Selective introduction of fluorine atoms to the tert-carbons of functionalized adamantanes by BrF3

► Fluorination of functionalized adamantanes was performed with BrF3. ► Three to two fluorine atoms were selectively introduced to their tert-carbons. ► From methyl adamantane-1-carboxylate, methyl 3,5,7-trifluoroadamantane-1-carboxylate was selectively formed. ► Unexpected reactions, such as fluorination of carbonyl group, also occurred.