A Novel Hydrocarbon, 8,10‐Dimethylidenetricyclo[7.1.1.0 2,7 ]undeca‐2,4,6‐triene: Synthesis of benzopinane skeleton via di‐π‐methane rearrangement of benzonorbornadiene system

The [4 + 2] cycloadduct 17 of 2,3‐dimethylidene‐1,2,3,4‐tetrahydro‐1,4‐methanonaphthalene and 4‐phenyl‐4 H ‐1,2,4‐triazole‐3,5‐dione (PTAD) was subjected to a triplet‐sensitized di‐π‐methane rearrangement. Hydrolysis of the resulting urazol 18 gave the hydrocarbon 7 . Hydrolysis of 18 at lower base concentrations led to isomeric stable semicarbazides 24 and 25 , which were submitted NiO 2 or MnO 2 oxidation, to give the target compound 7 , and oxidation products 26 and 27 .