GB843690A - Improvements in or relating to pyrazolone derivatives - Google Patents

Abstract

The invention comprises pyrazolone derivatives of the general formula: <FORM:0843690/IV(b)/1> (wherein R1 represents an alkyl group of 1-4 carbon atoms, R2 represents hydrogen or an alkyl group of 1-4 carbon atoms, and R3 and R4 are similar or dissimilar and each represent hydrogen, an alkyl group of 1-4 carbon atoms, an alkenyl group of 2-4 carbon atoms, or a phenyl, benzyl, nitrophenyl, chlorophenyl or tolyl group, or R3 and R4 jointly represent a -CH2-CH2-CH2- linkage forming a five membered ring with the adjacent carbon atoms), and their physiologically acceptable acid addition salts, and the preparation thereof by condensing a piperidyl-4-hydrazine of the general formula: <FORM:0843690/IV(b)/2> with a b -keto-acid or functional derivative thereof of the general formula: R3-CO-CHR4-COX (wherein X represents a hydroxy group, an alkoxy group of 1-6 carbon atoms or a primary or secondary amino group), followed, if desired, by salinification with an acid. The condensation is preferably effected in the neighbourhood of ambient temperature in an inert solvent, which may subsequently be removed by vacuum distillation. When R2 is other than hydrogen it usually yields a mixture of isomers, which may be separated if desired. The products are useful as antipyretic and analgesic agents, or as intermediates therefor. a -Butyrylphenylacetic acid ethyl ester is prepared by the action of ethanol and hydrogen chloride on a -butyryla -phenylacetonitrile, which in turn is prepared by condensing ethyl butyrate with benzyl cyanide in the presence of sodium ethoxide. Specifications 632,832, 843,688 and 843,689 are referred to.