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Analysis of Interconversion between Atropisomers of Chiral Substituted 9,9’‐Bicarbazole
Author(s) -
Kobayashi Toshifumi,
Ishiwari Fumitaka,
Fukushima Takanori,
Hanaya Kengo,
Sugai Takeshi,
Higashibayashi Shuhei
Publication year - 2021
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.202001385
Subject(s) - atropisomer , racemization , chemistry , enantiomer , bond cleavage , transition state , cleavage (geology) , chirality (physics) , stereochemistry , computational chemistry , crystallography , catalysis , organic chemistry , nambu–jona lasinio model , chiral symmetry breaking , geotechnical engineering , physics , quantum mechanics , fracture (geology) , engineering , quark
Interconversion of atropisomers of chiral 3,3’‐di‐ tert ‐butyl‐9,9’‐bicarbazole linked by a single N−N bond was analyzed by DFT calculations and experiments. The calculations revealed that the trans transition state has a lower energy for the interconversion than the cis transition state. The lowest transition state of interconversion between natural dixiamycins A and B containing a 9,9’‐bicarbazole structure was found to be the trans transition state. The calculations also indicated that degradation through N−N bond cleavage was faster than racemization. Atropisomeric enantiomers of 3,3’‐di‐ tert ‐butyl‐9,9’‐bicarbazole were resolved by chiral HPLC for the first time, and then racemization and N−N bond cleavage were investigated by heating experiments, showing that racemization did not take place below the degradation temperature.