Nucleophilic reactivity. Kinetics of reactions between diarylamines N-anions and hexafluorobenzene or pentafluoropyridine in dimethyl sulfoxide

Article abstract of DOI:10.1023/A:1012391231937

Rate constants of reactions between sodium salts of diarylamines N-anions and hexafluorobenzene and pentafluoropyridine in DMSO at 25°C were determined. The Bronsted factors for substrates under consideration are 0.14 and 0.34 respectively. These data evi

Full text of DOI:10.1023/A:1012391231937

Russian Journal of Organic Chemistry, Vol. 37, No. 2, 2001, pp. 260 269. Translated from Zhurnal Organicheskoi Khimii, Vol. 37, No. 2, 2001,
pp. 273 282.
Original Russian Text Copyright
,
2001 by Os kina, Vlasov.
Nucleophilic Reactivity. Kinetics of Reactions
between Diarylamines N-Anions and Hexafluorobenzene
or Pentafluoropyridine in Dimethyl Sulfoxide*
,
I. A. Os kina and V. M. Vlasov
Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences,
Novosibirsk, 630090 Russia
Received April 14, 2000
Abstract Rate constants of reactions between sodium salts of diarylamines N-anions and hexafluorobenzene
and pentafluoropyridine in DMSO at 25 C were determined. The Bronsted factors for substrates under
consideration are 0.14 and 0.34 respectively. These data evidence a considerable effect of substrate
electrophilicity on the reactivity of diarylamines N-anions in the SNAr reactions. Deviations of the Bronsted
plot from linearity for the reactions of hexafluorobenzene with aryl-and diarylamines N-anions may be due
to the difference in internal barriers of these reactions.
Linear correlations for free energies of various
kinds, e.g. equations of Swaine-Scott, Edwards,
Bro/ nsted or Ritchi are important for the study of
nucleophilic reactivity [1, 2]. The Bro/ nsted equation
turned out especially useful for description of SN2-
reactions [3, 4]. Yet the range of Bro/ nsted factor
0.81 at R = Cl and R = NO2 respectively although
the rates differ by 4 orders of magnitude [8]. For the
same reaction at R = CHO in EtOH at 40 C the
value is smaller, 0.56 [9], and at R = NO2 in
Nuc
MeOH at 25.9 C and 50 C the value of the factor
increases to 0.91 [10, 11]. However for the
Nuc
reactions of picrylchloride with substituted phenolates
in 75% aqueous ethanol at 30 C the Nuc value equals
to 0.83 [12] although the reaction velocity increases
by four orders of magnitude as compared with the
preceding reaction of 2,4-dinitrochlorobenzene. The
Bro/ nsted plots for reactions of 4-nitro- and 2,4-di-
nitrochlorobenzenes with substituted thiophene oxides
in methanol and 95% aqueous ethanol have slopes
equal to 0.48 and 0.65 respectively whereas the
reactivity of both substrates differs by 6 orders of
magnitude [13].
(
0.2 0.5 [3]) for SN2-reactions is not char-
Nuc
acteristic of SNAr-reactions where the value
varies in wider limits (0.2 0.9) [5, 6]. One causeNoucf
variation in the SNAr-reactions is the consider-
Nuc
able influence of the steric effects in the nucleophile;
their increase reduces the
Another reason for variations in the
factor value [6].
Nuc
value is the
Nuc
electrophilicity of a substrate although this cause of
variations in the Bro/ nsted factor is less understood
(cf. [5]).Thus the
factor for the reaction of
Nuc
4-nitrofluorobenzene with a series of arylfluorenyl
anions is by 0.11 0.15 greater than for reaction of
the less electrophilic 4-cyanofluorobenzene with a
series of 9-methylfluorenyl anions in DMSO [5].
Similarly for the reaction of amines with picryl-
The above values of
for SNAr reactions of
Nuc
C-, N-, O-, and S-nucleophiles were obtained under
different reaction conditions. This fact hampers the
analysis of the effect of substrate electrophilicity on
chloride the
value is by 0.12 greater than for the
the
value. We formerly reported on reactivity of
Nuc
Nuc
reaction of amines with 2,4-dinitrochlorobenzene in
arylamines N-anions toward 4-nitrofluorobenzene and
hexafluorobenzene in DMSO at 25 C. The reaction
rates with hexafluorobenzene were higher [6, 14]. Yet
the published data on reactivity of 4-nitrofluoro-
benzene and hexafluorobenzene toward methylate ion
[15, 16], thiophenolate ion [15, 17], azide ion
[15, 18], and piperidine [18, 19] demonstrated that
the rate constant of reaction of the above ions with
4-nitrofluorobenzene was about one order of
magnitude greater than that with hexafluorobenzene.
water medium [7]. Slight variations in the
factor
are also observed for reactions of O- andNSuc-anions
with various arenes. For the reaction of substituted
phenolates with 2-nitro-4-R-chlorobenzenes in 80%
aqueous dioxane at 65 C the
factor is 0.76 and
Nuc
*
The study was carried out under financial support of the
Russian Foundation for Basic Research (project Leading
Scientific School no. 96-15-97562).
