5 : 5-Disubstituted barbituric and thiobarbituric acid derivatives of the formula FORM:0595867/IV/1 where Y is either oxygen or sulphur and where R and R1 are alkyl or alkenyl groups, like or unlike and each containing not more than 6 carbon atoms, the sum of the carbon atoms in R and R1 not exceeding 10, are prepared by condensing an alkylthioethyl-alkyl disubstituted malonic or cyanoacetic acid ester with urea or thiourea in the presence of an alkali metal or alkalene earth metal alcoholate. If desired, the compound so produced may be treated with a salt-forming compound to form a salt. Compounds mentioned for this purpose include an alkali metal, a stoichiometric equivalent of an alkaline earth metal, ammonium, mono-alkyl ammonium, dialkyl ammonium, alkanol ammonium, or a stoichiometric equivalent of alkalene diammonium. The condensation is preferably conducted in the presence of an organic solvent. When cyanoacetic esters are used as starting materials, these first yield iminobarbiturates which are then hydrolysed to the corresponding barbituric acids as described in Specification 587,519. In examples: (1) b -n-butylthioethyl-ethyl malonic ester and urea are added to an alcoholic solution of sodium ethoxide, and the mixture refluxed to give 5-b -n-butylthioethyl-5-ethyl barbituric acid; (2) b -n-butyl-thioethyl-isopropyl malonic ester is condensed with urea as in example (1) to give 5 - b - n - butylthioethyl - 5 - isopropyl bar bituric acid; (3) b -(1-methylbutyl)-thioethyl malonic ester is condensed with urea as in example (1) to give 5-b -(1-methylbutyl)-thioethyl-5-ethyl barbituric acid; (4) b -ethylthioethyl allyl malonic ester is condensed with urea as before to give 5-b -ethylthioethyl-5-allyl barbituric acid; (5) b -ethylthioethyl isoamyl malonic ester is condensed with thiourea as before to give 5-b -ethylthioethyl-5-isoamyl thiobarbituric acid; (6) b -n-butylthioethyl isopropyl malonic ester is condensed with thiourea as before to give 5-b -n-butylthioethyl-5-isopropyl thiobarbituric acid; (7) b -n-butylthioethyl allyl malonic ester is condensed with thiourea as before to give 5-b -butylthioethyl allyl thiobarbituric acid. The sodium salts of the above-mentioned acids may be prepared by dissolving the acid in hot alcohol and adding a solution of sodium in hot alcohol. The compounds of the present invention act as sedatives and hypnotics, which have a range of action from long to ultra-short. Other salts mentioned include the calcium salts and the ammonium, primary and secondary alkylamine, alkylolamine and alkylene diamine salts. Disubstituted malonic esters used in the present process are prepared by condensing b -chloroethyl sulphides with sodio-monoalkylmalonic esters in an inert solvent. Disubstituted cyanoacetic esters are prepared in a similar manner, starting from sodiomonoalkyl cyanacetic esters.
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