- Access to 2-Aminopyridines - Compounds of great biological and chemical significance
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2-Aminopyridines are key structural cores of bioactive natural products, medicinally important compounds, and organic materials and thus, extremely valuable synthetic targets. The few reported 6-substituted 2-aminopyridines and the lack of flexible, efficient and general applicable methods for their synthesis demonstrates the urgent need of new methods for their preparation. Reactions between 2,6-dibromopyridine and primary or secondary, cyclic or acyclic, and aliphatic or aromatic amines were shown to selectively yield the respective 6-bromopyridine-2-amines in very high yields which were successfully used as substrates for subsequent C-C cross-coupling reactions. The recently introduced dichloro-bis[1-(dicyclohexylphosphanyl)piperidine]palladium (1) was used as catalyst for the cross-coupling of 6-bromopyridine-2-amines with arylboronic acids, diaryl- and dialkylzinc reagents or olefins and hence, is also an excellent C-C cross-coupling catalyst for this type of substrate. Moreover, all the reaction protocols presented were in each of the catalyses uniformly applied. The scope of both the amination and the cross-coupling reactions are well defined and allow one to simply adapt the reaction protocols directly to other amines and/or coupling partners and, thus, provide for the first time a very flexible and generally applicable reaction protocol to get access to 2-aminopyridines.
- Bolliger, Jeanne L.,Oberholzer, Miriam,Frech, Christian M.
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p. 945 - 954
(2011/06/19)
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- Reaction of Aromatic N-Oxides with Dipolarophiles. V. 1,3-Cycloaddition of 2-Substituted Pyridine N-Oxides with Phenyl Isocyanates
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The reaction of 2,3-lutidine N-oxide (I) with phenyl isocyanate (IIa) in dimethylformamide at 110 deg C gave a 1:2 adduct (IIIa).Under reflux in ethanolic potassium hydroxide, IIIa readily lost a component of IIa and was converted to 5-methyl-6-N-phenylca
- Hisano, Takuzo,Matsuoka, Toshikazu,Fukunaga, Kazuhiro,Ichikawa, Masataka
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p. 3776 - 3781
(2007/10/02)
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