Mechanistic Studies of Nickel-Catalyzed Hydroarylation of Styrenes

Abstract

The mechanism of nickel-catalyzed hydroarylation of styrenes has been explored with density functional theory. Instead of the stepwise pathway via a Ni­(II)–H species, computational results unveil that the concerted RO–H oxidative addition/olefin insertion takes place kinetically favorable to generate the alkylnickel­(II) species, which further undergoes transmetalation and reductive elimination to yield the hydroarylated product. The origins of regio- and stereoselectivity were revealed via analyzing the electronic and steric effects of the key transition states.

Development and Mechanistic Studies of (E)-Selective Isomerization/Tandem Hydroarylation Reactions of Alkenes with a Nickel(0)/Phosphine Catalyst

“…In these reports, it is often suggested that the oxidative addition of an alcohol to the nickel(0) center to generate a nickel hydride species is a key step in the formation of the alkyl nickel­(II) species (path A). However, computational studies have suggested that the oxidative protometallation of alkenes by the nickel(0) complex and a hydroxy group would be a reasonable mechanism for the hydroarylation (path B). , Thus, the mechanisms underlying the nickel-catalyzed alkene isomerization and hydroarylation remain partially elusive.…”

Nickel-catalyzed hydroarylation reaction: a useful tool in organic synthesis

“…The computational results described the actual origins of the stereo and regioselectivity (Scheme 6). 25 This approach demonstrated that the mechanism could have proceeded via the generation of the kinetically-favored alkylnickel(II) intermediate directly from the concerted R-OH oxidative addition/olefin migratory insertion step, followed by transmetallation and reductive elimination of C and D to generate the desired corresponding product 11. The branching selectivity was caused by a combination of steric repulsions between the substrate and the phenyl group's electronic effect on the charge distribution over the C α vC β bond.…”

Nickel Hydride Catalyzed Remote Hydroarylation of Olefins

“…7e, 14 To date, progress on asymmetric catalysis has focused on enantioselective hydroarylation. [20][21][22][23][24][25] In 2019, Ni-catalyzed enantioselective hydroarylation of styrenes with arylboronic acids was demonstrated by Zhou et al 20 22 . Due to the low reactivity of hydronickelation, the alkene scope in this reaction is limited to β-unsubstituted styrenes.…”

“…7e, 14 To date, progress on asymmetric catalysis has focused on enantioselective hydroarylation. [20][21][22][23][24][25] In 2019, Ni-catalyzed enantioselective hydroarylation of styrenes with arylboronic acids was demonstrated by Zhou et al 20 using a spiro aminophosphine ligand L9 and by Mei's group 21 who used a bisoxazoline ligand L10 (Scheme 7). As shown in the originally proposed Ni(0)/Ni(II) catalytic cycle, enantioselective syn-hydrometallation of a ligated key intermediate RO-Ni(II)-H II into styrene 1 was suggested as path a, the enantiodetermining step.…”

“…Recently, however, computational studies by Cheng et al showed that path b, a kinetically favorable pathway proceeding via concerted hydronickelation, is more reasonable. 22 Due to the low reactivity of hydronickelation, the alkene scope in this reaction is limited to -unsubstituted styrenes.…”