Synthesis of Butadiynyl-Strapped Corona[6]arenes and Their Selective Anion Binding Properties

A number of butadiynylene-strapped O₆-corona[6]arenes were synthesized straightforwardly through intramolecular oxidative homocoupling of O₆-corona[6]arenes, which contained at least two N-propargyl-phthalimide segments. The mono-macrocyclic reactants were prepared from the reaction between 3,6-dichlorotetrazine and N-propargyl-3,6-dihydroxyphthalimide and another 1,4-dihydroxybenzene derivative with roughly a 3:2:1.3-1.5 ratio in a one-pot reaction manner. The synthesized butadiynylene-strapped corona[3]arene[3]tetrazines acted as highly selective electron-deficient macrocyclic hosts to form 1:1 complexes with thiocyanate in solution, and the association constant (K_a) was up to 1390 M^-1. The anion-π noncovalent interactions provided the driving force for host-guest complexation.