Electrochemical reduction of phthalide has been explored at a carbon cathode in dimethylformamide with the aid of cyclic voltammetry and controlled�potential electrolysis.  Previous work conducted with a mercury cathode found o-toluic acid and phthalide as products when the post�electrolysis solution is extracted in the presence of an acid.  In the present work, the formation of the o-toluate anion, via reduction of phthalide at a carbon cathode, has been investigated.  Analysis of the post�electrolysis solution, by means of gas chromatography and gas chromatography�mass spectrometry, revealed that the products are phthalide and an o-toluate ester.  Employment of different tetraalkylammonium salts as electrolytes directly impacts the o-toluate ester that is formed.   Conversely, if the post�electrolysis solution is extracted in an acid environment, as previously done, no ester is detected and only o-toluic acid and phthalide are seen.  This demonstrates the importance of the work-up procedure on the observed products, as well as the possible chemistry that may take place in a gas chromatograph.  Lastly, when D2O is added to the solution before an electrolysis, deuterated products are observed at the end of the experiment.  A mechanistic interpretation of these results will be discussed.

Electrochemical reduction of phthalide at a carbon cathode in dimethylformamide in the presence of tetraalkylammonium salts

246th National Meeting (2013)

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