Herbicidal 2-phenoxy propionic acid derivs. prodn. - from 2-chloro-propionic acid and corresp. phenol in presence of base, with azeotropic water removal

摘要

Prodn. of propionic acid derivs. of formula (I) and their salts comprises reacting phenols (II) with excess 2-chloropropionic acid (III). In the formulae, W is H or alkali metal; Z = O or CH2; When Z = O, X = Cl, Br or CF3 and Y is H or Cl, and when Z = CH2, X = Cl and Y = H or Cl. Reaction is carried out in a water-immisicible solvent while distilling out water-introduced (or present) and simultaneously adding the calculated amt. (or a slight excess) of aq. alkali hydroxide. Alternatively, a mixt. of (II) and (III) (or its methyl ester) is heated under reduced pressure with the calculated amt. of alkali while distilling out water. (I) are herbicides, esp. for grasses and also precursors for other selective herbicides. Excess alkali is not present during reaction so hydrolysis of (III) to lactic acid is suppressed. Yields of (I) of 99.5-99.9% are achieved with a relatively small excess of (III).