Chromium-Catalyzed Borylative Coupling of Aliphatic Bromides with Pinacolborane by Hydrogen Evolution

The chromium-catalyzed borylative coupling between aliphatic bromides and pinacolborane (HBpin) is described. This reaction was promoted by low-cost and bench-stable CrCl 3 as a precatalyst combined with 4,4′-di- tert -butyl-2,2′-dipyridyl and aluminum, presenting a rare example of using HBpin as a borane reagent by coupling with alkyl bromides in forming borylated alkanes. Mechanistic studies indicate that aluminum plays important roles in the formation of reactive Cr species and aliphatic radicals, which lead to (alkyl)Cr by reaction with HBpin to give the products.