Pillar-Shaped Cavitands

Significance

The pillar-shaped cyclic pentamer, DMpillar[5]arene, was selectively obtained from the condensation of dimethoxybenzene (DMB) with paraformaldehyde using BF₃×OEt₂ as catalyst (22% yield). In contrast, the use of H₂SO₄, AlCl₃, FeCl₃, TiCl₄, or SnCl₄ as catalyst yielded a mixture of cyclic pentamer and polymer. X-ray crystallo­graphy confirmed the structure of DMpillar[5]ar­ene as a symmetrical para-bridged pentamer of DMB. A cyclic pentamer of hydroquinone, pillar[5]arene, was prepared from DMpillar[5]arene in 30% yield.