Synthesis, structure, fullerene-binding and resolution of C3-symmetric cavitands with rigid and deep cavities

Abstract

An efficient palladium-catalyzed Suzuki–Miyaura coupling method involving the reaction between CTV-Br₃ and a variety of aryl and heteroaryl boronic acids in the presence of indolyl phosphane ligands has been developed. This reaction procedure provided a series of C₃-symmetric aryl-extended rigid cavitands for the first time. X-ray crystal structure analysis revealed that the phenyl substituted cavitand 5a has much larger rim edges and cavity height. This macrocyclic host adopts a linear head-to-tail “hand-shake” self-inclusion arrangement in the crystalline state. The fluorescence of 5a was considerably quenched upon the addition of C₆₀, with a binding constant of 78 700 ± 2300 dm³ mol⁻¹ and a 1 : 1 stoichiometry according to the Job's plot. The interaction of C₆₀ with 5a in the excited state is stronger than that with CTV, which could be attributed to more binding sites in the extended arms of 5a. Moreover, optically active C₃-symmetric cavitands (+)- and (−)-6 were easily obtained with high efficiency through chemical resolution.