1070-4280/01/3702-0260$25.00 2001 MAIK Nauka/Interperiodica

NUCLEOPHILIC REACTIVITY
261
Still greater difference in reactivity toward, e.g.,
methylate ion is observed in reaction with hexafluoro-
benzene and pentafluoropyridine: it reaches about
7 orders of magnitude [20]. Therefore in this study
we undertook an investigation of reactivity of a series
of diarylamines N-anions with these substrates sig-
nificantly different in electrophilicity.
Table 1. Second order rate constants (k) for reactions
of diarylamines N-anions N Ar Na+ (Ia VIIa) with
hexafluorobenzene and pentafluoropyridine in DMSO at
25 C, and acidity of compounds ArNHAr (I VII) in
DMSO (pK), 25 C
1 b
Compd.
no.
Compd.
no.
k 103, l mol 1 s
pKa
ArNHAr
ArN Ar Na+
C6F6
C5F5N
I
9.4
12.0
12.6
13.3
14.7
15.1
17.45
Ia
IIa
0.212 0.070 2.31 0.40
(3)
0.373 0.078
(4)
(3)
II
III
IV
V
IIIa
IVa
Va
31.1 1.4
(7)
84.1 12.4
(5)
(1)
1.53 0.43
(4)
VI
VII
VIa
VIIa
169 23
(3)
2.47 0.60
(4)
Ar = C6F5, Ar = 4-C5F4N (I, Ia, VIII, XII); Ar =
C6F5, Ar = 4-ClC6F4 (II, IIa, IX); Ar = Ar = C6F5
(III, IIIa, VIII); Ar = C6F5, Ar = 4-CH3C6F4 (IV,
IVa, XIII); Ar = Ph, Ar = 4-CNC6F4 (V, Va, X);
Ar = Ph, Ar = 4-C5F4N (VI, VIa, XIV); Ar = Ph,
a
Relative scale with respect to 9-phenylfluorene standard,
pKst 18.5; pK values from [23].
In parenthesis is given the number of determinations.
b
Ar
= 4-NO2C6H4 (VII, VIIa, XI).
and basicity of these anions in the SNAr reactions due
to the solvation effect of the electron-acceptor groups
in DMSO. Such effect was demonstrated for SN2
reactions [4]. However the effect of enhanced solva-
tion of the resonance-located electron-acceptor groups
in N-anions Ia VIIa apparently should not affect the
relation between the nucleophilicity and basicity of
these anions since a correlation exists between the
basicity of N-anions in the gas phase and DMSO [6,
22, 23]. The lack of deviations from the correlation
plot evidences the proportionality conservation in the
effect of the enhanced solvation of the substituents
[24].
The choice of N-anions of diarylamines Ia VIIa
is justified by the fact that this anion series includes
sufficiently large range of basicities (Table 1) for
revealing the causes of variations in the factor
for SNAr reactions. Although N-anions of diarNyul-c
amines I IV unlike those of diarylamines V VII
contain at the reaction center additional ortho-
fluorines the latter would not contribute any sterical
effect into the nucleophilicity of the N-anions Ia IVa
originating from diarylamines since the sterical
constants of the phenyl and ortho-fluorophenyl groups
have close values (Rs 0.145 and 0.152 respectively
[21]). Besides previously was demonstrated that in
reaction with 4-nitrofluorobenzene the Bro/ nsted cor-
relation between nucleophilicity and basicity is valid
for N-anions of both fluorinated and unfluorinated
aryl- and diarylamines [6]. This fact evidences that
the steric effect of ortho-fluorine atoms in the benzene
ring is insignificant. As seen from the structure of
N-anions Ia VIIa [equation (1)], nearly all of them
contain electron-acceptor groups in the resonance
positions of the benzene ring. The presence of these
groups may affect the relation between nucleophilicity
The acidity of diarylamines I VII in DMSO and
the rate constants of the second order for the reaction
of N-anions Ia VIIa with hexafluorobenzene and
pentafluoropyridine in DMSO at 25 C are presented
in Table 1. Kinetic data show that the reactivity of
hexafluorobenzene toward N-anions Ia VIIa is lower
than that of pentafluoropyridine within the total
basicity range. Therewith the variation of rate con-
stants is well consistent with Bro/ nsted equations (2)
and (3) (see the figure, plots 1 and 2):
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 2 2001

262
OS,KINA, VLASOV
logk(C6F6) = 0.14 pK 5.03; r 0.980, s 0.123, n 4 (2)
observed an increase in the factor
reaction of arylamines N-anions wNituhc 4-nitrofluoro-
benzene (figure, plot 4, 0.28) to the reaction of
the same anions with hexaflourobenzene (figure, plot
in going from
logk(C5F5N) = 0.34 pK 5.77; r 0.989, s 0.015, n 4 (3)
Nuc
5,
0.74). Thus in the same range of basicity
The validity of Bro/ nsted relations (2) and (3)
evidences that sterical and solvation effects of sub-
stituents proportionally affect both the basicity and
nucleophilicity of N-anions Ia VIIa. At the same time
variaNtiuocn the Bro/ nsted factor again increases with the
growing electrophilicity of the substrate (cf. plots 1
and 2, 4 and 5 on the figure).
the change in the value of the Bro/ nsted factor
Nuc
The comparison of Bro/ nsted factors for the reac-
tions of hexafluorobenzene with N-anions of diaryl-
from 0.14 to 0.34 in going from hexafluorobenzene
to pentafluoropyridine shows that within the same
range of nucleophile basicity variation the substitution
selectivity grows with increasing electrophilicity of
the substrate. The latter statement contradicts the
reactivity selectivity principle. It was shown earlier
that the principle was valid for the SNAr reactions
[25]. However many examples exist that demonstrate
no general applicability of the principle [26].
amines (
0.14) and arylamines (
0.74)
Nuc
Nuc
suggests that within a vide range of basicity variation
for these anions ( 14 pK units) the Bro/ nsted plots
deviate from linearity (plots 1 and 5 on the figure).
