Synthesis of butadiyne-bridged [4n] metacyclophanes having exo-annular t-butyl groups

Butadiyne-bridged [44]- and [48]metacyclophanes having exo-annular t-butyl groups were prepared by intermolecular Eglinton coupling of the dimeric unit or by intramolecular ring closure of the linear tetramer. Comparison of the 1H and 13C NMR spectra of [44]metacyclophane with those of [48]cyclophane and diphenylbutadiyne revealed its prominent geometrical feature due to deformation of the triple bonds from linearity. The [44]Metacyclophane was converted into [08]thiophenometacyclophane in good yield by treatment with sodium sulfide.