Novel Structures from Tris(benzocyclobutadieno)cyclohexatriene: Triscyclopropanation and Trisoxacyclopropanation to the First [2.1.2.1.2.1]Hexaannulanes

Surprisingly thermally stable, the hexaannulanes 1 can be heated without decomposition to 200 °C (1a) or 180 °C (1b). They are accessible in good yields from tris(benzocyclobutadieno)cyclohexatriene by cyclopropanation with Et2Zn or by epoxidation with 3,3-dimethyl-1,2-dioxacyclopropane, respectively, and were characterized by spectroscopy and X-ray crystallography in the case of 1a for a hexakis(trimethylsilyl) derivative.