Silyl-substituted tetrathia[7]helicenes: Synthesis, X-ray characterization and reactivity

We describe the synthesis of trialkylsilyl- substituted trans1,2-bis(thieno[3,2-e]benzothiophene-2-yl)ethenes as suitable soluble precursors for the preparation of the corresponding silylated tetrathia[7]helicenes, which, in turn, can be desilylated or transformed into dihalogen -substituted derivatives through electrophilic substitution of silyl substituents. X-ray structural studies showed that the presence of the two triiso-propylsilyl groups on the terminal thiophene rings accounts for the high solubility of the alkene and for the very large dihedral angle in the helicene. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).