IS SELECTIVE MONOSUBSTITUTION OF DIHALIDES VIA S(RN)1 REACTION FEASIBLE - AN ELECTROCHEMICAL APPROACH FOR DICHLOROARENES

1,4-Dichlorobenzene and dichloropyridines undergo S(RN)1 reactions wit h various nucleophiles upon electrochemical initiation. Substitution c an compete with reduction only when indirect electrolyses at low curre nt are performed. Selective formation of monosubstitution products is observed when the nucleophiles used behave as electron-donating groups when attached to the aromatic moiety, a situation which is just the o pposite of what had been observed when the same reactions were initiat ed photochemically. This surprising difference in behavior can be rati onalized in terms of different capabilities of both activation methods to generate the key monosubstitution anion radical, ArNuX(.-). Kineti c and thermodynamic data concerning the reactivity of dichloroarenes i n such processes are presented and discussed.