Abstract
The synthesis of [2.2](1,4)tropylioparacyclophane tetrafluoroborate (1) is described. It is prepared from [2.2]para- cyclophane (4) in six steps in 27%overall yield. Reduction of 4 with Na/NH3 affords the tetrahydroderivativetricyclo[8.2.2.24·7]- hexadeca-l(12),4,7 (15),10(13)-tetraene (5). Treatment of 5 with KO-r-Bu/CHBr3 at 0 °C gives a 4:1 mixture of mono- and dicarbene adducts 11,1 l-dibromotetracyclo[8.3.2.24'7.0l0l2]heptadeca-I(14),4,7(I7)-triene (6a) and 11,11,14,14-tetrabrom- opentacyclo[8.3.3.2.04'l5.0lo'l2]octadeca-l(17),6-diene (6b), respectively. Monocarbene adduct 6a is treated with DDQ and the resulting 11,1 l-dibromotetracyclo[8.3.2.24'7.0l0 l2]heptadeca-l(14),4,6,16-tetraene (7), dehydrobrominated with pyri- dine to give 11 -bromotricyclo[8.3.2.25'7]heptadeca-1 (14),4,6,10(15),! 1,16-hexaene (8). Bromide 8 is reduced with tert-butyl- lithium giving tricyclo[8.3.2.24-7]heptadeca-l(14),4,6,10(15),! 1,16-hexaene (9). Treatment of 9 with trityl fluoroborate af- fords the title compound, 1. Characterization and spectral comparisons of the above compounds are described. Cyclophane 1 exhibits a broad band at 323 nm in its electronic spectrum indicative of an intramolecular charge-transfer interaction be- tween the neutral and charged aromatic rings.