TY - JOUR
T1 - Analysis of Interconversion between Atropisomers of Chiral Substituted 9,9’-Bicarbazole
AU - Kobayashi, Toshifumi
AU - Ishiwari, Fumitaka
AU - Fukushima, Takanori
AU - Hanaya, Kengo
AU - Sugai, Takeshi
AU - Higashibayashi, Shuhei
N1 - Funding Information:
This work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant No. 20K05499 (S.H.). Part of the calculations was performed using Research Center for Computational Science, Okazaki, Japan.
Publisher Copyright:
© 2020 Wiley-VCH GmbH
PY - 2021/1/22
Y1 - 2021/1/22
N2 - 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.
AB - 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.
KW - Atropisomer
KW - Axis chirality
KW - Bicarbazole
KW - Optical resolution
KW - Racemization
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U2 - 10.1002/ejoc.202001385
DO - 10.1002/ejoc.202001385
M3 - Article
AN - SCOPUS:85097280517
SN - 0365-5490
VL - 2021
SP - 449
EP - 451
JO - Justus Liebigs Annalen der Chemie
JF - Justus Liebigs Annalen der Chemie
IS - 3
ER -