- A Three-Step Pyridoannelation of Carbonyl Compounds
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The elaboration of a pyridine nucleus onto an α-methylene carbonyl compound can be accomplished through a three step reaction sequence based on the regiospecific alkylation of N,N-dimethylhydrazones with bromoethyl-1,3-dioxolane.Scope and limitations of the new method are considered.
- Marchetti, Mauro
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p. 1761 - 1765
(2007/10/02)
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- Regioselective Addition of Grignard Reagents to 1-Acylpyridinium Salts. A Convenient Method for the Synthesis of 4-Alkyl(aryl)pyridines
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The addition of Grignard reagents to 1-acylpyridinium salts afforded 1-acyl-2-alkyl(aryl)-1,2-dihydropyridines and 1-acyl-4-alkyl(aryl)-1,4-dihydropyridines.The regioselectivity of this reaction, 1,2- vs. 1,4-addition, was examined and found to be dependent upon the structures of the Grignard reagent and the 1-acyl group.Pyridine, 2-picoline, and 3-picoline were studied, and in most cases, significant amounts of 1,4-addition occurred.When a catalytic amount of cuprous iodide was present, nearly exclusive 1,4-addition resulted.The crude 1,4-dihydropyridines were aromatized by heating with sulfur to provide 4-substituted pyridines and picolines in good yield and high isomeric purity.
- Comins, Daniel L.,Abdullah, Abdul H.
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p. 4315 - 4319
(2007/10/02)
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