Thionyl Chloride → 4-Chloropyridine-3-carbonyl chloride

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Reaktionsschritte

o-Halogeno-(hetero-)aryl-carboxylic acid halides which can be employed in the process according to the invention, and processes for their preparation, are known. Thus, for example, J. Am. Chem. Soc. 40,233 (1908) describes the preparation of 2-ethylmercapto-6-chloropyrimidine-5-carboxylic acid chloride by reacting 2-ethylmercapto-4-oxo-3,4-dihydropyrimidine-5-carboxylic acid with phosphorus oxychloride. The reaction of 2-hydroxy-quinoxaline-3-carboxylic acid with thionyl chloride in the presence of a catalytic amount of dimethylformamide to give 2-chloroquinoxaline-3-carboxylic acid chloride is described in Arch. Pharm. 306, 401 (1973). The reaction 4-chloronicotinic acid with thionyl chloride under reflex to give 4-chloronicotinic acid chloride is described in J. Chem. Soc. (C), 1966, 1816.

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