Reaction of 3-cyanochromones with pyridinium phenacylide

Full text of DOI:10.1007/s10593-013-1175-7

Chemistry of Heterocyclic Compounds, Vol. 48, No. 10, January, 2013 (Russian Original Vol. 48, No. 10, October, 2012)
REACTION OF 3-CYANOCHROMONES
WITH PYRIDINIUM PHENACYLIDE
M. Yu. Kornev1, V. S. Moshkin1, O. S. El'tsov1, and V. Ya. Sosnovskikh1*
Keywords: betaines, 3-cyanochromones, pyridinium phenacylide, nucleophilic 1,4-addition.
The reaction of 3-cyanochromones with N- and C-nucleophiles begins with an attack at C-2 atom with
subsequent opening of the γ-pyrone ring and recyclization at the C=O or C≡N groups [1-3]. Nucleophilic
1,2-addition at the cyano group usually does not occur [1], while the reactions with aromatic amines [4] and
methylenetriphenylphosphorane (Ph3P=CH2) [5] terminate at the stage of open products 1 and 2. Since the
assumption of a number of workers of possible addition of nucleophiles at the cyano group was subsequently
shown to be incorrect [1], the reports in the literature on the synthesis of azirines 3a,b from the corresponding
3-cyanochromones 4a,b and pyridinium phenacylide [6] are cast in doubt and require verification.
We have found that 3-cyanochromone 4a and 3-cyano-6-methylchromone 4b react with
phenacylpyridinium bromide in the presence of one or two equivalents of potassium carbonate in acetone at
reflux over 8 h, analogously to phophorus ylide Ph3P=CH2, i.e., through Michael addition of pyridinium
phenacylide formed in situ with subsequent opening of the pyrone ring to give highly stable ylides 5a,b in 72-
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77% yield. The structure of these ylides was confirmed by IR, H NMR, and C NMR spectroscopy. Heating
ylide 5a at reflux in glacial acetic acid for 2 h gives the starting 3-cyanochromone 4a. Under conditions
described for the preparation of azirines 3a,b using four equivalents of potassium carbonate [6], we isolated
only a complex, intractable mixture. Products of addition at the CN group, namely, azirines 3a,b, could not be
detected despite variation of the conditions. 1,3-Dipolar cycloaddition at the double bond of the pyrone ring
leading to indolizines [7] was also not observed.
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The signals in the H and C NMR spectra were assigned on the basis of 2D H-13C HSQC, HMBC,
and H-1H COSY experiments in the case of betaine 5a. The most informative cross peaks in the 2D HMBC
spectrum in DMSO-d6 are H-6'/C-5, H-3'/C-5, H-3/C-5, H-3/C-4, and H-3/CN. The singlet for H-3 proton is
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*To whom correspondence should be addressed, e-mail: vyacheslav.sosnovskikh@usu.ru.
1Ural Federal University named after the First President of Russia B. N. Yeltsin, 51 Lenina Ave.,
Yekaterinburg 620000, Russia.
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Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1678-1680, October, 2012.
Original article submitted September 18, 2012.
0009-3122/13/4810-1565©2013 Springer Science+Business Media New York
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found at 7.85 ppm, while the broadened signal for the phenol proton is at 9.80-10.80 ppm. The upfield dublet
for H-6' proton points to an absence of intramolecular hydrogen bonding in the salicyloyl fragment, which
results in phenyl ring deviation from the molecular plane [4]. The IR spectra of betaines 5a,b show absorption
bands for the C≡N group at 2172-2183 cm-1 and two C=O groups at 1608-1580 cm-1, indicating extensive
delocalization of negative charge (for comparison, this band is at 1661 cm-1 for the chromone 4a and 1614 cm-1
for the ylide 2 [5]).
The IR spectra were recorded on a Bruker Alpha spectrometer with an ATR attachment (ZnSe crystal).
