Reaction of Dihalodiboranes(4) with a N‐Heterocyclic Silylene: Facile Construction of 1‐Aryl‐2‐Silyl‐1,2‐Diboraindanes

Dihalodiboranes(4) react with a N‐heterocyclic silylene (NHSi) to generate NHSi adducts of 1‐aryl‐2‐silyl‐1,2‐diboraindanes, as was confirmed by X‐ray crystallography, featuring the functionalization of both B−X (X=halogen) bonds and a sp3‐ or sp2‐C−H bond under mild conditions. Coordination of a third NHSi to the proposed 1,1‐diaryl‐2,2‐disilyldiborane(4) intermediates, generated by a twofold B−X insertion, may be crucial for the C−H borylation that leads to the final products. Notably, our results demonstrate the first C−H borylation with a strong B−F bond activated by silylene insertion. A domino reaction of dihalodiborane(4) with three equivalents of N‐heterocyclic silylene (NHSi) readily generated a NHSi adduct of 1‐aryl‐2‐silyl‐1,2‐diboraindane and a HX insertion product (see scheme). The first C−H borylation with a strong B−F bond activated by silylene insertion was demonstrated by the analogous reaction of a difluorodiborane(4).