Selective mono- and diamination of some polyhalogenbenzenes in anhydrous ammonia

Article abstract of DOI:10.1016/j.jfluchem.2015.09.003

Aminodefluorination of polyhalogenbenzenes (chloropentafluoro-, 1,3-dichlorotetrafluoro-, sym-trichlorotrifluoro-, 1,2,3,5-tetrafluoro- and 1,2,4,5-tetrafluoro-3-trifluoromethylbezenes) in anhydrous ammonia was investigated. The optimal conditions for sel

Full text of DOI:10.1016/j.jfluchem.2015.09.003

Accepted Manuscript
Title: Selective mono- and diamination of some
polyhalogenbenzenes in anhydrous ammonia
Author: Vladimir I. Rodionov Tamara A. Vaganova Evgenij
V. Malykhin
PII:
S0022-1139(15)00268-7
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.jfluchem.2015.09.003
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3-9-2015
5-9-2015
Please cite this article as: V.I. Rodionov, T.A. Vaganova, E.V. Malykhin, Selective
mono- and diamination of some polyhalogenbenzenes in anhydrous ammonia, Journal
of Fluorine Chemistry (2015), http://dx.doi.org/10.1016/j.jfluchem.2015.09.003
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*Graphical Abstract - Pictogram
Page 1 of 19

*Graphical Abstract - Synopsis
Page 2 of 19

*Highlights (for review)
Highlights
Aminodefluorination of polyhalogenbenzenes in anhydrous ammonia was investigated.
The optimal conditions for selective introducing one and two amino groups were elucidated.
Purification of the crude products is feasible by using simple experimental procedures.
Potentially scalable method to prepare valuable polyfluoroarylenediamines was developed.
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*Manuscript
Click here to view linked References
Selective mono- and diamination of some polyhalogenbenzenes
in anhydrous ammonia
Vladimir I. Rodionov, Tamara A. Vaganova, Evgenij V. Malykhin*
N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry,
Siberian Branch of the Russian Academy of Sciences,
Lavrentґev Avenue 9, 630090 Novosibirsk, Russian Federation.
E-mail: malykhin@nioch.nsc.ru
Aminodefluorination of polyhalogenbenzenes (chloropentafluoro-, 1,3-
dichlorotetrafluoro-, sym-trichlorotrifluoro-, 1,2,3,5-tetrafluoro- and 1,2,4,5-
tetrafluoro-3-trifluoromethylbezenes) in anhydrous ammonia was investigated.
The optimal conditions for selective preparation of mono- and diamino
derivatives, which are ensured by the reaction temperature, were elucidated. In
some examples of diamine synthesis, in order to improve the selectivity of second
aminodefluorination, it is advisable to separate the isomeric monoamino
derivatives produced in the first step of the synthesis.
Keywords: polychlorofluorobenzenes; anhydrous ammonia; aminodefluorination;
nucleophilic substitution; polyhalogenaromatic amines
Page 4 of 19

