Pyrano[4, 3-d]pyrimidinium salts 3.* Reactions of 1, 3-dimethyl-2, 4-dioxo-1/7, 3/7-pyrano[4, 3-d]pyrimidinium salts with azomethines

Article abstract of DOI:10.1007/s11172-009-0196-y

Reactions of1, 3-dimethyl-2, 4-dioxo-15, 35-pyrano[4, 3-d]pyrimidinium salts with azomethines have been studied. The reactions lead to 1, 3-dimethyl-2, 4-dioxo-1H, 3H-pyrido-[4, 3-d]pyrimidinium salts and aromatic aldehydes.

Full text of DOI:10.1007/s11172-009-0196-y

Russian Chemical Bulletin, International Edition, Vol. 58, No. 7, pp. 1465—1468, July, 2009
1465
Pyrano[4,3ꢀd]pyrimidinium salts
3.* Reactions of 1,3ꢀdimethylꢀ2,4ꢀdioxoꢀ
1H,3Hꢀpyrano[4,3ꢀd]pyrimidinium salts with azomethines
V. V. Kostrub and E. B. Tsupak
Department of Chemistry, South Federal University,
7 ul. Zorge, 344090 RostovꢀonꢀDon, Russian Federation.
Fax: +7 (863) 297 5267. Eꢀmail: dastr@yandex.ru
Reactions of 1,3ꢀdimethylꢀ2,4ꢀdioxoꢀ1H,3Hꢀpyrano[4,3ꢀd]pyrimidinium salts with azomeꢀ
thines have been studied. The reactions lead to 1,3ꢀdimethylꢀ2,4ꢀdioxoꢀ1H,3Hꢀpyridoꢀ
[4,3ꢀd]pyrimidinium salts and aromatic aldehydes.
Key words: pyrano[4,3ꢀd]pyrimidinium salts, azomethines, pyrido[4,3ꢀd]pyrimidinium salts,
aromatic aldehydes, recyclization.
Among various transformations of fused pyrylium salts,
reactions with azomethines are of importance. Benzoꢀ
[c]pyrylium perchlorates quantitatively and stereoseꢀ
lectively add Schiff bases, that leads to derivatives of
3,4ꢀdihydroisoquinolinium salts2,3 (Scheme 1). Appaꢀ
rently, the process follows a concerted [4+2]ꢀcycloꢀ
addition mechanism, since annulation with the benzene
ring imparts noticeable heterodiene character to the pyꢀ
rylium ring.
uracil fragment is not aromatic4—6 and cannot signifiꢀ
cantly disturb aromaticity of the pyrylium fragment in the
molecule. It turned out that a shortꢀtime heating pyrimiꢀ
dopyrylium salts 1 and 2 with Schiff bases in acetic acid
leads to 1,3ꢀdimethylꢀ2,4ꢀdioxoꢀ1H,3Hꢀpyrido[4,3ꢀd]ꢀ
pyrimidinium salts 3 and 4 and corresponding aldehydes
(Scheme 2). When the experiments were performed in
DMF and MeCN at room temperature and upon heating,
similar results were obtained.
In the present work, we study the reaction of 1,3ꢀdiꢀ
methylꢀ2,4ꢀdioxoꢀ1H,3Hꢀpyrano[4,3ꢀd]pyrimidinium salts
with azomethines. The structure of these salts considerꢀ
ably differs from that of benzo[c]pyrylium salts, since the
The structures of the products indicate that the transꢀ
formation under consideration is an exchange process
known for the monocyclic pyrylium salts,7 in the course of
which the onium O atom of the pyrylium ring is substitutꢀ
ed for the imine N atom of the azomethine, thus transꢀ
forming to ammonium.
* For Part 2, see Ref. 1.
Scheme 1
R = H, Ph
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1422—1425, July, 2009.
1066ꢀ5285/09/5807ꢀ1465 © 2009 Springer Science+Business Media, Inc.

