Catalytic Asymmetric Hydroalkenylation of Vinylarenes: Electronic Effects of Substrates and Chiral N‐Heterocyclic Carbene Ligands

Abstract

An asymmetric tail-to-tail cross-hydroalkenylation of vinylarenes with terminal olefins was achieved by catalysis with NiH complexes bearing chiral N-heterocyclic carbenes (NHCs). The reaction provides branched gem-disubstituted olefins with high enantioselectivity (up to 94 % ee) and chemoselectivity (cross/homo product ratio: up to 99:1). Electronic effects of the substituents on the vinylarenes and on the N-aryl groups of the NHC ligands, but not a π,π-stacking mechanism, assist the steric effect and influence the outcome of the cross-hydroalkenylation.

Two-step synthesis of chiral fused tricyclic scaffolds from phenols via desymmetrization on nickel

“…2). It is worth mentioning that despite much exploration of the use of chiral NHCs, there has been less reports with nickel-catalyzed reactions 31–40 . N -(2-Biphenyl)- ( L*1 ) and N -(2-isopropylphenyl)- ( L*2 ) substituted NHCs 41 were ineffective to give 3aa .…”

Cobalt-catalysed asymmetric hydrovinylation of 1,3-dienes

“…1 . In a related reaction, Ho et al reported 42 dimerization of vinylarenes and 1-alkenes catalysed by N -heterocyclic carbene complexes of Ni( ii )-salts to give uncommon tail-to-tail dimerization products ( 7 , eqn (2)). …”

Synthesis, Structures and Properties of Half‐Sandwich Nickel(II) Complexes with Backbone‐Modified NHC Ligands

“…Because the steric demands of N ‐mesityl‐ and N ‐benzyl‐substituted NHCs are different,27 the effects of the electronic properties of the NHC ligands on this catalytic process could be compared in the series of N , N′ ‐dimesityl complexes 1b , 1c , 1a , 1g and 1h : that is, in the order of decreasing donor strength of ligands (IMes 2Me > IMes Me > IMes ≈ IMes OPiv > IMes O ). Because all of them provide the same yields of polystyrene, these results suggest that factors other than the electronics of the NHCs define the overall efficiency of this catalytic system 28…”