Glycoluril derivatives as precursors in the preparation of substituted cucurbit[n]urils

Abstract

Substituted glycolurils are of considerable interest for the synthesis of cucurbit[n]uril-type macrocyclic receptors. Thus, the present work investigates the formation and characterization of tetrahydroimidazo[4,5-d]imidazole-2,5(1H,3H)dione (=glycoluril) and its derivatives. Acid-catalysed condensation reactions of these substances with formaldehyde lead to different products, depending on the reaction conditions chosen. Tetracyclic diethers are formed at low temperatures and long reaction times. Oligomeric chains are produced at temperatures higher than 50°C. Chains of suitable length are able to close in a cyclocondensation reaction under the formation of macrocyclic compounds of the cucurbit[n]uril type.