Patent ID: 6452019
Filing Date: 2002-09-17
Classification: C07D

Abstract:
Process for the preparation of 4,5-diamino-1-(2â€²-hydroxyethyl)-pyrazole and acid addition salts thereof which comprises the steps of:(i) heating a mixture comprising an alkyl(ethoxymethylene)cyanoacetate, 2-hydroxy-ethylhydrazine and an alkanol to form a product solution of 5-amino-4-alkoxy-carbonyl-1-(2â€²-hydroxyethyl)pyrazole (I) in an alkanol; (ii) heating the mixture of the product solution of step (i) and aqueous alkali metal hydroxide to saponify the alkoxycarbonyl ester group of (I) and remove alkanol present from the mixture and adding sufficient acid to produce an aqueous product mixture of 5-amino-4-carboxy-1-(2â€²-hydroxyethyl)pyrazole (II); (iii) separating (II) from the product mixture of step (ii) to obtain (II) as a water-wet solid; (iv) heating water-wet (II) from step (iii) to remove water and to decarboxylate (II) to produce 5-amino-1-(2â€²-hydroxyethyl)pyrazole (III); (v) contacting (III) with an inorganic acid in an alkanol and contacting the resulting solution of the acid salt of (III) with a nitrosating agent under essentially anhydrous conditions to convert the acid salt of (III) to the acid salt of 5-amino-1-(2â€²-hydroxyethyl)-4-nitrosopyrazole (IV); (vi) separating the acid salt of (IV) from the product mixture of step (v) to obtain the acid salt of (IV) as an alkanol-wet solid; (vii) dissolving the alkanol-wet acid salt of (IV) from step (vi) in an alkanol to produce an alkanol solution of the acid salt of (IV) and adding a base to the solution to produce an alkanol solution of 5-amino-1-(2â€²-hydroxyethyl)-4-nitrosopyrazole (V); (viii) contacting the alkanol solution of (V) from step (vii) with hydrogen in the presence of an insoluble hydrogenation catalyst under hydrogenation conditions of temperature and pressure to produce a product solution of 4,5-diamino-1-(2â€²-hydroxyethyl)pyrazole in an alkanol; and (ix) separating the insoluble hydrogenation catalyst from the product solution produced in step (viii) to obtain an alkanol solution of 4,5-diamino-1-(2â€²-hydroxyethyl)-pyrazole.