Patent ID: 8884028

Claim:
A process for preparing a compound of formula III wherein R 1 is CF 3 , CF 2 H or CFH 2 , and R 3 is C 1 -C 6 alkyl, comprising a) reacting compounds of formula (IV), (V) and (VI) wherein R 3 is as defined for the compound of formula III, R 4 OM (V) wherein M is a lithium, sodium or potassium ion and R 4 is C 1 -C 6 alkyl, and wherein R 1 is as defined for the compound of formula III and R 5 is C 1 -C 6 alkyl, to form an enolate of formula VII wherein M is as defined for formula V and R 1 and R 3 are as defined for the compound of formula III, and b) releasing the compound of formula VIII wherein R 1 and R 3 are as defined for the compound of formula III, from the enolate of formula VII by means of an acid, c) converting the compound of formula VIII, in the presence of the salt formed from cation M and the anion of the acid in step b), to a compound of formula II, wherein R 1 and R 3 are as defined for the compound of formula III and R 2 is C 1 -C 6 alkyl, and d) reacting the compound of formula II with methylhydrazine in the presence of water to form a compound of formula III e) separating the compound of formula III from the salt formed from cation M and the anion of the acid in step b) wherein step d) is carried out in the presence of a water-immiscible solvent and in step e) the compound of formula III is separated from the salt by separating the organic phase containing the compound of formula III from the aqueous phase containing the salt.