Process for producing valproic acid

A process for producing valproic acid, comprising:

• (a) dialkylating a beta-ketoester represented by formula (1):
• ##STR7## with a propyl halogenide represented by formula (2):
• X(CH.sub.2).sub.2 CH.sub.3 ( 2)
• by contacting
• (i) an aqueous phase comprising water, a base and a phase-transfer catalyst represented by the formula Q.sup.+ X.sup.-, and
• (ii) an organic phase comprising the beta-ketoester represented by formula (1) and the propyl halogenide represented by formula (2), wherein the molar ratio (2):(1) is from 5:1 to 15:1,
• at 60.degree.-80.degree. C. for at least 25 hours, followed by removing excess (2), to produce a reaction mixture comprising said aqueous phase and said organic phase, wherein said organic phase contains a dialkyl-beta-ketoester represented by formula (3):
• ##STR8## (b) contacting the reaction mixture from step (a) with an alkali at 70.degree.-90.degree. C. for at least 20 hours, to produce in said aqueous phase a salt represented by formula (4):
• ##STR9## (c) acidifying said aqueous phase to produce valproic acid represented by formula (5):
• ##STR10## wherein R is an alkoxy group having 2-5 carbon atoms;
• R' is an alkyl group having 1-4 carbon atoms;
• X is chlorine, bromine or iodine;
• Q.sup.+ is quatenary ammonium or phosphonium;
• and
• X.sup.- is an anion.