Synthesis and cycloaddition of N-substituted pyrroles with polyfluorinated substituents

Article abstract of DOI:10.1007/s11172-006-0063-z

Reactions of N-pyrrolylpotassium with fluorinated electrophiles yielded N-substituted pyrroles containing polyfluoroalkyl, polyfluoroalkenyl, polyfluoroalkylsulfonyl, and polyfluoroaryl substituents. N-Polyfluoro- substituted pyrroles did not isomerize at ≥100°C; they were found to be reactive in [4+2] cycloaddition reactions with perfluorobut-2-yne.

Full text of DOI:10.1007/s11172-006-0063-z

1948
Russian Chemical Bulletin, International Edition, Vol. 54, No. 8, pp. 1948—1953, August, 2005
Synthesis and cycloaddition of Nꢀsubstituted pyrroles
with polyf luorinated substituents
S. V. Moiseev and N. V. Vasil´evꢀ
Military Academy of Radioactive, Chemical, and Biological Defense,
13 per. Brigadirsky, 105005 Moscow, Russian Federation.
Phone: +7 (495) 265 9318
Reactions of Nꢀpyrrolylpotassium with fluorinated electrophiles yielded Nꢀsubstituted pyrꢀ
roles containing polyfluoroalkyl, polyfluoroalkenyl, polyfluoroalkylsulfonyl, and polyfluoroaryl
substituents. NꢀPolyfluoroꢀsubstituted pyrroles did not isomerize at >100 °C; they were found
to be reactive in [4+2] cycloaddition reactions with perfluorobutꢀ2ꢀyne.
Key words: Nꢀ(polyfluoroalkenyl)pyrroles, Nꢀ(polyfluoroalkylsulfonyl)pyrroles, Nꢀ(pentaꢀ
fluorophenyl)pyrrole, 7ꢀazabicyclo[2.2.1]heptadiene, cycloaddition.
Scheme 1
First representatives of Nꢀpolyfluoroalkylpyrroles
(1,1,2,2ꢀtetrafluoroethylꢀ, 2ꢀchloroꢀ1,1,2ꢀtrifluoroethylꢀ,
and 1,1,2,3,3,3ꢀhexafluoropropylpyrroles) were obtained
rather long ago1,2 by addition of pyrrole to polyfluorinated
alkenes at 100 °C in the presence of metallic potassium.
In the same studies,1,2 two examples of the synthesis of
Nꢀ(polyfluoroalkenyl)pyrroles, namely, Nꢀ(2ꢀchloroꢀ
difluorovinyl)pyrrole and 2ꢀfluoroꢀ2ꢀphenylꢀ1,1ꢀdipyrꢀ
rolylethylene, were reported, although the researchers
themselves were doubtful about their structures. 3,4ꢀDiꢀ
methylꢀ1ꢀpentafluorophenylpyrrole was obtained by deꢀ
sulfooxidation of the corresponding thiazine oxide with a
solution of alkali in aqueous alcohol and this was the only
example of the synthesis of fluorinated arylpyrrole.3
The goal of the present study was to investigate the
preparative possibility of using Nꢀpyrrolylpotassium to
obtain pyrroles containing polyfluorinated substituents at
the N atom. Earlier,4 Nꢀpyrrolylpotassium was prepared
by a reaction of pyrrole with solid KOH followed by dryꢀ
ing. Our attempted synthesis of Nꢀsubstituted pyrroles by
reactions of the reagent thus prepared with polyfluoroꢀ
olefins failed. The major process was mineralization of
fluoroolefins by the action of KOH.
We found that reactions of chlorotrifluoroethylene and
perfluoropropylene with Nꢀpyrrolylpotassium (in situ preꢀ
pared by dissolution of metallic potassium in an excess of
pyrrole (1 : 1.2) in ether) occur even at –60 °C and
proceed exothermically to give 2 : 7 and 2 : 5 mixtures of
Nꢀpolyfluoroalkylꢀ and Nꢀpolyfluoroalkenylpyrroles 1, 2
and 3, 4, respectively. Repeated fractionation of these
mixtures allowed individual compounds 1, 3 and 2, 4 to
be isolated in low (≤5%) yields (Scheme 1).
