Restriction of the inversion process of the 1,3-bridged ring of the rigid conformer of 24-methyl-2,17-dithia[3.3](2,2')biphenyleno(1,3)cyclophane

Abstract

The title compound 3 was prepared via a cyclization reaction between two known precursors. It is confirmed that the inversion process of the 1,3-bridged ring in the 2,17-dithia[3.3](2,2')biphenyleno(1,3)cyclophane system was restricted with a conformational energy barrier of >84 kJ mol-1. The adopted rigid conformation is represented by 3a (or 3b) having the methyl protons located above the cavity of one of the benzene rings. This is consistent with the preferred conformation derived from semiempirical molecular orbital PM3 calculations. All the protons in this rigid conformer could be assigned by its COSY spectra and results from a series of NOE experiments.