Selenation electrochemical

Selenium is stable in water and in aqueous solutions over the entire pH interval in the absence of any oxidizing or reducing agent. Selenium can be electrochemically reduced to hydrogen selenide or to selenides that are unstable in water and aqueous solutions. It can be oxidized to selenous acid or selenites and further (electrolyti-cally) to perselenic acid (H2Se20s). Selenic and selenous acids and their salts are stable in water. The selenides, selenites, and selenates of metals other than the alkali metals are generally insoluble. 

Skyllas-Kazacos M, Miller B (1980) Studies in selenous acid reduction and CdSe film deposition. J Electrochem Soc 127 869-873... 

Rastogi AC, Balakiishnan KS, Garg A (1993) A new electrochemical selenization technique for preparation of metal-selenide semiconductor thin films. J Electrochem Soc 140 2373-2375... 

Baranski AS, Fawcett WR, Gatner K, Me Donald AC, MacDonald JR, Selen M (1983) Structural and compositional characterization of mixed CdS-CdSe films grown by cathodic electrodeposition. J Electrochem Soc 130 579-583... 

Alanyahoglu M, Demir U, Shannon C (2004) Electrochemical formation of Se atomic layers on Au(lll) surfaces the role of adsorbed selenate and selenite. J Electroanal Chem 561 21-27... 

Oxyselenation is a powerful tool for functionalization in synthetic organic chemistry. Electrochemically generated [Br]+ or bromine reacts with (PhSe)2, producing PhSeBr. Attack of PhSeBr on the olefin (25) gives a selenated intermediate followed by solvolysis to provide (26) and a bromide ion (Scheme 11). A typical electrolysis is carried out in a MeOH-Et4NBr/H2S04 (trace)/(PhSe)2-(Pt) system in an undivided cell. Some results... 

White, A.F. (1990) Hetero electrochemical reactions associated with oxidation of ferrous oxide and selenate surfaces. In Hochella,... 

Positively polarized selenation reagents for oxyselenation reactions can be substituted by an indirect electrochemical procedure in which the bromide ion acts as the redox catalyst. The active bromine species generates the phenylselenyl cation from the added diphenyl diselenide (Eq. (48) Table 4, No. 21-26)... 

The synthetic applicability of the electrochemical oxy-transposition may be demonstrated by the one-step synthesis of d -dihydroactinidiolide 60 from the carboxylic acid 59 in 73 % yield. The lactone 60 may be produced by electrochemical intramolecular oxyselenylation followed by elimination of selenic acid (Scheme 3-21)68>. 

An electrochemical synthetic process (see Qiapter 7.1, this volume) has been reported which requires only a catalytic amount of the selenating agent, and converts an alkene to the allylic alcohol in an aqueous cell, or to the allylic methyl ether if the electrolysis is run in methanol, as in equaticxi (9).t ... 

Cathodic reduction of diphenyl diselenide produces a benzeneselenolate, which catalyzes the reduction of a, -epoxy carbonyl compounds into -hydroxy carbonyl compounds in the presence of a proton source (Scheme 16) [21]. This electrochemical method is applicable to the selenation of haloalkanes, epoxides, and enones [22]. Electrochemical reduction of elemental selenium to diselenide dianion (Se ) and selenide dianion (Se ) is also possible [23]. 

Uneyama and coworkers reported electrochemical generation of PhSeF for fluoro-selenation of alkenes and alkynes and recycling of the selenenylating reagent [52] ... 

Several reports were published on the PT/metal hybrids or PT/inorganic nanocomposites. Novel bithiophene with a pendant fullerene substituent was synthesized by electrochemical polymerization [350]. It was revealed that a photoinduced electron was transferred from the donor cable (PT) to the pendant acceptor cable (fullerene moieties). On the other side, it was demonstrated that a highly conducting cobalt selen-PT hybrid material catalyzed... 

Selenate is accnmulated in plant cells against an electrochemical potential (or gradient) by active transport driven by ATP (ATPase). Se04 readily competes with the uptake of S04 , and both anions appear to be taken-np by a nnmber of sulphate transporters in the root plasma membrane (Abrams et al. 1990). The sulphate transporters modulate Se uptake in bacteria and yeasts, and at least two types of these transporters are also present in plants. The S/Se transporters described belong to two main classes (de Filippis 2010) ... 

Electrochemically induced reactions have been a feature of selenium chemistry in the past two or three years. This year a potentially useful synthesis of ap-unsaturated aldehydes (279) has been reported and involves electrochemical generation of the active selenating species from diphenyl diselenide. Propargyl alcohols are thus selenated to give (279) in good to excellent yields. The ap-unsaturated aldehydes (279) are also formed when 1-lithioselenoalkenes, RCH=C(Li)SePh, react with DMF. Various other a-substituted alkenes are obtained in a similar fashion when DMF is replaced by other electrophiles. 

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