Process for preparing dihydroisoxazole derivatives

A process for preparing a compound of formula (I),

• in which
• R1 is ketone
• R2 is phenyl which is substituted once or more often independently of one another by halogen or C1-C4-alkylsulfonyloxy;
• and
• R3 is selected from the group consisting of chlorine and bromine;
• comprising reacting a compound of formula (II),
• in which
• R3 is as defined above;
• via an elimination reaction to form a compound of formula (III)
• and reacting the compound of formula (III) which are in situ with a compound of formula (IV)
• in which R2 is as defined above in the presence of a base, an acid and a solvent in acidic pH to form the compound of formula (I).