Zr-Catalyzed Assembly of 1,1,1-Triborylalkanes from Alkenes and HBpin

Multiboronated compounds play more and more significant roles in the chemical community, and 1,1,1-triborylalkanes have emerged as versatile building blocks in organic synthesis. However, efficient strategies for the assembly of such compounds are very rare. A general and atom-economical synthesis of 1,1,1-triborylalkanes from various alkenes with pinacolborane (HBpin) is reported for the first time. The success of this transformation relies on the use of the commercially available Schwartz reagent (Cp2ZrHCl) as a catalyst, enabling sequential dehydrogenative borylation and hydroboration. This reaction demonstrates excellent selectivity, high yields, and broad functional group tolerance. Mechanistic investigations reveal that the process begins with two consecutive dehydrogenative borylations catalyzed by zirconium, producing a 1,1-diborylalkene intermediate, which subsequently undergoes hydroboration with HBpin to afford 1,1,1-triborylalkanes. Notably, this approach allows for remote 1,1,1-triboration of internal alkenes.