R = Cl (1, 2), CF3 (3, 4)
NꢀPolyfluoroalkenylpyrroles were selectively obtained
with Nꢀpyrrolylpotassium dried in vacuo. Reactions of the
dispersed Nꢀpyrrolylpotassium thus prepared with chloroꢀ
trifluoroethylene, perfluoropropylene, and perfluoroisoꢀ
butylene in ether proceed exothermically at –60 °C to
give polyfluoroalkenylpyrroles 2, 4, and 5 in satisfactory
yields (Scheme 2). The reaction with the most reactive
polyfluoroalkene (perfluoroisobutylene) also yielded diꢀ
substituted olefin 6. Pyrroles 2 and 4 were obtained as
mixtures of the geometrical Z,Eꢀisomers in the 7 : 5 ratio
for compound 2 and of the E,Zꢀisomers in the 8 : 1 ratio
for compound 4. Pyrroles 2 and 4 were distilled over dry
KOH to remove minor amounts of polyfluoroalkylpyrroꢀ
les 1 and 3, which can form in the presence of water or
pyrrole traces. The Zꢀisomer of compound 2 and the
Eꢀisomer of compound 4 were dominant (>95%). This
follows from the constants of F—F spinꢀspin coupling in
the 19F NMR spectra (Jtrans = 126.2 and 127.7 Hz, reꢀ
spectively) characteristic of the transꢀarranged F atoms
relative to the double bond. The increase in the content of
It should be noted that pyrrole does not react with
fluoroolefins in the absence of potassium.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1890—1895, August, 2005.
1066ꢀ5285/05/5408ꢀ1948 © 2005 Springer Science+Business Media, Inc.

NꢀPolyfluoroꢀsubstituted pyrroles
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 8, August, 2005
1949
the Zꢀisomer of pyrrole 2 and the Eꢀisomer of pyrrole 4 is
probably due to Z,Eꢀisomerization in the presence of fluoꢀ
ride ions.
potassium with trifluoromethanesulfonyl chloride afforded
no pyrrole 7; instead, polymerization of the reaction mixꢀ
ture took place. The ambiguity of the reactions of polyꢀ
fluoroalkanesulfonyl chlorides with amines was reported
earlier.5
The reaction of Nꢀpyrrolylpotassium with perfluoroꢀ
benzene occurred only upon prolonged heating to give
monoꢀ and disubstitution products 9 and 10 (Scheme 4)
separated by fractional sublimation.
Scheme 2
Scheme 4
Compound
R1
F
CF3
CF3
R2
Cl
F
2
4
5
CF3
In contrast to hydrocarbon analogs,4 Nꢀsubstituted
pyrroles 2, 4, and 9 were not isomerized at high temperaꢀ
tures (200—250 °C) even upon prolonged heating.
The high stabilities of the pyrroles obtained made it
possible to study their properties in [4+2] cycloaddition
reactions. It is known6 that pyrrole itself behaves ambiguꢀ
ously in such reactions.
It turned out that alkenylpyrroles 2 and 4 react with
such a reactive dienophile as perfluorobutꢀ2ꢀyne even at
20 °C; however, the process was accompanied by oligoꢀ
merization giving rise to unidentified resinous products.
The [4+2] cycloaddition reactions of Nꢀsubstituted
pyrroles 8, 9, and 11* with perfluorobutꢀ2ꢀyne afforded
7ꢀazabicyclo[2.2.1]heptadienes 12, 13, and 14. NꢀPentaꢀ
fluorophenylpyrroles 9 and 11 slowly reacted at room
temperature, while the reaction with sulfonylpyrrole 8
occurred only at 120 °C. The cycloaddition rate of pyrrole
9 was appreciably higher at 100 °C (Scheme 5).