Apparently the deviation from linearity cannot be
ascribed to the effect of different spatial reasons for
N-anions of aryl- and diarylamines since the re-
activity of these anions toward 4-nitrofluorobenzene
is virtually the same in the same range of basicity
To analyze the cause of
factor variation at
Nuc
variation (
0.24 and 0.28 [6], plots 3 and 4 on
the figure).Nuc
further extension of the basicity range of the N-anions
we invoked the previously obtained data on reactivity
of arylamines N-anions toward hexafluorobenzene
[27] and of aryl- and diarylamines N-anions toward
4-nitrofluorobenzene [6] in the range f Basicity vari-
ation of the N-anions from 15 to 25 pK units. The
corresponding Bro/ nsted plots are given on the figure
(plots 3 5). The data show that in the range of
N-anions basicity variation from 15 to 25 pK units is
The known cases of deviation of Bro/ nsted plots
from linearity in the nucleophilic substitution are due
to the nonthermodynamical reasons: changes in the
mechanism of reaction, solvation of nucleophiles,
nature of the nucleophilic center in the nucleophile,
and sterical effects [4, 28]. At minimal influence of
structural and solvation characteristics the reactivity
Bro/nsted plots for reactions of diarylamines N-anions Ia, IIa, Va, VIIa with hexafluorobenzene (plot 1, 0.14), of diaryl-
amines N-anions Ia, IIIa, IVa, VIa with pentafluoropyridine (plot 2, 0.34), of diarylamines N-anions with p-nitrofluoro-
benzene (plot 3, 0.24) [6], of arylamines N-anions with p-nitrofluorobenzene (plot 4, 0.28) [6], and arylamines N-anions
with hexafluorobenzene (plot 5, 0.74) [25] in DMSO at 25 C.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 2 2001

NUCLEOPHILIC REACTIVITY
263
variation is described by a linear Bro/ nsted plot. For
instance, for reactions of alkyl halides with the C-,
N-, O-, and S-anions the Bro/ nsted plot is linear
within a wide basicity range ( 10 16 pK units [3, 4,
28, 29]) apparently due to the high internal barrier
G0 for SN2 reactions [4, 28]. The expression for
estimation of variations in the Bro/ nsted factor may be
derived by successive differentiating of Marcus equa-
tion (4) and equation (5) with respect to G0 [30]:
N-anions and hexafluorobenzene should result in a
notable increase in the
factor and to deviation
from linearity in the plotNoufc G versus G0. Con-
sequently the deviation from linearity of the Bro/ nsted
plot for reactions of aryland diarylamines anions with
C6F6 may be due to the significant change in the
values of internal barriers, i.e. to the dissimilar struc-
ture of the transition state in both reactions (plots 1
and 5, see figure). In the faster reaction of C6F6 with
arylamines N-anions (
0.74) the degree of charge
transfer from the nucleoNpuhcile to the substrate is higher
than in the same reaction with the N-anions of diaryl-
G
=
G0
+
1/2 G0 + ( G0)2/16 G0,
(4)
where
G
is the free activation energy, G0
amines (
0.14) [33]. This statement is confirmed
Nuc
is the free energy of reaction,
G0 is the
by a greater sensitivity of the logarithms of the rate
constants in reactions of C6F6 with N-anions of aryl-
amines to their redox potentials than to the redox
potentials of diarylamines N-anions [14]. Thus to the
internal barrier or the free activation energy at
G0 = 0. Then
=
1/2 +
G0/8 G0,
(5)
(6)
Nuc
higher
the reactNioucn rate to variation in the redox potentials
of anions, and at the limiting value 1 [3] we
value corresponds a greater sensitivity of
(
Nuc)/ ( G0) = 1/8 G0.
Nuc
can expect that the reaction mechanism SNAr will
transform into SET mechanism (cf. [23]).
Equation (6) expresses the variation in
as a
Nuc
function of the internal barrier of the reaction G0.
In reactions of hexafluorobenzene with each series of
N-anions originating both from aryl- and diaryl-
amines the Bro/ nsted plots are valid (straight lines 1
and 5, see figure) indicating the linear variation of the
internal barrier G0 as a function of the free energy
of the reactions G corresponding to both plots [31].
