| 摘要 |
A novel process for producing 2,3,5-trichloropyridine is described. In this process, 2,3,4,5-tetrachloropyridine is reacted, in an alkanephosphonic acid dialkyl ester (dialkyl alkane phosphonate) having 1 to 4 carbon atoms in each of the alkyl groups or in a phosphoric acid trialkyl ester (trialkyl phosphate) having 1 to 4 carbon atoms in each of the alkyl groups as the solvent, at 60 DEG to 120 DEG C., in the presence of 1.4 to 2.8 mols, per mol of 2,3,4,5-tetrachloropyridine, of an ammonium salt of an inorganic or organic acid, with 1.2 to 1.6 gram atoms of zinc per mol of 2,3,4,5-tetrachloropyridine, the 2,3,4,5-tetrachloropyridine being selectively dechlorinated in the 4-position. 2,3,5-Trichloropyridine is a valuable intermediate for producing herbicidally effective alpha -[4-(3',5'-dichloropyrid-2-yloxy)-phenoxy-]-alkanecarboxylic acids and derivatives thereof. There are also described novel ammonium salts of methanephosphonic acid monomethyl ester, in the presence of which salts the selective dechlorination of 2,3,4,5-tetrachloropyridine in the 4-position is advantageously performed.
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