Electro-organic Synthesis of Some Natural Products Analogues

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Addis Ababa Universty


In this project an attempt was made to prepare lignans by oxidative and reductive coupling of the a-enolates and a-bromo derivatives of substituted propiophenones respectively. Propiophenone derivatives were prepared by the addition of ethylmagnesium iodide to substituted benzaldehydes followed by oxidation of the intermediate alcohols with Jones’ reagent. The a-bromo propiophenone derivatives were prepared by treating the ketones obtained with bromine in chloroform solution. Prior to preparative electrolysis of the a-enolates and a-bromo derivatives, the working potentials were determined by cyclic voltammetry and PC polarography. It was found out that the carbonyl functional group was reduced at a potential greater than -1.9V and C-Br bond it was cleaned to the corresponding free radical or carbanion in the potential range of -0,2V to -1.4V. Preparative electrolysis of 3,4-methylenedioxypropiophenone in methanol containing, sodium methoxide and pota - ssium iodide at 1.05V (divided cell)gave the a-hydroxy prcpiophenone derivatives. The methyl, ether propiophenone derivatives were also obtained when the ketones were electrolyzed at various working potentials in qqueousmethanol medium containing the electrolytes sodium hydroxide and potassium iodide. Exhaustive preparative electrolysis of the a-bromo-3,4-dimethoxynropiophenone derivative at -1.7V vs SCE using platinum electrode(divided cell)gave a lipnan of the 1,4-diaroylbutane derivatives.