Mendeleev Commun., 2011, 21, 36–37
CF3
CF3
N
CF3
N
O
O
O
R2
R1
R2
R1
R2
R1
R2
R1
N
Ar
Ar
Ar
N
Ar
(CF3CO)2O
N
N
N
N
N
N
N
N
–OCOCF3
–OCOCF3
–OCOCF3
A
Polymer
CF3
CF3
N
O
R2
R1
O
R2
R1
R2
R1
O
N
Ar
Ar
HOCOCF3
O
O
Ar
+
N
–OCOCF3
CF3
N
N
N
N
– [HC=CH2]
–OCOCF3
H
N
N
CF3
7
4 Ar = Ph
5 Ar = 4-EtOC6H4
6 Ar = 4-O2NC6H4
HC CH2 –OCOCF3
HC CH
HOCOCF3
+
Polymer
Scheme 2
conducting (5.0´10–11 for undoped and 1.1´10–7 S cm–1 for
I2-doped samples) polymers. Their polyconjugated structure is
also confirmed by IR (broad absorptions in the region 1700–
1300 cm–1 with maxima at 1680, 1500 and 1380 cm–1)12 and
UV spectra (broad absorptions in the region 400–500 nm with
This work was supported by the Russian Foundation for Basic
Research (grant no. 09-03-00158).
References
1 B. A. Trofimov, E. Yu. Schmidt, A. I. Mikhaleva, A. M. Vasil’tsov, A. B.
Zaitsev, N. S. Smolyanina, E.Yu. Senotrusova,A. V. Afonin, I. A. Ushakov,
K. B. Petrushenko, O. N. Kazheva, O. A. Dyachenko, V. V. Smirnov, A. F.
Schmidt, M. V. Markova and L. V. Morozova, Eur. J. Org. Chem., 2006,
4021.
2 (a) A. I. Mikhaleva and E. Yu. Schmidt, in Selected Methods for Synthesis
and Modification of Heterocycles, ed. V. G. Kartsev, IBS Press, Moscow,
2002, vol. 1, pp. 334–352; (b) R. J. Tedeschi, in Encyclopedia of Physical
Science and Technology, 3rd edn., ed. R. A. Meyers, Academic Press,
San Diego, 2001, vol. 1, pp. 55–89; (c) Z. Wang, in Comprehensive
Organic Name Reactions and Reagents, Wiley, London, 2009, part 3,
paragraph 626.
3 (a) E. Yu. Schmidt, A. I. Mikhaleva, A. B. Zaitsev, A. M. Vasil’tsov and
N. V. Zorina,ARKIVOC,2005,vii,11;(b)A. I. Mikhaleva,E. Yu. Schmidt,
A. V. Ivanov, A. M. Vasil’tsov, E. Yu. Senotrusova and N. I. Protsuk, Zh.
Org. Khim., 2007, 43, 236 (Russ. J. Org. Chem., 2007, 43, 228).
4 E. Yu. Schmidt, E. Yu. Senotrusova, I. A. Ushakov, N. I. Protsuk, A. I.
Mikhaleva and B. A. Trofimov, Zh. Org. Khim., 2007, 43, 1502 (Russ. J.
Org. Chem., 2007, 43, 1495).
l
max = 442 nm13).‡
Apparently, the site of the primary attack by the trifluoroacetyl
cation is neither the pyrrole ring nor N-vinyl group, but nitrogen
atom of the azo group adjacent to the benzene ring. This is in
agreement with data on the protonation of pyrroles 1a–e.5 The
deep charge-transfer from the pyrrole moiety of the molecule
onto the azo group has been previously detected by NMR and
UV spectroscopy.1 Thus, one may assume that the cation A
(chaperoned by the trifluoroacetate anion) is the key intermediate
of this reaction (Scheme 2).
In such a cation, the positive charge should be mainly con-
centrated on the pyrrole nitrogen due to even greater electron
density transfer from the pyrrole counterpart of the molecule
towards the ionized azo group. One of the anticipated pathways of
the intermediate A fragmentation is elimination of the vinyl cation
with further release of proton. The latter protonates trifluoro-
acetamide moiety with the N–N bond cleavage. This leads to the
formation of N-aryl-2,2,2-trifluoroacetamides 4–6 and unstable
2,2,2-trifluoro-N-(2H-pyrrol-2-ylidene)acetamides 7 (Scheme 2),
which are finally transformed to polyconjugated polymers.
The reaction found substantially contributes to understand-
ing the reactivity of 2-arylazo-1-vinylpyrroles, especially their
behaviour in the presence of strong electrophiles. This result is
of significance for the prediction of other electrophilic trans-
formations of 2-arylazo-1-vinylpyrroles.