EXPERIMENTAL
IR spectra were recorded on UR-20 spectrophoto-
meter from 1% solutions of compounds in CHCl3,
CCl4 or from KBr pellets containing 0.25% of com-
1
pound. H and 19F NMR spectra were registered on
The observed increase in the value of
Nuc
spectrometers Varian 56/60 A, Bruker WP 200 SY
and AC 200, references TMS and hexafluorobenzene
respectively. Mass spectra were measured on Finni-
gan Mat 8200 instrument at ionizing energy 70 eV,
temperature in the ionizing chamber 100 200 C. The
reaction mixtures were analyzed by GLC on HP5890
and LKhM devices (thermal conductivity detector,
factor with growing basicity of the N-anions in their
reaction with hexafluorobenzene (plots 1 and 5, see
figure) may be interpreted proceeding from equation
(6). It is known that a small G0 value is character-
istic of fast reactions with a high Bro/ nsted factor
[4, 8]. Assuming that the basicity with respect to
carbon changes in parallel with the basicity with
respect to hydrogen [3] we take the range of basicity
variation of N-anions around 14 pK 40 units or
1
ramp from 50 to 270 C at 10 deg min , stationary
phase SKTFT-803 on Chromaton HMDC-N, carrier
1
1
gas helium, flow rate 60 ml min ; the quantitative
19 kcal mol as estimate for the free energy of the
analysis of the reaction mixtures was carried out by
internal normalizing procedure, the components were
identified by comparison with authentic samples.
reaction G . This estimation is fairly approximate
since the basicity of the charged anions with respect
to carbon is known to be higher than their basicity
with respect to hydrogen [32]. As follows from equa-
tion (6) the value of the internal barrier G0 of the
reaction between C6F6 and N-anions is equal to
Commercial DMSO was purified and dried by
3
4
vacuum distillation on CaH2 at 10
10 mm, DMF
was distilled in a vacuum on phosphorus pentoxide as
described in [34]. Commercial sodium hydride before
use was washed with anhydrous hexane and dried
under inert atmosphere. Commercial hexafluoro-
benzene before use was dried over molecular sieves.
Commercial bromobenzene was distilled in a vacuum
before use. The copper powder was prepared as
described in [35]. Commercial 4-nitrodiphenylamine
1
4 kcal mol at change in the Bro/ nsted factor of
0.74 0.14 = 0.6. This value is obviously under-
estimated since the real range of basicity variation of
N-anions with respect to carbon should be considerab-
ly wider. Although the estimation of the internal
barrier value is approximate we still can presume that
the decrease in the value of the internal barrier G0
with growing velocity of reaction the between
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 2 2001

264
OS,KINA, VLASOV
(VII) was before use recrystallized from ethanol;
N-(4-tetrafluoropyridyl)pentafluoroaniline (I),
4-chlorononafluorodiphenylamine (II), decafluoro-
diphenylamine (III), 4-methylnonafluorodiphenyl-
amine (IV), 4-cyano-2,3,5,6-tetrafluorodiphenyl-
amine (V), di-N,N -(4-tetrafluoropyridyl)pentafluoro-
aniline (XII), 9-carbomethoxyfluorene (XV) were
obtained by known procedures; their physical con-
stants are consistent with the published data [6, 27,
36, 37].
19F NMR spectrum (CHCl3, F, ppm): 1.90 m
(4F, F3 ,5 ), 9.18 m (2F, F4 , J2 ,4 19 Hz), 9.58 m
(2F, F3,5), 14.36 m (4F, F2 ,6 ), 73.73 m (2F, F2,6).
Found, %: C 40.34; F 53.56; N 5.45. C17F14N2.
Calculated, %: C 40.96; F 53.41; N 5.62.
N-(4-Chloro-2,3,5,6-tetraflyorophenyl)deca-
fluorodiphenylamine (IX). Into a four-neck flask
equipped with a stirrer, a reflux condenser, a thermo-
meter, and a dropping funnel was charged 0.206 g
(8.58 mmol) of sodium hydride, 5 ml of DMF, and at
stirring was added to the suspension within 1 h a solu-
tion of 1 g (2.87 mmol) of decafluorodiphenylamine
(III) and 1.16 g (5.72 mmol) of pentafluorochloro-
benzene in 15 ml of DMF at 20 25 C. Then the reac-
tion mixture heated to 90 C and maintained at this
temperature for 3 h, then cooled to room temperat
ure, neutralized with 5% HCl, extracted with ether,
the extract was washed with water, and dried on
CaCl2. The residue after the solvent was distilled off
(1.45 g) contained according to GLC 5% of com-
pound IX. By TLC on a glass plate 20 20cm, SiO2,
eluent CCl4, we isolated 0.08 g of a mixture contain-
ing 0.33 g (49%) of compound IX, yield 2.6%
(GLC), mp 124 126 C (sublimed at 130 C/2 3 mm).
19F NMR spectrum (CHCl3, F, ppm): 1.23 m (6F,
N-(2,3,5,6-Tetraflyoropyridyl)aniline (VI). To a
suspension of 0.26 g (0.108 mmol) of sodium hydride
in 2 ml of DMF was added while stirring and at
20 25 C a solution of 2.73 g (0.162 mmol) of aniline
in 3 ml of DMF. The addition continued for 1 h.
Then was added 0.162 mmol of pentafluoropyridine.
The reaction mixture was left to stand for 2 h, then it
was diluted with ether, neutralized with 5% HCl,
extracted with ether, the extract was washed with
water and dried with MgSO4. After evaporating the
solvent the residue contained 2.21 g (84%) of com-
pound VI (GLC data). By recrystallization from
petroleum ether (bp 40 70 C) followed by sublima-
tion at 90 C/2 3 mm we obtained 1.44 g (55%) of
compound VI, mp 92 93 C. IR spectrum (CHCl3, ,
1
4F3 ,5 , 2F3,5), 6.87 m (2F, F4 ), 13.34 m (6F, 4F2 ,6
,
cm ): 973 s (C F), 1484 s (F-substituted arom.
