Strategies for the Photocatalytic Generation of Carbanion Equivalents for Reductant-Free C–C Bond Formations

Accounts of Chemical Research, Journal Year: 2020, Volume and Issue: 54(1), P. 242 - 252

Published: Dec. 16, 2020

ConspectusThe use of photocatalysis in organic chemistry has encountered a surge novel transformations since the start 21st century. The majority these are driven by generation and subsequent reaction radicals, owing to intrinsic property common photocatalysts transfer single electrons from their excited state. While this is powerful elegant method develop transformations, several research groups recently sought further extend toolbox into realm polar ionic reactivity formation cationic as well anionic key intermediates furnish desired product.Our group became especially interested photocatalytic carbon nucleophiles, overall transformation resembles classical organometallic reactions like Grignard, Barbier, Reformatsky reactions, which ubiquitous synthesis with broad applications valuable C–C bonds. Although frequently applied, still bears certain disadvantages; one necessity an (over)stoichiometric amount reducing metal. reducing, low-valent, metal solely applied activate starting material form carbanion synthon, while final product does generally not contain species. Hence, stoichiometric salt bound be generated at end each reaction, diminishing atom economy. visible light mild traceless activation agent drive chemical can means arrive more economic transformation, source avoided. Beyond this, vast pool methods offers potential employ easily available materials, simple unfunctionalized alkanes, open facile retrosynthetic pathways. However, mentioned above, dominated open-shell radical reactivity. With neutral radicals showing intrinsically different than species, strategies expressing behavior need developed order achieve goal.In last couple years, toward aim have been reported our others. This Account aims give overview existing photocatalytically centered anions or equivalents those As main concept omit reductant (like low-valent reactions), only redox-neutral reductant-free were taken closer consideration. We present selected examples important try illustrate intentions concepts behind

Language: Английский

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Cp₂TiCl₂-Catalyzed Photoredox Allylation of Aldehydes with Visible Light

ACS Catalysis, Journal Year: 2020, Volume and Issue: 10(6), P. 3857 - 3863

Published: Feb. 28, 2020

A Barbier-type Cp2TiCl2-mediated (10 mol %) photoredox allylation of aldehydes under irradiation with visible light (blue light-emitting diodes (LEDs), 450 nm) and in the presence an organic dye (3DPAFIPN, 5 allylbromides is described.

Language: Английский

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Asymmetric 1,4-functionalization of 1,3-enynes via dual photoredox and chromium catalysis

Nature Communications, Journal Year: 2022, Volume and Issue: 13(1)

Published: Aug. 26, 2022

Abstract The merger of photoredox and transition-metal catalysis has evolved as a robust platform in organic synthesis over the past decade. stereoselective 1,4-functionalization 1,3-enynes, prevalent synthon synthetic chemistry, could afford valuable chiral allene derivatives. However, tremendous efforts have been focused on ionic reaction pathway. radical-involved asymmetric 1,3-enynes remains prominent challenge. Herein, we describe three-component 1,4-dialkylation via dual chromium to provide allenols. This method features readily available starting materials, broad substrate scope, good functional group compatibility, high regioselectivity, simultaneous control axial central chiralities. Mechanistic studies suggest that this proceeds through redox-neutral

Language: Английский

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Merging Carbonyl Addition with Photocatalysis

Accounts of Chemical Research, Journal Year: 2022, Volume and Issue: 55(8), P. 1135 - 1147

Published: March 31, 2022

The carbonyl group stands as a fundamental scaffold and plays ubiquitous role in synthetically important chemical reactions both academic industrial contexts. Venerable transformations, including the aldol reaction, Grignard Wittig Nozaki-Hiyama-Kishi constitute vast empowering synthetic arsenal. Notwithstanding, two-electron mechanisms inherently confine breadth of accessible reactivity topological patterns.Fostered by rapid development photoredox catalysis, combing well-entrenched addition radicals can harness several unique increasingly sustainable transformations. In particular, unusual carbon-carbon carbon-heteroatom disconnections, which are out reach chemistry, be conceived. To meet this end, novel strategy toward utilization simple compounds intermolecular radical acceptors was developed. reaction is enabled visible-light photoredox-initiated hole catalysis. situ Brønsted acid activation moiety prevents β-scission from occurring. Furthermore, regioselective alkyl obviates use metals, ligands, or additives, thus offering high degree atom economy under mild conditions. On basis same concept work Schindler co-workers, carbonyl-olefin cross-metathesis, induced visible light, has also been achieved, leveraging Prins-elimination sequence.Recently, dual chromium catalysis developed us Kanai, complementary approach to revered reaction. Leveraging intertwined synergy between light metal, radical-to-polar crossover transformations eminent molecular motifs have Reactions such redox-neutral allylation aldehydes alkylation harvest power enable catalytic metal. Overall, exquisite levels diastereoselectivity enforced via highly compact transition states. Other examples, dialkylation 1,3-dienes propargylation portray versatile combination multicomponent coupling endeavors. Highly valuable motifs, commonly occur complex drug natural product architectures, now accessed single operational step. Going beyond addition, seminal contributions Fagnoni MacMillan preconized photocatalytic HAT-based acyl formation key aldehyde valorization strategy. Our articulated concept, carboxy hydrogen abstractors regio- chemoselective alkynylation trifluoromethylthiolation.This Account, narrative our others' at interface radical-based photochemistry, aims provide core guiding foundations disruptive developments. We envisage that extending crossovers manifolds, taming less-activated carbonyls, processes, merging electron steps with energy-transfer events will propel breakthroughs near future.

Language: Английский

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Alkyl/Glycosyl Sulfoxides as Radical Precursors and Their Use in the Synthesis of Pyridine Derivatives**

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(31)

Published: June 1, 2022

We report here the use of simple and readily available alkyl sulfoxides as precursors to radicals their application in preparation pyridine derivatives. show that sulfoxides, N-methoxy pyridinium salts fluoride anions form electron donor-acceptor (EDA) complexes solution, which, upon visible light irradiation, undergo a radical chain process afford various derivatives smoothly. This reaction displays broad scope with respect both pyridiniums. The synthetic versatility handle chemistry adds power precursors. Glycosyl are converted corresponding pyridyl C-glycosides high stereoselectivities. Computational experimental studies provide insights into mechanism.

Language: Английский

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