Conversion of dihalo cpds. to the mono halo cpds. - by selective removal of a halogen atom

摘要

Dihalo cpds. are converted into mono halo cpds. by reacting a compound contng. the group: where X=halogen, in the presence of a proton donor (liquid), with a salt of a transition metal which can form cations of various valencies, whereby the cation acts at a lowr valency:- Ro X2 + 2 m+ + R'OH Ro HX + (MOR')+ X=halogen; RoX2=dihalo cpd; RoHX=mono halo cpd; M=transition metal which can form the monovalent cation M+ and the divalent cation M++ R'OH=the proton donor; R'=H or organic radical The oxidised cation may be converted to the reduced cation "in situ" using reducing agents such as salts of bisulphite, -metabisulphite, -thiosulphate, SO2, H2S etc. The reaction is applicable to all compounds contng. two carbonyl groups. It is esp. valuable in the production of 2-halo acetoacetamid, an intermediate for insecticides, by converting the undesirable 2,2-dihalo acetoacetamide to the monohalo cpd.