The Difluoromethyl Group as a Masked Nucleophile: A Lewis Acid/Base Approach

The difluoromethyl group (R–CF2H) imparts desirable pharmacokinetic properties to drug molecules and is commonly targeted as a terminal functional group that is not amenable to further modification. Deprotonation of widely available Ar–CF2H starting materials to expose nucleophilic Ar–CF2– synthons represents an unexplored, yet promising route to construct benzylic Ar–CF2–R linkages. Here we show that the combination of a Brønsted superbase with a weak Lewis acid enables deprotonation of Ar–CF2H groups and capture of reactive Ar–CF2– fragments. This route provides access to isolable and reactive Ar–CF2– synthons that react with a broad array of electrophiles at room temperature. The methodology is highly general in both electrophile and difluoromethyl (hetero)­arene and can be applied directly to the synthesis of benzylic difluoromethylene (Ar–CF2–R) linkages, which are useful lipophilic and metabolically resistant replacements for benzylic linkages in medicinal chemistry.