Synthesis of condensed mesoionic heterocycles. Intramolecular cyclization of 3-acetonyl(phenacyl)-1,2,3-triazolium-5-olates [3]

Full text of DOI:10.1007/s10593-006-0103-5

Chemistry of Heterocyclic Compounds, Vol. 42, No. 3, 2006
SYNTHESIS OF CONDENSED MESOIONIC
HETEROCYCLES. INTRAMOLECULAR CYCLIZATION
OF 3-ACETONYL(PHENACYL)-1,2,3-TRIAZOLIUM-5-OLATES
Yu. I. Nein, E. A. Savel'eva, Yu. A. Rozin, V. A. Bakulev, and Yu. Yu. Morzherin
Keywords: nitrogen-containing mesoionic heterocycles, pyrazine, 1,2,3-triazole, alkylation reactions,
condensation.
There are several known approaches to synthesis of monocyclic mesoionic heterocycles [1]. At the same
time, the number of examples of mesoionic condensed zwitterionic heterocycles is quite limited [2]. Earlier we
proposed a novel method for synthesis of zwitterionic 1,2,3-triazolopyrazines and -triazepines [3, 4]. In this
work, we have shown that in contrast to 3-cyanomethyl-1,2,3-triazolium-5-olates [3], in the presence of basic
reagents 3-acetonyl(phenacyl)-1,2,3-triazolium-5-olates 1a,b do not undergo ring closure to form
triazolopyrazines 2 but rather form the corresponding enolates 3a,b. We have observed that upon treatment with
polyphosphoric acid, intramolecular condensation of the carbonyl and amide moieties of the triazole molecule 1
occurs and [1,2,3]triazolo[1,5-a]pyrazines 2a,b are formed. Under similar conditions, 3-cyanomethyl-1,2,3-
triazolium-5-olates are converted to the starting 5-hydroxy-1,2,3-triazoles 4. Thus we propose a novel method
for synthesis of mesionic [1,2,3]triazolo[1,5-a]pyrazines.
O
H
O
H
N
N
R2
O
+
N
R2
OH
HalCH2COR3
Na2CO3, DMF
–
N
N
R3
O
N
N
N
R1
R1
1a,b
4
H3PO4
EtONa
∆
R2
N
R3
+
Na
O
H
O
N
–
R2
O
+
N
+
N
–
–
O
O
R3
N
N
N
N
R1
R1
3a,b
2a,b
1–3 a R1 = R2 = C6H4OMe-4, R3 = Me, b R1 = N=CHC6H4Me-4, R2 = Me, R3 = C6H4Cl-4
__________________________________________________________________________________________
Ural State Technical University, Ekaterinburg 620002, Russia; e-mail: morzherin@htf.ustu.ru.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 462-463, March, 2006. Original article
submitted January 24, 2006.
412
0009-3122/06/4203-0412©2006 Springer Science+Business Media, Inc.

1
The H and 13C NMR spectra were obtained on a Bruker DRX-400 (400 MHz and 100 MHz) in
DMSO-d6, internal standard TMS. The mass spectra were recorded on a MAT11 (electron impact, 70 eV).
6-Methyl-2,5-di(4-methoxyphenyl)-4-oxo-2H-[1,2,3]triazolo[1,5-a]pyrazinium-3-olate
(2a).
Compound 1a (0.20 g, 0.6 mmol) [5] in orthophosphoric acid (5 ml) was heated at 100°C in a glycerol bath until
completely dissolved and then for another 3 h. The solution was cooled down and diluted with water (25 ml) at
0°C, the precipitate was filtered out and the reaction product was crystallized from alcohol. Yield 0.16 (80%);
1
mp 287-288°C. Mass spectrum, m/z (Irel, %): 378 [M]+ (42). H NMR spectrum, δ, ppm (J, Hz): 8.03 (2H, d,
J = 7.9, ArH); 7.50 (4H, d, J = 7.9, ArH); 7.38 (4H, d, J = 7.7, ArH); 7.03 (1H, s, H-7); 6.82 (1H, d, J = 7.7,
ArH); 3.98 (3H, s, OMe); 3.92 (3H, s, OMe); 2.42 (3H, s, Me). Found, %: N 14.59. C20H18N4O4. Calculated, %:
N 14.81.
6-(4-Chlorophenyl)-5-methyl-2-(4-methylbenzylideneamino)-4-oxo-2H-[1,2,3]triazolo[1,5-a]-
pyrazinium-3-olate (2b) was obtained analogously from compound 1b [4]. Yield 88%; mp 226-230°C. Mass
spectrum, m/z (Irel, %): 395 (14), 393 [M]+ (43). 1H NMR spectrum, δ, ppm (J, Hz): 2.41 (3H, s, CH3); 7.29 (2H,
d, J = 8.1, ArH); 7.47 (1H, s, H-7); 7.57 (4H, t, J = 8.8, ArH); 7.78 (2H, d, J = 8.1, ArH); 9.35 (1H, s, N=CH).
13C NMR spectrum, δ, ppm (J, Hz): 21.2 (q, J = 124.0, CH3), 31.7 (q, J = 142.0, NCH3), 105.4 (d, J = 201.6,
C(7)), 108.6 (d, J = 4.0, C(3a)), 128.4 (d, J = 169.0, Carom), 129.9 (d, J = 165.6, Carom), 129.7 (m, Carom), 129.9 (m,
Carom), 130.0 (d, J = 167.7, Carom), 131.1 (d, J = 168.7, Carom), 135.1 (m, Carom), 140.2 (m, C(6)), 142.4 (m, Carom),
150.2 (s, C(3)), 153.4 (d, J = 166.0, N=CH), 154.2 (s, C(4)). Found, %: C 60.85; H 4.01; N 17.45. C20H16ClN5O2.
Calculated, %: C 61.00; H 4.09; N 17.78.
This research was carried out with the financial support of the Russian Foundation for Fundamental
Research (grant 04-03-96116-p2004urala).
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