1
2F2,6). Elemental composition and molecular weight
were determined from high-resolution mass spectrum.
Found: M 530.94879. C18H9F5N2O2. Calculated: M
530.94935.
ring), 3416 m (NH). H NMR spectrum (DMSO, ,
ppm): 7.02 7.12 m (3H, H2,4,6), 7.25 7.31 m (2H,
H
3,5), 9.40 s (1H, NH). 19F NMR spectrum external
reference C6F6, DMSO, F, ppm): 12.69 m (2F,
3,5), 71.20 m (2F, F2,6). Elemental composition and
molecular weight were determined from high-resolu-
tion mass spectrum. Found: 242.04689.
C11H6F4N2. Calculated: M 242.04670.
F
N-(4-Cyano-2,3,5,6-tetraflyorophenyl)penta-
fluorodiphenylamine (X). Into a stainless steel
ampule was charged 0.2 g (0.562 mmol) of N-(4-
cyano-2,3,5,6-tetraflyorophenyl)pentafluoroaniline
(V) , 1 ml of bromobenzene, and 0.12 g (1.87 mmol)
of copper powder. The ampule was heated on metal
bath at 240 245 C for 43 h. The reaction mixture
was cooled to room temperature, filtered, the filtrate
was evaporated, and the residue was subjected to
chromatography (Al2O3, eluent CHCl3). We obtained
0.22 g (9%) of compound X, mp 172 174.5 C.
1H NMR spectrum (DMSO-d6, , ppm): 7.09 7.50
m (5H, H arom). 19F NMR spectrum (external
reference C6F6, DMSO-d6, F, ppm): 0.49 m (2F,
M
N-(2,3,5,6-Tetraflyoropyridyl)decafluorodiphenyl-
amine (VIII). Into a four-neck flask equipped with a
stirrer, reflux condenser, thermometer, and dropping
funnel was charged 0.08 g (3.16 mmol) of sodium
hydride, 2 ml of DMF, and at stirring was added to
the suspension within 40 min a solution of 1 g
(2.87 mmol) of decafluorodiphenylamine (III) in
5 ml of DMF at 20 25 C. Then to the reaction
mixture was added 0.97 g (5.74 mmol) of penta-
fluoropyridine, and the mixture was heated to 80 C.
The reaction mixture was maintained at this tempera-
ture for 2 h 40 min, then cooled to room temperature,
neutralized with 5% HCl, extracted with ether, the
extract was washed with water, and dried on magnes-
ium sulfate. The residue after evaporating the solvent
(1.24 g) was recrystallized from CCl4. We obtained
0.68 g (48%) of compound VIII, mp 117 118 C. IR
F
3 ,5 ), 6.41 m (1F, F4 ), 15.64 m (2F, F2,6), 17.79 m
(2F, F2 ,6 ), 28.52 m (2F, F3,5). Elemental composi-
tion and molecular weight were determined from
high-resolution mass spectrum. Found: M 432.03089.
C19H5F9N2. Calculated: M 432.03089.
N-(4-Nitrophenyl)pentafluorodiphenylamine
(XI). Into a four-neck flask equipped with a stirrer, a
reflux condenser, a thermometer, and a dropping
1
spectrum (CCl4, , cm ): 1000 s (C F), 1525 s
(F-substituted arom. ring).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 2 2001

NUCLEOPHILIC REACTIVITY
265
funnel was charged 0.08 g (3.3 mmol) of sodium
hydride, 1.01 g (5 mmol) of hexafluorobenzne, 1 ml
of DMF, and at stirring was added to the suspension
within 5 min a solution of 0.2 g (0.99 mmol) of
4-nitrodiphenylamine (VII) in 2 ml of DMF and the
reaction mixture was maintained at 20 25 C for
1.5 h. The reaction mixture was neutralized with 5%
HCl and acidified to weakly acid reaction by litmus.
The reaction mixture was left overnight, the separated
precipitate was filtered off, washed with water, and
dried. From 0.15 g of the precipitate was isolated by
TLC (Al2O3, CHCl3) 0.099 g (28%) of compound
Found:
494.0089.
M
494.0088. C18H3F13N2. Calculated:
N,N-Di-[4-(2,3,5,6-tetrafluoro)pyridyl]aniline
(XIV). To a suspension of 0.042 g (1.75 mmol) of
sodium hydride in 1 ml of DMF was added dropwise
within 20 min a solution of 0.2 g (0.83 mmol) of
N-(2,3,5,6-tetraflyoropyridyl)aniline (VI) in 3 ml of
DMF; then was added a solution of 0.28 g
(1.66 mmol) of C5F5N in 1 ml of DMF, and the
mixture was left standing at 20 25 C for 2 h. The
reaction mixture was diluted with ether, neutralized
with 5% HCl, extracted with ether, the extract was
washed with water, and dried on MgSO4. On
evaporating the solvent the residue according to GLC
contained 0.22 g (69%) of compound XIV that was
separated by TLC (SiO2, eluent 10 vol% CHCl3 in
CCl4) We obtained 0.17 g (52%) of compound XIV,
1
XI, mp 266 268 C. IR spectrum (CHCl3, , cm ):
1005 s (C F), 1317 s (NO2), 1512 s (F-substituted
arom. ring), 1588 s (NO2). 1H NMR spectrum
(acetone-d6, , ppm): 7.12 m (2H, H2,6), 7.32 7.52
m (5H, H arom), 8.14 m (2H, H3,5, J2,3 9 Hz).
