Chiral Molecular Glass: Synthesis and Characterization of Enantiomerically Pure Thiophene‐Based [7]Helicene

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Abstract
Synthesis of thiophene‐based [7]helicenes, which are functionalized for both design of organic chiral glasses with strong chiroptical properties and for further homologation to higher [n]helicenes, is reported. The key synthetic transformations are kinetic resolution of the intermediate diketone and the annelation step forming the center benzene ring by means of an intramolecular McMurry reaction. Based upon X‐ray crystallographic determinations of the absolute configurations for (+)‐enantiomers of the diketone and the [7]helicene, stereochemical correlation between the (R) axial chirality of the diketone and the (M) helical chirality of the [7]helicene is established. One such enantiopure trimethylsilyl‐substituted [7]helicene possesses enchanced chiroptical properties and forms a chiral molecular glass.