We recently reported that sulfoxonium and sulfonium methylides are generated upon treatment of storable, dry mixtures of Me3S(O)I/ KOt-Bu and Me3SI/NaH, respectively, with carbonyl compounds in DMSO to conveniently and rapidly afford the corresponding epoxides by the Corey-Chaykovsky reaction (Ciaccio et al., Synth. Commun. 2003, 33, 2135). Using mixtures of Me3S(O)I/ KOt-Bu and Me3S(O)I/ NaH under similar conditions, we now report that various a,b-unsaturated ketones afford the corresponding cyclopropyl ketones in good yields. This “instant methylide” modification of the Corey-Chaykovsky cyclopropanation reaction offers a convenient and experimentally simple preparation of cyclopropyl ketones, with advantages over conventional procedures: ease of handling (mixtures of sulfoxonium salt and base can be stored indefinitely under anhyd. conditions); in most cases, methylides are generated in the presence of the carbonyl substrate; reaction times are relatively short. Preliminary results suggest that aziridination of suitably substituted imines is possible.
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