Formal Insertion of Alkenes Into C(sp3 )-F Bonds Mediated by Fluorine-Hydrogen Bonding.

ABSTRACT

C-F Insertion reactions represent an attractive approach to prepare valuable fluorinated compounds. The high strength of C-F bonds and the low reactivity of the fluoride released upon C-F bond cleavage, however, mean that examples of such processes are extremely scarce in the literature. Here we report a reaction system that overcomes these challenges using hydrogen bond donors that both activate C-F bonds and allow for downstream reactions with fluoride. In the presence of hexafluoroisopropanol, benzyl and propargyl fluorides undergo efficient formal C-F bond insertion across α-fluorinated styrenes. This process, which does not require any additional fluorinating reagent, occurs under mild conditions and delivers products featuring the gem-difluoro motif, which is attracting increasing interest in medicinal chemistry. Moreover, readily available organic bromides can be engaged directly in a one-pot process that avoids the isolation of organic fluorides.