Process for preparing 2,6-dialkylphenylacetic acids

Process for preparing compounds of formula (I)

• in which
• R1 and R2 independently of one another represent C1-C6-alkyl,
• and
• R3 represents hydrogen, C1-C6-alkyl, fluorine or chlorine,
• (1) reacting one or more compounds of formula (II)
• in which R1, R2 and R3 have the definitions given above,
• with magnesium in the presence of a solvent to give one or more compounds of formula (III),
• in which R1, R2 and R3 have the meanings given above;
• (2) the one or more compounds of formula (III) are reacted with one or more compounds of formula (IV)
• in which
• R4 and R5 independently of one another represent C1-C6-alkyl or together represent —(CH2)2—X—(CH2)2—, wherein
• X represents CH2, oxygen or sulfur,
• to give a compound of formula (V)
• in which R1, R2, R3, R4 and R5 have the definitions given above;
• (3) the one or more compounds of formula (V) are reacted by hydrolysis under acidic conditions to give one or more compounds of formula (VI)
• in which R1, R2 and R3 have the definitions given above,
• (4) one or more compounds of formula (VI) are hydrogenated to give one or more compounds of formula (VII)
• in which R1, R2 and R3 have the definitions given above,
• in the presence of a catalyst;
• (5) one or more compounds of formula (VII) are reacted to give one or more compounds of formula (VIII)
• in which R1, R2 and R3 have the definitions given above, and
• Y represents chlorine, bromine, OSO2Me, OSO2(4-Me-Ph) or OSO2CF3,
• (6) one or more of the compounds of formula (VIII) are reacted with a cyanide of formula (IX)
• MCN (IX),
• in which
• M represents lithium, sodium or potassium,
• to give one or more compounds of formula (X)
• in which R1, R2 and R3 have the definitions given above;
• (7) one or more of the compounds of formula (X) are hydrolysed under acidic or basic conditions to give one or more compounds of formula (I)
• in which R1, R2 and R3 have the definitions given above.