| Abstract
| - The reactivities of the cyclic ketones cycloheptanone, cyclodecanone, and cycloundecanone withdimethylsulfoxonium methylide generated from trimethylsulfoxonium iodide and base (NaH) were studiedin diglyme at 130 °C. Oxiranes, which primarily form via the Corey reaction, lead to ring expansions togive oxetanes and oxacyclopentanes when an excess of dimethylsulfoxonium methylide is used. TheCorey reaction is suppressed in the presence of excess of base, and 1,3-terminal dienes form instead (weterm this reaction the Yurchenko diolefination). Our mechanistic proposal involves the deprotonation ofthe betaine that forms after the attack of dimethylsulfoxonium methylide on the carbonyl group of theketone. The key step of the diolefination reaction involves a [2,3]-sigmatropic rearrangement of the ylideto a γ-unsaturated sulfoxide with a barrier of 9.9 kcal/mol (ΔH298, MP2/cc-pVDZ, for the cycloheptanederivative). The elimination of sulfenic acid from the γ-unsaturated sulfoxide in the terminal step of thediolefination is associated with a higher barrier (17.3 kcal/mol) but is strongly accelerated in the presenceof base. The reactivity of cyclic ketones in the Yurchenko reaction depends on the ring size; medium-sized cyclodecanone is less reactive than either cycloheptanone or cyclododecanone.
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