Umpolung Approach for the α-Alkylation of Benzylic Amines Enabled by Superelectron Donors

Herein we describe a general transition-metal-free umpolung protocol for the synthesis of α-alkylated benzylic amines. By employing two distinct classes of ketimines and easily available alkyl thianthrenium salts as substrates, this method provides a flexible and straightforward approach to access structurally diverse α-alkylated benzylic amines under mild reaction conditions with high efficiency. Furthermore, this methodology could be extended to the regioselective alkylation of allylic amines and a-amino acid derivatives. Mechanistic investigations suggest that the deprotonated ketimines act as super electron donors (SEDs), engaging in intermolecular single-electron transfer (SET) with alkyl thianthrenium salts to generate key radical intermediates, which play a pivotal role in the base-promoted reaction pathway.