Polyhalogeno-aromatic compounds. Part XXII. Some reactions of tetrachloro-4-methylsulphonylpyridine and related compounds

Abstract

Tetrachloro-4-methylsulphonylpyridine (1a) reacted with small nucleophiles (e.g. NaCN, NaOH, NaOMe, and MeNH₂) by exclusive displacement of the methylsulphonyl group, with NN-dimethylamine by exclusive substitution in the 2-position, and with pyrrolidine by preferential substitution in the 2-position. With lithium aluminium hydride, compound (1a) gave a mixture of 2,3-dichloro-4-methylthiopyridine (major product), 2,3,6-trichloropyridine, and 2,3,6-trichloro-4-methylthiopyridine (trace). The mechanism of this reaction is discussed. Some reactions of tetrachloro-4-methylsulphinylpyridine and of the corresponding 4-methylthio-compound are also reported. Tetrachloro-2-dimethylamino-(and pyrrolidino-)pyridine reacted with potassium hydrogen sulphide in the 4-position. The resulting 4-mercapto-compounds were methylated, and 2,3,5-trichloro-6-dimethylamino-4-methylthiopyridine was oxidised with peroxyacetic acid to give 2,3,5-trichloro-6-dimethylamino-4-methyl-sulphinylpyridine.