GB786806A - Improvements in the preparation of dichloroacet-4-hydroxy-n-methylanilide - Google Patents

Abstract

Dichloroacet - 4 - hydroxy - N - methylanilide is prepared by reacting 4 - hydroxy - N - methylaniline or a water-soluble salt thereof with chloral cyanhydrin in the presence of an acid-binding agent. The chloral cyanhydrin may be prepared in situ, e.g. by reacting chloral hydrate with an alkali metal cyanide and an alkali metal bisulphite. The molecular ratio of 4-hydroxy-N-methylaniline to chloral cyanhydrin is preferably at least 1 : 1, and when the former compound is in the form of the free base a part thereof may act as the acid-binding agent. Other suitable acid-binding agents are tertiary alkyl amines and alkali metal hydroxides, carbonates and acetates, preferably in an amount of two equivalents per mol. of chloral cyanhydrin when using free 4-hydroxy-N-methylaniline and proportionately more when using a salt thereof, the reaction being advantageously performed in an organic solvent in the former case and in an aqueous medium in the latter case. Examples describe the reaction of: (1) preformed chloral cyanhydrin, free 4-hydroxy-N-methylaniline and triethylamine in pyridine; (2) the same reactants in dioxan; (3) as in (1) except that triethylamine is replaced by aqueous caustic soda; (4) chloral cyanhydrin, 4-hydroxy-N-methylaniline sulphate and triethylamine in water containing a trace of sodium sulphite; (5) as in (4) except that triethylamine is replaced by aqueous caustic soda; (6) as in (4) except that triethylamine is replaced by an aqueous solution of sodium carbonate; (7) as in (5) but using a larger amount of sodium sulphite; (8) chloral hydrate, sodium bisulphite and sodium cyanide in water, and the resulting solution with 4 - hydroxy - N - methylaniline sulphate and caustic soda; (9) as in (8) except that caustic soda is replaced by sodium carbonate; (10) 4 - hydroxy - N - methylaniline, potassium cyanide, sodium sulphite and chloral hydrate in water; (11) as in (10) with the addition of sodium acetate; (12) and (13) as in (10) with the addition of calcium carbonate and reduction of the amount of potassium cyanide; (14) as in (10) with the addition of sodium carbonate; (15) 4 - hydroxy - N - methylaniline sulphate, sodium acetate, sodium sulphite, potassium cyanide and chloral hydrate in water; (16) as in (15) except that sodium acetate is replaced by sodium carbonate; (17) and (18) 4-hydroxy-N-methylaniline sulphate, sodium sulphite, caustic soda, sodium cyanide and chloral hydrate in water. Specification 767,148 is referred to.