Difluorocarbene generation from TMSCF3 : kinetics and mechanism of NaI-mediated and Si-induced anionic chain reactions
Date
26/08/2020Author
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Abstract
The mechanism of CF2 transfer from TMSCF3 ( 1 ), mediated by TBAT (2–12 mol %) or by NaI (5–20 mol %), has been investigated by in situ/stopped-flow 19F NMR spectroscopic analysis of the kinetics of alkene difluorocyclopropanation and competing TFE/c-C3F6/homologous perfluoroanion generation, 13C/2H KIEs, LFERs, CF2 transfer efficiency and selectivity, the effect of inhibitors, and density functional theory (DFT) calculations. The reactions evolve with profoundly different kinetics, undergoing autoinhibition (TBAT) or quasi-stochastic autoacceleration (NaI) and cogenerating perfluoroalkene side products. An overarching mechanism involving direct and indirect fluoride transfer from a CF3 anionoid to TMSCF3 ( 1 ) has been elucidated. It allows rationalization of why the NaI-mediated process is more effective for less-reactive alkenes and alkynes, why a large excess of TMSCF3 ( 1 ) is required in all cases, and why slow-addition protocols can be of benefit. Issues relating to exothermicity, toxicity, and scale-up are also noted.
Citation
García-Domínguez , A , West , T H , Primozic , J J , Grant , K M , Johnston , C P , Cumming , G G , Leach , A G & Lloyd-Jones , G C 2020 , ' Difluorocarbene generation from TMSCF 3 : kinetics and mechanism of NaI-mediated and Si-induced anionic chain reactions ' , Journal of the American Chemical Society , vol. 142 , no. 34 , pp. 14649-14663 . https://doi.org/10.1021/jacs.0c06751
Publication
Journal of the American Chemical Society
Status
Peer reviewed
ISSN
0002-7863Type
Journal article
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Copyright © 2020 American Chemical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the author created accepted manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1021/jacs.0c06751
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