Calixhydroquinones: a novel access to conformationally restricted, meta-substituted calixarenes †
作者:Mark Mascal、Ralf Warmuth、Russell T. Naven、Ross A. Edwards、Michael B. Hursthouse、David E. Hibbs
DOI:10.1039/a906442g
日期:——
described. These macrocycles are activated towards meta substitution, and reaction with bromine gives the first examples of persubstituted, phenol-derived calixarenes. The effect of meta substitution on calixarene mobility is demonstrated by the fixation of an otherwise mobile calix[4] system in the partial cone conformer, and the slowing of the ring inversion rate in calix[8]arenes.
Calix[4]quinone (7) and calix[4]hydroquinone (6) have been synthesis using three different synthetic pathways. The first pathway to 7 from calix[4]arene (1) consists of six steps: acetylation, Fries rearrangement, Baeyer-Villiger oxidation after acetylation, hydrolysis, and oxidation. The second pathway to 7 from 1 consists of four steps: acetylation, Fries rearrangement, reaction of the product obtained by Fries rearrangement with sodium azide, and oxidation. The third pathway to 7 from 1 is most convenient and consists of three steps: diazo coupling reaction, reduction, and oxidation. The NMR behavior of 6 and 7 is described.