Hydrogen Peroxide → 4-n-Propyl-2-butyl-pyridine

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4-n-propyl-pyridine was prepared by alkylation of 4-picoline with sodium amide suspended in liquid ammonia and ethyl iodide, as described in Vogel's Textbook of Practical Organic Chemistry, Fourth Edition, p 903. It was obtained in good yield (77%). 2-cyano-4-n-propyl-pyridine was obtained from 4-n-propyl-pyridine following the procedure described by Shuman et al. [An Improved Synthesis of Homoproline and Derivatives Robert T. Shuman, Paul L. Ornstein, Jonathan W. Paschal, and Paul D. Gesellchen, J. Org. Chem. 1990, 55, 738-741]. In a first step, 4-n-propyl-pyridine (1 eq.) was converted into 4-n-propyl-pyridine N-oxide in glacial acetic acid, 30% hydrogen peroxide (1 eq.). Then, 4-n-propyl-pyridine N-oxide was converted into 2-cyano-4-n-propyl-pyridine in good yield (72%) with a modification of the Reissert-Henze reaction, reported by Fife [Fife, W. K. J. Org. Chem. 1983, 48, 1375.] 1-(4-propylpyridine-2-yl)pentan-1-one was obtained by treating the pyridyl cyanide with a small excess of the corresponding butyl magnesium iodide, as described by Teague et al. [Some Pyridylhydantoins P. C. Teague; A. R. Ballentine, G. L. Rushton J. Am. Chem. Soc 1953, 75, 3429-3430]. The ketone was separated from the reaction mixtures by extraction with chloroform, and obtained in relatively good yield (60%). 4-n-propyl-2-butyl-pyridine was obtained in high yield (85%) by a modified Wolff-Kishner reduction, as described by Huang-Minlon [A Simple Modification of the Wolff-Kishner Reduction, Huang-Minlon J. Am. Chem. Soc 1946, 68, 2487-2488].

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