Metal-free C-H borylation of N-heteroarenes by boron trifluoride.

Organoboron compounds are essential reagents in modern C-C coupling reactions. Their synthesis via catalytic C-H borylation by main group elements is emerging as a powerful tool alternative to transition metal based catalysis. Herein we report a straightforward metal-free synthesis of aryldifluoroboranes from BF3 and heteroarenes. The reaction is assisted by sterically hindered amines and catalytic amounts of thioureas. According to computational studies the reaction proceeds via frustrated Lewis pair (FLP) mechanism. The obtained aryldifluoroboranes are further stabilized against destructive protodeborylation by converting them to the corresponding air stabile tetramethylammonium organotrifluoroborates.