Novel annulene dications from methylated [2.2]metacyclophane monoenes and [e]-ring benzannelated dimethyldihydropyrene

Tetramethyl- and hexamethyl-substituted [2.2]metacyclophane monoenes (10 an d 11) are transformed into their corresponding trans-dimethyldihydroethanop henanthrenium dications (14(2+) and 15(2+)) in FSO3H . SbF5 (4:1) and FSO3H . SbF5 (1:1) with SO2ClF or SO2 as the solvent; these 10 pi -dications are equivalent to the C-4/C-5 diprotonated dications of the 2,7-dimethyl deriv ative of trans-DMDHP, 3a. The trans-12c,12d-dimethyl-12c,12d-dihydrobenzo[e ]pyrene (6) reacts with FSO3H/SO2ClF under surprisingly mild conditions to give initially a persistent diprotonated dication (6H(2)(2+)) and, subseque ntly, the oxidation dication (6(2+)); the 6(2+):6H(2)(2+) ratio reaches 4:1 after 1 week at low temperature. Protonation of the anti-metacyclophane (1 3) was also examined. Charge delocalization mode and tropicity in the resul ting dications are gauged via detailed NMR studies at 500 MHz.