Patent GB-679698-A (GB)
Title: New carboxylic acid-sulphonic acid mono-halides, new acylating agents and process for the manufacture thereof
Filed: 1950-07-20
Abstract: The invention comprises: monohalides of acids of the general formula <FORM:0679698/IV (b)/1> wherein A represents a furane or thiophene ring (which may contain further substituents, e.g. alkyl groups or halogen atoms); acylating agents comprising such a monohalide and an excess of a tertiary base; and the manufacture of these acylating agents by treating an acid of the general formula above or a mono- or di-alkali metal salt thereof in the presence of an excess of a tertiary base with an aromatic sulphohalide or especially with phosgene.  The tertiary base is advantageously pyridine, or may be a tertiary base stronger than pyridine (e.g. trimethylamine or especially triethylamine), in which case there is preferably also present an inert organic solvent (e.g. benzene, chlorobenzene, o-dichlorobenzene, 1 : 2 : 4-trichlorobenzene, nitrobenzene or dioxane).  Alternatively, the formation of the monohalide may take place in the presence of pyridine and a stronger tertiary base be then added.  The acylating agents can also be made by mixing the tertiary base with the monohalide prepared separately, e.g. by (a) treating a furane- or thiophene-carboxylic acid with chlorsulphonic acid to produce a chloride of the formula <FORM:0679698/IV (b)/2> or (b) sulphonating a furane- or othiphenecarboxylic acid halide (e.g. with sulphur trioxide in liquid sulphur dioxide or especially in methylene chloride) to yield a halide of the formula <FORM:0679698/IV (b)/3> The products are useful for the acylation of a variety of compounds containing -NH- or -OH groups, e.g. for the introduction of a second acyl group into a monoacylamino group, and especially for acylating certain azo dyestuffs.  In examples: (1) furane-2-carboxylic acid chloride is treated with sulphur trioxide in methylene chloride at - 10 DEG  C. to produce furane-2-carboxylic acid chloride-5-sulphonic acid, which may be mixed with pyridine; (2) furane-2-carboxylic acid is heated with chlorsulphonic acid to form furane-2-carboxylic acid-5-sulphonic acid chloride; (3) a mixture of furane-2-carboxylic acid-5-sulphonic acid and pyridine is treated with p-toluenesulphonic acid chloride or bromide; (4) the anhydrous disodium salt of furane-2-carboxylic acid-5-sulphonic acid is mixed with pyridine and treated with p-toluenesulphochloride; (5) furane-2-carboxylic acid-5-sulphonic acid is mixed with benzene and triethylamine and treated with p-toluenesulphochloride; (6) the anhydrous disodium salt of furane-2-carboxylic acid-3-sulphonic acid or its 5-bromo derivative, or of 3 : 3-dichlorofurane-2-carboxylic acid-5-sulphonic acid, is treated as in (4). 5-Chlorofurane-2-carboxylic acid-3-sulphonic acid and thiophene 2-carboxylic acid-5-sulphonic acid are additionally specified as starting materials and N-methylmorpholine as a tertiary base. Furane- and thiophene - 2 - carboxylic - 5 - sulphonic acids are obtainable by reacting furane- or thiophene-2-carboxylic acid with sulphur trioxide in liquid sulphur dioxide or advantageously in methylene chloride or ethylene chloride at low temperature, whereafter removal of the solvent leaves the desired acid in a dry form free from water of crystallization.  The preparation of the furane compound is described in detail.