Direct Conversion of <i>N</i>‑Alkylamines to <i>N</i>‑Propargylamines through C–H Activation Promoted by Lewis Acid/Organocopper Catalysis: Application to Late-Stage Functionalization of Bioactive Molecules

An efficient catalytic method to convert an α-C–H bond of N-alkylamines into an α-C–alkynyl bond was developed. In the past, such transformations were carried out under oxidative conditions, and the enantioselective variants were confined to tetrahydroisoquinoline derivatives. Here, we disclose a method for the union of N-alkylamines and trimethylsilyl alkynes, without the presence of an external oxidant and promoted through cooperative actions of two Lewis acids, B­(C6F5)3 and a Cu-based complex. A variety of propargylamines can be synthesized in high diastereo- and enantioselectivity. The utility of the approach is demonstrated by the late-stage site-selective modification of bioactive amines. Kinetic investigations that shed light on various mechanistic nuances of the catalytic process are presented.