Synthesis and Properties of 1,3,5,7-Tetra-tert-butyl-s-indacene

To check the influence of substituents on the bonding of the 12π-perimeter of s-indacene, a tetraalkyl derivative, the title compound 1, was synthesized. 1, red needles, is weakly paratropic. Crystal structure analysis and NMR investigations indicate a delocalized or a localized π-electron system with only a small energy barrier between the π-bond isomers.