Asymmetric Nickel‐Catalysed Cross‐Hydrovinylation of Two Terminal Alkenes

Abstract

Pushing the boundaries: The asymmetric 1,2‐hydrovinylation of styrene derivatives with terminal alkenes is realised by using a nickel catalyst and specially designed chiral NHC ligands to achieve a new level of complexity for the tail‐to‐tail cross‐coupling of alkenes by CH activation.

Chiral N‐Heterocyclic Carbene Ligands Enable Asymmetric C−H Bond Functionalization

“…Transition metal-catalyzed 1,2-hydrovinylation of two terminal alkenes via CÀH functionalization can lead to a number of products with high degree of functional density. [51] The use of chiral NHC ligand in asymmetric nickel-catalyzed cross-hydrovinylation was reported by Ho and co-workers in 2015 (Scheme 15). [52] The intermolecular tail-to-tail hydroalkenylation of vinylarenes 53 with terminal olefins 54 was catalyzed by in situ generated NiH [53] complexes bearing C 1 -symmetrical NHC L36 and afforded the chiral gem-disubstituted olefin products 55 with high enantioselectivity.…”

“…Transition metal‐catalyzed 1,2‐hydrovinylation of two terminal alkenes via C−H functionalization can lead to a number of products with high degree of functional density . The use of chiral NHC ligand in asymmetric nickel‐catalyzed cross‐hydrovinylation was reported by Ho and co‐workers in 2015 (Scheme ) .…”

[(NHC)NiIIH]‐Catalyzed Cross‐Hydroalkenylation of Cyclopropenes with Alkynes: Cyclopentadiene Synthesis by [(NHC)NiII]‐Assisted C−C Rearrangement

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Ac ross-hydroalkenylation/rearrangement cascade (HARC), using ac yclopropene and alkyne as substrate pairs, was achieved for the first time by using new [(NHC)Ni-(allyl)]BAr F catalysts (NHC = N-heterocyclic carbenes). [8] Thei ntermediates,s uch as the reactive vinyl metal carbenoids and the cyclopropane ions,are often trapped by either nearby functional groups on the skeleton or external nucleophiles (Scheme 1a), providing ag eneral route to substituted furans,p yrans,a nd acyclic products.T ransition-metal hydride catalysts or their equivalents [9] could potentially be one of the most ideal approaches for cyclopropene functionalization since it could insert into the olefin and allow subsequent insertions of various reaction partners.However, their use in selective transformation of 1 is rarely reported. The mild reaction conditions employed may serve as an entry for exploring (NHC)Ni II -assisted vinylcyclopropane rearrangement reactivity.

Cyclopropenes (1)are important building blocks in organic synthesis,a nd significant advances for their synthesis have been made recently by using new transition-metal catalysts.

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“…Other than the use of traditional methods, [1] catalysts like Au, [2] Rh, [3] Cu, [4] Zn, [5] Pt, [6] and Pd [7] are particularly useful in ring-opening reactions of 1. [8] Thei ntermediates,s uch as the reactive vinyl metal carbenoids and the cyclopropane ions,are often trapped by either nearby functional groups on the skeleton or external nucleophiles (Scheme 1a), providing ag eneral route to substituted furans,p yrans,a nd acyclic products.T ransition-metal hydride catalysts or their equivalents [9] could potentially be one of the most ideal approaches for cyclopropene functionalization since it could insert into the olefin and allow subsequent insertions of various reaction partners.However, their use in selective transformation of 1 is rarely reported. [7] An umber of other possible reactivities of 1 with transition-metal hydride lead to unfavorable consumption of 1,and have severely limited the progress of the crossreaction development.…”