1. Introduction
Various mono- and diamino derivatives of polyhalogenarenes are demanded for high-tech
processes and materials. In particular, diaminopolyfluoroarenes serve as structural blocks in the
synthesis of materials used in optical communication devices, nanofilters and membranes, laser
media, nonlinear optics and molecular electronics [1-5]. Exhaustively halogenated arylenediamines
were shown [1, 6] to be the valuable monomers for polymers applicable as transmission medium in
optoelectronics, since replacing all aromatic hydrogen atoms by halogenes (fluorine, chlorine)
improves the key property of material, i.e. transparency at the wavelengths of 1.3 and 1.5 μm, called
telecommunications “transparency windows”. Partially fluorinated amines are widely used for the
synthesis of polyimides with improved characteristics [7-9], pharmaceutical preparations [10-12]
and chemical remedies of plant protection [13]. For example, to construct
polyfluorobenzoazaheterocycles exhibiting a variety of biological activity [10, 12], polyfluorinated
aromatic amines with a nonsubstituted position ortho to the amino group were employed as the
universal building blocks [14, 15].
The most convenient method for preparing such compounds appears to be
aminodefluorination of electrophilic polyfluoroarenes. This process efficiently occurs in anhydrous
ammonia applied as a reagent and a solvent simultaneously. In the works [16-18] by example of
aminodefluorination of perfluoro(het)arenes (benzene, naphthalene, pyridine), we have shown that
the anhydrous ammonia has several advantages over the other aminating systems, i.e. aqueous and
aqueous-alcohol ammonia. These advantages consist in i) selectivity of synthesis of arenes
containing one or two amino groups due to a significant differences in the reaction conditions; ii) a
high purity of products owing to the absence of hydrodeflurination realized in aqueous ammonia
medium [19]; iii) processability and scalability of the method as a general route to synthetically
important polyluorinated anilines and aromatic diamines.
The purpose of the present work is to extend the reported aminodefluorination protocol [16-
18] to polychlorofluorobenzenes and partially fluorinated benzenes with the aim of preparing
valuable polyhalogenaromatic mono- and diamines.
2. Results and discussion
Polychlorofluorobenzenes containing one, two or three chlorine atoms are formed as by-
products in the synthesis of hexafluorobenzene from hexachlorobenzene (Halex process) [20-22],
which makes them potential starting materials for preparing functionalized polyhalogenarenes.
Reactions of chloropentafluorobenzene (1a), 1,3-dichlorotetrafluorobenzene (2a) and sym-
trichlorotrifluorobenzene (3a) with ammonia in aqueous and aqueous-alcoholic media were
described in the works [23-26] and used to synthesize their amino derivatives. However, these
processes are not sufficiently site-selective and accompanied by the formation of
Page 5 of 19

