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We monitored the progress of formation of dimethoxypillar5arene by size-exclusion chromatography. Surprisingly, the cyclization reaction completely finished in just 3 min. By improving the reaction conditions and purification process, we successfully obtained dimethoxypillar5arene in a short time and in high yield (71%) from commercially available reagents. By improving the deprotection reaction of the methoxy moieties, pillar5arene was isolated quantitatively. Single crystal X-ray analysis confirmed the structure of pillar5arene in the solid state.
Ogoshi et al. (2010) studied this question.