The template-directed syntheses of two [2]rotaxanes, one carrying one and the other two triphenylphosphonium stoppers, have been achieved using a threading-followed-by-stoppering approach. Either one or two benzylic bromide functions located at the para -positions of dibenzylammonium-based ions, which become encircled by dibenzo[24]crown-8 macrocycles during the initial thermodynamically controlled phases that mark the recognition events serve as sites for nucleophilic attack by triphenylphosphine during the subsequent kinetic stages that lead to the formation of the two [2]rotaxanes.
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Rowan et al. (1999) studied this question.
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