An Amphiphilic Pillar[5]arene as Efficient and Substrate-Selective Phase-Transfer Catalyst

An amphiphilic macrocyclic compound consisting of 10 tetra-alkyl phosphonium bromide groups and a pillar[5]arene core was prepared. This compound was soluble in both aqueous and organic media and acted as a highly efficient and substrate-selective phase-transfer catalyst. In particular, oxidation of the linear alkene1-hexene to 1-pentanal by KMnO4 was >99%, whereas that of the branched alkene 4-methyl-1-hexene was only 31%, under ideal conditions.