1466
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 7, July, 2009
Kostrub and Tsupak
Scheme 2
Compound
Ar1
Ar2
Ar3
R
X–
1a, 3a
1a, 3b
1b, 3c
1b, 3d
2a, 4a
2a, 4b
2b, 4c
2b, 4d
Ph
Ph
Ph
Ph
Ph
4ꢀBrC6H4
4ꢀBrC6H4
Br–
Br–
Br–
Br–
ClO4–
ClO4–
ClO4–
ClO4
4ꢀMeOC6H4
4ꢀBrC6H4
4ꢀFC6H4
Ph
4ꢀMeOC6H4
4ꢀBrC6H4
4ꢀFC6H4
4ꢀMeOC6H4
4ꢀMeOC6H4
3ꢀNO2C6H4
Ph
4ꢀMeOC6H4
4ꢀMeOC6H4
3ꢀNO2C6H4
Ph
Ph
H
H
H
Ph
–
4ꢀBrC6H4
4ꢀBrC6H4
Ph
Ph
H
The structurally related Nꢀarylpyrido[4,3ꢀd]pyrimiꢀ
dinium salts have been obtained by us earlier resulting
from the recyclization of pyrimidopyrylium salts upon the
are found as the singlets at δ 3.17—3.19 and 3.71—3.74. In
the IR spectra of pyrimidopyridinium salts 3 and 4, there
are observed the absorption maxima for the carbonyl
groups in the region 1615—1690 cm–1 (characteristic
of the amide carbonyl group absorption9), and in the case
of perchlorates 4, there are also absorption bands at
1084—1096 cm–1 related to the perchlorate ion.
Taking into account that water is present in the reacꢀ
tion mixture in only trace amounts, we did not consider
a possibility of recyclization of the pyrylium ring upon
the action of arylamine, which can be formed during
hydrolysis of the Schiff base, by a simple nucleophile subꢀ
stitution.8
1
action of primary aromatic amines.8 The H NMR specꢀ
tra of 5,6,7ꢀtriarylpyrido[4,3ꢀd]pyrimidinium bromides 3
exhibit the signals for the protons of three aromatic subꢀ
stituents in the region δ 6.46—7.68 and the singlet at
δ 7.54—7.68, which belongs to the proton C(8)H. The
signals for the protons of the Nꢀmethyl groups in the form
of two singlets are found at δ 3.27—3.31 and 3.60—3.77.
1
The H NMR spectra of 5,6ꢀdiarylpyrido[4,3ꢀd]pyrimiꢀ
dinium perchlorates 4 contain signals for the protons of
two aromatic substituents in the region δ 6.95—7.57 and
two doublets at δ 9.21—9.25 and 8.19—8.24, which are
related to the protons C(7)H and C(8)H, respectively.
The protons of two methyl groups on the uracil N atoms
It is possible that pyrylium ring of cations 1 and 2 is
transformed to pyridinium one according to the mechaꢀ
nism described earlier7 for similar reaction in the series of
Scheme 3

