Selective Boryl‐Anion Migration in a Vinyl sp²−sp³ Diborane Induced by Soft Borane Lewis Acids

Abstract

An intramolecular 1,2-boryl-anion migration from boron to carbon has been achieved by selective activation of the p system in [(vinyl)B 2 Pin 2 )] À using "soft" BR 3 electrophiles (BR 3 = BPh 3 or 9-aryl-BBN). The soft character is key to ensure 1,2-migration proceeds instead of oxygen coordination/B À Oactivation. The BR 3 -induced 1,2-boryl-anion migration represents at riple borylation of av inyl Grignardr eagent using only B 2 Pin 2 and BR 3 and forms differentially protected 1,1,2-triborylated alkanes.N otably,b yi ncreasing the steric bulk at the b position of the vinyl Grignardr eagent used to activate B 2 Pin 2 ,1 ,2-boryl-anion migration can be suppressed in favor of intermolecular {BPin} À transfer to BPh 3 ,t hus enabling simple access to unsymmetrical sp 2 À sp 3 diboranes.

Synthesis of 1,3‐Bis‐(boryl)alkanes through Boronic Ester Induced Consecutive Double 1,2‐Migration

“…These results indicate that the cascade does not occur through a radical process. Considering these findings and Inglesons work, [14] we suggest the following mechanism (Scheme 5 c). ICH 2 Bpin acts as soft Lewis acid, which triggers the first 1,2-migration of the boron ate complex 2.…”

“…[13] In 2018, Ingleson and co-workers demonstrated that soft boron-based Lewis acids (BPh 3 and 9-Ph-BBN) induce 1,2-boron migration of a vinyl diboron ate complex to enable the one-pot synthesis of 1,1,2-triborylated alkanes (Scheme 1 b). [14] Inspired by this reaction, we envisioned that commercially available ICH 2 Bpin would react with vinyl boron ate complexes to form 1,3-bis-(boryl)alkanes (Scheme 1 c, pin = pinacolato). We considered that ICH 2 Bpin acting as a soft electrophile would induce a Zweifel-type 1,2-R M -migration of a vinyl boron ate complex to form the 1,2-diborylated alkane intermediate I that might engage in a subsequent Matteson rearrangement [6b] to afford a 1,3-bis-(boryl)alkane.…”

One pot conversion of phenols and anilines to aldehydes and ketones exploiting α gem boryl carbanions

“…We have also taken the 11 B-NMR, which supports the probable mechanism by observing three different peaks (10.85, 33.04, 36.22) from the crude reaction mixture (Supplementary Fig. 25) 46,47 . The presence of IM-7 was further confirmed by HRMS data and 11 B-NMR data.…”

An Olefinic 1,2‐Boryl‐Migration Enabled by Radical Addition: Construction ofgem‐Bis(boryl)alkanes

“…[11] Among various organoboron compounds, gem-bis-(boryl)alkanes have drawn increasing attention in recent years due to their unique reactivity in both catalytic and noncatalytic processes to access value-added chemicals. [16] This transformation is conceptually related to the Zweifel reaction, but the use of such boron "ate" complex can make Bpin act as am igrating group.Notably,this Lewis acid-induced reaction was sensitive [15] Very recently,I ngleson and coworkers demonstrated a1 ,2-metalate rearrangement of avinyl diboronate complex induced by soft boranes including BPh 3 and 9-Ph-BBN ( Figure 1b).…”