Chem. Abstrs, 2003, 138, 90676.
15. T. Homer, J. Chem. Soc. B, 1966, 141.
3
the pressure outlet valve. Water was added to the reaction mixꢀ
ture followed by treatment similar to that described above. The
mixture of products was analyzed by 19F NMR and GCꢀMS.
The loading of reagents, the reaction conditions, and the prodꢀ
uct yields are given in Table 1.
1
6. A. A. Shtark, T. V. Chuikova, G. A. Selivanova, V. D. Shteinꢀ
garts, Zh. Org. Khim., 1987, 23, 2574 [Russ. J. Org. Chem.
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Received March 5, 2008;
in revised form November 12, 2008