hydrodefluorinated by-products that make difficult and tricky the purification of the crude reaction
mixture. Carrying out of the reaction in anhydrous ammonia significantly improves the synthetic
result. Thus, in the relatively mild conditions (Entry 1, Table 1; Scheme 1) 1a can be converted into
4-chlorotetrafluoroaniline (1b) mixed with a small amount of ortho-isomer 2-
chlorotetrafluoroaniline (85:15). Recrystallization of the crude product in Entry 1 results in the pure
amine 1b. According to [23], in aqueous ammonia the isomeric chlorotetrafluoroanilines are formed
in the ratio 70:22 in 48 h at 120 °C (the molar ratio 1a:NH3 is 1:23). Thus, aminodefluorination of
1a in anhydrous ammonia occurs at the lower temperature and is characterized by the higher
regioselectivity.
Both these facts appear to be provided by effects of the medium. Anhydrous liquid ammonia
as a medium for SNAr-processes behaves like a dipolar aprotic solvent [27-29] due to weak
solvation of nucleophiles by means of hydrogen bonds. Consequently, reactivity of nucleophiles in
anhydrous ammonia is higher [27] than that in polar protic solvents [30, 31]. Therefore, a transition
state of the nucleophile addition stage is more reagent-like in anhydrous ammonia as compared to
that in aqueous and aqueous-alcoholic media, and regioselectivity is more dependent on the
polyhalogenarene structure [18]. In the considered aminodefluorination process, the total activating
inductive effect (-I) of two ortho-fluorines, being a factor that acts in the early transition state [32,
33], increases the preference of the nucleophile addition to the position 4 in compound 1a.
Use of monoamine 1b as a substrate for the introduction of a second amino group is more
expedient than one-pot bis-aminodefluorination of 1a, because this enables to exclude the formation
of 2-chloro-4,5,6-trifluoro-1,3-phenylenediamine and to get 4-chloro-2,5,6-trifluoro-1,3-
phenylenediamine (1c) selectively (Entry 2, Table 1; Scheme 1). The yield and purity of 1c thus
obtained are significantly higher than after reaction of 1a in aqueous ammonia [23], wherein a
sample of 1c with 91 % purity was isolated in yield 56 % and its purification from isomeric diamine
to 97 % purity led to a decrease in the yield to 30 %.
Scheme 1. Aminodefluorination of polychlorofluorobenzenes 1a-3a
The synthesis of 2,4-dichloro-3,5,6-trifluoroaniline (2b) was described both starting from
1,3-dichlorotetrafluorobenzene 2a [24] and from the mixture of isomeric
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dichlorotetrafluorobenzenes containing 65-70 % of 2a [25]. The use of this accessible mixture as a
starting material is a real advantage of the method; however, to isolate the desired product 2b a
laborious procedure, i.e. preparative chromatography, was applied in [25]. We carry out the reaction
in anhydrous NH3 at 15 °C (cf. 80 °C in [25] and 180 °C in [24]) on the mixture of isomeric
dichlorotetrafluorobenzenes. In these conditions, 2a predominantly undergoes aminodefluorination
over the other isomers and the formed amines can be separated from unreacted halogenebenzenes as
hydrochloric salts (Entry 3, Table 1; Scheme 1). Crystallization of the crude product obtained by
decomposing the salts, affords amine 2b, purity 95%. Reaction of this compound with anhydrous
ammonia (Entry 4, Table 1), as well as in the case of monochloro derivatives 1a,b, is more selective
than one-pot bis-aminodefluorination of 2a. 4,6-Dichloro-2,5-difluoro-1,3-phenylenediamine (2c)
can be isolated from the crude product in a preparative scale with purity >98% using the technique
based on the different capacity of diamines to form complexes with 18-crown-6 [16-18]. A method
for producing a diamine 2c described previously [25] involves the chromatographic separation of a
compounds mixture formed at ammonolysis of isomeric dichlorotetrafluorobenzenes in aqueous
ammonia.
Table 1
Experimental conditions and product yields for reactions of polyhalogenearenes with anhydrous
NH3.
Reactant amountsa Reaction conditions
Substrate NH3 Temperature Time
Reaction products
Polyhalo-
genarene
Entry
Crude
product
Isolated
product
Amines
(g)
(ml)
(°C, ±5)
(h)
24
200
30
20
5
yields (g) yields (g/%)
1
2
10
30
70
9b
5.3
12
6.5/65
4.5/70
8.3/51
2.5/80
2.3/77
1.8/62
7.4/75
4.6/72e
6.7/68
1.8/70g
3.8/76
2.3/77
1a
1b
2ac
2b
3a
3a
4a
4b
4a
5b
6a
6a
1b
1c
2b
2c
3c
3d
4b
4c
4c
5c
6b
6c
6.5
16.7
3.0
3.0
3.0
10
20
155
15
3
30
4
20
135
60
2.8
2.7
2.5
9.1
9.2e
7.5
2.7g
4.3
2.6
5
20
6
20
150
115
210
220
200
60
80
36
36
68
280
15
20
7
30
8
10
15d
15f
15d
50
9
10
10
11h
12
3.0
5.0
3.0
50
130
Page 7 of 19

