Chemistry of Heterocyclic Compounds, Vol. 46, No. 12, March, 2011 (Russian Original Vol. 46, No. 12, December, 2010)
NOVEL METHOD FOR THE peri-ANNELATION
OF PYRROLE RING TO PERIMIDINES
A. V. Aksenov1*, N. A. Aksenov1, A. E. Tsys’1, and O. N. Nadein1
Keywords: nitroethane, perimidines, polyphosphoric acid, 1H-1,5,7-triazacyclopenta[c,d]phenalenes, peri-
annelation.
We have previously developed a series of methods for the peri-annelation of a pyrrole ring to a
perimidine [1-3]. The drawback of these methods is the need for initially functionalizing the perimidines. In this
work we propose a method for removing this drawback based on our recently reported system of reagents for
acetamidation of aromatic compounds, viz. nitroethane and polyphosphoric acid (PPA) [4, 5]. It was found that
reaction of 1 mmol of perimidines 1a-c with nitroethane (0.1 g, 1.33 mmol) in PPA** (2-3 g) at 95-105ºC for
3 h (TLC monitoring) followed by 4 h at 150-160ºC (again TLC monitoring) gave the 1H-1,5,7-triaza-
cyclopenta[c,d]phenalenes 3a-c in 46-54% yields.
The reaction includes an intermediate formation of acetamides 2a-c [4] which give compounds 3a-c via
thermal cyclization.
R
R
R
N
NH
O
N
NH
N
N
EtNO2
PPA
HN
N
H
Me
Me
3a–c
1a–c
2a–c
1–3 a R = H, b R = Me, c R = Ph
1H NMR spectra were recorded on a Bruker WP-200 instrument (200 MHz) using TMS as internal
standard. Monitoring of the reaction course and the purity of the compounds synthesized was carried out on
Silufol UV-254 plates in the solvent system ethyl acetate–alcohol (1:1).
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* To whom correspondence should be addressed, e-mail: k-biochem-org@stavsu.ru, alexaks05@rambler.ru.
** PPA with an 86% P2O5 content was prepared by method [6].
1Stavropol State University, Stavropol 355009, Russia.
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Translated from Khimiya Geterotsiklicheskikh Soedinenii, No 12, pp. 1909-1910, December, 2010.
Original article submitted November 23, 2010.
0009-3122/11/4612-1547©2011 Springer Science+Business Media, Inc.
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