Allenyl Radicals in Organic Synthesis: Challenges and Recent Advances

Yu, Yang; Zhang, Jitang

doi:10.1002/ejoc.202201017

Cited by 7 publications

(7 citation statements)

References 136 publications

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“…1,3-Enynes are readily available materials that participate in a range of synthetically useful transformations . In particular, trifluoromethyl functionalization of a 1,3-enyne through a radical pathway has attracted notable attention in recent years. − For example, Liu, Lin, and co-workers realized the copper-catalyzed synthesis of CF 3 -substituted allenyl nitriles . Yang and co-workers demonstrated a copper-catalyzed three-component synthesis of CF 3 -substituted allenyl chlorides .…”

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confidence: 99%

Synthesis of Trifluoromethyl-Substituted Allenols via Catalytic Trifluoromethylbenzoxylation of 1,3-Enynes

Yang

Shi

et al. 2023

ACS Catal.

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Allenol has been identified as a versatile building block for organic synthesis, and numerous efforts have been made to synthesize and apply allenol. However, limited efforts have been made to obtain a trifluoromethyl-substituted allenol. Here, by using a readily available 1,3-enyne as the starting material, a coppercatalyzed trifluoromethylbenzoxylation process was developed for efficient synthesis of trifluoromethyl-substituted allenols using Togni-II reagent as the reaction partner. Triple roles of the Togni-II reagent, including as the source of the trifluoromethyl group, as the source of the hydroxyl group, and as the oxidant, were elucidated in this transformation. Moreover, late-stage diversification was performed, which revealed the application potential of trifluoromethyl-substituted allenols for the preparation of various trifluoromethyl-substituted compounds.

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confidence: 99%

Synthesis of Trifluoromethyl-Substituted Allenols via Catalytic Trifluoromethylbenzoxylation of 1,3-Enynes

Yang

Shi

et al. 2023

ACS Catal.

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“…Photoredox catalysis has gained significant attention in chemical synthesis over the last decade due to its effectiveness in the activation of small molecules . The underlying mechanism is mostly single-electron transfer (SET), for which the photocatalysts (PCs) provide easy access . This type of electron transfer reactivity is described by the reduction potentials of redox couples, which can be written as follows: normalM + + normale − = normalM normalM + normale − = normalM − …”

Section: Introductionmentioning

confidence: 99%

Prediction of Redox Power for Photocatalysts: Synergistic Combination of DFT and Machine Learning

Fehér

Madarász

Stirling

2023

J. Chem. Theory Comput.

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The accurate prediction of excited state properties is a key element of rational photocatalyst design. This involves the prediction of ground and excited state redox potentials, for which an accurate description of electronic structures is needed. Even with highly sophisticated computational approaches, however, a number of difficulties arise from the complexity of excited state redox potentials, as they require the calculation of the corresponding ground state redox potentials and the estimation of the 0–0 transition energies (E 0,0). In this study, we have systematically evaluated the performance of DFT methods for these quantities on a set of 37 organic photocatalysts representing 9 different chromophore scaffolds. We have found that the ground state redox potentials can be predicted with reasonable accuracy that can be further improved by rationally minimizing the systematic underestimations. The challenging part is to obtain E 0,0, as calculating it directly is highly demanding and its accuracy depends strongly on the DFT functional employed. We have found that approximating E 0,0 with appropriately scaled vertical absorption energies offers the best compromise between accuracy and computational effort. An even more accurate and cost-effective approach, however, is to predict E 0,0 with machine learning and avoid the use of DFT for excited state calculations. Indeed, the best excited state redox potential predictions are achieved with the combination of M062X for ground state redox potentials and machine learning (ML) for E 0,0. With this protocol, the excited state redox potential windows of the photocatalyst frameworks could be adequately predicted. This shows the potential of combining DFT with ML in the computational design of photocatalysts with preferred photochemical properties.

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“…Given the widespread synthetic utility of cumulenes, the synthesis of functionalized allenes such as allenols and allenones has attracted considerable interest from the synthetic community. As one of the direct allenylation strategies, the transition metal-catalyzed addition reactions to 1,3-enynes provide the metalated allenyl intermediates that lead to the related allenyl products under thermodynamic control (Scheme a). The metalated allenyl intermediate was first utilized by the Lu’s group to give CN-substituted allenes under the visible light-induced dual Ir-photoredox/Cu-catalyzed 1,4-carbocyanation of 1,3-enynes (Scheme b) .…”

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confidence: 99%

“…The fate of the t -butoxy radical is governed by the ample presence of TBHP, where the formation of the t -butyl peroxy radical and t -BuOH should be encouraged . A ready availability of the t -butyl peroxy radical species initiates the radical addition to the alkene moiety of enynones 1 , where the resulting α-keto radical species C can be stabilized by the adjacent carbonyl and alkynyl groups . The final radical–radical coupling between the sulfonyl radical B and the α-keto radical C occurs at the γ-carbon of enynones 1 with less steric effect to give the allene product 3 .…”

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confidence: 99%

Photoredox-Catalyzed 1,4-Peroxidation–Sulfonylation of Enynones: A Three-Component Radical Coupling Approach for the Synthesis of Highly Functionalized Allenes

Bhatt,

Miyake,

Nakamura

et al. 2024

Org. Lett.

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An Eosin Y-catalyzed visible light-promoted 1,4peroxidation−sulfonylation of enynones was achieved to give tetrasubstituted allenes. The photoredox catalysis of Eosin Y allowed the concomitant formation of peroxy and sulfonyl radicals, where the preferential peroxy radical addition to the alkene moiety of enynones resulted in the subsequent α-keto radical−sulfonyl radical cross couplings. The developed photoredox catalysis of Eosin Y demonstrates a regioselective 1,4-diradical addition strategy, opening up a new possibility of diradical functionalization of conjugate systems.

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Allenyl Radicals in Organic Synthesis: Challenges and Recent Advances

Cited by 7 publications

References 136 publications

Synthesis of Trifluoromethyl-Substituted Allenols via Catalytic Trifluoromethylbenzoxylation of 1,3-Enynes

Synthesis of Trifluoromethyl-Substituted Allenols via Catalytic Trifluoromethylbenzoxylation of 1,3-Enynes

Prediction of Redox Power for Photocatalysts: Synergistic Combination of DFT and Machine Learning

Photoredox-Catalyzed 1,4-Peroxidation–Sulfonylation of Enynones: A Three-Component Radical Coupling Approach for the Synthesis of Highly Functionalized Allenes

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