According to NMR data, compounds 12, 13, and 14
contain no syn—antiꢀisomers, as has been noted7 for
7ꢀazanorbornadienes with an alkyl substituent at the
N atom.
Polyfluoroalkenylpyrroles 2 and 4—6 are stable comꢀ
pounds. Pyrroles 2 and 4 are resistant to hydrolysis; in a
homogeneous acetone—water solution, the double bond
of the alkenyl fragment remains unchanged for a long
period of time.
NꢀSulfonylꢀcontaining pyrroles were obtained by reꢀ
actions of polyfluoro sulfonyl fluorides with Nꢀpyrrolylꢀ
potassium at low temperatures. NꢀPyrrolylpotassium exoꢀ
thermically reacted with trifluoromethanesulfonyl fluoꢀ
ride at –70 °C. The resulting product was Nꢀtrifluoroꢀ
methylsulfonylpyrrole 7 (~70%, 1H NMR) and up to 30%
of the starting pyrrole was recovered, which were not
separated by fractionation. Pyrrole 7 was separated from
the starting pyrrole by treating the resulting mixture with
HCl, which causes pyrrole polymerization. NꢀSubstituted
pyrrole 7 polymerizes to a lesser degree (Scheme 3). The
reaction of Nꢀpyrrolylpotassium with perfluoroꢀ2ꢀethoxyꢀ
ethanesulfonyl fluoride also occurred at low temperatures:
in this case, substituted pyrrole 8 can be easily purified
by fractionation in vacuo. The reaction of Nꢀpyrrolylꢀ
The [4+2] cycloaddition reaction of tetrafluoroꢀ1,4ꢀ
dipyrrolylbenzene 10 with perfluorobutꢀ2ꢀyne at 20 °C
yielded a mixture of diꢀ and monocycloadducts 15 and 16
(1H and 19F NMR data); however, only bis(7ꢀazaꢀ
norbornadienyl)tetrafluorobenzene 15 was isolated in the
individual state (Scheme 6).
Scheme 3
* 3,4ꢀDimethylꢀNꢀpentafluorophenylpyrrole 11 was prepared as
described earlier.3
RF = CF3 (7), CF3CF2OCF2CF2 (8)

1950
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 8, August, 2005
Moiseev and Vasil´ev
Scheme 5
Experimental
H and 19F NMR spectra were recorded on Bruker ACꢀ300
1
and Bruker WPꢀ200 SY spectrometers (300.13 and 188.31 MHz,
respectively). Chemical shifts were referenced to Me4Si (1H)
and CF3COOH (19F) as the external standards. Mass specꢀ
tra were recorded on a GCꢀMS spectrometer based on an
HP 5890 II Series gas chromatograph with an HP 5972A MSD
massꢀselective detector. IR spectra (thin film) were recorded on
a Hitachi 127ꢀ30 IR spectrometer. The elemental analysis data,
1H and 19F NMR spectra, IR spectra, physicochemical characꢀ
teristics, and yields of the compounds obtained are given in
Table 1. Commercial reagents were used. Solvents were preꢀ
pared according to known recommendations.8 Compound 11
was synthesized as described earlier.3
Compound
RF
CF3CF2OCF2CF2SO2
C6F5
R
H
H
12
13
14
C6F5
Me
Scheme 6
Synthesis of mixtures of Nꢀsubstituted pyrroles 1 and 2, 3
and 4 (general procedure). Powdered metallic potassium (2.9 g,
75 mmol) was added to a stirred solution of pyrrole (6.0 g,
90 mmol) in anhydrous diethyl ether (30 mL). The mixture was
stirred for 20 h and then the corresponding polyfluoroalkene
(90 mmol) was rapidly added at –60 °C. After warming to ambiꢀ
ent temperature, the reaction mixture was filtered and the preꢀ
cipitate was washed with ether (3×10 mL). The combined filꢀ
trates were fractionated in vacuo to collect mixtures of comꢀ
pounds 1 and 2 (b.p. = 31—34 °C (15 Torr)) and 3 and 4 (b.p. =
54—58 °C (45 Torr)) in the 2 : 7 and 2 : 5 ratios, respectively.
