ISSN 1070-4280, Russian Journal of Organic Chemistry, 2014, Vol. 50, No. 7, pp. 1066–1067. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © A.S. Bunev, V.E. Statsyuk, G.I. Ostapenko, P.P. Purygin, 2014, published in Zhurnal Organicheskoi Khimii, 2014, Vol. 50, No. 7,
pp. 1081–1082.
SHORT
COMMUNICATIONS
Boger Synthesis of 2-Azolyl-Substituted Pyridines
A. S. Bunev, V. E. Statsyuk, G. I. Ostapenko, and P. P. Purygin
Togliatti State University, ul. Belorusskaya 14, Togliatti, 445667 Russia
e-mail: a.s.bunev@gmail.com
Received November 15, 2013
DOI: 10.1134/S1070428014070264
We previously demonstrated the possibility for syn-
thesizing hitherto unknown 3-azolyl-1,2,4-triazines
from readily accessible azole-1-carboxamidrazones
and 1,2-diketones [1, 2]. In continuation of our studies
on the synthetic potential of azole-1-carboxamid-
razones, we have synthesized 2-azolylpyridines IIIa
and IIIb by the Boger reaction [3, 4]. In the first step,
amidrazones Ia and Ib reacted with a 40% solution of
glyoxal in methanol at room temperature to produce
1,2,4-triazines IIa and IIb in 86 and 90% yield,
respectively. Triazines IIa and IIb were then brought
into the Boger reaction with norbornadiene, and we
succeeded in isolating azolylpyridines IIIa and IIIb
from the reaction mixtures. Although several synthetic
approaches to azolylpyridines have been reported
[5–7], they require the use of metal-containing cata-
lysts, and the isolation procedure is relatively complex.
The procedure described by us ensures preparation of
azolylpyridines in two steps with good yields without
chromatographic purification.
cumene was heated for 15 h under reflux. The mixture
was then evaporated on a rotary evaporator, the residue
was dissolved in 70 mL of ethyl acetate–hexane (1:5),
the solution was filtered through a layer of silica gel,
the filtrate was evaporated, and the residue was recrys-
tallized from a minimum volume of ethyl acetate–
hexane (1:1).
2-(1H-Imidazol-1-yl)pyridine (IIIa). Yield 1.03 g
(71%), mp 38–39°C; published data [9]: mp 37–39°C.
IR spectrum, ν, cm–1: 2784–2738, 1617, 1528, 1326,
1
1177, 828. H NMR spectrum, δ, ppm: 8.52 t (1H, Py,
J = 1.2 Hz), 8.47 d.d.d (1H, Py, J = 4.9, 1.9, 0.8 Hz),
8.01–7.92 m (2H, Im, Py), 7.82–7.76 m (1H, Im),
7.35 d.d.d (1H, Py, J = 7.4, 4.9, 0.9 Hz), 7.13–7.09 m
(1H, Im). 13C NMR spectrum, δC, ppm: 148.9, 148.6,
139.7, 134.9, 130.0, 122.3, 116.5, 112.7. Found, %:
C 66.23; H 4.90; N 28.91. C8H7N3. Calculated, %:
C 66.19; H 4.86; N 28.95.
1-(Pyridin-2-yl)-1H-benzimidazole (IIIb). Yield
1.43 g (73%), mp 60–61°C. IR spectrum, ν, cm–1:
2866–2749, 1621, 1481, 1305, 1247, 1195, 811.
1H NMR spectrum, δ, ppm: 8.64–8.61 m (1H, BIm),
8.61 s (1H, BIm), 8.10–8.06 m (1H, BIm), 7.94–
7.86 m (2H, Py, BIm), 7.60 d (1H, Py, J = 8.2 Hz),
7.43–7.34 m (2H, Py, BIm), 7.31 d.d.d (1H, Py, J =
Amidrazones Ia and Ib were synthesized as
described in [2, 8], and 1,2,4-triazines IIa and IIb, as
described in [1].
A mixture of 10 mmol of 1,2,4-triazine IIa or IIb
and 1 mL (10 mmol) of norbornadiene in 50 mL of
13
Ht
7.4, 4.9, 7.4 Hz). C NMR spectrum, δC, ppm: 149.9,
N
Ht
MeOH
149.5, 144.5, 141.3, 138.9, 131.1, 132.1, 124.2, 123.3,
121.8, 120.6, 114.4, 112.7. Found, %: C 73.88; H 4.69;
N 21.57. C12H9N3. Calculated, %: C 73.83; H 4.65;
N 21.52.
O
+
H2N
N
O
N
N
NH2
Ia, Ib
IIa, IIb
The IR spectra were recorded in KBr on an FSM-
13
, i-PrPh, 150°C
1201 spectrometer. The 1H and C NMR spectra were
N
Ht
obtained on a Bruker AM-400 instrument at 400 and
100 MHz, respectively, using DMSO-d6 as solvent and
tetramethylsilane as internal reference. The elemental
analyses were obtained on a Vario El Cube analyzer.
IIIa, IIIb
Ht = 1H-imidazol-1-yl (a), 1H-benzimidazol-1-yl (b).
1066
Bunev
