From Chrysene to Double [5]Helicenes

Abstract

AbstractGlyoxylic functionalization of chrysene by Friedel–Crafts acylation with ethyl chloroglyoxylate or by bromination followed by substituent exchange enables the formation of bis[5]helicene‐tetracarboxylates and tetracarboxdiimides through Perkin reactions and palladium‐catalyzed cyclizations. Tetrasubstituted bishelicenic dichrysenoanthracenes and dinaphthochrysenes are thus obtained from chrysene in four to six steps. In the cyclization to dinaphthochrysenes, a rearrangement of the conjugated carbon skeleton is identified as side reaction. In solution, the diimides form mixtures of M,P‐ and M,M/P,P‐diastereomers, which equilibrate at room temperature when the helices are distant but equilibrate only upon heating when the helices are close and acting in concert. The nonplanar arene geometry allows close π‐contacts in two dimensions between neighboring molecules in the crystal.