Remarkably facile ring-size control in macrocyclization: Synthesis of hemicucurbit[6]uril and hemicucurbit[12]uril

Abstract

A question of concentration: The condensation of ethyleneurea and formaldehyde can be controlled perfectly by the HCl concentration to provide either a hemicucurbit[6]uril 1, which functions as a host, or hemicucurbit[12]uril 2, which acts as a gelating agent, in yields of 94 and 93%, respectively.