Synthesis of Crownophanes by Means of Intramolecular [2+2] Photocycloaddition of Styrene Derivatives and Their Complexing Ability
Seiichi INOKUMA and Jun NISHIMURA*
Department of Chemistry, Gunma University; 1-5-1 Tenjin-cho,
Kiryu-shi 376-8515 Japan
A new type of crown compounds were efficiently prepared by means of intramolecular [2+2] photocycloaddition of styrene derivatives, which were named “crownophanes” due to possessing both crown ether and cyclophane moieties. It was found that prototypical crownophane showed relatively high Li+ ion selectivity on the solid-liquid extraction. Simple and appropriate modification of the crown compounds was performed, taking the complexation with Li+ ion into consideration. Crownophanes bearing two cyclobutane rings (crownopaddlanes) extracted the ion exclusively and quantitatively. A double-looped crownophane with two crown ether moieties selectively transported size-complementary dibasic acids in the liquid membrane system. Heterocrownophanes, which have sulfur or nitrogen atoms in and on the crown ether ring systems, were also prepared by this method and found to extract Ag+ ion with high selectivity and efficiency, and among others the crownophane possessing pyridine rings on the aromatic nuclei recorded the perfect selectivity on the liquid-liquid extraction.
At the preparation of a tertiary amine-containing crownophane (cryptocrownophane), the photochemical cyclization was successfully carried out in the presence of γ-CD.
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