Verfahren zur Herstellung neuer Pyridazincarbonsaeureester

The invention comprises 1 : 4-dihydro-4-oxo-1 - R - pyridazine - 3 - carboxylic acids and alkyl esters thereof in which R represents an unsaturated heterocyclic monocyclic residue, such as pyridyl, thiazolyl and thienyl. The esters are preferably those with an alkyl substituent in the 6-position of the pyridazine nucleus and in particular those of the formula in which R1 is a C1-3 alkyl group. The 1 : 4-dihydro - 4 - oxo - 1 - R - pyridazine - 3 - carboxylic acids are prepared by hydrolysing the correspondingly substituted 2 : 4-dioxo-3-heterocyclyl - azo - 2 : 3 - dihydro - pyrans, e.g. with an alkali. The alkyl esters of 1 : 4-dihydro-4-oxo - 1 - R - pyridazine - 3 - carboxylic acids are prepared from the corresponding acids by methods known per se for esterifying carboxylic acids, e.g. by reaction with an alkanol, a metal alcoholate, an alkyl halide or a diazoalkane. The examples describe the preparation of 1 : 4 - dihydro - 4 - oxo - 6 - methyl - 1-pyridyl - (31) - pyridazine - 3 - carboxylic acid and the methyl and ethyl esters thereof, and of 1 : 4 - dihydro - 4 - oxo - 6 - methyl - 1 - thiazolyl-(21) - pyridazine - 3 - carboxylic acid and the methyl ester thereof.ALSO:Dyestuffs are made by coupling 2 : 3-dihydro-2 : 4-dioxo-6-methylpyran with diazotized 3-aminopyridine or 2-aminothiazole.ALSO:A pharmaceutical composition comprises an alkyl ester of a 1 : 4-dihydro-4-oxo-1-R-pyridazine-3-carboxylic acid, wherein R represents an unsaturated heterocyclic monocyclic residue (e.g. pyridyl, thiazolyl and thienyl), in admixture with a pharmaceutical carrier suitable for enteral, parenteral or topical administration. The alkyl esters are preferably those with an alkyl substituent in the 6-position of the pyridazine nucleus and in particular those of the formula in which R1 is a C1-3 alkyl group. Specified carriers are starches, gelatine, lactose, magnesium stearate, talc, vegetable oil, benzyl alcohols, gums, polyalkylene glycols, petroleum jelly and cholesterol. Preserving agents, stabilizing agents, wetting or emulsifying agents, osmotic pressure regulants, buffers and other medicaments may also be present. The composition may be in the form of tablets, dragees, solutions, suspensions or emulsions.