19F NMR spectrum (acetone-d6, F, ppm): 1.05 m
(2F, F3,5), 6.26 m (1F, F4), 17.48 m (2F, F2,6).
Elemental composition and molecular weight were
determined from high-resolution mass spectrum.
Found: M 380.0563. C18H9F5N2O2. Calculated: M
380.0584.
1
mp 179 181 C. IR spectrum (CHCl3, , cm ): 978
s (C F), 1500 s (F-substituted arom. ring). H NMR
1
spectrum (acetone, , ppm): 7.37 m (5H, H arom).
19F NMR spectrum (acetone, F, ppm): 15.7 m (2F,
F
3,5), 73.0 m (2F, F2.6). Elemental composition and
molecular weight were determined from high-resolu-
tion mass spectrum. Found: 391.03552.
C16H5F8N3. Calculated: M 391.03561.
M
N, N-(4-Methyl-2, 3, 5, 6-tetrafluorophenyl)-
(2 ,3 ,5 ,6 -tetrafluoropyridyl)pentafluoroaniline
(XIII). Into a glass reactor connected to a vacuum
line were placed glass balls containing sealed in a
vacuum precisely weighted amounts of sodium
hydride (0.0325 g, 1.35 mmol), 4-methylnonafluoro-
diphenylamine (0.202 g, 586 mmol), pentafluoro-
pyridine (0.198 g, 1.17 mmol), and 65% HNO3. The
1,4-Bis[N,N -(phenyl-4-nitrophenyl)]tetrafluoro-
phenylenediamine (XVI). Into a four-neck flask
equipped with a stirrer, a reflux condenser, a thermo-
meter, and a dropping funnel was charged 0.336 g
(14 mmol) of sodium hydride, 1 ml of DMF, and at
stirring was added dropwise to the suspension within
5 min a solution of 1 g (4.67 mmol) of 4-nitrodi-
phenylamine (VII) in 5 ml of DMF. Then was added
dropwise within 5 min a solution of 1.74 g
(9.4 mmol) of hexafluorobenzene in 4 ml of DMF.
The mixture was held at 20 25 C for 5 h 50 min.
Then to the reaction mixture was added 5% HCl to
slightly acid reaction toward litmus, the products
were extracted into dichloromethane, the extract was
washed with water, and dried with CaCl2. The liquid
residue after evaporation of the solvent (4.46 g) was
diluted with water, the separated precipitate was
filtered off and dried. After double recrystallization of
the precipitate from CHCl3 we obtained 0.74 g (55%)
of compound XVI, mp 274.5 276 C. IR spectrum
4
reactor was sealed, evacuated to 10 mm Hg, 7 ml
of DMF was added, and then the reactor was sealed
off the vacuum line. The glass ball were crushed in
succession to produce N-anion, then to react it with
pentafluoropyridine for 2 h at room temperature.
Finally the mixture was neutralized with the 65%
HNO3, the system was opened to the atmosphere, the
reaction mixture was extracted with ether, the extract
was washed with water, and dried on MgSO4. The
residue after evaporation of the ether contained
according to GLC 0.23 g (79%) of compound XIII.
The product was isolated by column chromatography
(Al2O3, eluent 5 vol% CHCl3 in CCl4). We obtained
0.083 g (17%) of compound XIII, mp 101.5 103 C.
1
IR spectrum (CHCl3, , cm ): 1000 s (C F), 1500 s
1
1
(CHCl3, , cm ): 1315 s (NO2), 1500 s (F-sub-
(F-substituted arom. ring). H NMR spectrum (CCl4,
stituted arom. ring), 1575 s (NO2). 1H NMR
spectrum (CDCl3, , ppm): 6.3 m (4H, H2,6), 8.10
m (4H, H3,5, J2,3 10 Hz), 7.31 7.34 m (10H, H
arom). 19F NMR spectrum (CDCl3, F, ppm): 16.28
s (4F, F2 ,3 ,5 ,6 ). Elemental composition and mole-
cular weight were determined from high-resolution
, ppm): 2.93 s (3H, CH3). 19F NMR spectrum
(CCl4, F, ppm): 1.4 m (2F, F3 ,5 ), 8.3 m (1F,
F4 ), 9.1 m (2F, F3 ,5 ), 12.2 m (2F, F2,6), 14.3 m
(2F, F2 ,6 ), 20.1 m (2F, F3,5), 73.5 m (2F, F2 ,6 ).
Elemental composition and molecular weight were
determined from high-resolution mass spectrum.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 2 2001

266
OS,KINA, VLASOV
mass spectrum. Found: M 574.1231. C30H18F4N4O4.
Calculated: M 574.1264.
Generation of pairs of sodium salts of anions
IIIa + IVa, IIIa + XVa, VIa + XVa in DMSO.
