Process for preparing aryl- and heteroarylacetic acid derivatives

A process for preparing a compound of formula (III)

• in which
• Ar is the group
• Ar is a heteroaromatic radical or
• Ar is 1- or 2-naphthyl,
• where R5, R6, R7, R8 and R9 are the same or different and are each independently hydrogen, halogen, optionally halogen-substituted C1-C6-alkyl, C1-C6-alkoxy, phenyl, —CO—C1-C3-alkyl, —COO—C1-C6-alkyl or —COO—C6-C10-aryl,
• R3 is hydroxyl, in each case optionally substituted C1-C8-alkyl, C1-C8-alkoxy, phenyl, aryl, phenoxy or aryloxy, or NR4R4′,
• where R4 and R4′ are the same or different and are each independently hydrogen, C1-C4-alkyl, phenyl optionally substituted by C1-C3-alkyl which may be substituted by fluorine or chlorine, or by nitro, cyano or di-C1-C3-alkylamino, or, together with the nitrogen atom to which they are bonded, are a saturated or unsaturated, substituted or unsubstituted cycle,
• comprising, reacting a compound of formula (I)
• in which
• R1 is hydrogen or C1-C8-alkyl,
• R2 is hydrogen or C1-C8-alkyl, or
• R1 and R2 together with the atoms to which they are bonded are a saturated or unsaturated, substituted or unsubstituted cycle,
• and Ar is as defined above
• with a compound of formula (II)
• in which
• Hal is halogen,
• and R3 is as defined above,
• in the presence of a palladium catalyst, a phosphine ligand, an inorganic base, and a phase transfer catalyst, optionally using an organic solvent.