CYCLOPHANES .13. APPROACHES TO THE SYNTHESIS OF CORANNULENE

The dithia[3, 3](2, 7)naphthalenoparacyclophanes (12) and (13) were synthesized and then ring- contracted either by Wittig or Stevens rearrangements to the [2, 2]cyclophanes (17), (18) and (20). Elimination of the sulfur functional groups gave [2, 2](2, 7)naphthalenoparacyclophane-l, ll-diene (6) and l, 12-dimethyl[2, 2](2, 7)naphthalenoparacyclophane-l, ll-diene (7) which were characterized and their stereochemistry in solution determined from their 1H n.m.r. spectra. The [2, 2]cyclophane (8) was prepared by photochemical elimination of sulfur from the dithiacyclophane (12) in trimethyl phosphite. Attempts to convert the cyclophanes (6), (7) and (8) into corannulenes are described. The stereochemistry of compounds (8) and (13) is also discussed together with the effect of the methyl groups in cyclophanes such as compound (13) on the subsequent ring-contraction and elimination reactions. © 1979 ASEG.