Triple fractionation of these mixtures on an efficient column
allowed individual compounds 1—4 to be isolated in <5% yields.
The physicochemical properties of compounds 1 and 3 agree
with the earlier reported data.1,2
Synthesis of Nꢀ(polyfluoroalkenyl)pyrroles (general proceꢀ
dure). Nꢀ(2ꢀChlorodifluorovinyl)pyrrole (2), Nꢀ(pentafluoropropꢀ
1ꢀenyl)pyrrole (4), Nꢀ(heptafluoroisobutꢀ1ꢀenyl)pyrrole (5), and
hexafluoroꢀ1,1ꢀbis(pyrrolꢀ1ꢀyl)isobutylene (6). Powdered metalꢀ
lic potassium (2.9 g, 75 mmol) was added to a stirred solution of
pyrrole (6.0 g, 90 mmol) in anhydrous diethyl ether (30 mL).
The reaction mixture was stirred for 20 h and the solvent and
the excess of pyrrole were removed in vacuo (2 Torr, 1 h).
NꢀPyrrolylpotassium was dried and dry diethyl ether (30 mL)
was added with stirring, whereupon the corresponding polyꢀ
fluoroalkene (90 mmol for pyrroles 2 and 4 and 50 mmol for
pyrroles 5 and 6) was rapidly added at –60 °C. The occurring
reaction was exothermic. After warming to ambient temperaꢀ
ture, the reaction mixture was filtered, the precipitate was washed
with ether (3×10 mL), and the filtrates were fractionated. Pyrꢀ
roles 2 and 4 were isolated as mixtures of the Z,Eꢀisomers with
possible admixtures of Nꢀpolyfluoroalkylpyrroles 1 and 3. The
individual Zꢀ and Eꢀisomers of compounds 2 and 4, respecꢀ
tively, were obtained by distillation over powdered KOH
(760 Torr). In the case of perfluoroisobutylene, no polyꢀ
fluoroalkylpyrroles were detected.
7ꢀAzanorbornadienes are stable compounds, which
decompose only at high temperatures according to the
retro [4+2] cycloaddition mechanism. For instance,
Nꢀperfluorophenylꢀ7ꢀazabicyclo[2.2.1]heptaꢀ2,5ꢀdiene
13 underwent retrodiene decomposition at ~170 °C to
give a 5 : 1 mixture of pyrroles 9 and 17 (1H and 19F NMR
and GCꢀMS data) (Scheme 7).
Scheme 7
Compounds 9 and 17 are close in physicochemical
properties and cannot be separated by fractional subliꢀ
mation.
Thus, the reactions of Nꢀpyrrolylpotassium with
fluoroꢀcontaining reagents provide additional preparaꢀ
tive possibility of obtaining a number of new Nꢀsubstiꢀ
tuted pyrroles with polyfluoroalkenyl, polyfluoroaryl,
and polyfluoroalkylsulfonyl substituents. Compounds of
this type are thermodynamically stable and resistant to
hydrolysis but they are sufficiently reactive in [4+2]
cycloaddition to such a strong dienophile as perfluoroꢀ
butꢀ2ꢀyne.
Nꢀ(Trifluoromethylsulfonyl)pyrrole (7). Powdered metallic
potassium (2.9 g, 75 mmol) was added to a stirred solution of
pyrrole (6.0 g, 90 mmol) in anhydrous diethyl ether (30 mL).
