Mechanistic Studies in Photocatalysis

Angewandte Chemie International Edition, Год журнала: 2018, Номер 58(12), С. 3730 - 3747

Опубликована: Окт. 19, 2018

Abstract The fast‐moving fields of photoredox and photocatalysis have recently provided fresh opportunities to expand the potential synthetic organic chemistry. Advances in light‐mediated processes mainly been guided so far by empirical findings quest for reaction invention. general perception, however, is that entering a more mature phase where combination experimental mechanistic studies will play dominant role sustaining further innovation. This Review outlines key consider when developing photochemical process, best techniques available acquiring relevant information. discussion use selected case highlight how investigations can be instrumental guiding invention development synthetically useful photocatalytic transformations.

Язык: Английский

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The Persistent Radical Effect in Organic Synthesis

Angewandte Chemie International Edition, Год журнала: 2019, Номер 59(1), С. 74 - 108

Опубликована: Май 22, 2019

Abstract Radical–radical couplings are mostly nearly diffusion‐controlled processes. Therefore, the selective cross‐coupling of two different radicals is challenging and not a synthetically valuable transformation. However, if have lifetimes they generated at equal rates, will become dominant process. This high cross‐selectivity based on kinetic phenomenon called persistent radical effect (PRE). In this Review, an explanation PRE supported by simulations simple model systems provided. Radical stabilities discussed within context their lifetimes, various examples PRE‐mediated radical–radical in synthesis summarized. It shown that restricted to coupling with transient radical. If one partner longer‐lived than other radical, operates achieved. important point expands scope chemistry. The Review divided into parts, namely 1) or organic 2) “radical–metal crossover reactions”; here, metal‐centered species more generally transition‐metal complexes able react discussed—a field has flourished recently.

Язык: Английский

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Seeing the Light: Advancing Materials Chemistry through Photopolymerization

Angewandte Chemie International Edition, Год журнала: 2018, Номер 58(16), С. 5170 - 5189

Опубликована: Авг. 1, 2018

The application of photochemistry to polymer and material science has led the development complex yet efficient systems for polymerization, post-functionalization, advanced materials production. Using light activate chemical reaction pathways in these not only leads exquisite control over dynamics, but also allows synthetic protocols be easily achieved. Compared polymerization mediated by thermal, chemical, or electrochemical means, photoinduced can potentially offer more versatile methods macromolecular synthesis. We highlight utility as an energy source mediating photopolymerization, present some promising examples which are advancing production through their exploitation photochemistry.

Язык: Английский

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Multi‐Photon Excitation in Photoredox Catalysis: Concepts, Applications, Methods

Angewandte Chemie International Edition, Год журнала: 2020, Номер 59(26), С. 10266 - 10284

Опубликована: Янв. 16, 2020

Abstract The energy of visible photons and the accessible redox potentials common photocatalysts set thermodynamic limits to photochemical reactions that can be driven by traditional visible‐light irradiation. UV excitation damaging induce side reactions, hence or even near‐IR light is usually preferable. Thus, photochemistry currently faces two divergent challenges, namely desire perform ever more thermodynamically demanding with increasingly lower photon energies. pooling low‐energy address both challenges simultaneously, whilst multi‐photon spectroscopy well established, synthetic photoredox chemistry has only recently started exploit processes on preparative scale. Herein, we have a critical look at developed mechanistic concepts, discuss pertinent experimental methods, provide an outlook into possible future developments this rapidly emerging area.

Язык: Английский

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Rapid Assessment of the Reaction‐Condition‐Based Sensitivity of Chemical Transformations

Angewandte Chemie International Edition, Год журнала: 2019, Номер 58(25), С. 8572 - 8576

Опубликована: Апрель 1, 2019

Abstract A systematic, user‐friendly assessment tool that delivers a clear overview of the sensitivity reactions to key parameters is highly desirable. Herein, development such method described. The intuitive, standardized presentation results in radar diagram enables protocol be rapidly assessed. This was applied five different visible‐light‐mediated photochemical reactions, and were correlated underlying mechanism. Ultimately, we believe this will help increase uptake new synthetic methods their reproducibility.

