Samarium dibromide

While it is recognized that samarium diiodide (Sml2) is by far the most utilized reductant among Sm(II) halides, samarium dichloride (SmCh) and samarium dibromide (SmBr2) have been used in a number of applications. The main limitation of these two reductants is their... 

Lebrun, A., Namy, J.-L., and Kagan, H. B., Samarium dibromide, an efficient reagent for pinacol coupling reactions. Tetrahedron Lett., 34, 2311,1993. 

The divalent compounds of samarium primarily are halides, the reddish-brown crystalline dichloride, SmCb [13874-75-4] the dark-brown diiodide, Sml2 [32248-43-4] and the dark brown dibromide, SmBr2 [50801-97-3]. Samarium also forms a difluoride, SmF2 [15192-17-3]. The trivalent salts of these halogens are more stable than their divalent counterparts. 

The reaction of a vicinal dibromide with triethylamine and DMF with micro-wave irradiation leads to vinyl bromide. Alkenes are formed from vicinal bromides by heating with iron in methanol " or samarium in the presence of TMSCl and a trace of water. a,(3-Dibromo amides are converted to conjugated amides upon photolysis in methanol. ... 

After glycosidation, the dibromodisaccharide formed (see Scheme 31) can be further activated by reductive debromination with zinc, samarium iodide or iodide ion [23] to give the corresponding NPG which is ready to react with another molecule of dibromide A. 

SiBr2[g] SILICON DIBROMIDE (GAS) 1485 SmCI2 SAMARIUM DICHLORIDE 1533... 

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. 

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