Site-Selective Tertiary Alkyl-Fluorine Bond Formation from α-Bromoamides Using a Copper/CsF Catalyst System

A copper-catalyzed site-selective fluorination of alpha-bromoamides possessing multiple reaction sites, such as primary and secondary alkyl-Br bonds, using inexpensive CsF is reported. Tertiary alkyl-F bonds, which are very difficult to synthesize, can be formed by this fluorination reaction with the aid of an amide group. Control experiments revealed that in situ generated CuF2 is a key fluorinating reagent that reacts with the tertiary alkyl radicals generated by the reaction between an alpha-bromocarbonyl compound and a copper(I) salt.