Rearrangements of long-lives carbocations derived from 9-hydroxy-1,8,9,10,10,11,12-heptamethyltricylco[6.2.2.0(2,7)]-dodeca-2(7),3,5,11-tetrane in superacids

Rearrangements of long-lived carbocations formed from endo-9-hydroxy-1,8,9, 10, 10,11,12-heptamethyltricyclo [6.2.2.0(2,7)]dodeca-2(7),3,5,11-tetraene in the system HSO3F-SO2ClF-CD2Cl2 at -95 degreesC and having 6,7-benzobicyc lo[3.2.1]octadiene and 5,6-benzotricyclo[3.2.1.0(2,7)]octene structures wer e studied by H-1 and C-13 NMR spectroscopy. Degenerate rearrangements of si milar cations derived under the same conditions from the 9-CD3-analog of th e title compound were examined by the H-2 NMR method. Raising the temperatu re results in formation of benzobicyclo[3.3.0]octadiene (benzopentalene) st ructures. The calculated (MINDO/3) heats of formation of isomeric carbocati ons are consistent with the experimental data. The mechanisms of the observ ed rearrangements are discussed.