Solid-phase approaches toward cyclic oligomers

Strategies were sought to effect cyclizations of oligo(m-phenylene ethynyle ne) by exploiting pseudo-high dilution effects on polymer supports. Using P d/Cu-catalyzed coupling protocols, Merrifield's resin (1% crosslinked chlor omethylated polystyrene) proved inadequate for site isolation; inter-site c ouplings ensued on the flexible support. Conversely, use of the Argopore re sin, a more highly crosslinked polystyrene, inhibited inter-site interactio ns, and no identifiable final product could be separated from the resin. Sp ectroscopic and mass spectrometric methods indicated that the product from the Argopore resin might be a threaded catenane. (C) 2001 Elsevier Science Ltd. All rights reserved.