A new one pot reaction of perimidines with nitroethane and sodium nitrite in polyphosphoric acid

Full text of DOI:10.1007/s11172-013-0154-6

Russian Chemical Bulletin, International Edition, Vol. 62, No. 4, pp. 1127—1128, April, 2013
1127
A new one pot reaction of perimidines with nitroethane
and sodium nitrite in polyphosphoric acid
A. V. Aksenov, N. A. Aksenov, A. E. Tsys´, V. I. Goncharov, and S. N. Ovcharov
North Caucasus Federal University,
1a ul. Pushkina, 355009 Stavropol´, Russian Federation.
Fax: +7 (865) 235 4033. Eꢀmail: alexaks05@rambler.ru
Scheme 1
Development of new efficient synthetic methods for
poorly available compounds possessing useful properties is
an actual problem. Polynuclear aromatic and heteroꢀ
aromatic compounds with periꢀannulated fiveꢀmembered
rings belong to such compounds. If there are known plenty
of methods for the periꢀannulation of pyrrole1—4 and furan4
ring to naphthalene derivatives, only several examples are
described for the periꢀannulation of pyrazole ring.4—6
In the present work, we suggest a method for the synꢀ
thesis of compounds containing such a fragment, which is
based on the reaction of electrophilic acetamidation of
arenes with nitroethane in PPA recently discovered in our
laboratory.7—9
We showed that the reaction of perimidines 1a—c and
nitroethane in the molar ratio of 1 : 2 (Scheme 1) in the
presence of catalytic amounts of DABCO in polyphosꢀ
phoric acid (PPA) at 100—105 C for 3 h with subsequent
addition of NaNO2 in the amount equimolar to that of
nitroethane and heating for another 6 h at this temperaꢀ
ture leads to 1,2,5,7ꢀtetraazacyclopenta[c,d]phenalenes
5a—c in 26—33% yields. Earlier, such compounds were
obtained in close yields using the following synthetic seꢀ
quence: the Schmidt reaction—nitrosation5 (starting from
6(7)ꢀacetylperimidines) and amination of perimidines 1a—c
with sodium azide in PPA with subsequent nitrosation.6
The method suggested in this work has the following adꢀ
vantages as compared to those developed earlier. First, it
does not require preliminary functionalization of perimꢀ
idines 1a—c; second, no use of sodium azide in acidic
medium is needed and, therefore, no highly toxic and exꢀ
plosive HN3 is liberated. Probably, Nꢀoxides 4a—c were
another reaction products, which were not isolated beꢀ
cause of their good solubility in water. A suggestion on
their formation made based on the Scheme shown below
was confirmed by the fact that they were converted to
1,3,6,8ꢀtetraazapyrenes 6a—c by the reduction with zinc
dust. The yields of compounds 6a—c starting from perimꢀ
idines 1a—c were 40—44%.
It is probable that the reaction follows the following
course. The acetamidation of perimidines 1a—c leads to
acetamidamides 2a—c, whose nitrosation8 gives the interꢀ
R = H (a), Me (b), Ph (c)
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 1127—1128, April, 2013.
1066ꢀ5285/13/6204ꢀ1127 © 2013 Springer Science+Business Media, Inc.

