A general, asymmetric redox arylation of ynamides and thioalkynes with chiral sulfoxides is reported. This is the first example of a general 1,4-chirality transfer from sulfur to a carbon stereocenter through a sulfonium [3,3]-sigmatropic rearrangement. This reaction delivers α-arylated thioesters and amides under mild conditions in an atom-economical manner. The products are formed in high yields with enantiomeric ratios up to 99.5:0.5. Quantum chemical calculations suggest a mechanism for the chirality transfer from sulfur to carbon and explain the experimentally observed correlation of the enantioselectivity with both the catalyst and the substrate.

Cationic cyclopropanation involves the γ-elimination at carbocations to form a new σ-C−C bond through proton loss. While exceedingly rare in bulk solution, it is recognized as one of the main biosynthetic cyclopropanation pathways. Despite the rich history of bioinspired synthetic chemistry, cationic cyclopropanation has not been appropriated for the synthetic toolbox, likely due to the preference of carbocations to undergo competing E1 β-elimination pathways. Here, we present an in-depth synthetic and computational study of cationic cyclopropanation, focusing on the 6,8-cycloeudesmanes as a platform for this investigation. We were able to apply biomimetic cationic cyclopropanation to the synthesis of several 6,8-cycloeudesmanes and non-natural analogues�in doing so, we showcase the power of this transformation in the preparation of complex cyclopropanes.

Eine allgemeine asymmetrische Redoxarylierung von Inamiden und Thioalkinen mit chiralen Sulfoxiden wird vorgestellt. Es handelt sich um das erste Beispiel eines allgemeinen 1,4‐Chiralitätstransfers von Schwefel zu Kohlenstoff durch [3,3]‐sigmatrope Umlagerung eines Sulfoniumintermediats. Die Reaktion liefert α‐arylierte Thioester und Amide in atomökonomischer Weise und unter milden Bedingungen. Die Produkte werden in hohen Ausbeuten und mit bis zu 99.5:0.5 Enantiomerenverhältnis erhalten. Quantenchemische Rechnungen legen für den Chiralitätstransfer einen Mechanismus nahe, der mit den experimentell beobachteten Korrelationen zwischen Enantioselektivität und Katalysator/Substrat übereinstimmt.