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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.

A simple, modular method to prepare highly substituted pyridines in good isolated yields employs a cascade reaction comprising a novel Cu-catalyzed cross-coupling of alkenylboronic acids with α,β-unsaturated ketoxime O-pentafluorobenzoates, electrocyclization of the resulting 3-azatriene, and air oxidation.
S. Liu, L. S. Liebeskind, J. Am. Chem. Soc., 2008, 130, 6918-6919.

A single-step conversion of various N-vinyl and N-aryl amides to the corresponding pyridine and quinoline derivatives involves amide activation with trifluoromethanesulfonic anhydride in the presence of 2-chloropyridine followed by π-nucleophile addition to the activated intermediate and annulation. Compatibility of this chemistry with various functional groups is noteworthy.
M. Movassaghi, M. D. Hill, O. K. Ahmad, J. Am. Chem. Soc., 2007, 129, 10096-10097.

A range of highly functionalised pyridines is prepared from enamino and alkynones in a single synthetic step by the use of acetic acid or amberlyst 15 ion exchange resin at 50°C.
M. C. Bagley, J. W. Dale, J. Bower, Synlett, 2001, 1149-1151.

Polysubstituted pyridines are prepared in good yield and with total regiocontrol by the one-pot reaction of an alkynone, 1,3-dicarbonyl compound and ammonium acetate in alcoholic solvents. This new three-component heteroannulation reaction proceeds under mild conditions in the absence of an additional acid catalyst.
X. Xiong, M. C. Bagley, K. Chapaneri, Tetrahedron Lett., 2004, 45, 6121-6124.

Tri- or tetrasubstituted pyridines are prepared by microwave irradiation of ethyl β-aminocrotonate and various alkynones in a single synthetic step and with total control of regiochemistry. This new one-pot Bohlmann-Rahtz procedure conducted at 170°C gives superior yields to similar experiments conducted using conductive-heating techniques in a sealed tube.
M. C. Bagley, R. Lunn, X. Xiong, Tetrahedron Lett., 2002, 43, 8331-8334.

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.

A rhodium-catalyzed chelation-assisted C-H activation of α,β-unsaturated ketoximes and the reaction with alkynes affords highly substituted pyridine derivatives.
K. Parthasararathy, M. Jeganmohan, C.-H. Cheng, Org. Lett., 2008, 10, 325-328.

A convenient one-pot C-H alkenylation/electrocyclization/aromatization sequence allows the synthesis of highly substituted pyridine derivatives from alkynes and α,β-unsaturated N-benzyl aldimines and ketimines. The reaction proceeds through dihydropyridine intermediates.
D. A. Colby, R. G. Berman, J. A. Ellman, J. Am. Chem. Soc., 2008, 130, 3645-3651.

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.

A mild, efficient, and general aromatization of Hantzsch 1,4-dihydropyridines with oxygen was realized at room temperature with 5 mol % of 9-phenyl-10-methylacridinium perchlorate as photocatalyst, which could be easily recovered and reused.
X. Fang, Y.-C. Liu, C. Li, J. Org. Chem., 2007, 72, 8608-8610.

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.