A Copper(I)-Catalyzed Radical-Relay Reaction Enabling the Intermolecular 1,2-Alkylborylation of Unactivated Olefins

Abstract

The first catalytic intermolecular 1,2-alkylborylation reaction via a radical-relay mechanism between unactivated olefins, bis(pinacolato)diboron, and an alkyl electrophile is reported. Successful implementation of this method requires that the competing boryl substitution of the alkyl electrophile is retarded to facilitate the radical relay. This challenge was overcome using electronically or sterically demanding alkyl electrophiles, which results in the simultaneous and highly regioselective introduction of a gem-difluoro, monofluoro, tertiary, or secondary alkyl group and a boryl group across the CC double bond.

Alkene Difunctionalization Triggered by a Stabilized Allenyl Radical: Concomitant Installation of Two Unsaturated C−C Bonds

“…This process facilitates the incorporation of an alkenyl or alkynyl into target compounds, giving rise to multi‐functionalized alkene or alkyne adducts. The general protocol is initiated by the addition of an external radical to an alkene, forming a new alkyl radical intermediate which is involved in the ensuing transition‐metal catalyzed cross‐couplings, [2d,e,k,n,o] or trapped by radical acceptors, [2g, 3] such as the Fuchs reagent (Scheme 1 A, a). Alternatively, the nascent alkyl radical can undergo an intramolecular alkenyl or alkynyl migration by harnessing the tertiary allylic/propargylic alcohols as specific substrates (Scheme 1 A, b) [4] .…”

Alkene Difunctionalization Triggered by a Stabilized Allenyl Radical: Concomitant Installation of Two Unsaturated C−C Bonds

“…This process facilitates the incorporation of an alkenyl or alkynyl into target compounds, giving rise to multi‐functionalized alkene or alkyne adducts. The general protocol is initiated by the addition of an external radical to an alkene, forming a new alkyl radical intermediate which is involved in the ensuing transition‐metal catalyzed cross‐couplings, [2d,e,k,n,o] or trapped by radical acceptors, [2g, 3] such as the Fuchs reagent (Scheme 1 A, a). Alternatively, the nascent alkyl radical can undergo an intramolecular alkenyl or alkynyl migration by harnessing the tertiary allylic/propargylic alcohols as specific substrates (Scheme 1 A, b) [4] .…”

Pd/Cu-Catalyzed amide-enabled selectivity-reversed borocarbonylation of unactivated alkenes

“…Recently, several attractive strategies have emerged for the borofunctionalization of unactivated alkenes to give b-boryl products. [4][5][6][7] In 2015, Fu, Xiao and their co-workers established a copper-catalyzed regiodivergent alkylboration of alkenes. 4a In the same year, Miura and Hirano's group reported a coppercatalyzed aminoboration of terminal alkenes.…”

“…Subsequently, we evaluated the inuence of copper precursors. The NHC ligand is proved to be unnecessary as copper iodide can give the target product in 50% yield (Table 1, entries [5][6][7][8]. Various phosphine ligands were studied to examine ligand effects.…”

“…More recently, an intermolecular 1,2-alkylborylation of alkenes was described by Ito's research group. 5 A radical-relay strategy was used to achieve the targeted regioselective addition. Furthermore, Engle and co-workers explored a palladium-catalyzed 1,2-carboboration and -silylation reaction of alkenes.…”