Postulated fluoroalkylation

SCHEME 14.3 Postulated fluoroalkylation and zinc elimination mechanism. 

Recently, a quantitative study of the regiochemistry of addition of a number of different fluoroalkyl radicals to CHF = CF2, summarized in Table 6, indicated that the observed selectivity could be correlated with the postulated relative electrophilicity of the radicals, with the conclusion being reached that the secondary H-C5Fn(CF3)CF radical was the most electrophilic [94]. 

It was therefore reasonable for us to postulate that replacement of surface alkyl groups on the distan-noxanes with fluoroalkyl groups should render the molecules fluorophilic, and that mild catalysts would be accessible and workable under fluorous biphasic conditions. 

Since a review on Dewar heterocyclic compounds has been published recently102), in this chapter only some typical reactions of valence-bond isomers of heteroaromatic compounds will be discussed. The emphasis will be placed on the chemistry of trifluoromethylated Dewar thiophene and pyrroles, both of which are rare examples of stable valence-bond isomers of heterocyclic compounds. Since the isolation of valence-bond isomers of heteroaromatic compounds is mostly limited to the per-fluoroalkylated isomers, those postulated as intermediates are also included. 

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