Язык: Английский

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Catalysis with Palladium Complexes Photoexcited by Visible Light

Angewandte Chemie International Edition, Год журнала: 2019, Номер 58(34), С. 11586 - 11598

Опубликована: Янв. 2, 2019

Abstract Palladium catalysis induced by visible light is an emerging field of catalysis. In contrast to classical reactions catalyzed Pd complexes in the ground state, which mostly proceed through two‐electron redox processes, mechanisms these new methods based on photoexcited usually operate transfer a single electron. Such processes lead putative hybrid Pd/radical species, exhibit both radical and Pd‐type reactivity. This Minireview highlights recent progress this rapidly growing area.

Язык: Английский

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Catalytic Asymmetric C−H Functionalization under Photoredox Conditions by Radical Translocation and Stereocontrolled Alkene Addition

Angewandte Chemie International Edition, Год журнала: 2016, Номер 55(43), С. 13495 - 13498

Опубликована: Сен. 26, 2016

This work demonstrates how photoredox-mediated C(sp3)−H activation through radical translocation can be combined with asymmetric catalysis. Upon irradiation visible light, α,β-unsaturated N-acylpyrazoles react N-alkoxyphthalimides in the presence of a rhodium-based chiral Lewis acid catalyst and photosensitizer fac-[Ir(ppy)3] to provide C−C bond-formation product high enantioselectivity (up 97 % ee) and, where applicable, some diastereoselectivity (3.0:1 d.r.). Mechanistically, synthetic strategy exploits (1,5-hydrogen transfer) from an oxygen-centered carbon-centered subsequent stereocontrolled alkene addition.

Язык: Английский

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Photoredox Imino Functionalizations of Olefins

Angewandte Chemie International Edition, Год журнала: 2017, Номер 56(43), С. 13361 - 13365

Опубликована: Авг. 31, 2017

Abstract Shown herein is that polyfunctionalized nitrogen heterocycles can be easily prepared by a visible‐light‐mediated radical cascade process. This divergent strategy features the oxidative generation of iminyl radicals and subsequent cyclization/radical trapping, which allows effective construction highly functionalized heterocycles. The reactions proceed efficiently at room temperature, utilize an organic photocatalyst, use simple readily available materials, generate, in single step, valuable building blocks would difficult to prepare other methods.

Язык: Английский

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Electrophotocatalysis with a Trisaminocyclopropenium Radical Dication

Angewandte Chemie International Edition, Год журнала: 2019, Номер 58(38), С. 13318 - 13322

Опубликована: Июль 15, 2019

Visible-light photocatalysis and electrocatalysis are two powerful strategies for the promotion of chemical reactions. Here, these modalities combined in an electrophotocatalytic oxidation platform. This chemistry employs a trisaminocyclopropenium (TAC) ion catalyst, which is electrochemically oxidized to form cyclopropenium radical dication intermediate. The undergoes photoexcitation with visible light produce excited-state species oxidizing power (3.33 V vs. SCE) sufficient oxidize benzene halogenated benzenes via single-electron transfer (SET), resulting C-H/N-H coupling azoles. A rationale strongly behavior photoexcited provided, while stability catalyst rationalized by particular conformation cis-2,6-dimethylpiperidine moieties.

Язык: Английский

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A Supramolecular Radical Dimer: High‐Efficiency NIR‐II Photothermal Conversion and Therapy

Angewandte Chemie International Edition, Год журнала: 2019, Номер 58(43), С. 15526 - 15531

Опубликована: Сен. 3, 2019

Photothermal therapy at the NIR-II biowindow (1000-1350 nm) is drawing increasing interest because of its large penetration depth and maximum permissible exposure. Now, supramolecular radical dimer, fabricated by N,N'-dimethylated dipyridinium thiazolo[5,4-d]thiazole cation (MPT.+ ) cucurbit[8]uril (CB[8]), achieves strong absorption biowindow. The dimer (2MPT.+ -CB[8]) showed highly efficient photothermal conversion improved stability, thus contributing to inhibition on HegG2 cancer cell under 1064 nm irradiation even penetrating through chicken breast tissue. This work provides a novel approach construct chromophore tailor-made assembly organic radicals. It anticipated that this study new strategy achieve holds promises in luminescence materials, optoelectronic also biosensing.

Язык: Английский

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