Reactions with asymmetric diarylethylenes. Part XV. Dimerisation of 1,1-bis-p-alkoxyphenylethylenes

Abstract

Dimerisation of 1,1-bis-p-methoxy(or -ethoxy)phenylethylene with hydrogen chloride or bromide, trichloroacetic acid, or glacial acetic acid–sulphuric acid gave 1,1,3,3-tetrakis-p-methoxy(or -ethoxy)phenylbut-1-ene, identified on the basis of synthetic, degradative, and reduction studies and n.m.r. spectral evidence. Chlorination of the dimer gave the corresponding monomer and its chloro-derivative, whereas bromination gave the dibromo-dimer, which could be converted into the corresponding buta-1,3-diene. Iodination gave only the monomer. The mechanism of the reactions with bromine and chlorine is discussed.