This article reports the synthesis of the dimer of oxazaborolidinone (OxB), OxB 2 , a sterically hindered protecting group for boron. This highly congested unique diboron reagent functions as an efficient borylation agent, enabling the direct synthesis of alkylboron compounds, which has been challenging with conventional methods. Remarkably, despite its significant steric bulk, OxB 2 undergoes smooth transmetalation with a copper catalyst. Through complementary reductive borylation and cross‐coupling with alkyl halides, we successfully prepared a range of primary and secondary alkylboron compounds—traditionally unstable and difficult to access—as stable Alkyl‐OxB derivatives. Furthermore, the resulting Alkyl‐OxB derivatives can be readily deprotected under mild conditions to furnish the corresponding alkylboronic acids. Leveraging this property, we demonstrated the iterative Suzuki–Miyaura cross‐coupling of protected alkylboron species, a transformation that has remained elusive to date.
Nojiri et al. (Mon,) studied this question.