Highly Selective Synthesis of Pillar[n]arene (n = 5, 6)

An efficient and highly selective synthetic method toward the preparation of pillar­[n]­arenes (n = 5, 6) is reported, based upon a high solvent-dependent selectivity found in the condensation reaction between 1,4-dialkyloxybenzene and paraformaldehyde, involving methanesulfonic acid as catalyst. Pillar[6]­arene (P6) is obtained as the major product when using chloroform as solvent, while in dichloromethane pillar[5]­arene (P5) is the dominant product. Accordingly, a series of P5 and P6 have been selectively synthesized with excellent yield.