Samarium diiodide deoxygenation

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]. 

Georg, G. I. Cheruvallath, Z. S. Samarium diiodide-mediated deoxygenation of taxol a one-step synthesis of 10-deacetoxytaxol. J. Org. Chem., 1994, 59 4015 1018. 

The first chemical test of the aforementioned idea comes from experiments with the 0-labeled tricyclic trioxane (128) (Scheme 19) <92JA8328>. Samarium diiodide, dissolving zinc in acetic acid, and similar agents, bring about deoxygenation to 1,3-dioxolane (129). On the other hand, ferrous bromide in THF and hemin plus phenylmercaptan, taken as models for intraerythrocytic heme, isomerize (128) to the tetrahydrofuran (130) and the hydroxy-dioxolane (131). This result is explained in terms of the pair of oxy radicals, (132) and (133), that arise from ferrous ion-induced cleavage of the peroxide bond. It is believed that (132) yields (130) by C—C bond cleavage, and that (133) by... 

Georg GI, Cheruvallath ZS (1994) Samarium Diiodide-Mediated Deoxygenation of Taxol A One-Step Synthesis of 10-Deacetoxytaxol. J Org Chem 59 4015... 

Unprotected aldono-1,4-lactones can be deoxygenated in the a-position by treatment with samarium diiodide in aqueous THF. ... 

Per-benzoylated aldonolactones undergo a reductive elimination reaction with samarium diiodide leading to unsaturated derivatives (Scheme 3). Deoxygenation at the 2-position can also take place. The difference in the reductive elimination patterns between the D-g/uco and D-galacto isomers may be due to the axial disposition of the OBz in the galacto isomer. 

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). 

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