Electrochemical reductive hydrodehalogenation

Polyhaloacetic acids and their partially hydrodehalogenated products represent a second important family of herbicide-/pesticide-derived substrates. In their review on the environmental applications of industrial electrochemistry, Juttner and co-authors (Juttner et al. 2000) documented the electroreductive dechlorination of dichloroacetic acid (a by-product of monochloroacetic acid), a way to recover the valuable compound and avoid wastes. The electrochemical reduction of polychloro- and polybromo-derivatives was performed by Korshin and Jensen (2001) on Cu and Au cathodes. Complete dehalogenation was obtained for all substrates, but for monochloroacetic acid. To overcome the intrinsic poor reactivity of the monochloro-derivative the photoelectrochemical properties of a p-doped SiC electrode were investigated (Schnabel et al. 2001) however, the dehalogenation stopped at monochloroacetic acid. 

Cheng, H., Scott, K. and Christensen, P.A. (2003c) Hydrodehalogenation of 2,4-dibromophenol by electrochemical reduction. J. Appl. Electrochem. 33, 893-899. 

In outer-sphere SET reductions (e.g., in electrochemical dehalogenations), hydrogen abstraction by R leads to the product RH (i.e., no step related to (ii) is required to occur). Process (ii) follows generally the activation of the substrate in the proposed hydrodehalogenation cycles, but we know also of opposite examples [77, 82, 106, 112],... 

Electrochemical methods for the reduction of halides have also been used in synthesis. For example, in the presence of chromium(II) salts as catalysts, deoxynucleosides have been prepared in DMF solutions with the use of a platinum electrode32. a-Halocarbonyl compounds have also been hydrodehalogenated in this way63,64. It should be noted, however, that this method is not always successful and significant problems have been reported in some instances65. 

Minguzzi A, Lugaresi O, Aricci G, Rondinini S, Vertova A (2012) Silver nanoparticles for hydrodehalogenation reduction evidence of a synergistic effect between eatalyst and support. Electrochem Commun 22 25—28. doi 10.1016/j. elecom.2012.05.014... 

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