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Enantioselective Synthesis of Dithia[5]helicenes and their Postsynthetic Functionalization to Access Dithia[9]helicenes

2021; Wiley; Volume: 61; Issue: 6 Linguagem: Inglês

10.1002/anie.202114577

1521-3773

Valentina Pelliccioli, Thierry Hartung, Martín Simón, Christopher Golz, Emanuela Licandro, Silvia Cauteruccio, Manuel Alcarazo,

Photochromic and Fluorescence Chemistry

A highly enantioselective synthesis of 5,13-disubstituted dibenzo[d,d']benzo[1,2-b:4,3-b']dithiophenes is reported. Key for the successful assembly of these helical architectures is the last two successive Au-catalyzed intramolecular alkyne hydroarylation events. Specifically, the second cyclization is the enantiodetermining step of the whole process and provides the desired helicenes with excellent ee values when a TADDOL-derived 1,2,3-(triazolium)phosphonite moiety (TADDOL: α,α,α',α'-tetraaryl-1,3-dioxolane-4,5-dimethanol) is employed as an ancillary ligand. The absolute stereochemistry of the newly prepared structures has been determined by X-ray crystallography to be P; the optical properties of these heterohelicenes are also reported. A three-step procedure was subsequently developed that allows the transformation of the initially obtained dithia[5]helicenes into dithia[9]helicenes without erosion of the enantiopurity.