Patent GB-514203-A (GB)
Title: Process for the introduction of the thiocyano group into organic compounds
Filed: 1938-03-29
Abstract: 514,203. Thiocyano-derivatives. MANCHESTER OXIDE CO., Ltd., CLAYTON, J. H., and BANN, B. March 29, 1938, Nos. 9523/38, 4092/39, and 9789/39 (divided out of 513,473). [Class 2' (iii)] Thiocyano derivatives of aromatic compounds containing a nuclear hydroxyl or amino group (other than aniline or o-toluidine which are treated as in Specification 513,473) and 2- amino thiazoles are prepared by treatment of the above aromatic compounds in solution with a solution of an inorganic thiocyanate and a cupric salt, the reaction medium from which the product has to be recovered being mainly water. It is stated that the cupric thiocyanate will react preferentially with the organic compound before reacting with the water. Suitable parent materials mentioned include m-toluidine, ptoluidine, anthranilic acid, o-, m-, and pchloraniline, alpha or #-naphthylamine, o-, m-, and p-phenetidine, o-, m-, and p-anisidine, diphenylamine, phenol, alpha and #-naphthol, phenyl peri acid, phenyl glycine and ring substitutes thereof such as nitro, halogen carbonyl, sulphonic acid, alkyl, aryl, aralkyl, alkoxyl, aralkoxyl or amino derivatives. Thiocyanols mentioned include sodium and ammonium thiocyanates. It is preferred to add the cupric salt gradually so that the, thiocyanogen may be consumed as it is produced. It is also preferred when using amines as the parent material that a small quantity of acid be added to the aqueous solution of the thiocyanate at the beginning of the reaction. An excess of acid is however avoided. The acid may also be added in admixture with the cupric salt. A particularly suitable acid is oxalic acid but sulphuric or hydrochloric acid may be used. In some cases the addition of a water-miscible solvent such as an alcohol assists the reaction to proceed smoothly. It may be added in amounts up to 30 per cent., but the water must always be in large excess. The cupric salt may if desired be added as a finely ground powder instead of in solution. When the process of the present invention is carried out using as parent material an aromatic amino compound with another group in the para position to the amino group, there is a strong tendency for ring formation to take place with formation of the corresponding 2-amino-benzothiazole. Dispersing agents such as those known under the Registered Trade Mark " Igepon" may be added to assist the dispersion of the organic compound in the thiocyanate. In examples: (1) An aqueous solution of sodium thiocyanate is added to a dilute hydrochloric acid solution of paratoluidine, and then an aqueous solution of copper sulphate added slowly. The reaction product is diluted with water, filtered, and treated With sodium carbonate to give 2-amino- 6-methyl benzothiazole. (2) To an alcoholic solution of diphenylamine there are added simultaneously over a period of 1¢-2 hours aqueous solutions of sodium thiocyanate and copper sulphate. The product is worked up as above to give 4-4<1>-dithiocyanodiphenylamine. (3) 1-amino-2:5-dimethylbenzene is added to a dilute sulphuric acid solution of sodium thiocyanate, after the addition of copper sulphate and working up as before there is obtained 4- thiocyano-1-amino-2:5-dimethylbenzene. (4) An aqueous solution of sodium thiocyanate is acidified with dilute sulphuric acid and an aqueous solution of phenol poured in. Copper sulphate is now added slowly as before to give 4-thiocyanophenol. (5) An aqueous solution of sodium thiocyanate is added to an oxalic acid solution of dimethylaniline. After the addition of copper sulphate and working up there is obtained 4-thiocyano-dimethylaniline. (6) Anthranilic acid is added to a dilute sulphuric acid solution of sodium thiocyanate, and then copper sulphate added slowly to give 2-amino-5- thiocyanobenzoic acid. (7) A dilute sulphuric acid solution of orthochloraniline is stirred into an aqueous solution of sodium thiocyanate. Copper sulphate is added slowly and the product worked up to give 2-chloro-5-thiocyano-aniline (8) A hydrochloric acid solution of p-chloraniline is added to an aqueous solution of sodium thiocyanate and copper sulphate added slowly and the product worked up as before to give 2-amino-6-chloro-benzothiazole. (9) A hydrochloric acid solution of p-xylidine is added to an aqueous solution of sodium thiocyanate, and copper sulphate added slowly and the product worked up to give 4-thiocyano- 1-amino-2:5 dimethyl benzene. (10) Orthoanisidine is added to a hydrochloric acid solution of sodium thiocyanate followed by copper sulphate added slowly, and the product worked up as before to give 4-thiocyano-2-methoxyaniline. German Specification 579,818 is referred to.