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37.2.3.3 Method 3: Addition of a Sulfonium or Sulfoxonium Ylide

DOI: 10.1055/sos-SD-037-00188

Aggarwal, V. K.; Crimmin, M.; Riches, S.Science of Synthesis, (200837329.

Both sulfonium[‌43‌‌46‌] and sulfoxonium[‌47‌‌49‌] ylides are known to undergo epoxidation reactions in the presence of a carbonyl compound. Sulfoxonium ylides are far more stabilized than their sulfonium counterparts and, as a result, often give different and complementary regio-, chemo-, and stereoselectivity. For example, the reactions of dimethylsulfonium methylide (23) and dimethyloxosulfonium methylide (24) (Scheme 12) with α,β-unsaturated aldehydes or ketones give the corresponding epoxide and cyclopropane products, respectively {see also Science of Synthesis, Vol. 27 [Heteroatom Analogues of Aldehydes and Ketones (Section 27.1.3.2.1)]}. This difference in selectivity is attributed to the more stabilized sulfoxonium ylides undergoing reversible addition to the carbonyl moiety and nonreversible Michael addition. In contrast, the unstabilized sulfonium ylide undergoes nonreversible addition to the carbonyl moiety and gives the kinetic product.[‌48‌] The difference in stability, and hence nucleophilicity, between sulfonium and sulfoxonium ylides means that sulfoxonium ylides tend to require longer reaction times and higher temperatures to effect the epoxidation of carbonyl groups.

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