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

Butadiyne-bridged [4(4)]- and [4(8)]metacyclophanes having exo-annular t-bu tyl groups were prepared by intermolecular Eglinton coupling of the dimeric unit or by intramolecular ring closure of the linear tetramer. Comparison of the H-1 and C-13 NMR spectra of [4(4)]metacyclophane with those of [4(8) ]cyclophane and diphenylbutadiyne revealed its prominent geometrical featur e due to deformation of the triple bonds from linearity. The [4(4)]Metacycl ophane was converted into [0(8)]thiophenometacyclophane in good yield by tr eatment with sodium sulfide. (C) 2001 Elsevier Science Ltd. All rights rese rved.