Direct Photocatalyzed Hydrogen Atom Transfer (HAT) for Aliphatic C–H Bonds Elaboration

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 1875 - 1924

Published: Aug. 6, 2021

Direct photocatalyzed hydrogen atom transfer (d-HAT) can be considered a method of choice for the elaboration aliphatic C–H bonds. In this manifold, photocatalyst (PCHAT) exploits energy photon to trigger homolytic cleavage such bonds in organic compounds. Selective bond may achieved by judicious abstractor (key parameters are electronic character and molecular structure), as well reaction additives. Different classes PCsHAT available, including aromatic ketones, xanthene dyes (Eosin Y), polyoxometalates, uranyl salts, metal-oxo porphyrin tris(amino)cyclopropenium radical dication. The processes (mainly C–C formation) most cases carried out under mild conditions with help visible light. aim review is offer comprehensive survey synthetic applications d-HAT.

Language: Английский

---

Recent advances in visible light-activated radical coupling reactions triggered by (i) ruthenium, (ii) iridium and (iii) organic photoredox agents

Chemical Society Reviews, Journal Year: 2021, Volume and Issue: 50(17), P. 9540 - 9685

Published: Jan. 1, 2021

Visible light-activated reactions continue to expand and diversify. The example shown here is a Birch reduction achieved by organophotoredox reagents.

Language: Английский

---

Alkoxy Radicals See the Light: New Paradigms of Photochemical Synthesis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 2429 - 2486

Published: Oct. 6, 2021

Alkoxy radicals are highly reactive species that have long been recognized as versatile intermediates in organic synthesis. However, their development has impeded due to a lack of convenient methods for generation. Thanks advances photoredox catalysis, enabling facile access alkoxy from bench-stable precursors and free alcohols under mild conditions, research interest this field renewed. This review comprehensively summarizes the recent progress radical-mediated transformations visible light irradiation. Elementary steps radical generation either or central reaction development; thus, each section is categorized discussed accordingly. Throughout review, we focused on different mechanisms well impact synthetic utilizations. Notably, catalytic abundant still early stage, providing intriguing opportunities exploit diverse paradigms.

Language: Английский

---

Radical philicity and its role in selective organic transformations

Nature Reviews Chemistry, Journal Year: 2021, Volume and Issue: 5(7), P. 486 - 499

Published: June 22, 2021

Language: Английский

---

Photoinduced FeCl₃‐Catalyzed Alkyl Aromatics Oxidation toward Degradation of Polystyrene at Room Temperature^†

Chinese Journal of Chemistry, Journal Year: 2021, Volume and Issue: 39(12), P. 3225 - 3230

Published: Aug. 13, 2021

Main observation and conclusion While polystyrene is widely used in daily life as a synthetic plastic, the subsequently selective degradation still very challenging highly required. Herein, we disclose practical reaction for catalytically efficient oxidation of alkyl aromatics (including 1°, 2°, 3° aromatics) to carboxylic acids. dioxygen was sole terminal oxidant, this protocol catalyzed by inexpensive readily available ferric compound (FeCl 3 ) with irradiation visible light (blue LEDs) under only 1 atmosphere O 2 at room temperature. This system could further facilitate benzoic acid, providing an important tool generate high‐value chemical from abundant wastes.

Language: Английский

---

Iron-Catalyzed C(Sp³)–H Borylation, Thiolation, and Sulfinylation Enabled by Photoinduced Ligand-to-Metal Charge Transfer

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(13), P. 7600 - 7611

Published: March 23, 2023

Catalytic C(sp3)-H functionalization has provided enormous opportunities to construct organic molecules, facilitating the derivatization of complex pharmaceutical compounds. Within this framework, direct hydrogen atom transfer (HAT) photocatalysis becomes an appealing approach goal. However, viable substrates utilized in these protocols are limited, and site selectivity shows preference activated thermodynamically favored bonds. Herein, we describe development undirected iron-catalyzed borylation, thiolation, sulfinylation reactions enabled by photoinduced ligand-to-metal charge (LMCT) process. These exhibit remarkably broad substrate scope (>150 examples total), most importantly, all three show unconventional regioselectivity, with occurrence preferentially at distal methyl position. The procedures operationally simple readily scalable provide access high-value products from hydrocarbons one step. Mechanistic studies control experiments indicate that afforded is not only relevant HAT species but also largely affected use boron- sulfone-based radical acceptors.

