Catalytic Intermolecular C(sp)-H Amination: Selective Functionalization of Tertiary C-H Bonds Vs Activated Benzylic C-H Bonds

A catalytic intermolecular amination of nonactivated tertiary C(sp)-H bonds (BDE of 96 kcal·mol) is reported for substrates displaying an activated benzylic site (BDE of 85 kcal·mol). The tertiary C(sp)-H bond is selectively functionalized to afford α,α,α-trisubstituted amides in high yields. This unusual site-selectivity results from the synergistic combination of Rh(-tfpttl), a rhodium(II) complex with a well-defined catalytic pocket, with -butylphenol sulfamate (TBPhsNH), which leads to a discriminating rhodium-bound nitrene species under mild oxidative conditions. This catalytic system is very robust, and the reaction was performed on a 50 mmol scale with only 0.01 mol % of catalyst. The TBPhs group can be removed under mild conditions to afford the corresponding -free amines.