Cis-4-(2,2,3,3-tetrafluoropropoxy)cinnamonitrile and trans-4-(2,2,3,3-tetrafluoropropoxy)cinnamonitrile and a process for their preparation

摘要

Prodn. of cis-4-(2,2,3,3-tetrafluoropropoxy)cinnamic acid nitrile (1a) and trans-4-(2,2,3,3-tetrafluoropropoxy)cinnamic acid nitrile (1b), or prodn. of one of (1a) and (1b), comprises a) fractional distillation of a mixt. contg. (1a) + (1b) under reduced pressure to yield a fraction contg. at least 80 wt.% (1a) and a fraction contg. at least 80 wt.% (1b); and (b) purifying the fractions further by fractional crystallisation or melt crystallisation; or (c) isomerising one fraction to the thermodynamic equilibrium mixt. of (1a) + (1b) and returning to step a). Cis-4-(2,2,3,3-tetrafluoropropoxy)cinnamic acid nitrile of formula (Ia) and the trans isomer of formula (1b) are new.