Avenue to novel o-carboranyl boron compounds - reactivity study of o-carborane-fused aminoborirane towards organic azides

Herein we report the reactivity study of o-carborane-fused bis(trimethylsilyl)aminoborirane towards three different types of organic azides, i.e., aryl, alkyl, and silyl azides. The reaction with ArN3 (Ar = 2,6-iPr(2)C(6)H(4), 2,6-C6H3Cl2, 2,4,6-C6H2Br3, C6F5) resulted in the cycloaddition of ArN3 to the borirane BN unit accompanied by silyl migration. Conversely, in the reaction with BnN3, only the BnN3 : borirane 1 : 2 ring expansion product was obtained. Finally, the reaction with Me3SiN3 resulted in a formal nitrene insertion product under thermal conditions. All of the newly obtained o-carborane-fused BN-containing heterocycles were fully characterized, and the mechanism of these substituent-dependent reactions was studied using DFT calculations.