Language: Английский

---

Selective Degradation of Styrene‐Related Plastics Catalyzed by Iron under Visible Light**

ChemSusChem, Journal Year: 2021, Volume and Issue: 14(22), P. 5049 - 5056

Published: Sept. 12, 2021

Abstract Efficient degradation of plastics, the vital challenge for a sustainable future, stands in need better chemical recycling procedures that help produce commercially valuable small molecules and redefine plastic waste as rich source feedstock. However, corresponding methods, while being generally restricted to polar polymers, improvement. Particularly, chemically inert nonpolar major constitutes suffers from low selectivity very harsh transformation conditions. Herein, an efficient method was developed selective styrene‐related plastics under gentle conditions through multiple oxidation sp 3 C−H bonds C−C bonds. The procedure catalyzed with inexpensive iron salts visible light, using oxygen green oxidant. Furthermore, simple could be used degrade absence solvent natural conditions, highlighting potential application additives degradable plastics.

Language: Английский

---

Recent advances in difunctionalization of alkenes using pyridinium salts as radical precursors

Chemical Communications, Journal Year: 2022, Volume and Issue: 58(24), P. 3847 - 3864

Published: Jan. 1, 2022

This review summarises recent applications of pyridinium salts in radical-mediated difunctionalization alkenes. We hope this will provide a comprehensive overview topic and promote the wider development application salts.

Language: Английский

---

Photoinduced Ligand-to-Metal Charge Transfer (LMCT) of Fe Alkoxide Enabled C–C Bond Cleavage and Amination of Unstrained Cyclic Alcohols

Organic Letters, Journal Year: 2022, Volume and Issue: 24(3), P. 977 - 982

Published: Jan. 14, 2022

We report an alkoxy radical process for the C-C bond cleavage and functionalization of unstrained tertiary secondary cyclic alcohols. In absence a chlorine atom, readily available iron catalysts [Fe(OBu-t)3 or Fe(acac)3/t-BuONa] facilitate formation via direct ligand-to-metal charge transfer Fe alkoxide further enable ring opening amination The remote amino carbonyl compounds could be obtained with broad scope in up to excellent yields under mildly redox-neutral system. Light-driven electron transfer, formation, subsequent β-scission were keys transformation.

Language: Английский

---

Identification of Alkoxy Radicals as Hydrogen Atom Transfer Agents in Ce-Catalyzed C–H Functionalization

Journal of the American Chemical Society, Journal Year: 2022, Volume and Issue: 145(1), P. 359 - 376

Published: Dec. 20, 2022

The intermediacy of alkoxy radicals in cerium-catalyzed C–H functionalization via H-atom abstraction has been unambiguously confirmed. Catalytically relevant Ce(IV)–alkoxide complexes have synthesized and characterized by X-ray diffraction. Operando electron paramagnetic resonance transient absorption spectroscopy experiments on isolated pentachloro Ce(IV) alkoxides identified as the sole heteroatom-centered radical species generated ligand-to-metal charge transfer (LMCT) excitation. Alkoxy-radical-mediated hydrogen atom (HAT) verified kinetic analysis, density functional theory (DFT) calculations, reactions under strictly chloride-free conditions. These experimental findings establish critical role Ce-LMCT catalysis definitively preclude involvement chlorine radical. This study also reinforced necessity a high relative ratio alcohol vs Ce for selective alkoxy-radical-mediated HAT, seemingly trivial changes can lead to drastically different mechanistic pathways. Importantly, previously proposed radical–alcohol complex, postulated explain alkoxy-radical-enabled selectivities this system, examined scrutiny ruled out regioselectivity studies, experiments, high-level calculations. Moreover, peculiar selectivity generation LMCT homolysis heteroleptic analyzed back-electron (BET) may regulated efficiency formation ligand-centered radicals.

Language: Английский

---