meta-Bridged calixarenes with the methylene moiety possessing in/out stereochemistry of substituents†
meta-Substituted organomercury calixarenes and their corresponding iodo derivatives have been used for lithiation followed by a reaction with various aldehydes or ketones. The resulting diastereomers were in some cases separable using simple column chromatography. Subsequent intramolecular Friedel–Crafts alkylation led to calixarenes with an additional methylene bridge bearing two different substituents with in/out (relative to the cavity) stereochemistry. Our results indicate that the stereochemistry of the final cyclised product does not depend on the structure/stereochemistry of the starting compound, but rather it is influenced by the stability of the products. The relationship between the positions of these substituents and the complexation properties was demonstrated by 1H NMR titration experiments with N-methylpyridinium iodide.