Hydrodimerisation electrochimique de cetones aromatiques encombrees en milieu aprotique et en presence de chlorure de chrome

The electrochemical reduction of hindered aromatic ketones which are difficult to reduce alone, can be achieved in an aprotic medium (DMF) on a mercury pool cathode, in presence of Cr(III) chloride, at the reduction potential or the Cr(II)/Cr(0) system, but at a less negative potential than that of the ketone itself. There is selective hydrodimerisation into an α-glycol, with total lack of polymerisation. With dissymetric ketones, the dl-diastereoisomers of the diols are produced. The effect of chromium is due either to the reduction of a Cr-ketone complex or to the reduction of the ketone by a film of colloidal chromium on the electrode surface.