Some reactions of diethyl 2,3,5,6-tetrachloropyridin-4-ylmalonate

Polyhalogenoaromatic compounds. Part 40. Synthesis and thermal rearrangements of some polychloropyridines

“…The lH n.m.r. spectrum of the chloromethyl compound (23) was similar to that of the methyl compound (22). We can find no reference in the literature to the formation of chloromethyl derivatives during Claisen rearrangements of ally2 aryl ethers of this type.…”

Polychloroheteroaromatic Compounds

“…Phosphorus oxychloride alone converts 3,5,6-trichloro-2-hydroxy-4-methylpyridine into tetrachloro-4-methylpyridine [243] , 3,5-dichloro-2,4dihydroxypyridine into 2,3,4,5-tetrachloropyridine [244], 2,3dichloro-4-hydroxy-6-pyridone into 2,3,4,6-tetrachloropyridine, t [244a], 5-bromo-2,4-dihydroxy-3-nitropyridine into 5-bromo-2,4dichloro-3-nitropyridine [2441 , 3-bromo-5-chloro-2, 4-dihydroxypyridine into 3-bromo-2,4,5-trichloropyridine [236], 5-bromo-3chloro-2,4-dihydroxypyridine into 5-bromo-2,3,4-trichloropyridine [244,245] , and 3,5-dichloro-2-hydroxy-6-methylpyridine into 2,3,5-trichloro-6-methylpyridine [246].…”

“…A methyl group in a polychloropyridine is oxidized to a carboxyl group by alkaline potassium permanganate [243,267,297,330].…”

“…Polychloropyridinecarboxylic acids readily decarboxylate, usually on being heated in a suitable solvent [168,201,202,246,267]. (Tetrachloro-4-pyridyl)-and (2,3,5trichloro-4-pyridyl)-acetic acid similarly give tetrachloro-4-methyl- [243,330] and 2,3,5-trichloro-4-methyl~pyridine [297] , respectively. Tetrachloropyridine-2-carboxyIic acid chloride reacts normally with hydrazine at low temperatures to give the corresponding hydrazide, which gives a hydrazone derivative with acetone [369].…”

“…An attempt to prepare the hydrazide of tetrachloropyridine-2-carboxylic acid by treatment of the corresponding ethyl ester with hydrazine hydrate gave instead the hydrazide (199) of trichloro-4-hydrazinopyridine-2-carboxylic acid, which undergoes ready hydrolysis on treatment with concentrated sulphuric acid to the corresponding acid. It is noteworthy that the esters (200) may be prepared either by alkylation of compound (201) via its potassium salt, or directly from pentachloropyridine by a nucleophilic substitution reaction (Table 2.1) [243]. Considerable attention has been given to tetrachloro-4-mercaptopyridine and its derivatives, many of which are of interest as biological toxicants (see Chapter 4).…”