1,2‐Dialkylation of 1,1‐Arylboryl Alkenes Via Borata‐Alkene Intermediate

Abstract

We describe here the conjugate addition of tert‐butyllithium to vinyl systems of boronic esters to generate a borata‐alkene intermediate, followed by a sequential SN2 reaction with alkyl halides, at room temperature. We envisioned this goal through engaged C(sp3) chemical entities avoiding metal catalysts, additives, radical initiators or specific irradiation. This reaction guarantees that the new tetrasubstituted carbon formed retains all the C atoms from the three starting materials involved in the assembly.

Alkenylboronic Ester Activation to Nucleophilic Addition and Electrophilic Trapping with Carbonyl Groups

“…18 In this context, our group has recently demonstrated a polar addition of alkyllithium reagents to the terminal carbon of (1-arylvinyl)boronic acid pinacol esters C , as a result of the enhanced stability of the resulting α-arylboryl carbanion, followed by electrophilic trapping with a series of C(sp 3 )–X compounds through substitution pathways (Scheme 1d ). 19 With this 1,2-dicarbofunctionalization protocol, we have been able to generate two new C(sp 3 )–C(sp 3 ) bonds across an alkene, delivering valuable tetrasubstituted carbon centers in the absence of a catalyst, additive, or any type of radical initiator. We based our new reactivity on the remarkable stability of the α-arylboryl carbanion, which is due to the valence deficiency of the adjacent three-coordinate boron center, postulating the corresponding alkylideneborane resonance form (Scheme 1d ).…”

Three-Component Cross-Electrophile Coupling: Regioselective Electrochemical Dialkylation of Alkenes

“…Over the past decade, significant progress has been made in this area . Such reactions typically proceed in a redox-neutral fashion using an alkyl electrophile and an alkyl organometallic reagent and often also require a transition-metal catalyst and a directing group on the alkene (Scheme A). − However, the reliance on potent organometallic reagents such as organolithium, -magnesium, and -zinc complexes can limit the functional group compatibility and broader applicability of this approach.…”

Access to Diverse Organoborons by α-Deprotonation and Functionalization of Benzylboronates

“…Moreover, secondary benzylboronates can also serve as viable reaction partners, allowing for α-silylation, methylation, allylation, deuteration, and intramolecular cyclization ( 6ad – 6ah ). This method demonstrates high simplicity and efficiency in comparison to previous methods for the preparation of tertiary benzylboronates …”