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In‐Fjord Substitution in Expanded Helicenes: Effects of the Insert on the Inversion Barrier and Helical Pitch
Author(s) -
SuárezPantiga Samuel,
Redero Pablo,
Aniban Xaiza,
Simon Martin,
Golz Christopher,
Mata Ricardo A.,
Alcarazo Manuel
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202102585
Subject(s) - racemization , fjord , steric effects , substitution (logic) , biphenyl , helicene , inversion (geology) , chemistry , crystallography , stereochemistry , materials science , molecule , geology , computer science , oceanography , organic chemistry , structural basin , paleontology , programming language
A series of expanded helicenes of different sizes and shapes incorporating phenyl‐ and biphenyl‐substituents at the deepest part of their fjord have been synthesized via sequential Au‐catalyzed hydroarylation of appropriately designed diynes, and their racemization barriers have been calculated employing electronic structure methods. These show that the overall profile of the inversions (energies, number of transition states and intermediates, and their relative position) is intensively affected by the interplay of steric and attractive London dispersion interactions. Hence, in‐fjord substitution constitutes an additional tool to handle the mechanical properties in helicenes of uncommonly large diameter. The photochemical characterization of the newly prepared helical structures is also reported.