Mechanisms of electrochemical hydrogenation of fluoranthene in HMPA with ethanol and aqueous HCL as proton donors

Abstract

The electrochemical hydrogenation of the non-alternant aromatic hydrocarbon fluoranthene has been investigated in LiClO₄-hexamethylphosphoric triamide; it has been found that hydrogenation cannot be achieved satisfactorily, not even to the dihydro derivative, when ethanol is used as the proton donor, whether present during or added after electrolysis. On the other hand, reaction of a stock of fluoranthene dianion with aqueous hydrochloric acid proves to be a clean, easy way to prepare 1,2,3,10b-tetrahydrofluoranthene, a product which requires donation of four electrons to fluoranthene. A mechanism is discussed to account for such a transfer of electrons.