[2.2](4,4)ISOBENZOFURANOPHANES - SYNTHESIS, CHARACTERIZATION, AND REACTIVITY

The isomeric Diels-Alder adducts 3, obtained by cycloaddition of tetra phenylcyclopentadienone to the ,5:12,13-bis(oxanorbornadieno)[2.2]para cyclophanes syn,syn- and anti,-syn-2[], yield the unstable isobenzofu ranophane 4 by consecutive extrusion of carbon monoxide and tetrapheny lbenzene when heated to 180-degrees-C. The molecular ion of 4 was obse rved in the EI mass spectrum. The stable tetraphenyl-substituted analo gue 10 was synthesized independently from the previously unknown 4,5,1 2,13-tetrabenzoyl[2.2]paracyclophane (9). UV/Vis as well as fluorescen ce spectra and an X-ray crystal structure analysis of 9 are reported.