Abstract
Abstractmagnified imageDiastereomeric biaryliminium cations made of an (Ra)‐5,5′,6,6′,7,7′,8,8′‐octahydrobinaphthyl core and exocyclic appendages derived from (S)‐ or (R)‐3,3‐dimethylbutan‐2‐amine are effective asymmetric epoxidation catalysts for unfunctionalized alkenes. Herein, we report that the negative counterion of the iminium salts has to be chosen wisely. While the hexafluoroantimonate anion [SbF6−] is optimal for reliable results, one has to be careful about other anions and tetraphenylborate [BPh4−] in particular. We also detail that the so far unexplained “lack” of stereochemical control from the chiral exocyclic appendage in this type of catalysts is due to the existence of atropisomers around the N(sp2)C(sp3) bond that links the azepinium core to the exocyclic stereocenter. Finally, we develop a general model to predict with certainty the high selectivity in the formation of non‐racemic epoxides of defined absolute configuration.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.