Synthesis of bipyridyls
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
255
m.p. 63—65 °C). 1H NMR spectrum agrees with that given in
Ref. 10. Found (%): C, 77.06; H, 5.09; N, 17.85. C10H8N2.
Calculated (%): C, 76.90; H, 5.16; N, 17.94.
nated triazines form dihydrotriazines 5a,b. Elimination of
the proton gives dihydrotriazines 6a,b. The ring opening
in compounds 6a,b under the action of acid leads to
cations 7a,b, the intramolecular electrophilic addition
of which results in the formation of intermediates 8a,b.
The latter eliminate the amidine molecule to afford
products 3a,b.
In conclusion, the system of the reagents is efficient
not only for the periꢀannulation of the pyridine ring to
azaphenalenes, but also for the synthesis of 3ꢀsubstituted
pyridines.
2,6ꢀDimethylꢀ3,4´ꢀbipyridyl (3d). The yield was 0.059 g
1
(32%). Yellow oil. H NMR (CDCl3), δ: 2.43 (s, 3 H, Me(6));
2.45 (s, 3 H, Me(2)); 7.32 (d, 1 H, H(5), J = 7.9 Hz); 7.49 (d,
2 H, H(3´), H(5´), J = 4.9 Hz); 7.84 (d, 1 H, H (4), J = 7.9 Hz);
8.69 (d, 2 H, H(2´), H(6´), J = 4.9 Hz). Found (%): C, 78.35;
H, 6.51; N, 15.14. C12H12N2. Calculated (%): C, 78.23; H, 6.57;
N, 15.20.
References
1H NMR spectra were recorded on a Bruker WPꢀ200
spectrometer (200 MHz); Me4Si was used as the internal
standard. 1,3,5ꢀTriazine was purchased from Aldrich. 2,4,6ꢀTriꢀ
methylꢀ1,3,5ꢀtriazine was obtained by known procedure,6
allylpyridines were obtained by the procedure reported earlier.7
Synthesis of bipyridyls 3a—d (general procedure). A mixture
of the corresponding allylpyridine (2a,b) (0.119 g, 1 mmol), the
corresponding triazine (1.2 mmol), and PPA (3—4 g) was
vigorously stirred at 55—60 °C for 1 h, then at 120—130 °C for
7 h. The reaction mixture was cooled, poured in cold water
(30 mL) with stirring, made basic with aqueous ammonia to
рH ~8, saturated with potash, extracted with ethyl acetate
(6×50 mL). The solvent was evaporated. The residue was
separated by chromatography (eluent, dichloromethane).
2,3´ꢀBipyridyl (3a). The yield was 0.064 g (41%). Colorless
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1
oil (Ref. 8 data: oil). H NMR spectrum agrees with that given
in Ref. 8. Found (%): C, 77.08; H, 5.11; N, 17.81. C10H8N2.
Calculated (%): C, 76.90; H, 5.16; N, 17.94.
2´,6´ꢀDimethylꢀ2,3´ꢀbipyridyl (3b). The yield was 0.061 g
(33%). Yellow oil. 1H NMR (CDCl3), δ: 2.42 (s, 3 H, Me(6´));
2.46 (s, 3 H, Me(2´)); 7.27 (d, 1 H, H (5´), J = 7.9 Hz); 7.39
(dd, 1 H, H (5), J = 7.9 Hz, J = 4.9 Hz); 7.54 (d, 1 H, H (3),
J = 7.9 Hz); 7.59 (t, 1 H, H (4), J = 7.9 Hz); 8.21 (d, 1 H,
H (4´), J = 7.9 Hz); 8.89 (d, 1 H, H (6), J = 4.9 Hz). Found (%):
C, 78.39; H, 6.49; N, 15.12. C12H12N2. Calculated (%):
C, 78.23; H, 6.57; N, 15.20.
3,4´ꢀBipyridyl (3c). The yield was 0.069 g (44%).
Received July 18, 2008;
M.p. 62—64 °C (from light petroleum) (Ref.
9 data:
in revised form November 10, 2008