Intramolecular direct arylation in an A,C-functionalized calix[4]arene

Barton OG, Neumann B, Stammler H-G, Mattay J. Intramolecular direct arylation in an A,C-functionalized calix[4]arene. Organic & Biomolecular Chemistry. 2008;6(1):104-111.A recently developed efficient method for intramolecular direct arylation is employed on a doubly functionalized calix[4] arene fixed in the cone conformation. The reaction takes place in high yield leading to meta substituted calix[4]arenes. The functionalities are located at two opposite aromatic rings and the two possible diastereomers 1a and 1b are obtained in a 1 : 1 ratio. Full sets of data including crystal structures for both isomers are presented. The NMR data reveal that even at temperatures up to 120 degrees C both isomers are fixed in a flattened cone conformation with the substituted aromatic units pointing outwards