By samarium diiodide

The asymmetric synthesis of unsymmetrical vicinal diamines by samarium diiodide induced reductive coupling of nitrones derived from aUphatic aldehydes with optically pure N-tert-butanesulfinyl aromatic imines has been recently reported [41]. For example, the reaction between nitrone 55 and... 

Aryl ditellurides are cleaved by samarium diiodide (Sml2) to generate the new nucleophilic species diiodosamarium aryl tellurolate which reacts smoothly with alkyl and acyl... 

A reaction of dibromoacetic acid with different aldehydes promoted by Sml2, followed by an elimination reaction also promoted by samarium diiodide, affords ( > ,/l-unsaturalcd carboxylic acids with total stereoselectivity (Scheme 8).42 A mecha- (g) nism that involves chelation of the Sm(III) centre with the oxygen atom of the alcohol group through a six-membered chair-like transition state has been described. 

J. L. Chiara, J. Marco-Contelles, N. Khira, P. Gallego, C. Destabel, and M. Bemabe, Intramolecular reductive coupling of carbonyl-tethered oxime ethers promoted by samarium diiodide A powerful method for the stereoselective synthesis of aminocyclopentitols, J. Org. Chem., 60 (1995) 6010-6011. 

Skrydstrup, T, Mazeas, D, Elmouchir, M, Doisneau, G, Riche, C, Chiaroni, A, Beau, J M, l,2-cis-C-glycoside synthesis by samarium diiodide-promoted radical cychzations, Chem. Eur. J., 3, 1342-1356, 1997, and references therein. 

As an alternative to the Bu3SnH-phenylseleno glycoside chemistry, radicals may also be generated by samarium diiodide reduction of anomeric arylsulfonyl groups [115], (R=Ph] (O Scheme 55). 

Chiara, J. L. New reductive carbocyclizations of carbohydrate derivatives promoted by samarium diiodide. Carbohydrate Mimics 1998, 123-156. 

Kunishima, M. Generation and application of organosamariums mediated by samarium diiodide. Rev. on Heteroa. Chem. 1999, 21, 117-137. 

Molander, G. A., Etter, J. B. Lanthanides in organic synthesis. 8. 1.3-Asymmetric induction in intramolecular Reformatskii-type reactions promoted by samarium diiodide. J. Am. Chem. Soc. 1987, 109, 6556-6558. 

Aurrecoechea, J.M., Lopez, B., Fernandez, A., Arrieta, A., and Cossio, F.P., Diastereoselective synthesis of cycloalkylamines by samarium diiodide-promoted cyclization of a-amino radicals derived from a-benzotriazolylalkenylamines, 7. Org. Chem., 62, 1125, 1997. 

Iridium-oxygen heterocycles have been synthesized as described above viz. isocyanide insertion into an Ir—O bond <88JA3704 , by carbonylative phenylacetylene insertion between an Ir—O bond <90JA9627> and by samarium-diiodide-induced cyclization of (44) (Equation (6)) <900M1713>. 

Gross S, Reissig H-U (2003) Novel stereoselective syntheses of highly functionalized benzannulated pyrrolizidines and indolizidines by samarium diiodide induced cyclizations of indole derivatives. Org Lett 5 4305 307... 

Several examples of the stereoselective formation of cyclopentane rings promoted by samarium diiodide have been reported. Thus a pinacol-like coupling of a 1,5-dialdehyde derivative produced 75 in which the newly formed hydroxyl groups R, R were in a y/z-arrangement. (See Vol. 29, p.238, ref. 95 for a related reaction). In contrast, reaction of a 5-hexenal, produced by zinc-assisted Grob fragmentation of a methyl 6-deoxy-6-iodopyranoside, produced 76 and 77 in which the exocyclic groups R, R (or R, R ) were anti to each other. ... 

The conformationally constrained diacyl glycerol analogue 38 was prepared by samarium diiodide mediated reaction of known ketone 34 with methyl acrylate to give 35. Acid catalysed delactonization followed by periodate cleavage then gave 36, which was elaborated, via 37, to 38 (Scheme 6). Similar chemistry was employed to prepare 39 (and its -isomer), the side chain being introduced by aldol reaction. ... 

Cyclopentanoids have been prepared by samarium diiodide-catalysed reaction of 8 (R-Tbdms) with either aldehydes or ketones. The stereochemical outcome was dependent on the carbonyl compound used, with cyclohexanone giving 9 as a single product, while cyclohexane carboxaldehyde gave an isomeric mixture containing predominantly 10. ... 

The carbon-carbon double bonds can also be reduced by samarium diiodide-H20 system. 

As shown in Fig. 3.33, starting from the Diels-Alder product, reduction for removal of acetoxyl group by samarium diiodide was first tried. Compound 3.68 was obtained in 90 % yield. Using CCLj as the solvent and benzoyl peroxide as the... 

Sc(OTf)3 (4 mol%)-catalyzed addition of 1-trimethylsilyl nitropropanate to aryl and alkylimines was described [109]. The use of N-(4-methoxyphenyl)imines gave superior yields and/or diastereoselectivities of P-nitro amines in most cases (72-99% yield, antijsyn = 5/3-9/1). The products could be reduced to 1,2-diamines by samarium diiodide reduction, formation of the cyclic urea and cleavage of the 4-methoxyphenyl group with ceric ammonium nitrate (CAN). This methodology was later employed for the synthesis of pseudo-C2-symmetric triamines as candidates for human immunodeficiency virus (HIV) protease inhibition [110]. 

Samarium diiodide serves as an effective reductant for a variety of functional groups. Conjugated double bonds are readily reduced by Sml2 in the presence of proton donors such as methanol (Kagan and Namy, 1986). Inanaga (1990) has shown that alkynes are reduced efficiently to alkenes by samarium diiodide in the presence of catalytic amounts of cobalt (Co) complexes. Selective synthesis of (Z)-alkenes is possible due to the chemoselective nature of... 

Similarly, Chiara et al. reported a cascade reaction of 6-deoxy-6-iodohexopyranosides promoted by samarium diiodide [69]. A series of 6-deoxy-6-iodohexopyranosides with different configurations and substitution patterns was treated with Sml2 in THF/HMPA to give the desired cyclopentanols. For example. 

Kende AS, Mendoza JS. An improved variant of the Julia olefin synthesis-reductive elimination of (3-hydroxy imida-zolyl sulfones by samarium diiodide. Tetrahedron Lett. 1990 31(49) 7105-7108. 

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