EFFICIENT AND SELECTIVE SYNTHESIS OF CROWNOPADDLANES POSSESSING 2 CYCLOBUTANE RINGS AND EXCLUSIVE COMPLEXATION OF LITHIUM

A new type of Crown compounds (crownopaddlanes) bearing two cyclobutan e rings were efficiently and selectively prepared by means of intramol ecular [2 + 2] photocycloaddition of appropriate styrene derivatives, which was successfully carried out in cyclohexane under irradiation th rough a Pyrex filter. Crownopaddlanes 4a, 5, and 6 exclusively and qua ntitatively extracted Li+ on the solid-liquid extraction. Upon the com petitive extraction, 4a showed the highest selectivity toward Li+ over Na+ and K+ (Li+/Na+ = 610, Li+/K+ = 976). The structural factors work ing in the complexation of the crownopaddlane were examined by X-ray c rystallographic analysis.