Alkylpyridines nitration

Chlorination and bromination of pyridine and some alkylpyridines in the (3-position can be effected in the liquid phase at 100°C using excess AlCl3as catalyst. -Bromination of pyridine and 2- and 4-picoline is conveniently effected in oleum at 80-120°C. Bromination kinetics using HOBr in aqueous HC104 indicate that the partial rate factor for bromination of the pyridinium cation is 10 13, comparable to that for nitration. 

Alkylpyridines (picolines, and especially lutidines) can be nitrated much more readily, as Plazek [75] has shown. Introduction of the nitro group is greatly facilitated by the presence of the hydroxyl group in the pyridine ring. For example, 3-hydroxypyridine can be nitrated to 2-nitro-3-hydroxypyridine in good yield (Plazek and Rodewald [76]). It may be further nitrated to the dinitro derivative. From this, 3,5-dinitropyridine can be obtained (Plazek [77]). 

A number of publications also describe the air oxidation of the same pyridine substrates in the presence of cupric nitrate. Extensive work has also been reported on the fixed or fluidized bed vapor phase of alkylpyridines using vanadium catalysts. " The intermediate aldehydes can be isolated, but usually the conditions are set to minimize this side reaction. Vanadates, molybdates, and tin salts of these two oxyacids are also described as efTective catalysts in the high temperature oxidation of quinolines and isoquinolines. " ... 

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