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Lye K, Young RD. A review of frustrated Lewis pair enabled monoselective C-F bond activation. Chem Sci 2024; 15:2712-2724. [PMID: 38404400 PMCID: PMC10882520 DOI: 10.1039/d3sc06485a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Accepted: 01/07/2024] [Indexed: 02/27/2024] Open
Abstract
Frustrated Lewis pair (FLP) bond activation chemistry has greatly developed over the last two decades since the seminal report of metal-free reversible hydrogen activation. Recently, FLP systems have been utilized to allow monoselective C-F bond activation (at equivalent sites) in polyfluoroalkanes. The problem of 'over-defluorination' in the functionalization of polyfluoroalkanes (where multiple fluoro-positions are uncontrollably functionalized) has been a long-standing chemical problem in fluorocarbon chemistry for over 80 years. FLP mediated monoselective C-F bond activation is complementary to other solutions developed to address 'over-defluorination' and offers several advantages and unique opportunities. This perspective highlights some of these advantages and opportunities and places the development of FLP mediated C-F bond activation into the context of the wider effort to overcome 'over-defluorination'.
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Affiliation(s)
- Kenneth Lye
- Department of Chemistry, National University of Singapore 117543 Singapore
| | - Rowan D Young
- School of Chemistry and Molecular Biosciences, The University of Queensland St Lucia 4072 Australia
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Advances in Catalytic C–F Bond Activation and Transformation of Aromatic Fluorides. Catalysts 2022. [DOI: 10.3390/catal12121665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The activation and transformation of C–F bonds in fluoro-aromatics is a highly desirable process in organic chemistry. It provides synthetic methods/protocols for the generation of organic compounds possessing single or multiple C–F bonds, and effective catalytic systems for further study of the activation mode of inert chemical bonds. Due to the high polarity of the C–F bond and it having the highest bond energy in organics, C–F activation often faces considerable academic challenges. In this mini-review, the important research achievements in the activation and transformation of aromatic C–F bond, catalyzed by transition metal and metal-free systems, are presented.
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Mebs S, Beckmann J. In silico activation of dinitrogen with a light atom molecule. Phys Chem Chem Phys 2022; 24:20953-20967. [PMID: 35993454 DOI: 10.1039/d2cp02516g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The NN triple bond can be cleaved in silico with a light atom molecule containing only the earth abundant elements C, H, Si, and P. Extensive density functional theory (DFT) computations on various classes of peri-substituted scaffolds containing Lewis acidic and basic sites in the framework of frustrated Lewis pairs (FLP) indicate that the presence of two silyl cations and two P atoms in a flexible but not too flexible arrangement is essential for energy efficient N2-activation. The non-bonding lone-pair electrons of the P atoms thereby serve as donors towards N2, whereas the lone-pairs of N2 donate into the silyl cations. Newly formed lone-pair basins in the N2-adducts balance surplus charge. Thereby, the N-N bond distance is increased by astonishing 0.3 Å, from 1.1 Å in N2 gas to 1.4 Å in the adduct, which makes this bond prone to subsequent addition of hydride ions and protonation, forming two secondary amine sites in the process and eventually breaking the NN triple bond. Potential formation of dead-end states, in which the dications ("active states") aversively form a Lewis acid (LA)-Lewis base (LB) bond, or in which the LA and LB sites are too far away from each other to be able to capture N2, are problematic but might be circumvented by proper choice of spacer molecules, such as acenaphthalene or biphenylene, and the ligands attached to the LA and LB atoms, such as phenyl or mesityl, and by purging the reaction solutions with gaseous N2 in the initial reaction steps. Charge redistributions via N2-activation and splitting were monitored by a variety of real-space bonding indicators (RSBIs) derived from the calculated electron and electron pair densities, which provided valuable insight into the bonding situation within the different reaction steps.