Reactions of pyrano[4,3ꢀd]pyrimidinium salts
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 7, July, 2009
1467
Table 1. Yields, melting points, and elemental analysis data for compounds 3a—d and 4a—d
Comꢀ
pound
Yield
(%)
M.p./°C
Found
Calculated
Molecular
formula
(%)
С
Н
Hal
3a
3b
3c
3d
4a
4b
4c
4d
77
50
90
78
89
89
86
85
>350
55.80
55.98
55.07
55.19
56.24
55.98
62.35
62.56
48.41
48.25
47.63
47.80
48.38
48.25
54.47
54.62
3.52
3.65
3.88
3.80
3.57
3.65
3.93
4.08
3.16
3.28
3.53
3.46
3.20
3.28
3.66
3.71
27.39a
27.59
26.05a
26.23
27.34a
27.59
18.76b
19.07
22.12c
22.07
20.69c
20.87
21.96c
22.07
11.91d
11.79
C27H21Br2N3O2
C28H23Br2N3O3
C27H21Br2N3O2
C27H21BrFN3O2
C21H17BrClN3O6
C22H19BrClN3O7
C21H17BrClN3O6
C21H17ClFN3O6
279—284
290—295
282—286
309—312
239—242
297—299
289—292
a Hal = Br.
b Hal = Br + F.
c Hal = Br + Cl.
d Hal = Cl + F.
Table 2. IR and 1H NMR spectra of compounds 3a—d (in CDCl3) and 4a—d (in DMSOꢀd6)
Comꢀ
pound
IR,
ν/cm–1
1H NMR, δ (J/Hz)
3a
3b
3c
1627, 1690 (С=О)
1624, 1685 (С=О)
1628, 1688 (С=О)
1615, 1680 (С=О)
3.27 (s, 3 Н, N(3)Ме); 3.73 (s, 3 Н, N(1)Ме); 6.96—7.11 (m, 5 Н, Ar);
7.12—7.24 (m, 5 Н, Ar); 7.28 (d, 2 Н, 7ꢀAr, J = 8.77); 7.36 (d, 2 Н, 7ꢀAr,
J = 8.77); 7.54 (s, 1 H, С(8)H)
3.31 (s, 3 Н, N(3)Ме); 3.60 (s, 3 Н, N(1)Ме); 3.80 (s, 3 Н, OМе);
6.46 (d, 2 Н, Ar, J = 8.76); 7.19—7.29 (m, 3 Н, Ar); 7.34—7.45 (m, 6 Н, Ar);
7.55 (d, 2 Н, Ar, J = 8.42); 7.64 (s, 1 H, С(8)H)
3.27 (s, 3 Н, N(3)Ме); 3.76 (s, 3 Н, N(1)Ме); 7.05 (d, 2 Н, Ar, J = 8.85);
7.15—7.35 (m, 6 Н, Ar); 7.43—7.51 (m, 4 Н, Ar); 7.59—7.68 (d + s, 3 Н, Ar,
С(8)H, J = 6.64)
3d
4a
3.28 (s, 3 Н, N(3)Ме); 3.77 (s, 3 Н, N(1)Ме); 6.56—6.68 (m, 2 Н, Ar);
7.15—7.34 (m, 6 Н, Ar); 7.46—7.53 (m, 2 Н, Ar); 7.58—7.68 (m, 5 Н, Ar, С(8)H)
1632, 1686 (С=О);
1084 (Cl—O)
3.17 (s, 3 Н, N(3)Ме); 3.72 (s, 3 Н, N(1)Ме); 7.19 (d, 2 Н, H(3´), H(5´), 5ꢀAr,
J = 8.09); 7.36—7.57 (br.s + d, 7 Н, 6ꢀAr, H(2´), H(6´), 5ꢀAr, J = 8.42);
8.21 (d, 1 H, С(8)H, J = 7.41); 9.25 (d, 1 H, С(7)H, J = 7.07)
4b
1630, 1683 (С=О);
1096 (Cl—O)
3.19 (s, 3 Н, N(3)Ме); 3.74 (s, 6 Н, N(1)Ме, OMe); 6.95 (d, 2 Н, H(3″), H(5″),
6ꢀAr, J = 9.09); 7.23 (d, 2 Н, H(3´), H(5´), 5ꢀAr, J = 8.42); 7.39 (d, 2 Н,
H(2″), H(6″), 6ꢀAr, J = 9.09); 7.54 (d, 2 Н, H(2´), H(6´), 5ꢀAr, J = 8.42);
8.20 (d, 1 H, С(8)H, J = 7.41); 9.21 (d, 1 H, С(7)H, J = 7.41)
4c
4d
1625, 1685 (С=О);
1090 (Cl—O)
3.19 (s, 3 Н, N(3)Ме); 3.74 (s, 3 Н, N(1)Ме); 7.22—7.36 (m, 5 Н, 5ꢀAr);
7.43 (d, 2 Н, H(3″), H(5″), 6ꢀAr, J = 8.53); 7.63 (d, 2 Н, H(2″), H(6″), 6ꢀAr, J = 8.85);
8.24 (d, 1 H, С(8)H, J = 7.26); 9.23 (d, 1 H, С(7)H, J = 7.26)
1615, 1680 (С=О);
1090 (Cl—O)
3.16 (s, 3 Н, N(3)Ме); 3.71 (s, 3 Н, N(1)Ме); 7.17—7.31 (m, 7 Н, Ar);
7.46—7.54 (m, 2 Н, Ar); 8.19 (d, 1 H, С(8)H, J = 7.41); 9.21 (d, 1 H, С(7)H, J = 7.33)

