Process for preparing aryl- and heteroarylacetic acid derivatives

A process for preparing a compound of formula (III)

• in which
• Ar is a
• group,
• where
• R1, R2, R3, R4 and R5 are the same or different and are each independently hydrogen, amino, cyano, nitro, halogen, optionally halogen-substituted C1-C6-alkyl, C1-C6-thioalkyl, thiophenyl, C1-C6-alkoxy, C6-C10-aryloxy, phenyl, —CO—C6-C10-aryl, —CO—C1-C3-alkyl, —COO—C1-C6-alkyl or —COO—C6-C10-aryl,
• the Ar radical may additionally also be a heteroaromatic radical or
• the Ar radical may also be 1- or 2-naphthyl,
• and
• R6 and R7 are each independently optionally substituted C1-C8-alkyl, phenyl, aryl, or NR8R9,
• where R8 and R9 are the same or different and are each independently C1-C4-alkyl, or phenyl optionally substituted by optionally fluorine- or chlorine-substituted C1-C3-alkyl, 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,
• wherein an aryl or heteroaryl halide of formula (I)
• Ar—Hal (I)
• in which
• Hal is chlorine, bromine or iodine and
• Ar is as defined above,
• is reacted with a malonic ester of formula (II)
• in the presence of a palladium catalyst, of a phosphine ligand and
• A) of an inorganic base and of a phase transfer catalyst
• or
• B) of a mixture of inorganic bases, without using caesium carbonate or caesium bicarbonate, optionally using an organic solvent.