[Cl:1][C:2]1[N:7]=[C:6]([Cl:8])[C:5]([Cl:9])=[C:4](Cl)[C:3]=1[Cl:11].O>[Cl-].C[N+](C)(C)C.CC(C)P([O-])(=O)[O-].[Zn]>[Cl:8][C:6]1[C:5]([Cl:9])=[CH:4][C:3]([Cl:11])=[C:2]([Cl:1])[N:7]=1A suspension of 8.22 g (0.075 mol) of tetramethylammonium chloride in 90 ml of dimethylmethanephosphonate is heated for 1 hour at 160° C. It is then cooled to 90° C., and 12.57 g (0.05 mol) of pentachloropyridine and 3 ml of water are added. There is subsequently added portionwise, in the course of 30 minutes, 4.1 g (0.063 gram atom) of zinc dust. After completion of the addition of the zinc dust, the mixture is firstly stirred for 20 minutes and then filtered. The filtrate is poured into a solution of 12.5 ml of concentrated hydrochloric acid in 500 ml of water, and stirring is maintained for 2 hours. After filtration, the filter residue is washed with water and dried to yield 9.1 g (83.9% of theory) of crude 2,3,5,6-tetrachloropyridine which has a melting point of 88° to 89° C. and which contains, according to gas-chromatographical analysis, 91.25% of 2,3,5,6-tetrachloropyridine, 2.66% of 2,3,5-trichloropyridine, 2.59% of 2,3,6-trichloropyridine and 0.5% of pentachloropyridine.
Wird geladen…
