| abstract |
The invention relates to the process for preparation of cypermetrine isomers mixtures of formula Iwherein 1,3, and α-marked carbon atoms refer to chiralic carbon atom, and waved line indicates to cis or trans configuration relative to cyclopropane nucleus, which contains at least 95% of isomer pairs: IR trans S and IS trans R (Ib) or only IR cis S and IS cis R (Ia) mixture and the (Ib) isomer pair in the ratio of (Ia):(Ib)=55:45 - 25:75, obtained by type 2 asimmetric transformations, in the pressence of an amine base and protonic solvent between O°C and +25°C from the starting cypermetrine isomers mixture, having at least 90% wt % purity, containing and other cis or trans isomers, following after (Ib) pair of isomers or Ia+Ib pairs of isomers in undesired ratio.The process is carried out continuously in several conse cutive reactors. The cristals are formed at the end of reactors chain, which optional are separated from crystalls suspension. |