Synthetic Methods Driven by the Photoactivity of Electron Donor–Acceptor Complexes

Journal of the American Chemical Society, Journal Year: 2020, Volume and Issue: 142(12), P. 5461 - 5476

Published: March 5, 2020

The association of an electron-rich substrate with electron-accepting molecule can generate a new molecular aggregate in the ground state, called electron donor-acceptor (EDA) complex. Even when two precursors do not absorb visible light, resulting EDA complex often does. In 1952, Mulliken proposed quantum-mechanical theory to rationalize formation such colored complexes. However, and besides few pioneering studies 20th century, it is only past years that photochemistry has been recognized as powerful strategy for expanding potential visible-light-driven radical synthetic chemistry. Here, we explain why this photochemical approach was overlooked so long. We critically discuss historical context, scientific reasons, serendipitous observations, landmark discoveries were essential progress field. also outline future directions identify key advances are needed fully exploit photochemistry.

Language: Английский

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Aminoalkyl radicals as halogen-atom transfer agents for activation of alkyl and aryl halides

Science, Journal Year: 2020, Volume and Issue: 367(6481), P. 1021 - 1026

Published: Feb. 27, 2020

Organic halides are important building blocks in synthesis, but their use (photo)redox chemistry is limited by low reduction potentials. Halogen-atom transfer remains the most reliable approach to exploit these substrates radical processes despite its requirement for hazardous reagents and initiators such as tributyltin hydride. In this study, we demonstrate that α-aminoalkyl radicals, easily accessible from simple amines, promote homolytic activation of carbon-halogen bonds with a reactivity profile mirroring classical tin radicals. This strategy conveniently engages alkyl aryl wide range redox transformations construct sp3-sp3, sp3-sp2, sp2-sp2 carbon-carbon under mild conditions high chemoselectivity.

Language: Английский

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Twisted intramolecular charge transfer (TICT) and twists beyond TICT: from mechanisms to rational designs of bright and sensitive fluorophores

Chemical Society Reviews, Journal Year: 2021, Volume and Issue: 50(22), P. 12656 - 12678

Published: Jan. 1, 2021

The twisted intramolecular charge transfer (TICT) mechanism and twists beyond TICT have guided the creation of numerous bright sensitive fluorophores. We reviewed structure–property relationships these dyes with representative examples.

Language: Английский

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Generation of Alkyl Radicals: From the Tyranny of Tin to the Photon Democracy

Chemical Reviews, Journal Year: 2020, Volume and Issue: 120(17), P. 9790 - 9833

Published: Aug. 6, 2020

Alkyl radicals are key intermediates in organic synthesis. Their classic generation from alkyl halides has a severe drawback due to the employment of toxic tin hydrides point that "flight tyranny tin" radical processes was considered for long time an unavoidable issue. This review summarizes main alternative approaches unstabilized radicals, using photons as traceless promoters. The recent development photochemical and photocatalyzed enabled discovery plethora new precursors, opening world chemistry broader community, thus allowing era photon democracy.

Language: Английский

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Photochemical and Electrochemical Applications of Proton-Coupled Electron Transfer in Organic Synthesis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 2017 - 2291

Published: Nov. 23, 2021

We present here a review of the photochemical and electrochemical applications multi-site proton-coupled electron transfer (MS-PCET) in organic synthesis. MS-PCETs are redox mechanisms which both an proton exchanged together, often concerted elementary step. As such, MS-PCET can function as non-classical mechanism for homolytic bond activation, providing opportunities to generate synthetically useful free radical intermediates directly from wide variety common functional groups. introduction practitioner’s guide reaction design, with emphasis on unique energetic selectivity features that characteristic this class. then chapters oxidative N–H, O–H, S–H, C–H homolysis methods, generation corresponding neutral species. Then, reductive PCET activations involving carbonyl, imine, other X═Y π-systems, heteroarenes, where ketyl, α-amino, heteroarene-derived radicals be generated. Finally, we asymmetric catalysis materials device applications. Within each chapter, subdivide by group undergoing homolysis, thereafter type transformation being promoted. Methods published prior end December 2020 presented.

Language: Английский

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Visible light photocatalysis in the late-stage functionalization of pharmaceutically relevant compounds

Chemical Society Reviews, Journal Year: 2020, Volume and Issue: 50(2), P. 766 - 897

Published: Dec. 22, 2020

Recent developments and future prospects of visible-light photocatalysis in the late-stage functionalization pharmaceuticals natural bioactive compounds.

Language: Английский

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Recent Advances in Pyridinium Salts as Radical Reservoirs in Organic Synthesis

ACS Catalysis, Journal Year: 2019, Volume and Issue: 9(10), P. 8943 - 8960

Published: Aug. 28, 2019

Pyridinium salts are valuable building blocks, which have been widely applied in various organic transformations during the past few decades. In particular, N-functionalized pyridinium explored as convenient radical precursors, would go through reductive single-electron transfer. As a result, chemistry of such compounds for generating carbon-, nitrogen-, and oxygen-centered radicals has witnessed, remarkable progress achieved, making it hot topic over last five years. This Review describes recent advances area concerning development reactions involving synthesis.

Language: Английский

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Hantzsch esters: an emerging versatile class of reagents in photoredox catalyzed organic synthesis

Organic & Biomolecular Chemistry, Journal Year: 2019, Volume and Issue: 17(29), P. 6936 - 6951

Published: Jan. 1, 2019

This minireview highlights the recent advances in chemistry of Hantzsch esters photoredox catalyzed organic synthesis, with particular emphasis placed on reaction mechanisms.

Language: Английский

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Catalyst‐Free Deaminative Functionalizations of Primary Amines by Photoinduced Single‐Electron Transfer

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 58(17), P. 5697 - 5701

Published: Feb. 22, 2019

Abstract The use of pyridinium‐activated primary amines as photoactive functional groups for deaminative generation alkyl radicals under catalyst‐free conditions is described. By taking advantage the visible light absorptivity electron donor–acceptor complexes between Katritzky pyridinium salts and either Hantzsch ester or Et 3 N, photoinduced single‐electron transfer could be initiated in absence a photocatalyst. This general reactivity platform has been applied to alkylation (Giese), allylation, vinylation, alkynylation, thioetherification, hydrodeamination reactions. mild are amenable diverse range secondary pyridiniums demonstrate broad group tolerance.

Language: Английский

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Pyridinium Salts as Redox‐Active Functional Group Transfer Reagents

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 59(24), P. 9264 - 9280

Published: Oct. 10, 2019

Abstract In this Review, we highlight recent advances in the understanding and design of N‐functionalized pyridinium scaffolds as redox‐active, single‐electron, functional group transfer reagents. We provide a selection representative methods that demonstrate reactivity fundamental emerging field. The these reagents can be divided into two divergent pathways: homolytic fragmentation to liberate N‐bound substituent corresponding radical or an alternative heterolytic liberates N‐centered radical. A short description elementary steps involved induced by single‐electron is also critically discussed guide readers towards processes thought occur under conditions.

Language: Английский

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