Asymmetric Construction of α,γ-Disubstituted α,β-Butenolides Directly from Allylic Ynoates Using a Chiral Bifunctional Phosphine Ligand Enables Cooperative Au Catalysis

Abstract

A highly efficient construction of chiral γ-substituted α-allyl-α,β-butenolides with up to >99% enantiomeric excess from readily available allylic ynoates is realized. In this asymmetric gold catalysis, the cationic gold­(I) catalyst featuring a bifunctional phosphine ligand enables a four-step cascade which permits the conversion of a diverse array of allylic ynoates into valuable chiral α,γ-disubstituted α,β-butenolides.

Asymmetric gold catalysis enabled by specially designed ligands

“…Thereafter, T. Li, J. Zhu, and L. Zhang reported the application of this ligand for the synthesis of γ-substituted α-allyl-α,β-butenolides ( 11g ) from readily available allylic ynoates ( 11f ) (Scheme 11D). 105 Using L11 ligated gold complex, butenolide derivatives were obtained in excellent enantiomeric excesses (up to >99% ee) and yields (up to 92%). The DFT calculations provided the Gibbs energies for enantiodetermining transition states TS-11C and TS-11D , showing a lower reaction barrier for TS-11C which produces the major enantiomer.…”

Advances in Versatile Chiral Ligands for Asymmetric Gold Catalysis

“…Scheme 15. Enantioselective isomerization of β,γ-butenolides to chiral α,β-butenolides Additionally, the Zhang group reported that the asymmetric version of ynolates 37 to chiral α-Allyl-α,β-butenolides 38 was achieved with the aid of a (S)-L17-ligated gold catalyst (Scheme 16) [58]. As described, in this tandem reaction, the 'push' and 'pull' processes were involved several times for the generation of an allene intermediate, a furan intermediate and the isomerization product.…”

Chiral Ligands for Au(I), Au(III), and Au(I)/Au(III) Redox Catalysis

“…Very recently, in 2022, Li, Zhu and L. Zhang utilised their previously designed chiral bifunctional phosphine ligand (ent)-L28 for the synthesis of γ-substituted α-allyl α,β-butenolides 41 b from allylic ynoates 41 a, exhibiting an excellent ee of up to > 99 % and yields up to 92 % (Entry 41). [70]…”