Annelated Calixarenes Composed of Calixarenes with Hydroxy Groups in the Endo and Exo Position

Article abstract of DOI:10.1021/jo9511197

Various phenol-derived calix<4>arenes (3) bearing four hydroxy groups in the exo position have been prepared by uncatalyzed condensation of suitable dimers or tetramers with formaldehyde in xylene in yields up to 44percent.The tetra-tert-butyl compound (3a) has been shown by X-ray analysis to adopt a regular cone conformation (nearly identical in shape with the endo isomer) with two intramolecular O-H...O hydrogen bonds, while the corresponding dimer (6c) prefers a conformation (not possible in the calixarene) with two intramolecular O-H...?(arene) interactions.Condensation of exo-calix<4>arenes 3f,g with free ortho positions (easily available by debutylation) with bisbromomethylated dimers gave annelated double (9) and triple (10) calixarenes consisting of endo- and exo-calix<4>arene substructures in yields up to 24percent and 10percent, respectively.Molecular dynamics calculations suggest that the exo-calixarene part in 9 is less mobile than the entirely flexible 3, while the endo-calixarene part shows a higher mobility than usual.A complete interconversion cone -> cone is impossible, however, which enables the construction of inherently chiral molecules.