Sterically congested, geminal aryl-substituted, proton-ionizable sym-dibenzo-16-crown-5 lariat ethers: synthesis and alkali metal cation extraction

Three series of proton-ionizable sym-dibenzo-16-crown-5 ethers with sterically demanding 1-naphthyl, 2-naphthyl, and 9-phenanthryl geminal groups are synthesized and characterized. Variation of the proton-ionizable group includes oxyacetic acid and N-(X) sulfonyl oxyacetamide units with X = Me, Ph, C6H4-4-NO2, and CF3. For the latter series, variation of X provides 'tunable' acidity of the ligand. The metal ion-complexing properties of the proton-ionizable sym-(aryl)dibenzo-16-crown-5 compounds are probed by competitive solvent extraction of alkali metal cations from aqueous solutions into chloroform.