Synthesis, properties and optical resolution of rac-[n](1,6)heptalenophanes

[n](1,6)Heptalenophanes, rac-4a-c, having a five, six or seven membered met hylene bridge, respectively, across the 12 pi-perimeter were synthesized fr om rac-1,6- dimethylheptalene (1) in two steps. Detailed NMR and UV/vis stu dies of the new phanes reveal their bridged heptalene moiety to be more twi sted than that of the parent heptalene system. Furthermore, the reduction o f the [5](1,6)heptalenophane (4a) with lithium to its aromatic dianion 10 w ith 14 pi-electrons is presented. NMR spectra of the latter show that its p erimeter, although remarkable bent out-of-plane, still exhibits a considera ble aromatic ring current. Liquid chromatography with triacetyl cellulose a s stationary phase resulted in the optical resolution of racemic [5](1,6)he ptalenophane (4a). (C) 2000 Elsevier Science Ltd. All rights reserved.