4-Bromo-3-chloro-3,4,4-trifluorobutanoic acid → 3,4,4-Trifluoro-3-butenoic acid

In the second method the synthesis of 4-bromo-3-chloro-3,4,4-trifiuoro-butanoic acid (VIII) is followed by zinc dehalogenation to produce 3,4,4-trifiuoro-3-butenoic acid (IV). This compound is prepared by reacting 1-chloro-1,2-dibromotrifiuoroethane (VI) with ethyl vinyl ether in the presence of sodium dithionite and sodium bicarbonate in a manner analogous to that described in the Literature [Huang, Weiyuan; lu, long; Zhang, Yuanfa; Chin. J. Chem. 1990, (3), 281]. However, it is now found that the 4-bromo-3-chloro-3,4,4-trifluorobutanal intermediate (VII) is oxidized without isolation with sodium chlorite/hydrogen peroxide. In other words, instead of oxidation with Jones reagent, this method advantageously provides a process which can be carried out in one reaction vessel using preferred reagents and gives an unexpectedly high yield.