Sulfonium ylides have long occupied a privileged position in organic synthesis due to their use as synthetic reagents in such ubiquitous reactions as the Stevens rearrangement and the Corey-Chaykovsky reaction. In recent years the application of stabilised sulfonium ylides has been expanded to previously unreactive substrates though transition-metal-mediated activation, either through decarboxylative processes, or through p-acid activation. Previous work in our group has focussed on the synthesis of cyclopropanes and furans, through Au-catalysed cyclisation reactions of allyl ester- and propargyl ester-substituted sulfonium ylides respectively. Herein, we present an unusual case of catalyst-dependent selectivity in cycloisomerisation reactions of unsaturated, sulfur-tethered sulfonium ylides. Mechanisms for each transformation have been proposed, with support from computational calculations and mechanistic experiments. Applications of the resulting products in synthetic sequences is also discussed.

Catalyst-dependent selectivity in sulfonium ylide cycloisomerisation reactions with pi-acid catalysts

254th National Meeting (2017)

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