SELECTIVE GASEOUS PHASE CHLORINATION OF POLYCHLORINATED BETA-PICOLINES TO PRODUCE 2,3,5,6-TETRACHLOROPYRIDINE AND ITS PRECURSOR

摘要

PURPOSE: To obtain 2,3,5,6-tetrachloropyridine useful as an intermediate for the synthesis of an insecticide and a herbicide in a good yield by subjecting a specified starting compd. to selective gaseous phase chlorination in the presence of a Lewis acid catalyst carried on an inorg. carrier. ;CONSTITUTION: Starting polychloropicoline of formula I (X and X' are each H or Cl, but X' is not Cl when Y in a polychlorinated product is H) or a mixture of such polychloropicolines is brought into contact with chlorine in the gaseous phase at 250-45°C, preferably 340-380°C in the presence of a Lewis acid catalyst carried on an inorg. carrier and, optionally, of a gaseous inert diluent, preferably N₂ or carbon tetrachloride to obtain 2,3,5,6-tetrachloropyridine or a polychlorinated picoline product of formula II (Y is H or Cl). The carrier is preferably activated carbon and the Lewis acid catalyst is preferably a Lewis acid halide such as zinc chloride. The reaction pressure is preferably from atmospheric pressure to 50 psig and the reaction time is preferably 1-10 sec.;COPYRIGHT: (C)1994,JPO