173974-52-2Relevant academic research and scientific papers
Annelated Calixarenes Composed of Calixarenes with Hydroxy Groups in the Endo and Exo Position
Boeher, Volker,Doerrenbaecher, Ralph,Frings, Michael,Heydenreich, Mathias,Paoli, Diana de,et al.
, p. 549 - 559 (2007/10/03)
Various phenol-derived calixarenes (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-calixarenes 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-calixarene 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.
