Selective SN2 ring opening / C‐C coupling of vinyl epoxides and styrene oxide with diborylmethide lithium salts

: Vinyl epoxides and styrene oxide can react with diborylmethide lithium salts through an exclusive SN 2 borylmethylation/ring opening in a regio- and diastereoselective way, depending on the nature of the substrate. The ring-opening protocol provides homoallylboronates that can be transformed into challenging diastereomeric bishomoallylic alicyclic 1,3-diols. Unprecedented 3-borylated 1,2-oxaborolan-2-ol products were prepared by borylmethylation/ring opening of 2-methyl-2-vinyloxirane followed by intramolecular cyclization.