trans-Aminoboration across Internal Alkynes Catalyzed by B(C6F5)3 for the Synthesis of Borylated Indoles

We report here a facile B(C6F5)3 catalyzed trans-aminoboration of internal alkynes, furnishing 3-position borylated indoles at ambient temperature. This reaction proceeds with the breaking of a B–N bond and the formation of N–C and B–C bonds to produce indole and derivatives in one step. It works well for various boron reagents and alkynyl-anilines. The borylated indoles can be further derivatized to give column stable organoboron compounds that can be used for future functionalization.