Organic Chemistry: Current Research
Open Access

Anodic electro oxidation a key tool in the synthesis of natural quinones and kinetic study

10^th European Organic Chemistry Congress

March 21-22, 2019 | Rome, Italy

Guillermo A. Guerrero Vasquez, Carlos K. Z. Andrade, Jesus Ayuso, Jose M. G. Molinillo and Francisco A. Macias

BetaTec Hop Products Ltd., UK Universidade de Brasilia, Brazil Universidad de Cadiz., Spain

Posters & Accepted Abstracts: Organic Chem Curr Res

Abstract :

The formation of natural occurring quinones from protected intermediates compounds, involves a series of steps of oxidation and deprotection, whose limitations are the number of steps that involve a reduction in the yields and sensitive of the intermediate quinones to the Lewis acids1. The anodic electrooxidation methodology has showed to be an efficient procedure to generate the final deprotection and oxidation treatment2 that involved available starting materials in any organic chemistry laboratory. Experimental set-up was made with graphite electrodes under argon by using mixtures of LiClO4 (0.01 M) in H2O/CH3CN (1:1) as the electrolyte. When methoxy moiety is used as protective group, reaction proceeds in two steps. First step of oxidation: electrolysis at 1.71 V for 21 h to generate a quantitative mixture of structural isomers. Second step of demethylation and tautomerization: electrolysis at 3.09 V for 7 h transformed the structural isomers into the desired quinone target. By contrast, when using methylenedioxy as protector, no intermediate was observed by TLC. Both steps proceed at 1.7 V for 17 h to the clean conversion into quinones moiety. The reaction yields oscillate between 64-96%. Quinones crudes prepared by this methodology can be used directly in the following reaction steps. In addition, quinones can be easily purified by using a Sephadex LH- 20 column with isocratic H2O/CH3CN mixtures. The main problem is the retention of naftazarine derivatives in the stationary phase of the columns, which generates a reduction in the reaction yields (see table 1).A complementary study of chemical kinetics suggests a first order reaction and that this reaction is governed by a radical reaction.