Enantioconvergent Amination of Racemic Tertiary C–H Bonds

Journal of the American Chemical Society, Год журнала: 2020, Номер 142(49), С. 20902 - 20911

Опубликована: Ноя. 30, 2020

Racemization is considered to be an intrinsic stereochemical feature of free radical chemistry as can seen in traditional halogenation reactions optically active tertiary C-H bonds. If the facile process racemization could effectively combined with ensuing step bond formation enantioselective fashion, then it would give rise deracemizative functionalization racemic bonds for stereoselective construction chiral molecules bearing quaternary stereocenters. As a demonstration this unique potential chemistry, we herein report that metalloradical catalysis successfully applied devise Co(II)-based catalytic system enantioconvergent amination C(sp3)-H The key success development catalyst fitting steric, electronic, and environments D2-symmetric amidoporphyrin supporting ligand. existence optimal reaction temperature recognized important factor realization process. Supported by optimized ligand, catalyze 1,6-amination at temperature, affording α-tertiary amines excellent yields high enantiocontrol newly created Systematic studies, including experiments utilizing deuterium-labeled substrates model system, shed light on underlying mechanistic details new amination. remarkable power create stereocenters multiple functionalities from ubiquitous bonds, showcased bicyclic N-heterocycles, opens door future synthetic applications technology.

Язык: Английский

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Reductive Allylic Defluorinative Cross-Coupling Enabled by Ni/Ti Cooperative Catalysis

Organic Letters, Год журнала: 2019, Номер 21(20), С. 8316 - 8322

Опубликована: Окт. 1, 2019

Unactivated alkyl chlorides are abundant building blocks in organic synthesis, but they have been rarely engaged cross-electrophile coupling. Herein, we report a Ni/Ti-cocatalyzed reductive allylic defluorinative cross-coupling between trifluoromethyl alkenes and unactivated bromides, enabling the efficient preparation of diverse functional-group-rich gem-difluoroalkenes. Notably, synthesis gem-difluoroalkene analogues azaperone, haloperidol, benperidol was also accomplished using our method as key step.

Язык: Английский

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Asymmetric radical cyclopropanation of dehydroaminocarboxylates: Stereoselective synthesis of cyclopropyl α-amino acids

Chem, Год журнала: 2021, Номер 7(6), С. 1588 - 1601

Опубликована: Март 29, 2021

Язык: Английский

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Regiodivergent Hydroborative Ring Opening of Epoxides via Selective C–O Bond Activation

Journal of the American Chemical Society, Год журнала: 2020, Номер 142(33), С. 14286 - 14294

Опубликована: Июль 13, 2020

A magnesium-catalyzed regiodivergent C–O bond cleavage protocol is presented. Readily available magnesium catalysts achieve the selective hydroboration of a wide range epoxides and oxetanes yielding secondary tertiary alcohols in excellent yields regioselectivities. Experimental mechanistic investigations DFT calculations provide insight into unexpected regiodivergence explain different mechanisms activation product formation.

Язык: Английский

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Titanocenes as Photoredox Catalysts Using Green‐Light Irradiation

Angewandte Chemie International Edition, Год журнала: 2020, Номер 59(24), С. 9355 - 9359

Опубликована: Март 26, 2020

Abstract Irradiation of Cp 2 TiCl with green light leads to electronically excited [Cp ]*. This complex constitutes an efficient photoredox catalyst for the reduction epoxides and 5‐ exo cyclizations suitably unsaturated epoxides. To best our knowledge, system is first example a molecular titanium catalyst.

