New Insight into the Reactivity of S,S-Bis-ylide.

The present work focuses on the reactivity of S,S-bis-ylide 2 , which presents a strong nucleophilic character, as evidenced by reactions with methyl iodide and CO 2 , affording C-methylated salts 3 and betaine 4 , respectively. The derivatization of betaine 4 affords the corresponding ester derivative 6 , which is fully characterized by using NMR spectroscopy and X-ray diffraction analysis. Furthermore, an original reaction with phosphenium ions leads to the formation of a transient push-pull phosphino(sulfonio)carbene 8 , which rearranges to give stabilized sulfonium ylide derivative 7 .