The reaction mixture was stirred for 20 h and then trifluoroꢀ
methanesulfonyl fluoride (12.9 g, 85 mmol) was rapidly added
at –70 °C. After warming to ambient temperature, the reacꢀ
tion mixture was filtered, the precipitate was washed with ether
(3×10 mL), and the filtrate was fractionated. The resulting mixꢀ
ture of Nꢀsubstituted pyrrole 7 and the starting pyrrole was disꢀ

NꢀPolyfluoroꢀsubstituted pyrroles
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 8, August, 2005
1951
Table 1. 1H and 19F NMR and IR spectra, physicochemical characteristics, and yields of the compounds obtained
20
Comꢀ Yield B.p./°C nD
Found
Calculated
Molecular
formula
NMR,
δ (J/Hz)
IR,
ν/cm–1
(%)
N
pound (%)
(p/Torr)
[m.p./°C]
С
H
1H
19F
1a
4
52—53 1.4428 39.42 2.73 7.65 C6H5ClF3N 6.32 (ddd,
14.73 (ddd, 1 F, CFВ,
JAB = 213.8, JF,Fvic = 13.2,
JF,Hvic = 4.2); 18.23
2980
(CH);
1480
(50)
39.23 2.72 7.63
1 Н, CFH,
JH,F = 48.4,
JH,FA = 4.2,
JH,FB = 4.2);
6.38, 6.95
(ddd, 1 F, CFА, JAB
213.8, JF,Fvic = 13.9,
=
(С=С)
JF,Hvic = 4.2); 74.95 (ddd,
F, CHFCl, JF,H = 48.4,
JF,F = 13.2, JF,F = 13.9)
(both br.s,
2 H each, CH)
2b
75
128
1.4749 44.48 2.46 8.59 C6H4ClF2N c6.35, 6.85
48.11 (d, F, CF, JF,F
=
1675
44.36 2.45 8.56
(both br.s,
2 H each, CH)
d6.36, 6.90
126.2); 50.66 (d, F, CFCl,
JF,F = 126.2)
26.65 (d, F, CF, JF,F = 25.8);
34.09 (d, F, CFCl,
JF,F = 25.8)
(С=С)
(both br.s,
2 H each, CH)
5.12 (dddq,
1 H, CFH,
JH,F = 43.5,
JH,FA = 10.7,
JH,FB = 8.2,
JH,CF3 = 23.2);
6.35, 6.99
(both br.s,
2 H each, CH)
d6.41, 7.08
(both br.s,
2 H each, CH)
3
5
40—41 1.3820 38.55 2.32 6.51
(20) 38.71 2.30 6.45
C7H5F6N
1.02 (dd, 3 F, CF3, JCF ,F
=
2990
(CH);
1470
3
11.1, JCF ,H = 23.2); 9.93
(ddd, 1 F3, CFВ, JAB = 207.1,
JF,F = 21.7, JF,Hvic = 10.7);
(С=С)
16.3v9ic(ddd, 1 F, CFА, JAB
207.1, JF,F = 24.8, JF,H
=
=
vic
vic
8.2); 132.06 (dddq, F, CHF,
JH,F = 43.5, JH,F = 10.7,
JH,F = 8.2, JH,CF3 = 23.2)
–9.4 (dd, 3 F, CF3,
4e
65
108—110 1.4050 42.71 2.04 7.13
42.64 2.03 7.10
C7H4F5N
1680
(С=С)
JCF ,F = 22.5, JCF ,F = 12.5);
51.0 (dq, F, CF, JF3 ,CF
=
3
22.5, JF,F = 127.7); 1035.9
(dq, F, CF, JF,CF3 = 12.5,
JF,F = 127.7)
c6.35, 6.80
–8.70 (dd, 3 F, CF3,
(both br.s,
2 H each, CH)
JCF ,F = 12.0, JCF ,F = 9.6);
3
13.00 (dq, F, CF, 3
JF,CF = 9.6, JF,F = 3.7);