a An autoclave volume is 100 ml in Entries 11 and 12, and 50 ml in other Entries. The molar ratio
substrate:NH3 is varied from 1:10 to 1:20.
b In the mixture with 2-chlorotetrafluoroaniline (15% according to 19F NMR).
c 67 % in the mixture with isomeric dichlorotetrafluorobenzenes.
d Dioxane (20 ml) was used as co-solvent.
e The crude product contains 28% of 4b (according to 19F NMR), yield of pure 4c is given
considering the conversion.
f t-BuOMe (20 ml) was used as co-solvent.
g The crude product contains 15% of 5b (according to 19F NMR), yield of pure 5c is given
considering the conversion.
h Preparation of compound 6b was reported in [17].
Symmetrical trichlorotrifluorobenzene (3a) undergoes sufficiently selective mono-
aminodefluorination in aqueous-alcohol ammonia at 160 °C to form 2,4,6-trichloro-3,5-
difluoroaniline (3b) [26]. At 180 °C in this system, a mixture of approximately equal amounts of 3b
and 2,4,6-trichloro-5-fluoro-1,3-phenylenediamine (3c) is formed [26]. We have shown that in
anhydrous ammonia at 60 °C diamine 3c can be obtained in high yield and purity and no amount of
3b has been detected in the crude product (Entry 5, Table 1; Scheme 1).
The data obtained indicate that the replacement of fluorine atoms by chlorine atoms moving
from the substrate 1a to 2a and 3a considerably facilitates their aminodefluorination (cf. the time-
temperature modes in Entries 1-5, Table 1). This is due to the relative activating influences of
chlorine vs. fluorine on the rate constants of SNAr reactions (kCl/F ~3−4 for ortho-substituents; kCl/F
~30−35 for para- substituents) [32, 34]. Compound 3a, owing to the presence of three chlorine
atoms, at 150 °C in anhydrous ammonia is completely converted into 1,3,5-triamino-2,4,6-
trichlorobenzene (3d) (Entry 6, Table 1; Scheme 1). Introduction of three amino groups into mono-
and dichlorinated compounds 1a and 2a in anhydrous ammonia is possible in principle, but it
occurs under more hard conditions. Thus, compound 1a in 200 h at 180 ° C gives a mixture
containing 90% of diamine 1c and 10% of 1,3,5-triamino-2-chloro-4,6-difluorobenzene; compound
2a in 10 h at 180 ° C turns into a mixture of diamine 2c and 1,3,5-triamino-2,4-dichloro-6-
fluorobenzene in the ratio 77:23. These triamines were not isolated from the product mixtures and
the assumptions on their structures were based on the data of GC-MS and 19F NMR. 1,3,5-
Triamino-2-chloro-4,6-difluorobenzene has a molecular ion with m/z 193 and singlet at δ -166.4
ppm, 1,3,5-triamino-2,4-dichloro-6-fluorobenzene – a molecular ion with m/z 209 and singlet at δ -
162.2 ppm. The 19F NMR chemical shifts of these compounds are comparable with those calculated
by the additive scheme using substituent shielding parameters [35].
1,2,3,5-Tetrafluorobenzene (4a) is less reactive relative to nucleophiles in comparison with
completely halogenated benzenes 1a-3a. It was shown [36] that in aqueous ammonia at 250 °C 4a
affords the mixture of 2,3,5-trifluoroaniline (4b) and 2,5-difluoro-1,3-phenylenediamine (4c),
which were separated by chromatography in low yield. Preparative-scale synthesis of 4b was
Page 8 of 19

carried out starting from octafluorotoluene [14, 15] in four steps including hydrolysis of CF3 group
and decarboxylation. Diamine 4c was prepared from 2a via its reaction with hydrazine hydrate [37]
followed by the reduction of hydrazino to amino group and hydrodechlorination [38]. In anhydrous
ammonia at 115 °C 4a undergoes monoaminodefluorination at position 1 to form 4b (Entry 7, Table
1; Scheme 2). The high selectivity of the process is provided by the fact that the position 2 in
substrate is deactivated by the electron donor effect of a para-fluorine atom, and the position 5 −
also by the lack of ortho-fluorine atoms contributing to nucleophilic attack [32, 33]. Diamine 4c can
be prepared in comparable yields both from aniline 4b (Entry 8, Table 1) and via one-pot bis-
aminodefluorination of benzene 4a (Entry 9, Table 1) at 200-220 °C. Under incomplete conversion
(Entry 7, Table 1), diamine 4c is easily separated from unreacted 4b by crystallization.
Scheme 2. Aminodefluorination of tetrafluorobenzene 4a
Orientation of 4a aminodefluorination changes drastically upon the action of a charged
nucleophile NaNH2 in liquid ammonia at -60 °C [36]. Under these conditions, formed is a product
of the replacement of fluorine atom at the position 5, i.e. 3,4,5-trifluoroaniline (5b) (Scheme 2).
This change of orientation was suggested [36] to be due to the fact that the amide ion exhibits
protophilic activity and a mechanism which involves a benzine intermediate is implemented.
Aniline 5b thus obtained undergoes in anhydrous ammonia replacement of fluorine atom at a para-
position to hydrogen atom, to form previously unknown 4,5-difluoro-1,3-phenylenediamine (5c)
(Entry 10, Table 1; Scheme 2). At 200 °C the reaction proceeds slowly, but an increase of the
temperature to 220 °C intensifies hydrodefluorinaton at the para-position to the amino group to
form 5-fluoro-1,3-phenylenediamine. This compound was identified in the mixture according to 19F
NMR (δ -114.9 ppm, cf. [39]) and GC-MS data (m/z 126, [M]+). Separation of diamine 5c from
unreacted aniline 5b and from minor amount of hydrodefluorinated product (≤3%) was carried out
by means of complexation with 18-crown-6 similarly to [16-18].
Page 9 of 19

