title: Efficient and Selective Synthesis of Crownopaddlanes Possessing Two Cyclobutane Rings and Exclusive Complexation of Lithium.
abstract: A new type of crown compounds (crownopaddlanes) bearing two cyclobutane rings were efficiently and selectively prepared by means of intramolecular [2 + 2] photocycloaddition of appropriate styrene derivatives, which was successfully carried out in cyclohexane under irradiation through a Pyrex filter. Crownopaddlanes 4a, 5, and 6 exclusively and quantitatively extracted Li(+) on the solid-liquid extraction. Upon the competitive extraction, 4a showed the highest selectivity toward Li(+) over Na(+) and K(+) (Li(+)/Na(+) = 610, Li(+)/K(+) = 976). The structural factors working in the complexation of the crownopaddlane were examined by X-ray crystallographic analysis.
authors.affiliation: Department of Chemistry, Gunma University, 1-5-1 Tenjin-cho, Kiryu 376-8515, Japan.
authors.forename: Seiichi
authors.initials: S
authors.lastname: Inokuma
authors.forename: Masashi
authors.initials: M
authors.lastname: Takezawa
authors.forename: Hiroko
authors.initials: H
authors.lastname: Satoh
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Takashi
authors.initials: T
authors.lastname: Sasaki
authors.forename: Jun
authors.initials: J
authors.lastname: Nishimura