Quinones of Benzo- and Dibenzo-Crown Ethers: The preparation of the 1,4-quinones of benzo[15]crown-5 (1), benzo [18]crown-6 (2) and dibenzo[18]crown-6 (3) and their quinols is described. The quinones are obtained by Fremy salt oxidation of the corresponding 3-hydroxybenzo-crown ethers which are readily accessible by a double protective group synthesis from 1,2,3-trihydroxybenzene. The synthetic pathway also provides a general high yield preparation of 2,3-dialkoxyl-1,4-benzoquinones. The new crown ethers are characterised b y 1H- and 13C-N. M. R. as well as U. V. spectroscopy. Non-aqueous redox potentials are determined by cyclic voltammetry. Crystalline complexes of 1 and 2 with various ammonium, alkali, and alkaline earth cations are also described.
The crystalstructures and redox properties of p‐benzoquinone (BQ)‐fused [18]crown‐6 1 and bis‐BQ‐fused [18]crown‐6 2 were examined. The anion radicals of these BQ molecules were stabilized by addition of metal ions, through effective electrostatic interactions between the negatively charged BQ moiety and positively charged ion‐capturing [18]crown‐6 unit. The electrostatic interactions and solvation