Preparation of 1,4,5,8-tetra-tert-butyl-1,3,5,7-cyclooctatetraene by twofold SO2 extrusion

Oxidation of cis-1-transoid-1,2-cis-2-3,4,7,8-tetra-tert-butyl-9,10-dithiatricyclo[4.2.1.12,5]deca-3,7-diene 9,10-dioxide (2) by dimethyldioxirane gave the corresponding tetraoxide 4 quantitatively, which in turn provided 1,4,5,8-tetra-tert-butyl-1,3,5,7-cyclooctatetraene (6a) quantitatively by twofold thermal SO2 extrusion. The molecular structure of 6a is described on the basis of DFT calculations (B3LYP/6-31G(d) level) and X-ray crystallographic analysis.