Rh-Catalyzed Borylation of N-Adjacent C(sp3)-H Bonds with a Silica-Supported Triarylphosphine Ligand

Direct C(sp(3))-H borylation of amides, ureas, and 2-aminopyridine derivatives at the position alpha to the N atom, which gives the corresponding alpha-aminoalkylboronates, has been achieved with a heterogeneous catalyst system consisting of [Rh(OMe)(cod)](2) and a silica-supported triarylphosphine ligand (Silica-TRIP) that features an immobilized triptycene-type cage structure with a bridgehead P atom. The reaction occurs not only at terminal C-H bonds but also at internal secondary C-H bonds under mild reaction conditions (25-100 degrees C, 0.1-0.5 mol % Rh).