The experiments were carried on a glass sealed
system connected to a vacuum line and evacuated to
9-Carbomethoxy-9-(4-tetrafluoropyridyl)-
fluorene (XVII). To a suspension of 0.11 g
(4.6 mmol) of sodium hydride in 1.5 ml of DMSO in
an argon flow was added dropwise within 25 min at
stirring a solution of 0.5 g (2.2 mmol) of 9-carbo-
methoxyfluorene (XV) in 3.5 ml of DMSO. Then was
added 0.76 g (4.5 mmol) of pentafluoropyridine in
2 ml of DMSO, and the mixture was maintained at
20 25 C for 2 h. Then the reaction mixture was
neutralized with 5% HCl, extracted with ether, the
extract was washed with water and dried with
MgSO4. On removing the solvent the residue (1.07 g)
contained 81% of the product (GLC). On recrystal-
lization from petroleum ether (bp 70 100 C) we
obtained 0.42 g (53%) of compound XVII. mp 153
4
1 10 mm Hg. To a suspension of 2.56 mmol of
sodium hydride in 2 2.5 ml of DMSO was added
equimolar amounts (0.63 mmol each) of compounds
III + IV, III + XV, or VI + XV. The reaction
mixture was kept for 3 h at 20 25 C, then transferred
into an NMR tube. From the ratio of the chemical
shifts values of the corresponding atoms in the NMR
spectra of the neutral compounds, their anions, and
the mixtures was calculated the initial ratio of con-
centrations of the anions pairs: IIIa/IVa = 1.04,
IIIa/XVa = 0.81, VIa/XVa = 0.93. Parameters of
the spectra are given in Table 2.
Determination of rate constants for reactions of
diarylamines I, II, V, VII with hexafluorobenzene,
and of diarylamine III with pentafluoropyridine.
General procedure. All experiments were carried out
under argon atmosphere. Diarylamines and aryl-
fluorides were taken in a molar ratio at initial con-
1
155 C. H NMR spectrum (CDCl3, , ppm): 3.67 s
(3H, CH3), 7.31 8.03 m (8H, H arom). 19F NMR
spectrum (CDCl3, F, ppm): 24.2 m (2F, F3,5), 71.6
m (2F, F2,6). Found, %: C 63.97; H 2.94; F 20.14;
N 3.72. C20H11F4NO2. Calculated, %: C 64.34; H
2.95; F 20.37; N 3.75.
2
1
centration (3 6) 10 mol l , sodium hydride was
used in excess, 2 3 mol per 1 mol of diarylamine.
The rates were measured by potentiometric determin-
ation of fluoride ion with the use of lanthanum-
fluoride electrode [38]. The weighed portions of re-
agents were placed into evacuated glass balls; the
balls were charged into a glass reactor connected
to a vacuum line, the reactor was evacuated to
Generation of sodium salt of anion from N-(4-
tetrafluoropyridyl)pentafluoroaniline (Ia). Into an
NMR tube flushed with argon was charged 0.0299 g
(0.09 mmol) of compound I and 0.3 ml of DMSO,
and the 19F NMR spectrum was registered. Then was
added 0.0035 g (0.0648 mmol) of sodium methylate,
and the reaction mixture was left standing for 3 h.
Then the 19F NMR spectrum was again registered.
Trifluoromethylbenzene was used as internal refer-
ence. The parameters of the spectra are given in
Table 2.
4
1 10 mm Hg, solvent was added, and the reactor
was sealed off the vacuum line. The glass balls were
crashed in succession (first was generated the
N-anion); the reaction mixture was kept for a definite
time, and then the reaction was stopped by addition
of 65% nitric acid. The reaction mixture was trans-
ferred from the reactor into a volumetric flask of
50 ml capacity and the volume was completed to
50 ml with distilled water. The rate constant
Generation of sodium salts of anions from
compounds III, IV, VI, XV in DMSO. The experi-
ments were carried on a glass sealed system connect-
ed to a vacuum line and evacuated to 1 10 4 mm Hg.
To a suspension of 1.3 mmol of sodium hydride in
0.5 ml of DMSO was added 0.32 mmol of compound
III, IV, VI, or XV at 20 25 C. The reaction mixture
was kept for 3h, then transferred into an NMR tube,
the tube was sealed off from the vacuum system, and
the NMR spectra were registered. The system was
connected to air, the residue of the reaction mixture
was neutralized with 5% HCl, extracted with ether,
and the extract was dried with MgSO4. On evaporat-
ing the solvent the residue according to GLC con-
tained the initial compounds III, IV, VI, and XV.
1
(l mol 1 s ) was calculated by the equation for the
second order reaction basing on the content of
fluoride ion:
k = [2.303/ (a
b)]log[b(a
x)/a(b
x)],
where a and b are initial concentrations of the
1
reagents, mol l , x is the concentration of the reac-
1
tion product, mol l , is reaction time, s.
In the calculations of the Bro/ nsted factor
were used the rate constants evaluated with accouNnut-c
ing for the number of equivalent positions in the
hexafluorobenzene: k = k/6. The logarithms of the
rate constants of the reaction are listed in Table 1.
