The isomeric Diels-Alder adducts 3, obtained by cycloaddition of tetraphenylcyclopentadienone to the 4,5: 12,13-bis-(oxanorbornadieno) [~]. The in situ-trapping of the corresponding bis-aryne with furan yields the two products syn,syn-2[*] and unti,syn-2 (ratio 1 : l)r41. This mixture of isomeric compounds 2 reacts with two equivalents of tetraphenylcyclopentadienone in refluxing benzene to yield the insoluble Diels-Alder adducts 3L51 as a mixture of four diastereomers. When heated in o-dichlorobenzene solution or neat to 180°C, extrusion of carbon monoxide occurs, and isobenzofuran moieties are formed on both decks of the molecule by retro-Diels-Alder reaction to yield [2.2](4,7)isobenzofuranophane (4). The molecular ion of 4 was observed in the mass spectrum (E1 and FD) of 3, and the molecular formula was confirmed by high-resolution mass spectrometry. The highly reactive 4 can be trapped in situ when 3 is heated in o-dichlorobenzene solution in the presence of p-benzoquinone to yield the two diastereomeric [

Tropylidenes 16 and 17 were prepared from [2.2]paracyclophane (10). On treatment with the corresponding trityl salts they were converted into tropyliophanes 26a (tetrafluoroborate) and 26b (perchlorate). With acetone, 26a furnished trapping product 27, which underwent a homo-Diels-Alder addition with tetracyanoethylene to afford adduct 29. All