Synthesis of {242}- and {323}-p-octiphenyls

The introduction of rigid-rod molecules as privileged scaffolds has opened routes to otherwise problematic supramolecular architecture like artificial beta-barrels and functional supramolecules covering pores, hosts, sensors, and catalysts. The usefulness of p-oligophenyls for the construction of functional barrel-stave architecture has, however, been limited by uniform substitution along the rigid-rod scaffold. The objective of this report is to overcome this obstacle for the synthesis of p-octiphenyls with orthogonally protected carboxylic acid groups along the rigid-rod scaffold. In the reported {242}-p-octiphenyl 1, the two peripheral arene moieties carry carboxylic acid groups protected as benzyl esters, whereas the four central carboxylic acid groups are protected orthogonally as tert-butyl esters (Scheme 2). The complementary orthogonal protection of the three peripheral and the two central arenes is achieved in the {323}-p-octiphenyl 2 (Scheme 3). The realized {242}- and {323}-p-octiphenyls 1 and 2, respectively, provide a complete set for the general access to refined rigid-rod barrel-stave architecture with maximized functional plasticity. The need for resolution-enhanced (aliased) HMBC 2D-NMR spectroscopy to characterize these refined oligomers is described in the following publication in this issue of Helv. Chim. Acta.