Selective Boryl‐Anion Migration in a Vinyl sp2−sp3 Diborane Induced by Soft Borane Lewis Acids. Issue 40 (10th September 2018)

• Record Type: Journal Article
• Authors: Fasano, Valerio; Cid, Jessica; Procter, Richard J.; Ross, Emily; Ingleson, Michael J.
• Is Part Of: Angewandte Chemie international edition. Volume 57:Issue 40(2018)
• Page Start: 13293
• Page End: 13297
• Publication Date: 2018-09-10
• Subjects: boranes -- borylation -- Grignard reagents -- Lewis acids -- 1, 2-migration; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201808216
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: An intramolecular 1, 2‐boryl‐anion migration from boron to carbon has been achieved by selective activation of the π system in [(vinyl)B2 Pin2 )] − using "soft" BR3 electrophiles (BR3 =BPh3 or 9‐aryl‐BBN). The soft character is key to ensure 1, 2‐migration proceeds instead of oxygen coordination/B−O activation. The BR3 ‐induced 1, 2‐boryl‐anion migration represents a triple borylation of a vinyl Grignard reagent using only B2 Pin2 and BR3 and forms differentially protected 1, 1, 2‐triborylated alkanes. Notably, by increasing the steric bulk at the β position of the vinyl Grignard reagent used to activate B2 Pin2, 1, 2‐boryl‐anion migration can be suppressed in favor of intermolecular {BPin} − transfer to BPh3, thus enabling simple access to unsymmetrical sp 2 −sp 3 diboranes. Abstract : Selective π fishing : Selective activation of the π system in a vinyl sp 2 −sp 3 diborane with "soft" borane Lewis acids led to intramolecular 1, 2‐boryl‐anion migration from a boron atom to a carbon atom (see scheme) as opposed to oxygen coordination and B−O activation. This borane‐induced 1, 2‐boryl‐anion migration enabled the triple borylation of a vinyl Grignard reagent to form differentially protected 1, 1, 2‐triborylated alkanes.