Categories: Synthesis of N-Heterocycles >
Synthesis of pyridines and related compounds
Name Reactions
Hantzsch Dihydropyridine (Pyridine) Synthesis
Recent Literature
Addition of Grignard reagents to pyridine N-oxides in THF at room
temperature and subsequent treatment with acetic anhydride at 120°C afforded
2-substituted pyridines in good yields. By exchanging acetic anhydride for DMF
in the second step, 2-substituted pyridine N-oxides were obtained,
enabling the synthesis of 2,6-disubstituted pyridines.
H. Andersson, F. Almqvist, R. Olsson, Org. Lett., 2007,
9, 1335-1337.
The direct conversion of amides, including sensitive N-vinyl amides,
to the corresponding trimethylsilyl alkynyl imines followed by a
ruthenium-catalyzed protodesilylation and cycloisomerization gives various
substituted pyridines and quinolines.
M. Movassaghi, M. D. Hill, J. Am. Chem. Soc.,
2006, 128, 4592-4593.
Cationic rhodium(I)/modified-BINAP complexes catalyze a chemo- and
regioselective [2+2+2] cycloaddition of a wide variety of alkynes and
nitriles leading to highly functionalized pyridines under mild reaction
conditions.
K. Tanaka, N. Suzuki, G. Nishida, Eur. J. Org. Chem., 2006,
3917-3922.
Conversion of unsaturated ketones and aldehydes derived from the
cycloisomerization of primary and secondary propargyl diynols in the presence of
[CpRu(CH3CN)3]PF6 to 1-azatrienes and a
subsequent electrocyclization-dehydration provides pyridines with excellent
regiocontrol.
B. M. Trost, A. C. Gutierrez, Org. Lett., 2007,
9, 1473-1476.
Coupling of acetylene, nitrile, and a titanium reagent generated new
azatitanacyclopentadienes in a highly regioselective manner. The subsequent
reaction with sulfonylacetylene and electrophiles gave substituted pyridines
virtually as a single isomer. Alternatively, the reaction of
azatitanacyclopentadienes with an aldehyde or another nitrile gave furans or
pyrroles having four different substituents again in a regioselective manner.
D. Suzuki, Y. Nobe, R. Tanaka, Y. Takayama, F. Sato, H. Urabe, J. Am. Chem. Soc.,
2005, 127, 7474-7479.
In the presence of activated carbon, Hantzsch 1,4-dihydropyridines and
1,3,5-trisubstituted pyrazolines were aromatized with molecular oxygen to the
corresponding pyridines and pyrazoles in excellent yields.
N. Nakamichi, Y. Kawashita, M. Hayashi, Synthesis, 2004,
1015-1020.
4-Substituted-1,4-dihydropyridines are readily and efficiently aromatized in
only one minute using commercial manganese dioxide in the absence of an
inorganic support at 100 °C under microwave irradiation. This rapid
procedure gives the dehydrogenated or 4-dealkylated product in excellent
yield.
M. C. Bagley, M. C. Lubinu, Synthesis, 2006, 1283-1288.
Hantzsch 1,4-dihydropyridines undergo smooth aromatization catalyzed by
iodoxybenzoic acid (IBX) to afford the corresponding pyridine derivatives in
high yields. All the reactions were carried out in DMSO solvent at 80-85 °C
for a period of two to four hours to complete conversion of the substrates.
J. S. Yadav, B. V. S. Reddy, A. K. Basak, G. Baishya, A. V. Narsaiah, Synthesis, 2006, 451-454.
[bmim]OH, a basic ionic liquid, efficiently promotes a one-pot condensation of
aldehydes, malononitrile, and thiophenols to produce highly substituted
pyridines in high yields. The ionic liquid can be recovered and recycled.
B. C. Ranu, R. Jana, S. Sowmiah, J. Org. Chem., 2007,
72, 3152-3154.
Pyridine N-oxides were converted to 2-aminopyridines in a one-pot fashion
using Ts2O-tBuNH2 followed by in situ deprotection
with TFA. The amination proceeded in high yields, excellent 2-/4-selectivity,
and with good functional group compatibility.
J. Yin, B. Xiang, M. H. Huffman, C. E. Raab, I. W. Davies, J. Org. Chem., 2007,
72, 4554-4557.