Scheme 3. Aminodefluorination of heptafluorotoluene 6a
In α,α,α-2,3,5,6-heptafluorotoluene (6a) an electron withdrawing effect of trifluoromethyl
group activates positions 2 and 6 to a nucleophilic attack. As we have shown previously [17], arene
6a undergoes aminodefluorination in anhydrous NH3 at 60 °C to give 3,4,6-trifluoro-2-
trifluoromethylaniline (6b) (Entry 11, Table 1; Scheme 3). Bis-aminodefluorination of 6a occurs at
130 °C (Entry 12, Table 1). 4,6-Difluoro-2-trifluoromethyl-1,3-phenylenediamine (6c) thus
obtained contains no impurities in appreciable amount, so the crude product can be purified by
sublimation.
3. Conclusions
Thus, polychlorofluorobebzenes 1a-3a and partially fluorinated benzenes 4a and 6a undergo
aminodefluorination by the action of anhydrous ammonia to form mono- and diamino derivatives.
Bis-aminodefluorination occurs at significantly higher temperatures than monoaminodefluorination
(temperature differences is 60-160 °C), whereby conditions were found for selective introduction of
one or two amino groups. In the case of non-selective reactions of 1a and 2a, an intermediate
isolation of monoamines can enhance selectivity and yield of diamine, as well as simplify its
purification. Varying the nucleophile nature at the step of tetrafluorobenzene 4a amination (NH3 vs.
-NH2), resulting in a change of the replacement orientation [36], enables the synthesis of two
different diamines 4c and 5c from 4a. The results obtained confirm aminodefluorination of
electrophilic polyfluoroarenes with use of anhydrous ammonia as a reagent and a solvent
simultaneously to be a convenient and general route to polyfluoroaromatic mono- and diamines.
The mentioned advantages open up prospects for a large-scale use of these compounds in modern
materials and fine organic synthesis.
4. Experimental
4.1. Materials
The following commercial products were used: anhydrous NH3, 18-crown-6, tert-butyl methyl
ether (t-BuOMe), acetone, CH2Cl2, hexane, decane, H2, Pd/C (0.5%). K2CO3 and MgSO4 were
calcined prior to use.
Chloropentafluorobenzene (1a), mixture of dichlorotetrafluorobenzenes (the content of 1,3-
dichlorotetrafluorobenzene (2a) was 67%), sym-trichlorotrifluorobenzene (3a) were prepared as
described in [21], 1,2,3,5-tetrafluorobenzene (4a), 3,4,5-trifluoroaniline (5b), and octafluorotoluene
Page 10 of 19

