Reactions of perfluorobenzocycloalkenes with ethyl cyanoacetate and methyllithium and some transformations of the products

Reactions of perfluorobenzocycloalkenes (Ar_FF) with methyllithium and ethyl cyanoacetate involved replacement of fluorine atoms in positions 3 and 4 of perfluorocyclobutabenzene, position 5 of perfluoroindan, and position 6 of perfluorotetralin by CH₃ and CH(CN)COOEt groups. Hydrolysis of the resulting esters Ar_FCH(CN)COOEt gave the corresponding perfluoroarylacetic acids Ar_FCH₂COOH which were converted into dichloroacetyl chlorides Ar_FCCl₂COCl by treatment with PCl₅. The reaction of Ar_FCCl₂COCl with SbF₅ produced trifluoromethyl derivatives Ar_FCF₃. Decarboxylation of Ar_FCCl₂COOH in DMF afforded dichloromethyl derivatives Ar_FCCl₂H which reacted with CsF on heating to form difluoromethyl analogs Ar_FCF₂H.