Process for the preparation of 3-Alkoxy-2-methylbenzoic acids

Preparation of 3-alkoxy-2-methyl-benzoic acid compounds (I) involves: (a) reacting a naphthalene compound with alkali metal hydroxide in presence of water; (b) partially neutralizing; (c) treating with an alkyl halide, alkyl sulfonate or alkyl sulfate and (d) acidifying. Preparation of 3-alkoxy-2-methyl-benzoic acids of formula (I) involves: (a) reacting a naphthalene derivative of formula (III) with alkali metal hydroxide in presence of water; (b) partially neutralizing the reaction mixture (optionally after adding water, removing insolubles and/or removing undesirable soluble components); (c) reacting the mixture with an alkyl halide of formula R1X (IVa), an alkyl sulfonate of formula R1-OSO2-R8 (IVb) or a dialkyl sulfate of formula R1OSO2OR1 (IVc); and (d) acidifying the mixture. R1 = 1-14C alkyl, 7-20C aralkyl, 13-20C diarylalkyl, A-OR2 or A-NR3R4; A = 1-4C alkylene; R2, R3, R4 = Me, Et or isopropyl; R5-R7 = H, OH, NH2 or SO3M; M = H, ammonium, alkali metal or 1 equivalent of alkaline earth metal; X = Cl, Br or I, and R8 = 1-4C alkyl, 1-4C perfluoroalkyl, phenyl or p-tolyl. Die Erfindung betrifft ein verbessertes Verfahren zur Herstellung von 3-Alkoxy-2-methylbenzoesäuren durch Erhitzen von substituierten Naphthalinen in Gegenwart von Alkalimetallhydroxiden und anschließender Alkylierung.