Patent ID: 7485751

Claim:
A method of preparation of a single enantiomer from the racemate of an amidoacetonitrile compound of formula wherein R 1 , R 2 and R 3 , independently of each other, signify hydrogen, halogen, nitro, cyano, C 1 -C 6 -alkyl, halogen-C 1 -C 6 -alkyl, C 1 -C 6 -alkoxy, halogen-C 1 -C 6 -alkoxy, C 2 -C 6 -alkenyl, halogen-C 2 -C 6 -alkenyl, C 2 -C 6 -alkinyl, halogen-C 2 -C 6 -alkinyl, C 2 -C 6 -alkenyloxy, halogen-C 2 -C 6 -alkenyloxy, C 1 -C 6 -alkylthio, halogen-C 1 -C 6 -alkylthio, C 1 -C 6 -alkylsulfonyloxy, halogen-C 1 -C 6 -alkylsulfonyloxy, C 1 -C 6 -alkylsulfinyl, halogen-C 1 -C 6 -alkylsulfinyl, C 1 -C 6 -alkylsulfonyl, halogen-C 1 -C 6 -alkylsulfonyl, C 1 -C 6 -alkenylthio, halogen-C 1 -C 6 -alkenylthio, C 1 -C 6 -alkenylsulfinyl, halogen-C 1 -C 6 -alkenylsulfinyl, C 1 -C 6 -alkenylsulfonyl, halogen-C 1 -C 6 -alkenylsulfonyl, C 1 -C 6 -alkylamino, di-(C 1 -C 6 -alkyl)amino, C 1 -C 6 -alkylaminocarbonyl, di-(C 1 -C 6 -alkyl)aminocarbonyl, C 1 -C 6 -alkylsulfonylamino, halogen-C 1 -C 6 -alkylsulfonylamino, C 1 -C 6 -alkylcarbonyl, halogen-C 1 -C 6 -alkylcarbonyl, C 1 -C 6 -alkoxycarbonyl, unsubstituted or one- to five-fold substituted phenyl, unsubstituted or one- to five-fold substituted phenoxy, unsubstituted or one- to five-fold substituted phenylacetylenyl, unsubstituted or one- to four-fold substituted pyridyloxy, unsubstituted or one- to four-fold substituted pyridyl or unsubstituted or one- to seven-fold substituted naphthyl, the substituents in each case being selected from the group consisting of halogen, nitro, cyano, C 1 -C 6 -alkyl, halogen-C 1 -C 6 -alkyl, C 1 -C 6 -alkoxy and halogen-C 1 -C 6 -alkoxy, characterized in that 1) the racemate is separated into two pure enantiomers by standard methods and the eutomer is collected, 2) the distomer is re-racemized using basic catalysis and/or heating in a polar solvent, and 3) the resulting racemate is again subjected to the separation procedure of step 1) in a repetitive cycle.