Herein, direct unactivated C-N borylation of aromatic amines by a photocatalyst was achieved under mild and metal-free conditions. The C-N borylation of aromatic amines with bis(pinacolato)diboron (B2pin2) proceeded in the presence of a pyrene catalyst under light irradiation (λ = 365 nm) to afford desired borylated products and aminoborane as a byproduct. The yield of borylated product improved under a CO2 atmosphere. Reactions conducted in the presence of a stoichiometric amount of aminoborane under N2 or CO2 indicated that CO2 reduced the inhibitory effect of aminoborane. Optimal reaction conditions were applied to a variety of aromatic amines. Mechanistic studies suggested that the C-N bond cleavage and C-B bond formation proceeded via a concerted pathway.
Sekine Kuninobu-C-N Borylation-SI