摘要:
2,3,5,6-Tetrachloropyridine, and 2,3,6-tricholoro-5-(trichloromethyl)pyridine are prepared by selectively chlorinating polychlorinated β-picolines in the vapor phase between 250°C and 450°C in the presence of specific Lewis acid halide catalysts on an inorganic support. The gamma-position on the pyridine ring is usually not chlorinated in the starting material or reaction products. These compounds are useful intermediates to produce insecticides and herbicides.