Patent ID: 8604071

Claim:
A process for preparing a compound of formula (III): in which R 1 , R 2 independently of one another are phenyl, where each phenyl radical independently of the other may have 1 to 3 substituents selected from the group consisting of halogen, cyano, nitro, C 1 -C 4 -alkyl, halo-C 1 -C 4 -alkyl, hydroxyl, C 1 -C 4 -alkoxy, halo-C 1 -C 4 -alkoxy, mercapto, C 1 -C 4 -alkylthio, halo-C 1 -C 4 -alkylthio, sulfinyl, sulfonyl, C 1 -C 4 -alkylsulfonyl, phenylsulfonyl, phenyl, phenoxy, amino, C 1 -C 4 -alkylamino, di-C 1 -C 3 -alkylamino, —NHCO—C 1 -C 3 -alkyl, —NHCOO—C 1 -C 4 -alkyl, —COO—C 1 -C 4 -alkyl and —CONH—C 1 -C 4 -alkyl, where each of the substituents phenyl, phenoxy and phenylsulfonyl independently of the others may have 1 to 3 substituents selected from the group consisting of halogen and C 1 -C 4 -alkyl; and R 5 is hydrogen or methyl, comprising expoxydizing a compound of formula (V): to give a compound of formula (IV): and reducing the compound of formula (IV), wherein the reduction reaction is started while the amount of the compound of the formula (V) used in the reaction mixture is still at least 2 mol %.