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Enantioselective Synthesis of Polycyclic Aromatic Hydrocarbon (PAH)‐Based Planar Chiral Bent Cyclophanes by Rhodium‐Catalyzed [2+2+2] Cycloaddition
Author(s) -
Aida Yukimasa,
Nogami Juntaro,
Sugiyama Haruki,
Uekusa Hidehiro,
Tanaka Ken
Publication year - 2020
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.202001450
Subject(s) - enantioselective synthesis , cycloaddition , chemistry , bent molecular geometry , intramolecular force , rhodium , cyclophane , polycyclic aromatic hydrocarbon , circular dichroism , stereochemistry , crystallography , organic chemistry , catalysis , crystal structure
The enantioselective synthesis of polycyclic aromatic hydrocarbon (PAH)‐based planar chiral cyclophanes was achieved for the first time by the rhodium‐catalyzed intramolecular regio‐ and enantioselective [2+2+2] cycloaddition of tethered diyne‐benzofulvenes followed by stepwise oxidative transformations. The thus synthesized planar chiral bent cyclophanes, that possess bent p ‐terphenyl‐ and 9‐fluorenone‐cores, were converted to 9‐fluorenol‐based ones with excellent ee values of >99 % by diastereoselective 1,2‐reduction. These 9‐fluorenol‐based cyclophanes exhibited high fluorescence quantum yields, which were significantly higher than that of an acyclic reference molecule (78–82 % vs. 48 %). The bending effect on the chiroptical property was also examined, which revealed that the anisotropy factors ( g abs values) for electronic circular dichroism (ECD) of these 9‐fluorenol‐based planar chiral bent cyclophanes increase as the tether length becomes shorter.