ELECTROORGANIC REACTIONS .41. DIELS-ALDER REACTIONS OF O-QUINODIMETHANES FROM THE CATHODIC REDUCTION OF ALPHA,ALPHA'-DIBROMO-1,2-DIALKYLBENZENES

Cathodic reduction of alpha,alpha'-dibromo-1,2-dialkylbenzenes in DMF containing Et(4)N(+) Br- as supporting electrolyte, in the presence of dienophiles (e.g. maleic anhydride derivatives), yielded Diels-Alder adducts of o-quinodimethanes. Selective reduction of the benzylic dibromides was often possible even when their irreversible cyclic voltammetric reduction peak potentials were more negative than the E(o) values for the anhydrides. This might be a consequence of redox catalysis, with the anhydrides having a dual role as mediators and dienophiles.