Coldham, I. orcid.org/0000-0003-4602-6292, Choi, A., El-Tunsi, A. et al. (5 more authors) (2021) Asymmetric synthesis of 2-arylindolines and 2,2-disubstituted indolines by kinetic resolution. Chemistry - A European Journal, 27 (45). pp. 11670-11675. ISSN 0947-6539
Abstract
Kinetic resolution of 2-arylindolines (2,3-dihydroindoles) was achieved by treatment of their N - tert -butoxycarbonyl (Boc) derivatives with n -butyllithium and sparteine in toluene at –78 °C followed by electrophilic quench. The unreacted starting materials together with the 2,2-disubstituted products could be isolated with high enantiomer ratios. Variable temperature NMR spectroscopy showed that the rate of Boc rotation was fast (ΔG ‡ ≈ 57 kJ/mol at 195 K). This was corroborated by DFT studies and by in situ ReactIR spectroscopy. The enantioenriched N -Boc-2-arylindolines were converted to 2,2-disubstituted products without significant loss in enantiopurity. Hence either enantiomer of the 2,2-disubstituted products could be obtained with high selectivity from the same enantiomer of the chiral ligand sparteine (one from the kinetic resolution and the other from subsequent lithiation–trapping of the recovered starting material). Secondary amine products were prepared by removing the Boc group with acid to provide a way to access highly enantioenriched 2-aryl and 2,2-disubstituted indolines.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2021 Wiley-VCH GmbH. This is an author-produced version of a paper subsequently published in Chemistry - A European Journal. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | asymmetric synthesis; enantioselectivity; heterocycles; kinetic resolution; lithiation |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Chemistry (Sheffield) |
Funding Information: | Funder Grant number ROYAL SOCIETY SIF\R2\202031 ENGINEERING AND PHYSICAL SCIENCE RESEARCH COUNCIL EP/R024294/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 16 Jun 2021 12:48 |
Last Modified: | 10 Jun 2022 23:39 |
Status: | Published |
Publisher: | Wiley |
Refereed: | Yes |
Identification Number: | 10.1002/chem.202101248 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:175271 |