Asymmetric Redox Allylic Alkylation to Access 3,3'-Disubstituted Oxindoles Enabled by Ni/NHC Cooperative Catalysis.

The feasibility of cooperative catalysis between chiral N-heterocyclic carbenes and nickel in asymmetric reactions has been demonstrated convincingly. The high efficiency of this catalytic system enables the asymmetric allylic alkylation of isatin-derived enals with allylic carbonates and [3+3] annulation with racemic vinyl epoxides to provide straightforward access to highly enantioenriched 3,3'-disubstituted oxindoles. The great practicality of this method in organic synthesis has been showcased by facile product modification and enantioselective synthesis of the key building block to access (-)-debromoflustramine B.

Vicinal All-Carbon Quaternary Stereocenter Construction with Trifluoromethyl Groups via Organocatalytic Asymmetric Cascade Michael/Michael Reaction.

A thiourea organocatalyst efficiently promoted the asymmetric cascade Michael/Michael reactions between isatin-derived trifluoromethylacrylate and α-alkylidene succinimide, resulting in high yields of spirooxindole derivatives. These compounds exhibit vicinal all-carbon quaternary stereocenters and bear a trifluoromethyl group, with excellent enantioselectivities reaching up to 99 % ee. This work represents the first successful organocatalyst application for the direct construction of vicinal all-carbon quaternary stereocenters, featuring a trifluoromethyl group.

The Construction of All-Carbon Quaternary Stereocenters by Use of Pd-Catalyzed Asymmetric Allylic Alkylation Reactions in Total Synthesis.

All-carbon quaternary stereocenters have posed significant challenges in the synthesis of complex natural products. These important structural motifs have inspired the development of broadly applicable palladium-catalyzed asymmetric allylic alkylation reactions of unstabilized non-biased enolates for the synthesis of enantioenriched α-quaternary products. This microreview outlines key considerations in the application of palladium-catalyzed asymmetric allylic alkylation reactions and presents recent total syntheses of complex natural products that have employed these powerful transformations for the direct, catalytic, enantioselective construction of all-carbon quaternary stereocenters.