Highly Efficient “On Water” Catalyst‐Free Nucleophilic Addition Reactions Using Difluoroenoxysilanes: Dramatic Fluorine Effects

A remarkable fluorine effect on “on water” reactions is reported. The CF⋅⋅⋅HO interactions between suitably fluorinated nucleophiles and the hydrogen‐bond network at the phase boundary of oil droplets enable the formation of a unique microstructure to facilitate on water catalyst‐free reactions, which are difficult to realize using nonfluorinated substrates. Accordingly, a highly efficient on water, catalyst‐free reaction of difluoroenoxysilanes with aldehydes, activated ketones, and isatylidene malononitriles was developed, thus leading to the highly efficient synthesis of a variety of α,α‐difluoro‐β‐hydroxy ketones and quaternary oxindoles.