Catalytic Intermolecular C(sp<sup>3</sup>)–H Amination: Selective Functionalization of Tertiary C–H Bonds vs Activated Benzylic C–H Bonds
Erwan Brunard, Vincent Boquet, Elsa Van Elslande, Tanguy Saget, Philippe Dauban
Abstract
A catalytic intermolecular amination of nonactivated tertiary C(sp3)–H bonds (BDE of 96 kcal·mol–1) is reported for substrates displaying an activated benzylic site (BDE of 85 kcal·mol–1). The tertiary C(sp3)–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 Rh2(S-tfpttl)4, a rhodium(II) complex with a well-defined catalytic pocket, with tert-butylphenol sulfamate (TBPhsNH2), 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 NH-free amines.