4,15-Diamino[2.2]paracyclophane as a Starting Material for Pseudo-Geminally Substituted [2.2]Paracyclophanes

摘要

Diazotization of the title compound 3, followed by treatment of the formed bis(diazonium ion) with cuprous chloride, yields the pseudo-geminal dichloride 1. Similarly, 3 is converted into the bis(azide) 5 when sodium azide is used as the trapping nucleophile. Hypochlorite oxidation of 3 furnishes the azo compound 4, the first multi-bridged cyclophane with a bridge consisting only of heteroatoms. Reduction of 4 with zinc.acetic acid affords the substrate 3 again. Treatment of 4 with bromine/iron powder or iodine monochloride causes deazotization accompanied by halogen introduction in pseudo-geminal position (i.e., formation of 2 and 6, respectively). Flash vacuum pyrolysis (450 ℃, 0.01 Torr) of 4 produces the phenanthrene derivatives 13 and 14, while with tetracyanoethylene (TCNE) the azophane undergoes rapid cycloaddition at room temperature to give the [2 + 4] cycloadduct 16. The structures of 1, 2, 4-6, and 16 have been determined by X-ray structural analysis. Molecular packing patterns are determined by weak hydrogen bonds; a common packing pattern for cyclophane derivatives is ascribed to C-H…π interactions. Full bandshape analyses of the bridge proton signals in the ~1H NMR spectra of 1,2,6, and of the difluoro analogue 17 yielded the vicinal ~1H, ~1H coupling constants. These reflect the 1:1 equilibrium between the two skew conformations of the bridges.