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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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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Photons or Electrons? A Critical Comparison of Electrochemistry and Photoredox Catalysis for Organic Synthesis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 2487 - 2649

Published: Nov. 9, 2021

Redox processes are at the heart of synthetic methods that rely on either electrochemistry or photoredox catalysis, but how do and catalysis compare? Both approaches provide access to high energy intermediates (e.g., radicals) enable bond formations not constrained by rules ionic 2 electron (e) mechanisms. Instead, they 1e mechanisms capable bypassing electronic steric limitations protecting group requirements, thus enabling chemists disconnect molecules in new different ways. However, while providing similar intermediates, differ several physical chemistry principles. Understanding those differences can be key designing transformations forging disconnections. This review aims highlight these similarities between comparing their underlying principles describing impact electrochemical photochemical methods.

Language: Английский

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Photocatalytic Late-Stage C–H Functionalization

Chemical Reviews, Journal Year: 2023, Volume and Issue: 123(8), P. 4237 - 4352

Published: Jan. 24, 2023

The emergence of modern photocatalysis, characterized by mildness and selectivity, has significantly spurred innovative late-stage C–H functionalization approaches that make use low energy photons as a controllable source. Compared to traditional strategies, photocatalysis paves the way toward complementary and/or previously unattainable regio- chemoselectivities. Merging compelling benefits with workflow offers potentially unmatched arsenal tackle drug development campaigns beyond. This Review highlights photocatalytic strategies small-molecule drugs, agrochemicals, natural products, classified according targeted bond newly formed one. Emphasis is devoted identifying, describing, comparing main mechanistic scenarios. draws critical comparison between established ionic chemistry photocatalyzed radical-based manifolds. aims establish current state-of-the-art illustrate key unsolved challenges be addressed in future. authors aim introduce general readership functionalization, specialist practitioners evaluation methodologies, potential for improvement, future uncharted directions.

Language: Английский

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Transition Metal-Catalyzed Organic Reactions under Visible Light: Recent Developments and Future Perspectives

ACS Catalysis, Journal Year: 2020, Volume and Issue: 10(16), P. 9170 - 9196

Published: July 20, 2020

The development of transition metal (TM) catalysis for organic synthesis under visible light without recourse to typical photoredox catalysts has become a rapidly growing area research and been actively explored in the past several years. Distinct from extensively developed catalysis, which photocatalyst generally does not directly participate bond-forming process, photocatalyst/TM synergistic absorbs photon energy transfers TM catalyst through redox or transfer this Review focuses on summarizing recent developments photocatalytic reactions that use complexes both absorb catalytic bond formation involving covalently bonded intermediate. contents are categorized by used (Pd, Cu, Co, Ni, Mn, Au, Rh, Fe, Ru), with descending sequence according number examples reported each metal, provide an overview April 2020. Future perspectives personal opinions regarding expanding field also discussed.

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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Single Electron Transfer-Induced Redox Processes Involving N-(Acyloxy)phthalimides

ACS Catalysis, Journal Year: 2021, Volume and Issue: 11(3), P. 1640 - 1683

Published: Jan. 20, 2021

The past decade has witnessed the emergence of N-(acyloxy)phthalimides (NHPI esters) and its derivatives at forefront synthetic methods facilitating construction diverse molecular frameworks from readily available carboxylic acid feedstock. NHPI esters are predisposed to undergo reductive fragmentation via a single electron transfer (SET) process under thermal, photochemical, or electrochemical conditions generate corresponding carbon- nitrogen-centered radicals that participate in multitude transformations forge carbon–carbon carbon–heteroatom bonds. chemistry involving received broad applicability not only well-designed cascade annulations but also medicinal natural product synthesis. This comprehensive Review, broadly categorized according nature bond formation, details progress made this field since initial discovery by providing representative examples with mechanistic details, an emphasis on challenges future directions.

Language: Английский

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Enantioselective Radical Reactions Using Chiral Catalysts

Chemical Reviews, Journal Year: 2022, Volume and Issue: 122(6), P. 5842 - 5976

Published: Jan. 24, 2022

Benefiting from the impressive increase in fundamental knowledge, last 20 years have shown a continuous burst of new ideas and consequently plethora catalytic methods for enantioselective radical reactions. This review aims to provide complete survey progress achieved over this latter period. The first part focuses on use chiral organocatalysts, these include catalysts covalently linked substrate those that interact with by weaker interactions like hydrogen bonds. second is devoted transition-metal redox catalysis which organized according increasing atomic number first-row transition metals (Ti, Cr, Fe, Mn, Co, Ni, Cu). Bioinspired manganese- iron-mediated hydroxylations oxidations are also discussed. A specific section dedicated reactivity Ru, Rh, Ir complexes as Lewis acids special focus at metal. Absorption photons result different events such energy transfer, single-electron hydrogen-atom transfer facilitating formation radicals. Organocatalysis has been successfully combined photocatalysts, opened pathways enlarging precursors available. merger photocatalysis organo- or metalla-photocatalysis brought novelty allowed discovery large original transformations. enzyme-catalyzed reactions involving intermediates largely benefit visible-light irradiation included review. provides comprehensive inventory goal detailing reaction mechanisms involved transformations any nonspecialist could find their own creativity invent yet unknown applications.

Language: Английский

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Microfluidic electrochemistry for single-electron transfer redox-neutral reactions

Science, Journal Year: 2020, Volume and Issue: 368(6497), P. 1352 - 1357

Published: June 18, 2020

Electrochemistry offers opportunities to promote single-electron transfer (SET) redox-neutral chemistries similar those recently discovered using visible-light photocatalysis but without the use of an expensive photocatalyst. Herein, we introduce a microfluidic electrochemistry (μRN-eChem) platform that has broad applicability SET chemistry, including radical-radical cross-coupling, Minisci-type reactions, and nickel-catalyzed C(sp2)-O cross-coupling. The cathode anode simultaneously generate corresponding reactive intermediates, selective transformation is facilitated by rapid molecular diffusion across channel outpaces decomposition intermediates. μRN-eChem was shown enable two-step gram-scale electrosynthesis nematic liquid crystal compound, demonstrating its practicality.

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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