Wu, Xiao orcid.org/0000-0002-3089-9200, Chen, Chentuo, Guo, Ziyang et al. (2 more authors) (2019) Metal and halide free catalyst for the synthesis of cyclic carbonates from epoxides and carbon dioxide. ACS Catalysis. pp. 1895-1906. ISSN 2155-5435
Abstract
N,N′-Phenylenebis(5-tert-butylsalicylideneimine) is shown to be an effective single-component catalyst for the metal- and halide-free synthesis of cyclic carbonates from epoxides and carbon dioxide. Using this bis-phenolic catalyst, a series of eight epoxides has been converted into the corresponding cyclic carbonates. Many closely related catalyst structures were found to be catalytically inactive, and the structural features necessary for catalytic activity have been delineated. Unusually, reactions could be carried out under solvent-free conditions or in the green solvents 2-methyl tetrahydrofuran (2-MeTHF) and propylene carbonate. Stereochemical studies showed that carbon dioxide insertion occurs exclusively at the terminal end of the epoxide and does so with loss of stereochemical purity if a 1-deutero-2-alkyl epoxide is used as substrate. On the basis of this evidence, a dual activation mechanism is proposed in which one phenol acts as a Brønsted acid to activate the epoxide, while the other reacts with carbon dioxide to form a carbonic half-ester intermediate which then ring-opens the activated epoxide. Two pathways are subsequently available for cyclization to a cyclic carbonate which have opposite stereochemical consequences. The experimental results suggest that ring-opening of the epoxide by the carbonic half-ester is the rate-determining step of the catalytic cycle.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2019 American Chemical Society. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details. |
Keywords: | carbon dioxide,cyclic carbonate,epoxide,organocatalyzed,salophen |
Dates: |
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Institution: | The University of York |
Academic Units: | The University of York > Faculty of Sciences (York) > Chemistry (York) The University of York |
Depositing User: | Pure (York) |
Date Deposited: | 01 Feb 2019 14:20 |
Last Modified: | 21 Dec 2024 00:17 |
Published Version: | https://doi.org/10.1021/acscatal.8b04387 |
Status: | Published |
Refereed: | Yes |
Identification Number: | 10.1021/acscatal.8b04387 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:141916 |
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Filename: Salphen_catalyst_paper_revised_v2.docx
Description: Salphen catalyst paper revised v2