83.103(dq, F, CF,
JF,CF = 12.0, JF,F = 3.7)
3
5
6
26
32
117
1.4338 38.97 1.63 5.69
38.86 1.62 5.67
C8H4F7N
6.42, 6.97
(both s,
2 H each, CH)
–14.67 (qq, F, CF,
1690
(С=С)
JF,CF = 8.0, JCF ,F = 23.8);
3
–17.99 (dq, 3 F, 3CF3,
JCF ,CF = 8.0, JCF ,F = 23.8);
3
3
–18.81 3(dq, 3 F, CF3,
JCF ,CF = 8.0, JCF ,F = 8.0)
3
53—54 1.4842 49.18 2.73 9.56
(3) 48.98 2.72 9.52
C12H8F6N2
6.49, 6.78
(both br.s,
2 H each, CH)
–18.85 3(s, 6 F, CF33)
2950
(СH);
1640
(С=С)
2900
(СH)
7
8
11
47
37—38 1.4069 30.22 2.02 7.05 C5H4F3NO2S 6.49, 7.14
–0.37 (s, 3 F, CF3)
(22)
30.15 2.01 7.03
(both t, 2 H each,
CH, J = 2.1)
58
1.3649 26.38 1.10 3.85 C8H4F9NO3S 6.49, 7.15
4.39 (t, 2 F, CF2, J = 11.8);
9.65 (br.s, 3 F, CF3);
2930
(СH)
(11)
26.30 1.09 3.83
(both br.s,
2 H each, CH)
11.31 (t, 2 F, CF2, J = 11.8);
38.09 (br.s, 2 F, CF2(С2F5))
(to be continued)

1952
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 8, August, 2005
Moiseev and Vasil´ev
Table 1 (continued)
20
Comꢀ Yield B.p./°C nD
Found
Calculated
Molecular
formula
NMR,
δ (J/Hz)
IR,
ν/cm–1
(%)
N
pound (%)
(p/Torr)
[m.p./°C]
С
H
1H
19F
9
25
[63—64]
—
51.62 1.72 6.03
51.50 1.71 6.01
C10H4F5N
6.42, 6.88
(both br.s,
2 H each, CH)
68.21 (d, 2 F, C6F5, J = 20.1);
76.58 (t, F, C6F5, J = 20.1);
81.44 (t, 2 F,
2080
(СH);
1540
C6F5, J = 20.1)
68.69 (s, 4 F, C6F4)
(C=C)
2960
10
12
15 [129—131]
—
60.11 2.87 10.04 C14H8F4N2
60.00 2.86 10.00
6.35, 7.01
(both br.s,
2 H each, CH)
(СH);
1500
(C=C)
2970
55
56—58 1.3511 27.38 0.77 2.66 C12H4F15NO3S 5.58, 7.39
–13.49 (s, 6 F, CF3);
(1)
27.32 0.76 2.65
(both s,
2 H each, CH)
4.76 (t, 2 F, C2F4, J = 12.4);
10.21 (br.s, 3 F, CF3);
(СH);
1690
11.90 (t, 2 F, CF2, J = 12.4);
40.12 (br.s, 2 F, CF2 (C2F5))
–13.07 (s, 6 F, CF3);
78.05 (d, 2 F, C6F5, J = 20.4);
86.43 (t, 2 F, C6F5, J = 20.4);
86.93 (t, F, C6F5, J = 20.4)
–15.01 (s, 6 F, CF3);
77.62 (d, 2 F, C6F5, J = 21.1);
86.12 (t, 2 F, C6F5, J = 21.1);
87.15 (t, F, C6F5, J = 21.1)
–13.57 (s, 12 F, CF3);
(C=C)
13
14
71
77
[53—54]
[96—97]
—
—
42.61 1.02 3.55
42.53 1.01 3.54
C14H4F11N
C16H8F11N
5.58, 7.27
(both s,
2 H each, CH)
2950
(СH);
1700
(С=С)
2985
(СH);
1700
(С=С)
1750
(С=С)
45.43 1.90 3.33
45.39 1.89 3.31
1.88 (s,
6 H, Me);
5.22 (s,
2 H, CH)
15
16
17
30 [167—168]
(decomp.)
