Process for preparing 2,6-dialkylphenylacetic acids

A process for preparing compounds of formula (I)

• in which
• R1 and R2 represent methyl,
• and
• R3 represents chlorine,
• comprising:
• (1) reacting a compound of formula (II)
• in which R1, R2 and R3 have the definitions given above, with magnesium in the presence of a solvent to give a compound of formula (III),
• in which R1, R2 and R3 have the meanings given above;
• (2) the compound of formula (III) is reacted with a compound of formula (IV)
• in which
• R4 and R5 represent methyl,
• to give a compound of formula (V)
• in which R1, R2, R3, R4 and R5 have the definitions given above;
• (3) the compound of formula (V) is reacted by hydrolysis under acidic conditions to give a compound of formula (VI)
• in which R1, R2 and R3 have the definitions given above,
• (4) the compound of formula (VI) is hydrogenated to give a compound of formula (VII)
• in which R1, R2 and R3 have the definitions given above,
• in the presence of a catalyst;
• (5) the compound of formula (VII) is reacted to give a compound of formula (VIII)
• in which R1, R2 and R3 have the definitions given above, and
• Y represents chlorine or bromine,
• (6) the compound of formula (VIII) is reacted with a cyanide of formula (IX)
• MCN (IX),
• in which
• M represents sodium,
• to give a compound of formula (X)
• in which R1, R2 and R3 have the definitions given above;
• (7) the compound of formula (X) is hydrolysed under acidic or basic conditions to give the compound of formula (I)
• in which R1, R2 and R3 have the definitions given above.