Base-catalysed prototropic isomerization. Part VI. The isomerization of acetylenic hydrocarbons

Abstract

The isomerization of substituted 1,8-diphenylocta-3,5-diynes by potassium t-butoxide–t-butyl alcohol and by potassamide on alumina (a homogeneous catalyst) has been studied. The course of the reaction depends strongly on the catalyst and on the diyne. Conjugated tetraenes are obtained with both catalysts in the case of 1,8-di-phenylocta-3,5-diyne. In contrast, 1,8-bis-(2,4,6-trimethylphenyl)octa-3,5-diyne gives a conjugated tetraene on the heterogeneous catalyst, but migration of the triple bonds takes place in the homogeneous system giving 1,8-bis-(2,4,6-trimethylphenyl)octa-1,3-diyne.