Distance‐Triggered Distinct Aryl Migrations on Azidodiboranes

Derived from structurally similar precursors, two different azidodiboranes went through distinct aryl migration reactions triggered by different boron‐boron separation distances. Biphenylene based diborane with a shorter boron‐boron distance underwent heterolateral aryl migration to form a seven‐membered azadiborepin, while xanthrene based diborane with a longer boron‐boron distance afforded a stable bis‐azidoborane scaffold. The pyrolysis of such a bis‐azidoborane led to eight‐membered oxazadiborocine through homolateral aryl migration and subsequent [3+2] cycloaddition. Density functional theory (DFT) calculations unveiled that the boron‐boron separation distances were the intrinsic factors for the distinct migrations. Two bis‐haloboranes fused by biphenylene and xanthrene were employed to construct azidodiboranes but resulted in different products. The boron‐boron separation distances were identified as the intrinsic factors for the pathway‐selectivity.