A novel synthetic strategy for exchanging stoppers on rotaxanes, without them losing their integrity as interlocked molecules, is presented. The surrogate-stoppered  rotaxane contains one inert stopper and a triphenylphosphonium group attached to a benzylic position as a second reactive stopper in the dumbbell-shaped component which contains an ammonium (NH2+) ion recognition site, encircled by a crown ether (24C8 or 25C8) component. The strategy for exchanging stoppers relies upon the ability of a benzylic triphenyl-phosphonium function to undergo a Wittig reaction with a bulky aromatic aldehyde to form a 'stilbenoid'  rotaxane as a mixture of cis and trans isomers, without the occurrence of any dethreading of the crown ether ring component. The C=C double bonds can then be hydrogenated, using Adams' catalyst, to afford a new covalently modified rotaxane with two inert stoppers. Utilizing this strategy, larger interlocked molecular structures including a two-stationed rotaxane and a branched rotaxane have been prepared. Furthermore, initial studies, aimed at using this methodology to gain access to poly[n]rotaxane architectures, are presented.
|ジャーナル||Polymers for Advanced Technologies|
|出版ステータス||Published - 2002 10月|
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