A simple and efficient synthesis of paracyclophane derivatives based on self-organization of a quinodimethane is described. Treatment of dibromides 5a-d with mercury afforded in high yield the macrocyclic compounds 6a-d. Interestingly, these compounds change the color on grinding and heating, from colorless to violet. The structure of 6a-d was determined by spectroscopic analyses. Single-crystal structure analysis of 6b and 6c confirmed the proposed structure.
Wittig,G. et al., Justus Liebigs Annalen der Chemie, 1969, vol. 726, p. 188 - 200