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Affiliation(s)
- Stefan Mebs
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
| | - Jens Beckmann
- Institut für Anorganische Chemie und Kristallographie, Universität Bremen, Leobener Straße 7, 28359 Bremen, Germany
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Li L, Zhang X, Ning Y, Zhang X, Liu B, Zhang Z, Sivaguru P, Zanoni G, Li S, Anderson EA, Bi X. Carbodefluorination of fluoroalkyl ketones via a carbene-initiated rearrangement strategy. Nat Commun 2022; 13:4280. [PMID: 35879307 PMCID: PMC9314321 DOI: 10.1038/s41467-022-31976-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 07/12/2022] [Indexed: 11/09/2022] Open
Abstract
The C–F bond cleavage and C–C bond formation (i.e., carbodefluorination) of readily accessible (per)fluoroalkyl groups constitutes an atom-economical and efficient route to partially fluorinated compounds. However, the selective mono-carbodefluorination of trifluoromethyl (CF3) groups remains a challenge, due to the notorious inertness of C–F bond and the risk of over-defluorination arising from C–F bond strength decrease as the defluorination proceeds. Herein, we report a carbene-initiated rearrangement strategy for the carbodefluorination of fluoroalkyl ketones with β,γ-unsaturated alcohols to provide skeletally and functionally diverse α-mono- and α,α-difluoro-γ,δ-unsaturated ketones. The reaction starts with the formation of silver carbenes from fluoroalkyl N-triftosylhydrazones, followed by nucleophilic attack of a β,γ-unsaturated alcohol to form key silver-coordinated oxonium ylide intermediates, which triggers selective C–F bond cleavage by HF elimination and C–C bond formation through Claisen rearrangement of in situ generated difluorovinyl ether. The origin of chemoselectivity and the reaction mechanism are determined by experimental and DFT calculations. Collectively, this strategy by an intramolecular cascade process offers significant advances over existing stepwise strategies in terms of selectivity, efficiency, functional group tolerance, etc. The selective functionalization of trifluoromethyl groups is challenging due to the inertness of the C–F bonds. Here the authors report a method for the carbodefluorination of C–F bonds of fluoroalkyl ketones via a carbene-initiated rearrangement strategy.
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Affiliation(s)
- Linxuan Li
- Department of Chemistry, Northeast Normal University, Changchun, 130024, China
| | - Xinyu Zhang
- Department of Chemistry, Northeast Normal University, Changchun, 130024, China
| | - Yongquan Ning
- Department of Chemistry, Northeast Normal University, Changchun, 130024, China
| | - Xiaolong Zhang
- Department of Chemistry, Northeast Normal University, Changchun, 130024, China
| | - Binbin Liu
- Department of Chemistry, Northeast Normal University, Changchun, 130024, China
| | - Zhansong Zhang
- Department of Chemistry, Northeast Normal University, Changchun, 130024, China
| | | | - Giuseppe Zanoni
- Department of Chemistry, University of Pavia, Viale Taramelli 12, 27100, Pavia, Italy
| | - Shuang Li
- Department of Chemistry, Northeast Normal University, Changchun, 130024, China
| | - Edward A Anderson
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK
| | - Xihe Bi
- Department of Chemistry, Northeast Normal University, Changchun, 130024, China. .,State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, China.
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Li C, Manick AD, Dutasta JP, Chatelet B, Martinez A, Bugaut X. Frustrated Behavior of Lewis/Brønsted Pairs inside Molecular Cages. Org Chem Front 2022. [DOI: 10.1039/d2qo00011c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Different endohedrally functionalized cages were designed to investigate the effects of the size and shape of molecular cavities on the frustrated behavior of Lewis/Brønsted acid-base pairs and on catalytic activities....
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Sharma G, Newman PD, Platts JA. A review of quantum chemical studies of Frustrated Lewis Pairs. J Mol Graph Model 2021; 105:107846. [DOI: 10.1016/j.jmgm.2021.107846] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 01/13/2021] [Accepted: 01/20/2021] [Indexed: 11/16/2022]
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