Borole Formation by 1,1-Carboboration

Bis­(trimethylsilylethynyl)­di­phenyl­amino­borane was reacted with the strong Lewis acid B­(C6F5)3 at ambient temperature to give the borole 9 admixed with a small amount of its thermal follow–up product 12. Compound 9 was subsequently stabilized by adduct formation with pyridine (10). Treatment of bis­(trimethylsilylethynyl)­phenylborane with B­(C6F5)3 gave the borole 14, which reacted with 3-hexyne to give the [4 + 2] cycloaddition product 15.