– as described in [40, 36, 41] respectively; their physical properties were identical to those reported
in the literature.
α,α,α-2,3,5,6-Heptafluorotoluene (6a). A 200 ml autoclave was charged with
octafluorotoluene (30 g), K2CO3 (6 g), Pd/C (0.5%) (4.5 g) and decane (100 ml). The autoclave was
sealed, purged twice and charged with H2 to the pressure of 100 atm. The reaction mixture was
heated up to the 220 °C upon stirring by rotation of the autoclave and kept under these conditions
for 30 h, H2 being added up to 100 atm as expenditure. On completion, the autoclave was cooled
and the reaction mixture was filtered. Heptafluorotoluene 6a was distilled off from the solution (23
g, 83%), purity 97%, b.p. 110-113 °C, spectral data are identical to those reported in [42].
4.2. Methods
1H, 19F and 13C NMR spectra were recorded on NMR spectrometers Bruker AV-300 (300.13,
282.36 and 75.48 MHz for 1H, 19F and 13C correspondingly) using signals of solvents and C6F6 (δ =
-163.0 ppm from CCl3F) as internal standards; δ are given in ppm relative to TMS and CCl3F. IR
spectra were recorded on Bruker Vector-22 instrument in ATR mode. The precise molecular
weights of ions were determined by high-resolution mass spectrometry on Thermo Scientific DFS
instrument, ionizing energy 70 eV. GC-MS analyses of component mixtures were performed using
Hewlett Packard G1081A equipment comprising an HP 5890 Series II gas chromatograph and an
HP5971 mass-selective detector in the conditions described in [16].
4.3. Synthetic procedures
4.3.1. Typical procedure for the reaction of polyhalogenarenes with anhydrous NH3
Polyhalogenarene was placed into a steel autoclave equipped with two inlet/outlet valves. The
required amount of anhydrous liquid NH3 was added into the autoclave by self-flowing through a
measuring funnel with back pressure cooled to -33 °C and the autoclave was sealed. The reaction
mixture was heated up to the given temperature upon stirring by rotation of the autoclave and kept
under these conditions for the necessary time. On completion, the autoclave was cooled, NH3 was
slowly vented through an outlet valve, products were extracted with acetone and extract was
filtered. Solvent was evaporated to give a crude product, which was then purified. The reactant
amounts, reaction conditions, and product yields are listed in Table 1. Methods of isolation of
compounds and their characteristics are given below.
4.3.2. 4-Chloro-2,3,5,6-tetrafluoroaniline (1b)
The crude product (Entry 1, Table 1) was purified by crystallization from hexane, purity 99%,
mp 54-56 °C (cf. [43] mp 54-55 °C). IR: ν 3483, 3392, 3254, 3191 (NH2), 1657, 1612, 1504, 1175,
1111, 930, 881 cm-1. NMR spectral data are identical to those reported in [43].
4.3.3. 4-Chloro-2,5,6-trifluoro-1,3-phenylenediamine (1c)
Page 11 of 19

The crude product (Entry 2, Table 1) was purified by crystallization from hexane, purity
99%, mp 133-134 °C (cf. [23] mp 133.5-134.5 °C). IR: ν 3446, 3331, 3196 (NH2), 1660, 1626,
1602, 1504, 1434, 1307, 1270, 1178, 1112, 922, 849 cm-1. NMR spectral data are identical to those
reported in [23].
4.3.4. 2,4-Dichloro-3,5,6-trifluoroaniline (2b)
The crude product was synthesized from the mixture of isomeric dichlorotetrafluorobenzenes
(25 g) containing ~67 % of 1,3-isomer 2a (Entry 3, Table 1). After cooling and removing NH3 the
reaction mixture was dissolved in CH2Cl2 and filtered. Gaseous HCl was passed through the
solution up to the end of precipitation. The precipitate was filtered off and mixed with water,
agueous NaOH was added up to alkalescent pH. Anilines were extracted with CH2Cl2, the extract
was dried over MgSO4, and the extractant was distilled off. The crude product was purified by
crystallization from hexane, purity 95%. IR: ν 3502, 3403 (NH2), 1641, 1599, 1497, 1468, 1244,
1142, 899, 793 cm-1. NMR spectral data are identical to those reported in [25].
4.3.5. 4,6-Dichloro-2,5-difluoro-1,3-phenylenediamine (2c)
The crude product (Entry 4, Table 1) was purified by complexation with 18-crown-6 (3.1 g)
as described in [17], purity 99%, mp 137.5-138.7 °C (cf. [25] mp 136-136 °C). IR: ν 3448, 3340,
3190 (NH2), 1649, 1626, 1498, 1466, 1416, 1325, 1234, 1130, 862, 783 cm-1. NMR spectral data
are identical to those reported in [25].
4.3.6. 2,4,6-Trichloro-5-fluoro-1,3-phenylenediamine (3c)
The crude product (Entry 5, Table 1) was purified by crystallization from hexane, purity 99%,
mp 155.2-155.5 °C (cf. [26] mp 152-153 °C). IR and NMR spectral data are identical to those
reported in [26].
4.3.7. 1,3,5-Triamino-2,4,6-trichlorobenzene (3d)
The crude product (Entry 6, Table 1) was purified by crystallization from hexane, purity 97%,
mp 209-211 °C. IR: ν 3437, 3350, 3323 (NH2), 1616, 1454, 1137, 1057, 740, 719 cm-1. 1H NMR
(acetone-d6+DMSO-d6): δ 5.00 (br.s, NH2). 13C NMR (DMSO-d6): δ 93.2 (C-2, C-4, C-6), 140.8
(C-1, C-3, C-5). HRMS calcd. for C6H6N3Cl3: 224.9627, found: 224.9634.
4.3.8. 2,3,5-Trifluoroaniline (4b)
The crude product (Entry 7, Table 1) was purified by distillation to collect the fraction with
bp 175-177 °C. Purity of aniline 4b is >97%. IR: ν 3498, 3410, 3219 (NH2), 3095 (Car-H), 1657,
1606, 1523, 1464, 1236, 1203, 1126, 1047, 991, 829, 771 cm-1. NMR spectral data are identical to
those reported in [36].
4.3.9. 2,5-Difluoro-1,3-phenylenediamine (4c)
Page 12 of 19

