(4)PARACYCLOPHANE INTERCEPTED

Article abstract of DOI:10.1021/ja00242a036

Irradiation (254 nm) of 1,4-tetramethylene(Dewar benzene) (1a) at -20 deg C in THF leads to (4)paracyclophane (2a).In the absence of acid, 2a polymerizes immediately.In the presence of CF3COOH, adducts 6 and 7 are formed by protonation of 2a at a bridgehead carbon atom to give benzenonium ion 9a, followed by addition of a nucleophile, i.e., CF3COO(-) or THF, respectively, at the other bridgehead carbon, leading to a bridged 1,4-dihydrobenzene.The corresponding methanol adduct 8 is formed on irradiation of 1a in methanol solution in the presence of CF3COOH.The difference in behavior between 2a and its higher homologue is discussed on the basis of calculated charge densities.