ELECTROLYTIC REDUCTIVE COUPLING .17. A STUDY OF 1,2-DIACTIVATED OLEFINS .2. MACRO-ELECTROLYSES

The electrolytic reductive coupling of a variety of diactivated olefins, XCH=CHY, has been studied. The reduced dimeric products have been iso lated and carefully identified. Both symmetrical and unsymmetrical dimers were observed. The dimeric products are formed by two paths: the first involves the attack of the electrochemically generated anion radical on un reduced olefin; the second involves the protonation of the anion radical fol lowed by reduction to an anion and subsequent attack on the olefin. The isomer distribution in the dimeric product obtained by the first route is rationalized on the basis of the relative anion stabilizing ability of the acti vating groups in the acceptor molecule and the relative ability toward stabi lizing a radical site in the donor molecule. The possibility of forming cross-coupled products (between a diactivated olefin and a Michael acceptor) is limited to systems in which the electrochemically generated anion radical is relatively stable toward its parent olefin or in which the reduction poten tials of the pair are similar, i.e., ΔE1/2 < 0.4v. © 1969, The Electrochemical Society, Inc. All rights reserved.