Directionality in nanohoops

We will initially target an archetypal cyclopolyazulenylene, namely [8]CPAz2,6 (Fig. 5). Access to this unprecedented directional nanohoop will be achieved through use of Yamago's Pt-squares methodology. This in turn requires the preparation of a 2,6-functionalised biazulenyl precursor. We will use Nozoe's azulene synthesis followed by a divergent/convergent route employing an Ullmann coupling to give known biazulene tetraester A. Precedented functional group interconversion and decarboxylation will give key building block B. This in turn will be used to assemble the corresponding tetraplatinum complex. The directionality of building block biazulene B leads to the possibility of formation of multiple isomeric tetraplatinum complexes C-F (Figure 7). Quite probably the inherent dipole of B may lead to selectivity in favour of forming the desired C (containing only head-to-tail linkages) over isomers D-F (containing both head-to-tail and head-to-head linkages). However, regardless of the ratio of isomers, taking the mixture, effecting the oxidation/ reductive elimination and then separating the isomeric final products is a plausible approach, as shown by the work of Isobe, who used the same approach to access cyclopolychrysene isomers. Furthermore, the products arising from isomers D-F will be interesting structures in their own right.