Catalytic Lewis Base Additive Enables Selective Copper-Catalyzed Borylative α-C-H Allylation of Alicyclic Amines.

Functionalized alicyclic amines are important building blocks for the synthesis of bioactive natural compounds and drugs. Existing methods of functionalization are typically limited to the synthesis of protected amines or the use of highly basic organometallic reagents that can compromise functional group tolerance. Here, we report a novel approach that enables the transformation of O-benzoyl hydroxylamines into α-functionalized cyclic secondary amines by means of a copper-catalyzed regio-, stereo-, and chemoselective coupling with allenes and bis(pinacolato)diboron. A key feature of the present transformation is the use of a catalytic Lewis base additive which inhibits the competing C-N bond forming reaction between the catalytically generated boron-substituted allylcopper intermediate with the O-benzoyl hydroxylamine, thus enabling in situ transformation of the latter into an alicyclic imine which undergoes selective C-C bond formation with the allylcopper species.