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Iron-Catalyzed E‑Selective Dehydrogenative Borylation of Vinylarenes with Pinacolborane

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journal contribution
posted on 07.10.2016 by Chao Wang, Caizhi Wu, Shaozhong Ge
We report the dehydrogenative borylation of vinylarenes with pinacolborane (HBpin) catalyzed by an iron(0) complex “(PMe3)4Fe”. A variety of monosubstituted and disubstituted vinylarenes underwent this iron-catalyzed transformation, affording E-vinyl boronate esters (VBEs) selectively in high yields. In addition, we coupled this iron-catalyzed dehydrogenative borylation with further transformations of the resulting vinyl boronate esters and developed various one-pot procedures for the functionalization of the vinylic C–H bonds in vinylarenes. Mechanistic studies reveal that this Fe-catalyzed reaction proceeds through syn-insertion of vinylarenes into a Fe-boryl species followed by β-hydrogen elimination from a syn coplanar conformation of the borylalkyl iron intermediate.