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Russ.Chem.Bull., Int.Ed., Vol. 62, No. 4, April, 2013
Aksenov et al.
2ꢀMethylꢀ1,3,6,8ꢀtetraazapyrene (6a). The yield was 0.084 g
(43%). M.p. > 300 C (from ethanol; Ref. 5: m.p. > 300 C).
NMR spectrum corresponds to that given in the work.5
2,7ꢀDimethylꢀ1,3,6,8ꢀtetraazapyrene (6b). The yield was
0.084 g (40%). M.p. > 300 C (from ethanol; Ref. 10: m.p. > 300 C).
NMR spectrum corresponds to that given in the work.12
2ꢀMethylꢀ7ꢀphenylꢀ1,3,6,8ꢀtetraazapyrene (6c). The yield
was 0.13 g (44%). M.p. > 300 C (from ethanol; Ref. 10: m.p.
> 300 C). NMR spectrum corresponds to that given in the work.12
mediate compounds 3a—c. The latter are converted to
1,2,5,7ꢀtetraazacyclopenta[c,d]phenalenes 5a—c as a reꢀ
sult of the attack of the nitrogen atom of the acetamide
group or to 1,3,6,8ꢀtetraazapyrene Nꢀoxides 4a—c as
a result of the attack of the carbonyl group by the nitrogen
atom of the nitroso group.
In conclusion, a sequential reaction of perimidines with
nitroethane and sodium nitrite in PPA leads to a mixture
of 1,2,5,7ꢀtetraazacyclopenta[c,d]phenalenes and, probaꢀ
bly, 1,3,6,8ꢀtetraazapyrene Nꢀoxides, which can be easily
converted to the corresponding 1,3,6,8ꢀtetraazapyrenes.
Synthesis of 1,2,5,7ꢀtetraazacyclopenta[c,d]phenalenes 5a—c
and 1,3,6,8ꢀtetraazapyrenes 4a—c (general procedure). A mixꢀ
ture of the corresponding perimidine 1a—c (1 mmol), nitroꢀ
ethane (0.15 g, 2 mmol), and DABCO (0.011 g, 0.1 mmol) in
PPA* (2—3 g) was heated at 100—105 C for 3 h. Then, NaNO2
(0.138 g, 2 mmol) was added and heating at this temperature was
continued for another 6 h. The reaction mixture was cooled,
sequentially treated with water (50 mL) and 25% aqueous amꢀ
monia to pH = 8—9. The mother liquor was extracted with hot
benzene (50×5 mL). The solvent was evaporated to obtain
1,2,5,7ꢀtetraazacyclopenta[c,d]phenalenes 5a—c, which were
purified by recrystallization from benzene. The aqueous solution
was refluxed for 2 h with zinc dust (0.128 g, 2 mmol), followed by
the extraction with butanol (50×3 mL) to obtain 1,3,6,8ꢀtetraꢀ
azapyrenes 6a—c, which were purified by recrystallization from
ethanol.
NMR spectra were recorded on a Bruker WPꢀ200 spectromꢀ
eter (200 MHz) using SiMe4 as an internal standard. The reacꢀ
tion progress and the individuality of compounds synthesized
were carried out on Silufol UVꢀ254 plates in the system of solꢀ
vents ethyl acetate—ethanol, 1 : 1. Nitroethane and DABCO
were commercially available from Merck. Perimidine, 2ꢀmethꢀ
ylꢀ and 2ꢀphenylperimidines11 were obtained according to the
known procedures.
1,2,5,7ꢀTetraazacyclopenta[c,d]phenalene (5a). The yield
was 0.05 g (26%). M.p. 233 C (decomp., benzene; Ref. 5: m.p.
233 C (decomp.)). NMR spectrum corresponds to that given in
the work.5
6ꢀMethylꢀ1,2,5,7ꢀtetraazacyclopenta[c,d]phenalene (5b).
The yield was 0.056 g (27%). M.p. 231 C (decomp., benzene;
Ref. 5: m.p. 231 C (decomp.)). NMR spectrum corresponds to
that given in the work.5
6ꢀPhenylꢀ1,2,5,7ꢀtetraazacyclopenta[c,d]phenalene (5c).
The yield was 0.089 g (33%). M.p. 258 C (decomp., benzene;
Ref. 6: m.p. 258 C (decomp.)). NMR spectrum corresponds to
that given in the work.6
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 13ꢀ03ꢀ
003004a).
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* PPA with the 86% content of P2O5 was used; obtained accordꢀ
ing to the procedure published earlier.10
Received November 8, 2012;
in revised form February 22, 2013