Reaction of polyfluorinated β-ketoacid esters and their α-halo derivatives with phosphorus pentachloride

Conclusions

• 1. Fluorine-containing β-ketoesters and their α-chloro derivatives form fluorinated 3-chloror- and α,β-dichlorocrotonic esters, respectively, when boiled with PCl₅ in benzene, chloroform, and carbon tetrachloride. In POCl₃ the ester group also participates in the reaction. In this case the fluoroalkyl β-ketoesters are chlorinated in the α-position.

• 2. At 200°C α,α-dibromo-β-ketoesters react with PCl₅ via the ester group to form dibromomethyl fluoroalkyl ketones.

• 3. Fluorine-containing β-chlorocrotonic esters with perfluorinated substituents exist primarily as cis-s-cis isomers. The presence of a terminal hydrogen in the fluorinated substituent leads to a prevalence of the cis-s-trans isomer. The cis-s-cis isomer is the prevalent form in fluorines-containing α,β-dichlorocrotonic esters.