Язык: Английский

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Photocatalytic Anti‐Markovnikov Radical Hydro‐ and Aminooxygenation of Unactivated Alkenes Tuned by Ketoxime Carbonates

Angewandte Chemie International Edition, Год журнала: 2021, Номер 60(40), С. 21997 - 22003

Опубликована: Июль 13, 2021

Abstract A tunable photocatalytic method is reported for anti ‐Markovnikov hydro‐ and aminooxygenation of unactivated alkenes using readily accessible ketoxime carbonates as the diverse functionalization reagents. Mechanistic studies reveal that this reaction initiated through an energy‐transfer‐promoted N−O bond homolysis leading to alkoxylcarbonyloxyl iminyl radicals under visible‐light photocatalysis, followed by addition radical alkenes. By taking advantage different stability radicals, generated carbon either abstracts a hydrogen atom from media form hydrooxygenation product, or it trapped persistent furnish product. Notably, first example direct olefins with regioselectivity involving oxygen‐centered radical.

Язык: Английский

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Asymmetric Radical Process for General Synthesis of Chiral Heteroaryl Cyclopropanes

Journal of the American Chemical Society, Год журнала: 2021, Номер 143(29), С. 11121 - 11129

Опубликована: Июль 20, 2021

A highly efficient catalytic method has been developed for asymmetric radical cyclopropanation of alkenes with in situ-generated α-heteroaryldiazomethanes via Co(II)-based metalloradical catalysis (MRC). Through fine-tuning the cavity-like environments newly-synthesized

Язык: Английский

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Epoxide Electroreduction

Journal of the American Chemical Society, Год журнала: 2021, Номер 144(3), С. 1389 - 1395

Опубликована: Дек. 29, 2021

Selective hydrogenation of epoxides would be a direct and powerful approach for alcohol synthesis, but it has proven to elusive. Here, electrochemically epoxide using electrons protons as reductants is reported. A wide range primary, secondary, tertiary alcohols can achieved through selective Markovnikov or anti-Markovnikov ring opening in the absence transition metals. Mechanistic investigations revealed that regioselectivity controlled by thermodynamic stabilities situ generated benzyl radicals aryl-substituted kinetic tendency alkyl-substituted epoxides.

Язык: Английский

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Metalloradical Activation of In Situ-Generated α-Alkynyldiazomethanes for Asymmetric Radical Cyclopropanation of Alkenes

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(5), С. 2368 - 2378

Опубликована: Янв. 31, 2022

α-Alkynyldiazomethanes, generated in situ from the corresponding sulfonyl hydrazones presence of a base, can serve as effective metalloradicophiles Co(II)-based metalloradical catalysis (MRC) for asymmetric cyclopropanation alkenes. With D2-symmetric chiral amidoporphyrin 2,6-DiMeO-QingPhyrin optimal supporting ligand, system efficiently activate different α-alkynyldiazomethanes at room temperature highly broad range This catalytic radical process provides general synthetic tool stereoselective construction alkynyl cyclopropanes high yields with both diastereoselectivity and enantioselectivity. Combined computational experimental studies offer several lines evidence support underlying stepwise mechanism Co(II)-catalyzed olefin involving unique α-metalloradical intermediate that is associated two resonance forms α-Co(III)-propargyl γ-Co(III)-allenyl radical. The resulting enantioenriched cyclopropanes, showcased stereospecific transformations, may valuable building blocks organic synthesis.

Язык: Английский

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Direct and Selective Electrocarboxylation of Styrene Oxides with CO₂ for Accessing β‐Hydroxy Acids

Angewandte Chemie International Edition, Год журнала: 2022, Номер 61(38)

Опубликована: Июль 21, 2022

Abstract Highly selective and direct electroreductive ring‐opening carboxylation of epoxides with CO 2 in an undivided cell is reported. This reaction shows broad substrate scopes within styrene oxides under mild conditions, providing practical scalable access to important synthetic intermediate β ‐hydroxy acids. Mechanistic studies show that functions not only as a carboxylative reagent this but also promoter enable efficient chemoselective transformation additive‐free electrochemical conditions. Cathodically generated α ‐radical ‐carbanion intermediates lead the regioselective formation ‐carboxylation products.

Язык: Английский

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