Single-electron transfer reagent

The radical anionic character of the 1,4-diazabutadiene ligand was further proven in the heteroleptic complex CpfSm(tBuDAB), synthesized from the strong single electron transfer reagent SmCpf(THF)2 and the free ligand [173]. 

Xe-like electronic configuration is adopted. The + 2 oxidation state is most relevant for samarium (f6, near half-filled), europium (f7, half-filled), thulium (f13, nearly filled) and ytterbium (f14, filled). In order to attain the more stable + 3 oxidation state, Sml2 readily gives up its final outer-shell electron, in a thermodynamically driven process, making it a very powerful and synthetically useful single-electron transfer reagent. 

Divalent organolanthanide complexes can also initiate MMA polymerization. A divalent lanthanide complex, as a single-electron transfer reagent, can readily react with the monomer to generate a radical anion species, which subsequently couples into a bimetallic trivalent lanthanide enolate intermediate, which is the active center. Therefore, divalent organolanthanide complexes serve as bisinitiators for MMA polymerization [160]. 

The single-electron-transfer reagent samariiun(II) iodide (SmH) has been used extensively to intitiate radical reactions in solution and has now begun to find application in solid-phase synthesis. 

De Clercq [38] has utilized a sulfide linker, cleaved by a radical process initiated by electron transfer, in a solid-phase Julia-type olefination process. Alkylation of an aryl thiol resin followed by mCPBA oxidation gave supported sulfone 217 (Scheme 54). Successive treatment of the resin with n-butylhthium and an aldehyde followed by trapping of the resultant alkoxide with benzoyl chloride gave resin-bound a-benzoyloxy sulfone 218. Olefins 219 and 220 were released from the sohd support upon reduction with a single-electron-transfer reagent and elimination of the sulfone link-... 

Not unexpectedly, the promoters used for the activation of thioglycosides, including IDCP [565], IDCT [566], NIS [566,567], the NIS-TfOH system [565], and MeOTf [568], also promote the reactions of selenoglycosides. Activation of selenoglycosides by photo-induced electron transfer [569] and the single electron transfer reagent TBPA 99 [570] were also reported. Selenoglycosides can also be activated by I2 [254,571]. 

Use of Samarium(II) Iodide. In recent years, samarium(II) iodide has become a popular choice as a single-electron-transfer reagent for mild and selective reductive desulfonylations. This reagent is employed for the reduction of a wide variety of functionalized sulfones, principally 3-keto and vinylic sulfones (Eq. 89).149... 

SET (single-electron transfer) reagent 778 Shi epoxidation 525, 525 Shibata 966... 

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