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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