GB759064A - Sulphur-containing barbituric acids - Google Patents

Abstract

The invention comprises sulphur-containing barbituric acids of the general formula <FORM:0759064/IV(a)/1> wherein R is an alkyl radical containing 2 to 4 carbon atoms, Y is oxygen or sulphur and X is hydrogen or methyl, and salts thereof. The above compounds may be prepared by standard methods for the production of substituted barbituric acids, the most important of these being condensation of an appropriately substituted malonic acid ester with urea or thiourea, or the mono methyl derivatives thereof. Instead of the substituted malonic acid esters there can be used other reactive derivatives thereof such as amides, acid chlorides, nitriles, amide-esters or nitrile-esters and instead of the urea or thiourea components there can be used derivatives such as guanidine, isourea ether or dicyandiamidine. Alternatively unsubstituted or monosubstituted malonic acid derivatives may be used and the missing substituent or substituents introduced subsequent to the formation of the barbituric or thiobarbituric acid ring. The salts of the barbituric acid products can be formed by reacting the free acids with organic or inorganic bases; the sodium salts are obtained by shaking the acids in an aqueous or alcoholic solution, or in suspension, with the equivalent amount of caustic soda. In an example (1-methyl) - n - propyl - cyanoacetic acid - ethyl ester is refluxed in absolute alcohol containing sodium with b -methyl-mercapto-ethyl chloride to give b - methyl - thio - ethyl - (1 - methyl) - n propyl - cyanoacetic acid - ethyl ester. This compound is then condensed with urea by refluxing with sodium in absolute alcohol and the resulting b - methyl - thio - ethyl - (1 - methyl) - n-propyl-cyanoacetylurea on boiling with sulphuric acid gives 5 - b - methyl - thio - ethyl - 5 - (1-methyl)-n-propyl-barbituric acid. The sodium salt is prepared by reaction with caustic soda. In further examples compounds of the above general formula wherein R, X and Y have the following values are prepared similarly: (1) R = Et, X = H, Y = S; and its sodium salt. (2) R = n-Pr, X = H, Y = S; and its sodium salt. (3) R = iso-Bu, X = H, Y = O; and its trimethylamine salt. (4) R = iso-Bu, X = H, Y = S; and its sodium salt. (5) R = n-Pr, X = Me, Y = O; and its sodium salt. (6) R = n-Pr, X = Me, Y = S. (7) R = Et, X = Me, Y = O; and its sodium salt. In a further example b - methyl - thio - ethyl - (1 - methyl)-n-butyl-cyanoacetic acid ethyl ester in methanol is condensed with guanidine carbonate in benzene, in the presence of sodium. The resulting b - methyl - thio - ethyl - (1 - methyl) - n-butyl-cyano acetyl guanidine on boiling with sulphuric acid yields 5-b -methyl-thio-ethyl-5-(1-methyl)-n-butyl-barbituric acid. Specification 595,867, [Group IV), is referred to.