Towards a molecular anchor chain. Synthesis and catenations of spiro crown ethers

Two new crown ethers (1 and 2) featuring a spiro linked assembly of two to three individual macrorings have been synthesised. The syntheses were achieved by means of high dilution techniques and blocking/deblocking procedures, beginning with pentaerythritol as the basic building block. The spiro and dispiro crown ethers 1 and 2 participate in template-directed self-assembly reactions with 1,1'[1,4-phenylenebis(methylene)]bis-4,4'-bipyridinium bis(hexafluorophosphate) and 1,4-bis(bromomethyl)benzene at either one or both recognition sites. The resulting new [2]catenanes (12·4PF₆ and 14·4PF₆) and bis[2]catenanes (13·8PF₆ and 15·8PF₆), incorporating interlocked cyclobis(paraquat-p-phenylene) tetracations, were characterised by (dynamic) NMR spectroscopy and high resolution FAB mass spectrometry. The X-ray crystal structure of one of these spiro-linked bis[2]catenanes, namely 13·8PF₆, is reported.