- Electrochemical preparation of α,α′-dicarbonylselenides
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A facile preparation of α,α′-dicarbonylselenides has been performed by reaction of α-carbonyl selenocyanates with an enolate, electrogenerated by reduction of a carbon-halogen bond.
- Otero, María Dolores,Batanero, Belen,Barba, Fructuoso
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- Breaking bonds with electrons: Stepwise and concerted reductive cleavage of C-S, C-Se and Se-CN bonds in phenacylthiocyanates and phenacylselenocyanates
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The mechanistic aspects of the electrochemical reduction of phenacylthio- and selenocyanates have been studied. With phenacylthiocyanates (1), a change in the reductive cleavage mechanism is observed as a function of the substituent on the phenyl ring. While a stepwise mechanism involving the intermediacy of a radical anion is followed for substrates bearing a strong electron withdrawing group, such as cyano and nitro substituent (1d, 1e), and a concerted mechanism is favoured for compounds bearing an electron-donating or no substituent on the phenyl ring (1a-c). A regioselective bond cleavage leads to the fragmentation of the CH2-S bond with all compounds 1a-e, further yielding the corresponding 1,4-diketone (3) as products. Contrastingly, with phenacylselenocyanates (2), two different reductive cleavages occur involving the breaking of both the CH2-Se and Se-CN bonds. Several products are obtained, all coming from nucleophilic attack at the α (phenacyl) carbon or the selenium atom.
- Bouchet, Lydia M.,Peory, Alicia B.,Robert, Marc,Argüello, Juan E.
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p. 11753 - 11760
(2015/02/19)
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- ELECTROCHEMICAL SYNTHESIS OF SELENO AND TELLURO DERIVATIVES IN MeCN
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Large-scale electrolysis with concurrent sonication in MeCN allows for the synthesis of a large variety of seleno and telluro derivatives.Aliphatic chalcogenides REER or RER (E = Se, Te) can be prepared by reduction of E powder to E2(2-) or E(2-), followed by addition of an alkyl halide RX.Depending upon R, substitution can compete with homogeneous electron or H+ transfers.RE+ can be prepared by anodic oxidation of REER, and trapped by nucleophiles and olefins.The synthesis of aromatic chalcogenides ArEAr'can be carried out by electrochemically inducedSRN1 substitution.The yields are improved by redox catalysis.Under such conditions, the synthesis of PhEAr (Ar = NCC6H4, PhCOC6H4) proceeds in good yields.ArEEAr and ArEAr can be prepared by cathodic reduction of PhEAr.
- Degrand, Chantal,Prest, Rita,Nour, Mohamed
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p. 201 - 210
(2007/10/02)
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- SYNTHESES WITH DIKETO SELENIDES
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We report a) a modified synthesis of diketo selenides, b) preparation of 2,5-diacylselenophenes by condensation of diketoselenides with glyoxal, c) preparation of poly-substituted selenophenes by intramolecular reductive coupling reaction of diketo selenides with low-valent titanium reagent under controlled conditions (0 degC) followed by dehydratation of the resulting 3,4-dihydroxyselenolanes, and d) formation of 2,5-dihydroselenophenes and 1,3-dienes by treatment of diketo selenides with the low-valent titanium reagent in refluxing tetrahydrofuran.
- Nakayama, Juzo,Shibuya, Masahiro,Ikuina, Yoji,Murai, Fumito,Hoshino, Masamatsu
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p. 149 - 156
(2007/10/02)
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- A Seleno-Pummerer Rearrangement of Haloselenuranes
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When heated or treated with triethylamine in tetrahydrofuran, diacetonyl- and diphenacylselenium dichlorides and their derivatives undergo seleno-Pummerer rearrangement to give the corresponding α-chloro selenides in good yields.
- Nakayama, Juzo,Sugihara, Yoshiaki
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p. 1317 - 1318
(2007/10/02)
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- PREPARATION OF 2,5-DIACYLSELENOPHENES BY CONDENSATION 0F α,α'-DIKETOSELENIDES WITH GLYOXAL
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The reaction of selenium oxychloride with 2 equiv. of ketones affords α,α'-diketo selenide dichlorides (1) in excellent yields.Portionwise addition of 1 to a stirred two-phase mixture of an aqueous sodium dithionite solution and benzene gives α,α'-diketo
- Nakayama, Juzo,Shibuya, Masahiro,Hoshino, Masamatsu
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p. 909 - 912
(2007/10/02)
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