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Kostrub and Tsupak
The yields, melting points, and elemental analysis data for
compounds 3 and 4 are given in Table 1, their spectral characꢀ
teristics, in Table 2.
monocyclic pyrylium salts. The reaction starts from
the nucleophilic attack by the azomethine atom N on
one of the positions neighboring to the onium atom O,
which leads to the ring opening. The intermediate is transꢀ
formed to the fourꢀmembered complex by intramolecular
[2+2]ꢀcycloaddition. The latter eliminates an aldehyde
molecule to be transformed to Nꢀarylpyridinium ion 3, 4
(Scheme 3).
References
1. V. V. Kostrub, E. B. Tsupak, Yu. N. Tkachenko, M. A.
Shevchenko, Izv. Akad. Nauk, Ser. Khim., 2008, 1720 [Russ.
Chem. Bull., Int. Ed., 2008, 57, 1754].
In conclusion, it was shown that 1,3ꢀdimethylꢀ2,4ꢀ
dioxopyrano[4,3ꢀd]pyrimidinium derivatives by the reacꢀ
tion with azomethines, like monocyclic pyrylium salts,
are transformed to pyridinium salts. In contrast to benzoꢀ
[c]pyrylium salts, the salts studied by us do not give cyꢀ
cloaddition reaction with Schiff bases under analogous
conditions.
2. S. V. Verin, D. E. Tosunyan, P. I. Zakharov, V. K. Shevtsov,
E. V. Kuznetsov, Khim. Geterotsikl. Soedin., 1990, 26, 1177
[Chem. Heterocycl. Compd. (Engl. Transl.), 1990, 26, 980].
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Experimental
6. K. Ohkura, T. Ishihara, K. Nishijima, J. M. Diakur, K. Seki,
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8. E. B. Tsupak, M. A. Shevchenko, V. V. Kostrub, Yu. N.
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IR spectra were recorded on a Specord IRꢀ71 and Varian
FTꢀIR 1000 spectrophotometers in Nujol. 1H NMR spectra were
recorded on a Bruker Avance DPXꢀ250 spectrometer. TLC was
performed on aluminium oxide (Reaktiv Ltd.) with CHCl3 as an
eluent. Compounds 1 and 2 were synthesized according to the
procedures described earlier,1 azomethines, according to the
1
published procedures.10,11 In the H NMR spectra, assignment
of the signals for the protons of the methyl groups of the uracil
ring was made based on comparative analysis of the spectra
obtained by us earlier for the fused uracil derivatives.1,8,12,13
1,3ꢀDimethylꢀ2,4ꢀdioxoꢀ1H,3Hꢀpyrido[4,3ꢀd]pyrimidinium
salts 3, 4 (general procedure). A suspension of 1,3ꢀdimethylꢀ2,4ꢀ
dioxoꢀ1H,3Hꢀpyrano[4,3ꢀd]pyrimidinium salts 1, 2 (0.5 mmol)
and azomethine (0.55 mmol) in AcOH (2 mL) was heated
for 10 min, the solution was cooled, a precipitate formed
was filtered off, washed with AcOH and Et2O. If the precipiꢀ
tate of salts 3, 4 was not formed, the solution was concentrated
to dryness, rubbed with diethyl ether, filtered off, and washed
with Et2O. The salt was recrystallized from AcOH and dried
at 100 °C.
9. R. M. Silverstein, F. X. Webster, D. J. Kiemle, Spectrometric
Identification of Organic Compounds, 7th ed., Wiley, New
York, 2005, 512 p.
10. M. T. Bogert, Org. Synth., 1925, 5, 13.
11. Yu. A. Zhdanov, I. D. Sadekov, A. D. Garnovskii, V. I.
Minkin, Izv. Vuzov. Khim. Khim. Tekhnol. [Univ. Bull., Chem.
and Chem. Technol.], 1965, 8, 954 (in Russian).
12. E. B. Tsupak, M. A. Shevchenko, A. F. Pozharskii, Yu. N.
Tkachenko, Khim. Geterotsikl. Soedin., 2003, 39, 1096 [Chem.
Heterocycl. Compd. (Engl. Transl.), 2003, 39, 953].
13. E. B. Tsupak, M. A. Shevchenko, Izv. Akad. Nauk, Ser. Khim.,
2006, 2180 [Russ. Chem. Bull., Int. Ed., 2006, 55, 2265].
The formation of aromatic aldehyde Ar3CHO (see Scheme 3)
was fixed by chromatography of the residue obtained after conꢀ
centration of the filtrates of salts 3 and 4. A pure sample of the
corresponding aldehyde was used for the cospotting.
Received July 9, 2008;
in revised form February 3, 2009