- Tetrahydropyrido[d]pyridazinones - Promising scaffolds for drug discovery
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An approach to the synthesis of all possible tetrahydropyrido[d] pyridazinones has been developed. The method relies on the catalytic hydrogenation of the corresponding aromatic counterparts, which were obtained by cyclization of the relevant dibromomethyl-substituted pyridinecarboxylates with hydrazine. The synthetic schemes include 4-5 steps starting from commercially available materials. The tetrahydropyrido[d]pyridazinone scaffolds are combinations of a saturated heterocycle (piperidine) and a privileged aromatic heterocycle (pyridazinone); hence they are promising starting points for the design in medicinal chemistry.
- Yaremenko, Anatoliy G.,Volochnyuk, Dmitriy M.,Shelyakin, Vyacheslav V.,Grygorenko, Oleksandr O.
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p. 6799 - 6803
(2013/07/26)
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- Regioselective addition of Grignard reagents to the 1-phenoxycarbonyl salts of alkyl nikotinates
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The addition of Grignard reagents to the 1-phenoxycarbonyl salts of alkyl nicotinates affords substituted 1,2- and 1,4-dihydropyridines.The crude dihydropyridines were aromatized with o-chloranil or sulfur to give 6-and 4-substituted alkyl nicotinates.The regioselectivity of this two-step process, 6- vs. 4- substitution, was examined and found to be dependent upon the structure of the Grignard reagent.When a catalytic amount of cuprous iodide is present during the Grignard reaction, nearly exclusive 1,4- addition results.The crude 1,4-dihydropyridines were aromatized with sulfur to provide 4-substituted methyl nicotinates in moderate yield and high isomeric purity.
- Comins, Daniel L.,Stroud, Eric D.,Herric, James J.
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p. 151 - 157
(2007/10/02)
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- Multiple Paths for Photo-alkylation and -alkoxylation of 3-Pyridinecarboxylic Ester in Alcohol. Simultaneous Contribution of Several Kinds of Excited States
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UV-irradiation of methyl 3-pyridinecarboxylate (1) in acidic alcoholic solutions brings about the alkoxylation and alkylation at the pyridine ring.Photoalkylation occurs in several paths: 1) alkylation initiated by the triplet ?-?* state, 2) alkylation initiated by the triplet n-?* state of the carbonyl moiety of the ester group, 3) alkylation initiated by exciplex between a free base form of 1 and a pyridinium form of 1, and 4) alkylation promoted by chloride ions.Photoalkoxylation originates from a singlet excited state of 1.In the photoreactions of 1 in strongly a cidic methanolic solutions acidified with H2SO4, three kinds of excited states (two kinds of triplet states for alkylation and a singlet state for alkoxylation) contribute simultaneously.
- Sugimori, Akira,Tobita, Etsuo,Kumagai, Yasuyuki,Sato, Gen P.
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p. 1761 - 1766
(2007/10/02)
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- MULTIPLE PATHS FOR PHOTOALKYLATION OF PYRIDINECARBOXYLIC ESTERS IN ALCOHOLS
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Photochemical substitution of ring hydrogen of pyridinecarboxylic esters by alkyl groups derived from solvent alcohols occurs in several paths: 1) alkylation initiated by excited carbonyl moiety of the ester group and 2) alkylation initiated by the excitation of the ?-electronic system of the pyridine ring.In the photoreaction of methyl 3-pyridinecarboxylate in acidic methanol, three types of excited state (two triplet states for alkylation and a singlet state for alkoxylation) contribute simultaneously.
- Sugiyama, Toru,Tobita, Estuo,Takagi, Kyoko,Sato, Michitsugu,Kumagai, Yasuyuki,et al.
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p. 131 - 134
(2007/10/02)
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