Activation of C-F bonds α to C-C multiple bonds.

C-F bond activation has drawn a lot of attention in the past, and the case of C(sp3)-F bonds is particularly interesting as those are the strongest single bonds carbon makes with any other element. This Feature Article aims at highlighting our work and that of others on the successful approaches that led to the activation of such C-F bonds at benzylic, allylic, propargylic and allenylic positions, for both mono- and polyfluorides. We now hope that this will set ground for discussions, contribute to fostering new ideas, and thus help in pushing current frontiers further.

Highly regioselective gold-catalyzed formal hydration of propargylic gem-difluorides.

Herein, we report a highly regioselective gold-catalyzed formal hydration of propargylic gem-difluorides. Not only does this transformation provide access to versatile fluorinated building blocks that were difficult or hardly possible to access beforehand, but it also represents a rare case of a highly regioselective gold-catalyzed hydroalkoxylation of internal alkynes and puts forward the utility of the difluoromethylene unit as a directing group in catalysis.

Exploiting a Difference in Leaving Group Ability: An Approach to ß-Substituted Monofluoroalkenes Using gem-Chlorofluoropropenes.

The superior nucleofuge character of chlorine over fluorine was taken advantage of in the selective SN2' substitution reaction of gem-chlorofluoropropenes, allowing for the clean formation of ß-substituted monofluoroalkenes under metal-free conditions. Numerous N-, S-, O-, and C-nucleophiles behaved nicely in this system. Further synthetic transformations of selected monofluoroalkenes were also accomplished.

Halogenation of primary alcohols using a tetraethylammonium halide/[Et2NSF2]BF4 combination.

The halogenation of primary alcohols is presented. The use of a combination of tetraethylammonium halide and [Et(2)NSF(2)]BF(4) (XtalFluor-E) allows for chlorination and bromination reactions to proceed efficiently (up to 92% yield) with a wide range of alcohols. Iodination reactions are also possible albeit in lower yields.

Synthesis of 1,3,4-oxadiazoles from 1,2-diacylhydrazines using [Et2NSF2]BF4 as a practical cyclodehydration agent.

The preparation of 1,3,4-oxadiazoles from 1,2-diacylhydrazines using XtalFluor-E ([Et(2)NSF(2)]BF(4)) as cyclodehydration reagent is described. Various functionalized 1,3,4-oxadiazoles were synthesized and it was found that the use of acetic acid as an additive generally improved the yields.