Intriguing migrations in transient iminoborane adducts: two new pathways to aminoboranes

Two unusual reactions were demonstrated with iminoboranes, both leading to aminoboranes of the type R 2 B&z.dbd;NR 2 . In one case, a carboboration of di( tert -butyl)iminoborane with B(C 6 F 5 ) 3 led to ( t Bu)(C 6 F 5 )B-N( t Bu)(B(C 6 F 5 ) 2 ). In the other, a transient IDipp (1,3-di(2,6-diisopropylphenyl)imidazol-2-ylidene) adduct of MesBN t Bu undergoes a shift of one carbene-bound Dipp substituent to the iminoborane nitrogen atom, yielding (1-Dipp-imidazol-2-yl)(Mes)B-N(Dipp)( t Bu). Mechanistic DFT studies indicate the intermediacy of a borane·iminoborane adduct in the carboboration reaction. Two unusual reaction patterns of iminoboranes leading to aminoboranes are demonstrated: aryl-carboboration and carbene N-C bond activation.