Rapid and Modular Access to Vinyl Cyclopropanes Enabled by Air-stable Palladium(I) Dimer Catalysis

Diastereoselective cyclopropanation of α,β-unsaturated carbonyl compounds with vinyl sulfoxonium ylides

Herein, we report a three-component stereoselective cyclopropanation of vinyl sulfoxonium ylides with indane 1,3-dione and aldehydes under mild reaction conditions. In contrast to previous reports, the present work shows that electrophilic addition selectively takes place at the α-position of the vinyl sulfoxonium ylide. The interesting feature of this approach is that the multicomponent reaction selectively proceeds because of the difference in nucleophilic reactivity of vinyl sulfoxonium ylides and indane 1,3-dione with electrophilic partners, such as aldehydes and in situ generated arylidenes. Additionally, density functional theory (DFT) studies were conducted to investigate the difference in the reactivity of these reactants, as well as to unveil the mechanism of this three-component reaction. Furthermore, non-covalent interactions of selectivity-determining transition states explain the origin of the diastereoselectivity of cyclopropanation.

Highlights from the 57th Bürgenstock Conference on Stereochemistry 2024

Herein, we share an overview of the scientific highlights from speakers at the latest edition of the longstanding Bürgenstock Conference.

Palladium-Catalyzed Carbonylative Difunctionalization of Unactivated Alkenes Initiated by Unstabilized Enolates

This report describes the first example of palladium-catalyzed carbonylative difunctionalization of unactivated alkenes initiated by enolate nucleophiles. The approach involves initiation by an unstabilized enolate nucleophile under an atmospheric pressure of CO and termination with a carbon electrophile. This process is compatible with a diverse range of electrophiles, including aryl, heteroaryl, and vinyl iodides to yield synthetically useful 1,5-diketone products, which were demonstrated to be precursors for multi-substituted pyridines. A PdI -dimer complex with two bridging CO units was observed although its role in catalysis is not yet understood.

Sulfur-Mediated Formal Allylic C-H Cyclopropanation of α-Methylstyrenes

Allylic C-H cyclopropanation of α-methylstyrene and its derivatives was realized through a one-pot two-step sequence, formally converting two aliphatic C-H bonds to C-C bonds with a good yield and high diastereoselectivity, thus providing a quick entry to the synthetically useful vinyl cyclopropane structures.