Chan-Lam Amination of Benzylic Secondary and Tertiary Boronic Esters

The Cu-catalysed coupling of arylboronic acids with amines, known as the Chan-Lam reaction, is used widely to prepare aryl amines. In contrast, alkyl variants of this reaction, while highly desirable, are underdeveloped. Herein, we report a Chan-Lam coupling reaction of benzylic boronic esters with primary and secondary anilines to form valuable alkyl amine products. Both secondary and tertiary boronic esters can be used as coupling partners, with mono-alkylation of the aniline occurring selectively. This is a rare example of a transition metal-mediated transformation of a tertiary alkylboron reagent. The method is operationally simple and tolerates a broad range of functional groups. Initial investigation into the reaction mechanism suggests that transmetallation from B to Cu occurs through a single electron, rather than a two-electron process.