Synthesis of symmetrical polynitrohelicenes and their chiral recognition in the charge transfer complexation

Derivatives of optically active 1,12-dimethylbenzo[c]phenanthrene-5,8-dicar boxylic acid can be nitrated regioselectively, giving symmetrically polyfun ctionalized helicenes. The dicarboxylic acid or its dimethyl ester is dinit rated with fuming nitric acid in acetic acid at the 4,9-positions. When the reaction is conducted in fuming nitric acid, a 2,4,9,11-tetranitrohelicene is obtained. Analogously, 1,12-dimethylbenzo[c]phenanthrene-5,8-d gives 2, 11-dinitro- or 4,9-dinitrohelicene depending on the conditions, and the for mer compound is converted to a 2,4,9,11-tetranitrohelicene. The tetranitroh elicenes form charge-transfer (CT) complexes with an electron-rich chiral d iaminohelicene in solution. The studies on the chiral recognition reveal th at the combinations of the same configuration of the helicenes form more st able complexes than that of the enantiomeric helicenes.