The crude product was purified by crystallization from hexane (Entry 8, Table 1) or sublimed
(Entry 9, Table 1), purity 99%, mp 47-48 °C (cf. [36] mp 40-41 °C). IR and NMR spectral data are
identical to those reported in [38].
4.3.10. 4,5-Difluoro-1,3-phenylenediamine (5c)
The crude product (Entry 10, Table 1) was purified by complexation with 18-crown-6 as
described in [17], purity 98%. IR: ν 3437, 3334, 3213 (NH2), 3073 (Car-H), 1625, 1605, 1528, 1474,
1257, 1217, 1168, 1035, 989, 829, 780 cm-1. 1H NMR (acetone-d6) (Fig. S1a): δ 4.42, 4.62 (both
br.s of equal intensity, 2H each, NH2), 5.78 (ddd, 1H, JHH= 2 Hz, JHF= 6 Hz, 13 Hz, H-6), 5.91
(ddd, 1H, JHH= 2 Hz, JHF= 1.8 Hz, 7 Hz, H-2). 19F NMR (acetone-d6) (Fig. S1b): δ -176.7 (ddd, 1F,
JFF=20 Hz, JHF=6 Hz, 7 Hz, F-4), -141.5 (ddd, 1F, JFF=20 Hz, JHF=1.8 Hz, 13 Hz, F-5). HRMS
calcd. for C6H6N2F2: 144.0494, found: 144.0491.
4.3.11. 3,4,6-Trifluoro-2-trifluoromethylaniline (6b)
The crude product (Entry 11, Table 1) was purified by fractional distillation, purity 98%, bp
128-132 °C [17]. IR and NMR spectral data are identical to those reported in [17].
4.3.12. 4,6-Difluoro-2-trifluoromethyl-1,3-phenylenediamine (6c)
The crude product (Entry 12, Table 1) was extracted from the reaction mass using CH2Cl2
and purified by sublimation, purity 99%, mp 46-47 °C. IR: ν 3494, 3400, 3350, 3236 (NH2), 3109,
3078 (Car-H), 1639, 1502, 1323, 1111, 1092, 908, 872 cm-1. 1H NMR (acetone-d6) (Fig. S2a): δ
4.80 (br.s, 4H, NH2), 7.11 (t, 1H, JHF= 11 Hz, H-5). 19F NMR (acetone-d6) (Fig. S2b): δ -146.3 (d,
2F, JHF=11 Hz, F-4,6), -55.3 (s, 3F, CF3). HRMS calcd. for C7H5N2F5: 212.0367, found: 212.0363.
Acknowledgement
The work was financially supported by the Russian Foundation of Basic Research, Projects
14-29-08134-ofi-m and 15-03-02729-a.
Analytical and spectral studies were performed in the Collective Chemical Service Center of
SB RAS.
Supplementary data
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Scheme captions
Scheme 1. Aminodefluorination of polychlorofluorobenzenes 1a-3a
Scheme 2. Aminodefluorination of tetrafluorobenzene 4a
Scheme 3. Aminodefluorination of heptafluorotoluene 6a
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Figure(s)
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Figure(s)
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Figure(s)
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