Intermolecular insertion reactions of azides into 9-borafluorenes to generate 9,10-B,N-phenanthrenes.

The reactions of 9-borafluorenes with organic azides result in either the insertion of the α-nitrogen and elimination of N2 or the insertion of the γ-nitrogen to generate the corresponding phenanthrene analogues with boron and nitrogen in the 9- and 10-positions, respectively.