2,4-Dichloro-3,5,6-trimethylpyridine → 4-Chloro-2,3,5-trimethylpyridine

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Reaction Steps

200 g 4,6-dichloro-2,3,5-trimethylpyridine dissolved in 300 ml ethanol and 40 ml conc. sulphuric acid. 2 g 10% Pd/C was used as catalyst. The hydrogen pressure was 2 bar and the hydrogenation was stopped when 1 equivalent of hydrogen had been consumed. After evaporation of alcohol and dilution with water and adjustment of pH to 2.1 the water was extracted with toluene. The toluene contains all starting material and 6-chloro-2,3,5-trimethylpyridine and the water phase 4-chloro-2,3,5-trimethylpyridine and 2,3,5-trimethylpyridine. The pH of the water phase is adjusted to 4.6 and extracted with toluene (3x100 ml). All 4-chloro-2,3,5-trimethylpyridine is in the toluene layer and the 2,3,5-trimethylpyridine in the water. Evaporation of the toluene gave 4-chloro-2,3,5-trimethylpyridine in 78% yield (liquid). NMR: 2×3H, 2,3; 3H, 2,5(s); 1H, 8,25(s). (CDCl3)

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