Radical Markovnikov Hydroboration of Unactivated Terminal Alkenes With HBaza-Type Hydroborane via a Triple Catalysis.

Organoboron compounds are versatile building blocks for C─C and C-heteroatom bond formation, with broad applications in drug discovery and materials science. Hydroboration of alkenes with hydroboranes is a reliable route to access organoboron compoundsssssss, yet the Markovnikov-selective hydroboration of unactivated terminal alkenes remains challenging. In this study, we report a triple catalysis strategy for the highly Markovnikov-selective hydroboration of unactivated terminal alkenes with HBaza-type hydroborane (HBaza: 1,3,2-benzodiazaborolane). The reaction exhibits a broad substrate scope and good functional group compatibility, and has been successfully applied to the Markovnikov hydroboration of alkene derivatives from complex molecules. Further derivatizations of the resulting alkyl boron products, as well as the synthesis of biologically relevant molecules or intermediates, highlight the synthetic value of this method. Mechanistic studies support that this reaction proceeds via sequential metal-hydride hydrogen atom transfer (MHAT)-mediated radical generation and HBaza-involved radical borylation process under a triple photoredox, cobalt, and Brønsted acid catalysis.