Nickel‐Catalyzed Arylboration of Alkenylarenes: Synthesis of Boron‐Substituted Quaternary Carbons and Regiodivergent Reactions

Abstract

A method for the construction of boron‐substituted quaternary carbons or diarylquaternary carbons by arylboration of highly substituted alkenylarenes is presented. A wide range of alkenes and arylbromides can participate in this reaction thus allowing for a diverse assortment of products to be prepared. In addition, a solvent dependent regiodivergent arylboration of 1,2‐disubstituted alkenylarenes is presented, thus greatly increasing the scope of products that can be accessed.

Iron‐Catalyzed Regioselective Alkenylboration of Olefins

“…Amongst metal‐catalyzed regimes that were more widely explored, strategies that involved additions across π‐bonds followed by reaction with an organohalide (or pseudohalide) enable access to a diverse assortment of alkylboron products [2c–o] . Notably, extensive efforts have been devoted to implementing aryl‐boryl additions to olefins, mediated by either two‐catalyst (e.g.…”

“…Pd/Cu, Ni/Cu) [2c–g,o] or one‐catalyst (e.g. Ni, Cu) [2j–m] systems (Scheme 1 A). On the other hand, alkenylboration reactions were shown as logical extensions of arylboration, although reported examples remain scarce [2e–f,k,m] .…”

“…On the other hand, alkenylboration reactions were shown as logical extensions of arylboration, although reported examples remain scarce [2e–f,k,m] . For most transformations promoted by a single catalyst, the boroalkylmetal intermediate I (generated upon olefin borometallation) typically undergoes an oxidative insertion‐type process with the sp 2 ‐hybridized halide cross‐partner to give II before the ensuing reductive elimination delivers the final adduct [2j–m] (grey inset).…”

Nickel‐Catalyzed Regioselective Arylboration of Conjugated Dienes

“…Both 1,1‐ and 1,2‐disubstituted alkenes were found to generate the corresponding arylboration products under the same reaction conditions ( 9 f and 9 g ), although the latter afforded a lower yield. More importantly, a quaternary carbon center could also be constructed using this arylboration reaction ( 9 h ) [20] . Notably, when 1‐alkyl‐1,3‐diene was used, the 1,2‐addition product ( 5 t’ ) was still favored under these reaction conditions.…”

Palladium(0)‐Catalyzed Directed syn‐1,2‐Carboboration and ‐Silylation: Alkene Scope, Applications in Dearomatization, and Stereocontrol by a Chiral Auxiliary

“…Of the various coupling partners that can be engaged in 1,2‐carboboration, organohalides and pseudohalides are particularly important, given the structural diversity and widespread availability of these electrophiles (Scheme A). In this area, classical limitations have included the scope of compatible alkenes and associated issues with regiocontrol; indeed, the vast majority of successful examples involve activated alkenes, such as styrenes or norbornenes (Scheme B) . Previously, Xiao and Fu developed a Cu‐catalyzed regiodivergent 1,2‐alkylboration of non‐conjugated terminal alkenes containing a proximal heteroatom .…”