—
—
—
43.83 1.33 4.65 C22H8F16N2 5.55, 7.22
43.71 1.32 4.63
(both s,
4 H each, CH)
77.62 (s, 4 F, C6F4)
—
—
—
—
—
—
—
—
—
—
C18H8F10N2 5.67, 6.38, 6.87, –13.57 (s, 6 F, CF3);
—
—
7.29 (all s,
2 H each, CH)
7.28 (s,
73.79 (d, 2 F, C6F4, J = 13.9);
77.18 (d, 2 F, C6F4, J = 17.1)
–18.02 (s, 6 F, CF3); 71.69
(d, 2 F, C6F5, J = 20.3);
C12H2F11N
2 H, CH)
75.11 (t, 2 F, C6F5, J = 20.3);
82.88 (t, F, C6F5, J = 20.3)
a The physicochemical characteristics were reported earlier.2
b The mixture of the Zꢀ and Eꢀisomers in the 7 : 5 ratio.
c The Zꢀisomer.
d The EꢀIsomer.
e The mixture of the Eꢀ and Zꢀisomers in the 8 : 1 ratio.
solved in CH2Cl2 (5 mL) and HCl (5 mL) was added with
vigorous stirring. The precipitate that formed was filtered off
and washed with CH2Cl2 (3×5 mL). The organic layer was sepaꢀ
rated, dried with MgSO4, and fractionated.
Nꢀ(Perfluoroꢀ2ꢀethoxyethylꢀ1ꢀsulfonyl)pyrrole (8). Powdered
metallic potassium (2.9 g, 75 mmol) was added to a stirred
solution of pyrrole (5.4 g, 80 mmol) in anhydrous diethyl
ether (30 mL). The reaction mixture was stirred for 20 h and
2ꢀfluorosulfonylperfluorodiethyl ether (24.0 g, 75 mmol) was
added at –70 °C. The occurring reaction was exothermic. After
warming to ambient temperature, the reaction mixture was filꢀ
tered, the precipitate was washed with ether (3×10 mL), and the
filtrate was fractionated in vacuo.
anhydrous diethyl ether (30 mL). The reaction mixture was
stirred for 20 h and then perfluorobenzene (17.7 g, 95 mmol)
was added at room temperature. The resulting mixture was reꢀ
fluxed for 14 h, cooled to ambient temperature, and filtered.
The precipitate was washed with ether (2×10 mL). The comꢀ
bined filtrate was concentrated and the residue was separated by
fractional sublimation in vacuo (1 Torr).
Reactions of Nꢀsubstituted pyrroles 8, 9, and 11 with perꢀ
fluorobutꢀ2ꢀyne (general procedure). 7ꢀ(Perfluoroꢀ2ꢀethoxyethylꢀ
1ꢀsulfonyl)ꢀ2,3ꢀbis(trifluoromethyl)ꢀ7ꢀazabicyclo[2.2.1]heptaꢀ
2,5ꢀdiene (12), 7ꢀperfluorophenylꢀ2,3ꢀbis(trifluoromethyl)ꢀ7ꢀ
azabicyclo[2.2.1]heptaꢀ2,5ꢀdiene (13), and 5,6ꢀdimethylꢀ
7ꢀpentafluorophenylꢀ2,3ꢀbis(trifluoromethyl)ꢀ7ꢀazabiꢀ
cyclo[2.2.1]heptaꢀ2,5ꢀdiene (14). A mixture of the correspondꢀ
ing Nꢀsubstituted pyrrole (7.5 mmol) and perfluorobutꢀ2ꢀyne
(2.4 g, 15 mmol) was kept in a sealed glass tube at 120 °C for 6 h,
NꢀPentafluorophenylpyrrole (9) and perfluoroꢀ1,4ꢀbis(pyrrolꢀ
1ꢀyl)benzene (10). Powdered metallic potassium (2.9 g, 75 mmol)
was added to a stirred solution of pyrrole (5.4 g, 80 mmol) in

NꢀPolyfluoroꢀsubstituted pyrroles
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 8, August, 2005
1953
at 100 °C for 10 h, or at 20 °C for 20 days to give compounds 12,
13, or 14, respectively. The tube was cooled and volatile prodꢀ
ucts were removed. The residue was fractionated in vacuo (12)
or sublimed in vacuo (13, 14).
