Efficient syntheses of calix[4]arenes in the 1,2-alternate conformation via intramolecular benzoate ester migrations

✍ Scribed by Jeff A Lynch; Jeff J Mestayer; Michael T Blanda

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 160 KB
• Volume: 1
• Category: Article
• ISSN: 1472-7862
• DOI: 10.1016/s1472-7862(02)00005-9

✦ Synopsis

A previously known imidazole-initiated intramolecular ester migration was modified by replacing the imidazole with Cs 2 CO 3 to effect the efficient conversion of 25, 27-bis-p-methoxy-, 25,27-bis-p-fluoro and 25, 27-bisbenzoyloxycalix[4]arene in the flattened cone conformation to the corresponding 25,26-benzoyloxy compounds in the 1,2-alt. The rearrangement was highly efficient for the unsubstituted and methoxy-substituted esters; the 1,2-alternate isomers were isolated in 80-88% yield, but less efficient for the fluoro-substituted ester (isolated yield 58%). The p-methoxy-and p-fluoroesters were further functionalized in subsequent alkylation reactions with methyl p-toluenesulfonate and pentaethyleneglycol-di-p-tosylate to produce dimethoxy-and calixcrownester derivatives in the 1,2-alt. in moderate to good yields. The high yields of the 1,2-alt. are attributed to a p-metal template effect involving the soft cesium ion from the base, two aryl rings and the two phenolate oxygens of the deprotonated calixarene.