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The H and 13C NMR spectra were recorded on a Bruker Avance II spectrometer (400 and 100 MHz,
respectively) in DMSO-d6 with TMS as internal standard. The elemental analysis was carried out on an
automatic PE 2400 analyzer. The melting points were determined on an FP 62 instrument.
4-Cyano-5-(2-hydroxyphenyl)-1,5-dioxo-2-(pyridinium-1-yl)-1-phenylpent-3-en-2-ide
(5a).
A
mixture of 3-cyanochromone 4a (300 mg, 1.75 mmol), phenacylpyridinium bromide (490 mg, 1.76 mmol), and
anhydrous potassium carbonate (490 mg, 3.50 mmol) in dry acetone (100 ml) was heated at reflux for 8 h. The
orange recipitate formed was filtered off, washed with acetone and water, and dried. Yield 480 mg (72%). Yellow
crystals; mp 215-216°С (decomp.). IR spectrum, ν, cm-1: 2172, 1608, 1581, 1564, 1512, 1481. 1H NMR spectrum, δ,
ppm (J, Hz): 6.72 (1Н, t, J = 7.5, Н-5'); 6.80 (1Н, d, J = 8.2, Н-3'); 7.16 (1Н, td, J = 7.6, J = 1.5, Н-4'); 7.23 (1Н, d,
J = 7.5, Н-6'); 7.42-7.57 (3Н, m, H-3''',4''',5'''); 7.58-7.62 (2Н, m, H-2''',6'''); 7.85 (1Н, s, Н-3); 8.23 (2Н, t, J = 7.2,
Н-3'',5''); 8.69 (1Н, t, J = 8.0, Н-4''); 9.05 (2Н, d, J = 5.3, Н-2'',6''); 9.80-10.80 (1Н, br. s, ОН). 13C NMR spectrum, δ,
ppm: 116.4 (C-3'); 118.3 (C-5'); 119.0 (CN); 121.1 (C-2); 123.0 (C-4); 125.8 (C-1'); 127.8 (C-3'',5''); 128.2 (C-2''',6''');
128.3 (C-3''',5'''); 128.5 (C-6'); 130.5 (C-4'''); 131.1 (C-4'); 138.5 (C-1'''); 144.0 (C-3); 146.2 (C-4''); 149.1 (C-2'',6'');
155.8 (C-2'); 185.8 (C-1); 189.4 (C-5). Found, %: С 72.82; Н 4.34; N 7.34. C23H16N2O3·0.5H2O. Calculated, %:
C 73.20; H 4.54; N 7.42.
4-Cyano-5-(2-hydroxy-5-methylphenyl)-1,5-dioxo-1-phenyl-2-(pyridinium-1-yl)pent-3-en-2-ide (5b) was
obtained analogously to betaine 5a. Yield 0.88 g (77%). Yellow crystals; mp 209-211°С (decomp.). IR
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spectrum, ν, cm-1: 2183, 1605, 1580, 1564, 1514, 1494, 1473. H NMR spectrum, δ, ppm (J, Hz): 2.17 (3H, s,
СН3); 6.66 (1H, d, J = 8.2, Н-3'); 6.99 (1H, d, J = 8.2, Н-4'); 7.30 (1H, s, Н-6'); 7.43-7.53 (3H, m, H-3''',4''',5''');
7.62 (2H, d, J = 6.5, H-2''',6'''); 7.99 (1H, s, Н-3); 8.23 (2H, t, J = 6.7, Н-3'',5''); 8.68 (1H, t, J = 7.8, Н-4''); 8.97
(2H, d, J = 5.3, Н-2'',6''); 10.65 (1H, br. s, ОН). Found, %: С 73.90; Н 4.55; N 7.12. C24H18N2O3·0.5H2O.
Calculated, %: C 73.64; H 4.89; N 7.16.
This research was carried out with the financial support of young scientists at the Ural Federal
University within the development program of this university.
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