Chemistry of Optically Active Helicenes

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We developed a multigram synthesis of an optically pure helicene, 1, 12-dimethylbenzo [c] phenanthrene-5, 8-dicarboxylic acid, which enabled us to conduct studies on the chemistry of helicity in the molecules. The present study deals with the synthesis and properties of macrocyclic compounds containg the helicene.1. Cycloamides containing one to ten helicene units were synthesized by a two-directional method. Their structures were compared spectroscopically, and "ring effect" was observed in the compounds smaller than the pentamer. The larger compounds turned out to possess flexible structures.2. Cycloalkynes contining three to six helicenes were synthesized. The trimer was found to self-aggregate in organic solvents. The compound formed only dimer, and higher-aggregation was not observed in the concentration range examined. The chirality at the helicene moiety played an important role in the aggregation behaviors.3. Cyclic anhydrides containing three and four helicenes were synthesized by a one-pot method.4. Regioselective polynitration of the helicenedicarboxylate was examined, and methods to functionalize at the symmetrical positions were developed.5. The charge-transfer (CT) complexation of a tetranitrohelicene with pyrene was examined. The crystal structure of the optically active helicene was compared with the racemic derivative. Chiral recognition in the CT-complexation was also studied using the electron-deficient helicene and an elecron-rich helicene. The same configuration of the helicenes formed more stable complex.