反应详情

2-Methylpyridine of general structure III is prepared by α-methylation of substituted pyridine II using the method of Kray and Reinecke (J. Am. Chem. Soc., 1964, 86, 5355). Oxidation with m-chloroperbenzoic acid gives substituted 2-methylpyridine N-oxide IV. Treatment of the latter with phosphoryl chloride gives the 2-chloromethyl substituted pyridine VII. Alternatively, refluxing IV in acetic anhydride gives the 2-(acetoxymethyl) pyridine VII which is hydrolysed with aqueous base to the corresponding alcohol VII. When this hydroxymethyl derivative is treated with methanesulfonyl chloride in the presence of triethylamine, the 2-(methanesulfonyloxymethyl)pyridine is obtained, whereas treatment with brominetriphenylphosphine gives the 2-(bromomethyl)pyridine VII. When either the bromomethyl, chloromethyl, or the mesyloxymethyl pyridine derivative VII is refluxed in acetonitrile in the presence of triphenylphosphine, the corresponding phosphonium salt VIII is formed.