Electrochemical reduction of 1,1,4,4-tetraphenylbutatriene

Abstract

Polarograms and cyclic voltammograms for reduction of 1,1,4,4-tetraphenylbutatriene at mercury electrodes in dimethylformamide containing tetra-n-butylammonium perchlorate exhibit four waves; the first and second waves are due to stepwise formation of the radical anion and dianion of the starting material, whereas the third and fourth waves are attributable to reduction of 1,1,4,4-tetraphenyl-1,2-butadiene and 1,1,4,4-tetraphenyl-1-butene, respectively. Electrolysis of 1,1,4,4-tetraphenylbutatriene at potentials corresponding to the second wave yields 1,1,4,4-tetraphenyl-1,3-butadiene exclusively; at a slightly more negative potential, the latter undergoes reduction to 1,1,4,4-tetraphenyl-1-butene. When 1,1,4,4-tetraphenylbutatriene is electrolyzed in the presence of glacial acetic acid and at any potential on the first or second wave, a mixture of 1,1,4,4-tetraphenyl-1,2-butadiene (56%) and 1,1,4,4-tetraphneyl-2-butyne (43%) is produced. Electrolysis of 1,1,4,4-tetraphenylbutatriene at a potential on the third wave gives only 1,1,4,4-tetraphneyl-1-butene in the absence of a proton donor and a mixture of 1,1,4,4-tetraphenyl-2-butyne (50%) 1,1,4,4-tetraphenyl-1-butene (17%), and 1,1,4,4-tetraphenyl-2-butene (33%) in the presence of glacial acetic acid. At potentials on the fourth wave, electrolyses yield solely 1,1,4,4-tetraphenylbutane when no proton donor is present and a mixture of 1,1,4,4-tetraphenyl-2-butyne (50%), 1,1,4,4-tetraphenyl-2-butene (33%), and 1,1,4,4-tetraphenylbutane (17%) when an excess of glacial acetic acid is present.