[M – CF3]+ (37), 231 [300 – CF3]+ (6), 167 [C6F5]+ (37), 69
[CF3]+ (92).
References
Reaction of perfluoroꢀ1,4ꢀbis(pyrrolꢀ1ꢀyl)benzene (10) with
perfluorobutꢀ2ꢀyne. 7ꢀ{4ꢀ[2,3ꢀBis(trifluoromethyl)ꢀ7ꢀazabiꢀ
cyclo[2.2.1]heptaꢀ2,5ꢀdienꢀ7ꢀyl]ꢀ2,3,5,6ꢀtetrafluorophenyl}ꢀ
2,3ꢀbis(trifluoromethyl)ꢀ7ꢀazabicyclo[2.2.1]heptaꢀ2,5ꢀdiene (15)
and 7ꢀ[2,3,5,6ꢀtetrafluoroꢀ4ꢀ(pyrrolꢀ1ꢀyl)phenyl]ꢀ2,3ꢀbis(triꢀ
fluoromethyl)ꢀ7ꢀazabicyclo[2.2.1]heptaꢀ2,5ꢀdiene (16). A mixꢀ
ture of perfluoroꢀ1,4ꢀbis(pyrrolꢀ1ꢀyl)benzene 10 (0.6 g,
2.1 mmol) and perfluorobutꢀ2ꢀyne (2.1 g, 12.9 mmol) in dry
diethyl ether (5 mL) was kept in a glass tube at room temperaꢀ
ture for 30 days. The tube was cooled and volatile products were
removed. After warming to 20 °C, the mixture was concentrated
in vacuo (13 Torr) and the residue was recrystallized from hepꢀ
tane. 1,4ꢀDisubstituted perfluorobenzene 15 and a 1 : 2 mixture
of diꢀ (15) and monocycloadducts (16) were isolated (NMR
data). The components of the mixture were not separated.
Synthesis of a mixture of Nꢀpentafluorophenylꢀ3,4ꢀbis(triꢀ
fluoromethyl)pyrrole (17) and Nꢀpentafluorophenylpyrrole (9).
7ꢀAzanorbornadiene 13 (1 g, 2.5 mmol) was heated at 170 °C for
16 h and the residue was sublimed in vacuo (1 Torr). The resultꢀ
ing mixture of pyrroles 17 and 9 (1 : 5) was characterized by
NMR and GCꢀMS data. Compound 17: MS (EI, 70 eV),
m/z (Irel (%)): 369 [M]+ (100), 350 [M – F]+ (85), 300
1. Ch. S. Cleaver and D. C. England, Du Pont de Nemours and
Co., US Pat. 2,861,990, Nov. 25, 1958; Chem. Abstr., 1959,
53, 14123.
2. D. C. England, L. R. Melbi, M. A. Dietrich, and R. V.
Lindsey, Jr., J. Am. Chem. Soc., 1960, 82, 5116.
3. U. Jager and W. Sundermeyer, Chem. Ber., 1986, 119, 3405.
4. H. Fischer and H. Orth, Die Chemie des Pyrrols, J. Springer,
Berlin, 1934, Bd. I.
5. S. BeneficeꢀMalqueit, H. Blancou, R. Teissedre, and
A. Commeyras, J. Fluorine Chem., 1986, 31, 319.
6. J. C. Blazejewski, D. Cantacuzene, and C. Wakselman, Tetraꢀ
hedron Lett., 1975, 6, 363.
7. R. Kitzing, R. Fuchs, M. Joeux, and H. Prinzbach, Helv.
Chim. Acta, 1968, 51, 888.
8. A. Gordon and R. Ford, Chemist´s Companion. A Handbook of
Practical Data, Techniques, and References, Wiley Interscience,
New York—London—Toronto, 1972.
Received April 20, 2005;
in revised form July 20, 2005