Elimination samarium iodide

Zard and coworkers have developed a synthesis of substituted dienes by reductive elimination of allylic nitroacetates (equation 33)66. Allylic nitroacetates can be prepared by condensation of nitromethane with the carbonyl compound followed by addition of formaldehyde and acetylation67. Reductive elimination can be carried out by employing either chromous acetate or samarium iodide. 

The reductive elimination of 0-hydroxyimidazoyl sulfones by samarium iodide was claimed to be an improved variation of the Julia olefin synthesis [421]. 

Scheme 21 shows the reaction of the 2-deoxy-2-amino sugar 100 reacting with samarium iodide and cyclohexanone to give the desired C-glycoside 101 as the major compound [29]. When the azide was used in lieu of the protected amine fimction, only the product of elimination was formed. This indicates a possible complexation between the acetimido oxygen atom (Scheme 21, second equation) and the samarium atom, resulting in stabilization of the a-organosamarium species, since normally. 

Samarium iodide has been used to reduce sulfonylated oxabicydic substrates leading to the elimination of the ft oxygen moiety. Molander used this strategy for the synthesis of substituted cycloheptenes and cyclooctenes, Eq. 155 [81]. 

Synthesis of Alkenes by Reductive Elimination. The treatment of 2-halo-3-hydroxy esters and amides with samarium iodide leads to the corresponding di- or trisubstituted E)-a,p-unsaturated derivatives in high yields and diastereoselectivities (eqs 39 and 40). The precursors are readily accessible by condensation of the lithium enolate of a-haloesters or amides. If the substrate contains y,i5-unsaturation, the /3,y-unsaturated ester is generated in the process (eq 41). 

Samarium iodide can also be used as an alternative to sodium/ mercury amalgam for the reductive elimination of 1,2-acetoxy-sulfones in the Julia-Lythgoe olefination. The alkene is generated in a two-step process that first involves DBU or LDA treatment to generate a vinyl sulfone that is then reductively cleaved with samarium iodide (eq 44). The diastereoselectivity of both transformations is usually quite good and the method is compatible with the synthesis of monoalkenes as well as dienes and trienes. 

Reductive elimination of the />-tolylsulfinyl group from compound 210 with samarium(n) iodide was performed without isolation of the intermediate in situ after confirmation that (.V)-210 had reacted completely, giving the bicyclic lactam 213 (Scheme 26) <2001J(P1)2924>. 

Samarium(II) iodide, 46, 3 Sandmeyer reaction, 2, 7 Schiemann reaction, 5, 4 Schmidt reaction, 3, 8, 9 Selenium dioxide oxidation, 5, 8 24, 4 Seleno-Pummerer reaction, 40, 3 Selenoxide elimination, 44, 1 Shapiro reaction, 23, 3 39, 1 Silanes ... 

Addition of DBU to a solution of 149 in THF induced an elimination reaction accompanied by loss of a molecule of CO2 and provided the unstable amine 150, which was converted in situ into isocyanate 151 by reaction with phosgene and triethylamine. After filtration to remove hydrochloride salts, the solution of 151 was treated with samarium (II) iodide in the presence of lithium chloride. These conditions, which had been previously determined to be optimal for spirooxindole generation on a model system, provided compound 152 as an inseparable 7 1 mixture of diastereoisomers [43]. The major component of this mixture was determined by NOE analysis to have the required configuration, which is consistent with bond formation from the less hindered, convex face of 151 (Scheme 35). 

Promoted by samarium metal in the presence of a catalytic amount of iodine, the MBH adduets underwent reductive elimination to form ( )-methylcin-namic ester derivatives 368. However, allylic iodide derivatives, (2Z)-2-(iodo-methyl)alk-2-enoates 369, were obtained when the iodine was used in 1 1 ratio with metallic samarium. This method gave a new approaeh to the seleetive construction of stereo-defined trisubstituted alkenes with the simple Sm/l2 system (Scheme 3.164). ... 

For a more elaborate test case, the sidetracked acceptor 69 was prepared and coupling with 68a proceeded smoothly to give a dibromide. Zinc could not be used to restore the double bond, because of the sohd-sohd interaction that would be involved. A one-electron reductive elimination with samarium II iodide [24] proceeded smoothly, however, to give 70. Unfortunately, efforts to cleave the disaccharide from the solid support to produce 71 were unsuccessful. FTIR data suggested that addition to the double bond overwhelmed the cyclization reaction. 

Acetals derived from Dimethyl L-Tartrate react with Me2BBr to generate a-bromo ethers which react further with cuprate reagents to give optically active secondary alcohol derivatives (eq 14). The alcohols may be liberated by treatment with Samarium(II) Iodide or by a straightforward sequence of reactions (mesylation and elimination to form an enol ether followed by exposure to methoxide in refluxing methanol). Selectivity is enhanced by the... 

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