Direct nucleophilic aromatic substitution reactions in the syntheses of anthraquinone derivatives: Chemistry and binding of podands, crown ethers, and a cryptand

The direct nucleophilic aromatic substitution reactions of anthraquinones have permitted the syntheses of more than 30 novel podands, crown ethers and lariat ethers. Anthraquinones having (ethyleneoxy) n sidearms were obtained by direct displacement of chloride by the anion of CH 3 (OCH 2 CH 2 ) n OH. The ethyleneoxy‐substituted anthraquinones could, in turn, undergo direct replacement by nucleophiles that failed to displace chloride. This approach has been used for the preparation of two‐armed podand derivatives and several novel crown derivatives of anthraquinone. Binding comparisons are presented for several of these new anthraquinones. Direct substitution did not prove successful in the preparation of anthraquinone‐ [2 · 2] ‐cryptand which was obtained by alkylation. The crystal structure of the latter reveals an orientation of ring and anthraquinone appropriate for cation binding, a fact confirmed by cation binding constant measurements.