STEREOCHIMIE DE LA REDUCTION ELECTROCHIMIQUE D'α-CETOAMIDES OPTIQUEMENT ACTIVES I. ELECTROREDUCTION DE LA S(-) N-(α-METHYLBENZYL)BENZOYLFORMAMIDE
Electrochemical reduction of the title compound has been investigated in hydro-alcoholic medium, at a mercury cathode.Polarographic study shows adsorption of the substrate in very acidic medium (pH 5.5.Controlled potential electrolyses give the corresponding mandelamide in a quasi-quantitative yield; titration of the mixture of the two epimers is achieved by proton NMR at 300 MHz.In very acidic medium, preferential formation of the RS mandelamide is observed (higher optical yield:12.5percent).On the contrary, SS mandelamide is generally the main stereoisomerin acetic or ammoniacal buffer; however, when electroreductions are carried out at very cathodic potentials, again preferential formation of the RS epimer is observed.Stereochemistry of the reduction is explained taking into account conformations of the starting molecule and protonation of the carbanion resulting from a 2 electron reduction.
Boulmedais, Ali,Jubault, Michel,Tallec, Andre
p. 610 - 617
(2007/10/02)
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