Cyclic Sulfoxonium Ylides: Synthesis and Chemospecific Reactivity in the Catalytic Alkylation of Indoles

Abstract

The study of the reactivity of cyclic sulfoxonium ylides has been so far neglected, in particular for reactions that forms carbon‐carbon bond at the ylide carbon atom. Herein, we describe the synthesis of cyclic sulfoxonium ylides by palladium‐catalyzed intramolecular arylation and the reactivity of these ylides in the C3‐alkylation of indoles in the presence of either an acid catalyst or an iridium catalyst. This study revealed that acid catalysis is only efficient for cyclic sulfoxonium ylides in which the tether is a six‐membered lactone, whereas iridium catalysis was better suited to the reaction of cyclic sulfoxonium ylides in which the tether is a five‐membered ring ketone or lactone. The observed chemospecificity might be due to the relative basicity of the ylides under acid catalysis and to the steric hindrance around an iridium carbene intermediate when the reaction is conducted with the iridium catalyst.

Unveiling a Strategy for Ring Opening of Epoxides: Synthesis of 2-Hydroxyindolinylidenes Using α-Ester Sulfoxonium Ylides

“…Although some of the yields obtained might be considered low, we believe that, with further optimization, this protocol can yield higher results for specific nucleophiles. It is noteworthy that while there are several methods in the literature for synthesizing compounds similar to 8a – g , , none of them was applied with such a diverse array of nucleophiles, as demonstrated in this report.…”