1,2-Azaboretidine formation in the reactions of (boryl)(silyl)iminomethanes via possible generation of (amino)(boryl)carbene species

[Bis(diisopropylamino)boryl](organosilyl)(N-arylimino)methanes, which was formed in the reaction of aryl isocyanides with (organosilyl)bis(diisopropylamino)borane at room temperature, underwent new skeletal rearrangement reaction to provide aryl(1,2-azaboretidin-3-yl)(organosilyl)amines at 110 °C. Reaction of 1,2-diisocyanobenzene with the silylborane afforded 2-(organosilyl)-3-(1,2-azaboretidin-3-yl)-4,5-benzoimidazole, which was isolated as the corresponding borane complexes. The reactions may proceed through (amino)(boryl)carbene intermediates, which is formed via aza-Brook-type 1,2-silyl migration, giving the 1,2-azaboretidines by intramolecular insertion into the CH bonds α to the nitrogen atoms.