Construction of Vicinal Quaternary Centers via Ru-Catalyzed Enantiospecific Allylic Substitution with Lithium Ester Enolates
Sven M. Papidocha, Erick M. Carreira
Abstract
High Resolution Image Download MS PowerPoint Slide The installation of vicinal quaternary centers with absolute stereocontrol constitutes a considerable challenge in organic synthesis. Herein, we introduce a novel [Cp*Ru(MeCN) 3 ]PF 6 /phenoxythiazoline catalyst system that achieves enantiospecific allylic substitution of tertiary carbonates with α,α-disubstituted lithium ester enolates to give products containing vicinal quaternary centers. Noteworthy features include the direct use of nonstabilized ester enolates, a class of nucleophiles which has rarely been used in transition metal-catalyzed allylic substitution reactions. The approach is demonstrated for a broad scope of tertiary electrophiles as well as ester enolates and accomplishes stereoretentive substitution with excellent conservation of ee (89–99%) and branched/linear regioselectivities (up to 40:1).