Samarium diiodide epoxides

SAE reaction see Sharpless asymmetric epoxidation Saegusa oxidation 390 samarium diiodide 496, 633, 638 saponification 49, 207 sativene 382 f. 

The proposed mechanism includes a reductive epoxide opening, trapping of the intermediate radical by a second equivalent of the chromium(II) reagent, and subsequent (3-elimination of a chromium oxide species to yield the alkene. The highly potent electron-transfer reagent samarium diiodide has also been used for deoxygenations, as shown in Scheme 12.3 [8]. 

More recently, Doris et al. have described the reductive ring-opening of a-keto epoxides [16]. In this manner, p-hydroxy ketones can be obtained in high yields. The synthesis of enantiomerically pure compounds can easily be realized. The titanocene] 111) reagents are distinctly superior to samarium diiodide, which is also known to induce this transformation. 

Samarium diiodide promotes the reaction between epoxides and imines to form oxazolidinones <2000TL3389>. 

It should be noted that C-C bond scission in epoxides can be obtained if the radical formed is stabilized by aryl or vinyl substituents [26, 27]. In this manner tetrahydofurans can be obtained as shown in Scheme 15 [28] in reactions employing samarium diiodide as electron transfer reagent for radical generation [29],... 

Preparation. - The reaction of diphenylphosphinyl chloride with dicyclopentadienylsamarium (or samarium diiodide), followed by an alkyl halide (or alkyl tosylate, epoxide, or a,P-unsaturated ketone), provides a route to a... 

Samarium diiodide has been utilized for deoxygenation of diverse functional groups. These include the conversion of epoxides to olefins (Matsukawa et al., 1987), sulfoxides to sulfides, and aryl sulfones to sulfides (Honda et al., 1989). Examples are shown in eqs. (14)-(16). 

EPOXIDES Diphosphorus tetraiodide. Lithium. 3-Methyl-2-selenoxo-l,3-benzothiazole. Phosphorus triiodide. Lithium. Potassium iodide-Zinc-Phos-phorus(V) oxide. Samarium(II) iodide. Sodium O.O-diethyl phosphorotelluro-ate. Triphenylphosphine hydroiodide-Triplienylphosphine diiodide. 

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