1
The H and 19F NMR spectra of compounds III, IV,
VI, XV and their sodium salts IIIa, IVa, VIa, and
XVa are presented in Table 2.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 2 2001

NUCLEOPHILIC REACTIVITY
267
1
Table 2. Parameters of H and 19F NMR spectra of compounds I, III, IV, VI, XV and N-anions thereof Ia, IIIa, IVa,
VIa, XVa in DMSO at 25 C
19F NMR spectra, F, ppm,
1H NMR spectraa, , ppm,
external reference TMS
Compound
external
reference C6F6
2F2,6
2F3,5
F4
Aromatic protons
XH
R
(2F2 ,6
)
(2F3 ,5
)
C6F5NHC5F4N-4 (I)
16.47
1.73
(70.75)
0.20
(68.23)
1.36
7.11
3.47
0.9
9.84 s
(1H, NH)
(5.41)
14.12
(1.31)
9.66
C6F5N (Na+ )C5F4N-4
(Ia)
C6F5NHC6F5 (III)
8.72 s
(1H, NH)
(C6F5)2N Na+ (IIIa)
C6F5NHC6F4CH3-p (IV) 9.1 (8.0)
6.21
3.37
1.3 (17.1)
19.0
3.1
8.77 s
3.86 s
(1H, NH) (3H, CH3)
C6F5N (Na+ )C6F4CH3-p 7.3 (5.8)
((IVa))
3.5 (15.5)
71.20
20.2
2.81 s
(3H, CH3)
9.44 s
PhNHC5F4N-4 (VI)
12.69
3.23
7.29 7.36 m (2H, H3,5), 7.06
7.16 m (3H, H2,4,6
7.04 6.97 m (2H, H3,5), 6.59
)
(1H, NH)
PhN (Na+ )C5F4N-4
(VIa)
62.07
6.67 m (3H, H2,4,6
)
9-CH3CO2Flb (XV)
7.32 7.42 m (4H, H2,3,6,7), 7.64
7.67 m (2H, H1,8), 7.68 7.91 m
(2H, H4,5)
5.09 s
(H9)
3.70 s
(3H, CH3)
9-CH3CO2Fl (Na+ )
(XVa)
6.85 6.92 m (2H, H3,7), 7.14
7.22 m (2H, H2,6), 7.95 7.99 m
(2H, H1,8), 8.00 8.40 m (2H,
H4,5)
3.81 s
(3H, CH3)
(C6F5)2N Na+ (IIIa) +
C6F5N (Na+ )C6F4CH3-p 7.1 (6.0)
6.0
3.5
3.5 (15.4)
20.3
21.4
2.84 s
(IVa)
(3H, CH3)
(C6F5)2N Na+ (IIIa) +
9-CH3CO2Fl (Na+ )
(XVa)
PhN (Na+ )C5F4N-4
(VIa) +
7.60
3.36
2.13
14.7
6.83 7.31 m (4H, H2,3,6,7), 7.78
3.86 s
(3H, CH3)
8.34 m (4H, H1,4,5,8
)
62.26
6.65 6.89 m (3H, H2,4,6), 7.04
7.42 m (2H, H3,5)
9-CH3CO2Fl (Na+ )
(XVa)
6.89 7.04 m (2H, H3,6), 7.04
7.42 m (2H, H2,7), 7.92 8.12 m
(2H, H1,8), 8.02 8.48 m (2H,
H4,5)
3.85 s
(3H, CH3)
a
b
Proper value of intensity ratio.
Fl is fluorenyl.
The rate constants for each compound were
measured at least three times. The lack in the reaction
mixture of 1,4-bis[N,N -(phenyl-4 -nitrophenyl]tetra-
fluorophenylenediamine (XVI) in reaction between
4-nitrodiphenylamine N-anion and hexafluorobenzene
was checked by means of liquid chromatography
( Milichrom 2 , 100% methanol, silasorb C18) by
adding an authentic sample of XVI into the reaction
mixture.
Determination of rate constant for reaction of
N-(4-tetrafluoropyridyl)pentafluoroaniline (I) with
pentafluoropyridine. Glass balls containing weighed
portions of reagents: 0.0239 g (0.0712 mmol) of
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 2 2001

268
OS,KINA, VLASOV
Table 3 Relative rates of reaction with pentafluoro-
pyridine of anions IIIa, IVa, VIa, and XVa in DMSO
at 25 C
The yield of reaction products was estimated from
GLC data by adding the authentic samples. The
results of relative rate determinations are given in
Table 3. The determination of the relative rate of
reaction between N-anion VIa and pentafluoro-
pyridine was determined by comparison with the
anion XVa of 9-carbomethoxyfluorene since with
anion IVa the retention times of reaction products
XIII and XIV coincided preventing the evaluation of
their yields. The rate constants of anions IVa and VIa
in reaction with pentafluoropyridine listed in Table 1
were calculated using the rate constant determined in
reaction of N-anion IIIa with pentafluoropyridine.
N-anion
no.
krel
na
IIIa
IVa
VIa
XVa
1.0
2.7
5.4
5 ( 14.7)
5 ( 14.7)
3 ( 16.5)
3 ( 4.7)
22.0
a
n is number of experiments; deviations , % are given in
parentheses.
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compound I, 0.0117 g (0.0692 mmol) of pentafluoro-
pyridine, 0.0038 g (0.0704 mmol) of sodium methyl-
ate, and of 65% HNO3, and 1.8 ml of DMSO were
placed into a glass reactor connected to a vacuum
line. The reactor was evacuated to 1 10 4 mm Hg and
sealed off the vacuum line. By successive crushing of
balls with reagents was first generated anion Ia, then
the reaction mixture was maintained for a definite
time (10 55 min), then neutralized with 65% HNO3.
The mixture in a volumetric flask was diluted with
distilled water till precise volume of 50 ml, and the
content of fluoride ion was determined. The rate
constant was calculated by the equation for second
order reactions. The calculation results are presented
in Table 1.
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