5 E. Yu. Schmidt, E. Yu. Senotrusova, I. A. Ushakov, A. I. Mikhaleva and
B. A. Trofimov, Tetrahedron, 2009, 65, 4855.
6 (a) B. A. Trofimov, E. Yu. Schmidt, E. Yu. Senotrusova, I. A. Ushakov
andA. I. Mikhaleva, Zh. Org. Khim., 2009, 45, 1579 (Russ. J. Org. Chem.,
2009, 45, 1567); (b) E. Yu. Schmidt, E. Yu. Senotrusova, I. A. Ushakov,
O. N. Kazheva, O. A. Dyachenko, G. G. Alexandrov, A. V. Ivanov, A. I.
Mikhaleva and B. A. Trofimov, ARKIVOC, 2010, ii, 352.
7 B. A. Trofimov, A. I. Mikhaleva, S. E. Korostova, L. N. Sobenina, A. N.
Vasil’ev and L. V. Balashenko, Zh. Org. Khim., 1979, 15, 2042 (in
Russian).
8 (a) M. Hojo, R. Masuda and E. Okada, Synthesis, 1990, 347; (b) B. A.
Trofimov, E. Yu. Schmidt,A. I. Mikhaleva,A. M. Vasil’tsov, L. I. Larina
and L. V. Klyba, Mendeleev Commun., 1999, 238; (c) A. M. Vasil’tsov,
E.Yu. Schmidt,A. I. Mikhaleva,A. B. Zaitsev,O. A. Tarasova, A. V. Afonin,
D.-S. D. Toryashinova, L. N. Il’icheva and B. A. Trofimov, Zh. Org. Khim.,
2001, 37, 362 (Russ. J. Org. Chem., 2001, 37, 334).
N-(4-Ethoxyphenyl)-2,2,2-trifluoroacetamide 5: white crystals, mp 140–
142°C. 1H NMR (CDCl3) d: 7.82 (br.s, 1H, NH), 7.47 (d, 2H, o-H,
3J 8.9 Hz), 6.91 (d, 2H, m-H, 3J 8.9 Hz), 4.05 (q, 2H, CH2, 3J 7.0 Hz),
1.43 (t, 3H, Me, 3J 7.0 Hz). 13C NMR (CDCl3) d: 157.4 (p-C), 154.6 (q,
C=O, 2JC–F 37.0 Hz), 127.9 (i-C), 122.4 (o-C), 115.9 (q, CF3, 1JC–F 288.0 Hz),
115.2 (m-C), 63.9 (CH2), 14.8 (Me). IR (KBr, nmax/cm–1): 3309, 1702,
1619, 1548, 1516, 1480, 1306, 1255, 1239, 1174, 1156, 1047, 909, 833,
726, 516. Found (%): C, 51.46; H, 4.38; F, 24.32; N, 5.90. Calc. for
C10H10F3NO2 (%): C, 51.51; H, 4.32; F, 24.44; N, 6.01.
9 J. Szmuszkovicz, Advances in Organic Chemistry, Interscience, NewYork,
1963, pp. 25–58.
10 M. Hojo, R. Masuda, Y. Kokuryo, H. Shioda and S. Matsuo, Chem.
Lett., 1976, 499.
11 M. F. Shostakovsky, G. G. Skvortsova and E. S. Domnina, Usp. Khim.,
1969, 38, 892 (Russ. Chem. Rev., 1969, 38, 407).
N-(4-Nitrophenyl)-2,2,2-trifluoroacetamide 6: black crystals, mp 50–52°C.
1H NMR (CDCl3) d: 8.55 (br.s, 1H, NH), 8.26 (d, 2H, m-H, 3J 8.3 Hz),
7.81 (d, 2H, o-H, 3J 8.3 Hz). 13C NMR (CDCl3) d: 155.3 (q, C=O, 2JC–F
37.3 Hz), 145.2 (p-C), 141.1 (i-C), 125.2 (m-C), 120.5 (o-C), 115.5 (q,
CF3, 1JC–F 288.0 Hz). IR (KBr, nmax/cm–1): 3111, 2923, 1741, 1597, 1517,
1504, 1415, 1345, 1254, 1150, 1110, 908, 854, 752, 735, 691, 497. Found
(%): C, 41.98; H, 2.08; F, 24.21; N, 11.81. Calc. for C8H5F3N2O3 (%): C,
41.04; H, 2.15; F, 24.34; N, 11.96.
12 G. Socrates, Infrared and Raman Characteristic Group Frequencies:
Tables and Charts, 3rd edn., Wiley, Chichester, 2001, p. 272.
13 Handbook of Conducting Polymers: Conjugated Polymers: Theory,
Synthesis, Properties, and Characterisation, 3rd edn., eds. T. A. Skotheim
and J. R. Reynolds, CRC Press, Boca Raton, London, New York, 2007.
14 K. G. Rutherford, S. Y.-S. Ing (Yu) and R. J. Thibert, Can. J. Chem.,
1965, 43, 541.
‡
The detailed study of structure and properties of these polymers will be
Received: 24th June 2010; Com. 10/3546
published elsewhere.
– 37 –