Fourfold [2]Rotaxanes Based on Calix[4]arenes

摘要

It is now well established,that calix[4]arenes of type 1 substituted by urea groups at the wide rim form hydrogen-bonded dimeric capsules in apolar solvents.Their structure,first deduced from'H NMR spectra,was definitely confirmed by several single-crystal X-ray analyses.The interlocking urea residues of the two calix-[4]arenes"roughly"point in opposite directions.Functional groups attached to these urea residues can be covalently connected,e.g.by metathesis between alkenyl groups.If these functional groups are preorganized in heterodimers which are exclusively formed with tetratosyl ureas as template,multimacrocyclic compounds 2 are available in excellent yield from which the newly formed mac-rocycles can be detached in a final step.