Metacyclophanes and related compounds. Part 16. Preparation of 8-fluoro-t-butyl[2.2]metacyclophanes and their treatment with aluminium chloride–nitromethane in benzene

Abstract

The preparation of 8-fluoro-t-butyl[2.2] metacyclophanes (5) are described. Dithia[3.3]metacyclophane (3) and [3.3]metacyclophane bis(sulphones)(4) were obtained as a mixture of transoid and cisoid conformers, but [2.2]metacyclophanes (5) were exclusively obtained as the transoid conformer after pyrolysis of the sulphones (4). AlCl₃–MeNO₂-Catalyzed trans-t-butylation of 8-fluoro-16-methyl-5,13-di-t-butyl[2.2]metacyclophane (5a) in benzene under a variety of conditions failed to give 8-fluoro-16-methyl[2.2]metacyclophane (32) but, instead, the tetrahydropyrenes (33) and/or (34) were obtained depending upon the conditions used. Internally substituted [2.2]metacyclophanes were isomerized to the strainless [2.2] metacyclophanes and these were then oxidized to the tetrahydropyrene (33).