Reactions of Perfluorobenzocycloalkenes with Ethyl Cyanoacetate and Methyllithium and Some Transformations of the Products.

Reactions of perfluorobenzocycloalkenes (ArFF) 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 ArFCH(CN)COOEt gave the corresponding perfluoroarylacetic acids ArFCH2COOH which were converted into dichloroacetyl chlorides ArFCCl2COCl by treatment with PCl5. The reaction of ArFCCl2COCl with SbF5 produced trifluoromethyl derivatives ArFCF3. Decarboxylation of ArFCCl2COOH in DMF afforded dichloromethyl derivatives ArFCCl2H which reacted with CsF on heating to form difluoromethyl analogs ArFCF2H.