Chemoselective and metal-free reduction of α,β-unsaturated ketones by <i>in situ</i> produced benzeneselenol from <i>O</i>-(<i>tert</i>-butyl) Se-phenyl selenocarbonate
The carbon–carbondouble bond of arylidene acetones and chalcones can be selectively reduced with benzeneselenol generated in situ by reacting O-(tert-butyl) Se-phenyl selenocarbonate with hydrochloric acid in ethanol. This mild, metal-free and experimentally simple reduction procedure displays considerable functional-group compatibility, products are obtained in good to excellent yields, and the use
Cesium Salt-Catalyzed Addition of Diphenyl Dichalcogenides to Alkynes: Selective Synthesis of Bis- and Mono(phenylchalcogeno)alkenes
作者:Yutaka Nishiyama、Haruko Ohnishi、Yuya Koguma
DOI:10.1246/bcsj.82.1170
日期:2009.9.15
A cesium salt has a unique catalytic ability for the reaction of alkynes with diphenyl dichalcogenides. When the diphenyl dichalcogenides, such as the disulfide, diselenide, or ditelluride, were allowed to react with alkynes in the presence of a catalytic amount of a cesium fluoride or carbonate, the bisphenylchalcogenolation of the alkynes efficiently proceeded to give the corresponding vic-bis(phenylchalcogeno)alkenes in moderate to good yields with high selectivity. When H2O was added to the reaction medium, monophenylchalcogenolation of the alkynes occurred giving the mono(phenylchalcogeno)alkenes in moderate yields.
Addition of benzeneselenol to terminal alkynes HCdropCR, catalyzed by Pd(0) complexes, leads to formation of mixtures of mono- and bis(phenylseleno)alkenes, depending on the nature of the R substituent. Electron-donor groups (R = Bu, CH2OH, CH2NMe2) give rise to addition according to the Markownikoff rule, whereas from alkynes with electron-acceptor groups (R = Ph, COOMe) mixtures of products are formed as a result of side reactions. A probable reaction mechanism includes oxidative addition of benzeneselenol to the metal, alkyne insertion into the Pd-Se bond, and reductive elimination.
Free-radical additions of diselenides to dimethyl acetylenedicarboxylate, methyl propiolate, and dimethyl maleate