Enantioselective Synthesis of Chiral Cyclobutenes Enabled by Brønsted Acid-Catalyzed Isomerization of BCBs

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(39), С. 21152 - 21158

Опубликована: Сен. 21, 2023

Chiral cyclobutene units are commonly found in natural products and biologically active molecules. Transition-metal-catalysis has been extensively used asymmetric synthesis of such structures, while organocatalytic approaches remain elusive. In this study, bicyclo[1.1.0]butanes involved enantioselective transformation for the first time to offer a highly efficient route toward cyclobutenes with good regio- enantiocontrol. The utilization N-triflyl phosphoramide as chiral Brønsted acid promoter enables isomerization process proceed under mild conditions low catalyst loading well functional group compatibility. resulting could serve platform molecules downstream manipulations excellent reservation stereochemical integrity, demonstrating synthetic practicality developed method. Control experiments have also performed verify formation key carbocation intermediate at benzylic position.

Язык: Английский

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Multifunctional Zn-N4 Catalysts for the Coupling of CO₂ with Epoxides into Cyclic Carbonates

ACS Catalysis, Год журнала: 2023, Номер 13(15), С. 10386 - 10393

Опубликована: Июль 25, 2023

The catalytic conversion of greenhouse gas CO2 into valuable chemicals is a vital goal toward carbon balance and sustainability. In recent decades, the chemical fixation cyclic carbonates has gained much attention. this work, series zinc complexes bearing tetradentate aminopyridine (N4) ligands have been synthesized characterized. These were applied to coupling with epoxides in excellent yields broad substrate scope under cocatalyst- solvent-free conditions. Moreover, catalysts could be readily recovered reused five times without an obvious loss activity. Based on spectroscopic characterizations experimental results, catalyst Zn-3 (DAP-ZnBr2, DAP = 1,4-bis(2-pyridymethyl)-1,4-diazepane) found multifunctional because presence Lewis acidic center nuclephilic halide anion, one pyridine released for activation during reaction.

Язык: Английский

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Asymmetric Epoxidation of Alkenes Catalyzed by a Cobalt Complex

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(28), С. 15611 - 15618

Опубликована: Июль 5, 2023

Asymmetric epoxidation of alkenes catalyzed by nonheme chiral Mn–O and Fe–O catalysts has been well established, but Co–O for the purpose remain virtually undeveloped due to oxo wall. Herein is first reported a cobalt complex realize enantioselective cyclic acyclic trisubstituted using PhIO as oxidant in acetone, wherein tetra-oxygen-based N,N′-dioxide with sterically hindered amide subunits plays crucial role supporting formation intermediate electrophilic oxygen transfer. Mechanistic studies, including HRMS measurements, UV–vis absorption spectroscopy, magnetic susceptibility, DFT calculations, were carried out, confirming species quartet Co(III)-oxyl tautomer. The mechanism origin enantioselectivity also elucidated based on control experiments, nonlinear effects, kinetic calculations.

Язык: Английский

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Nature-Inspired Radical Pyridoxal-Mediated C–C Bond Formation

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(33), С. 23321 - 23329

Опубликована: Авг. 6, 2024

Pyridoxal-5'-phosphate (PLP) and derivatives of this cofactor enable a plethora reactions in both enzyme-mediated free-in-solution transformations. With few exceptions each category, such chemistry has predominantly involved two-electron processes. This sometimes poses significant challenge for using PLP to build tetrasubstituted carbon centers, especially when the reaction is reversible. The ability access radical pathways paramount broadening scope catalyzed by coenzyme. In study, we demonstrate PLP-based intermediate engage number C-C bond-forming reactions. By selection an appropriate oxidant, single-electron oxidation quinonoid can be achieved, which subsequently applied Through pathway, synthesized series α-tertiary amino acids esters investigate substrate identify nonproductive pathways. Beyond acid model system, that other classes amine substrates range small molecule reagents serve as coupling partners semiquinone radical. We anticipate versatile species will central development novel

Язык: Английский

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Bioinspired Non‐Heme Mn Catalysts for Regio‐ and Stereoselective Oxyfunctionalizations with H₂O₂

Chemistry - A European Journal, Год журнала: 2023, Номер 29(66)

Опубликована: Авг. 29, 2023

Abstract In recent years, metalloenzymes‐mediated highly selective oxidations of organic substrates under mild conditions have been inspiration for developing synthetic bioinspired catalyst systems, capable conducting such processes in the laboratory (and, future, industry), relying on easy‐to‐handle and environmentally benign oxidants as H 2 O . To date, non‐heme manganese complexes with chiral bis ‐amino‐ ‐pyridylmethyl structurally related ligands are considered possessing highest potential, having demonstrated ability to mediate a variety chemo‐ stereoselective oxidative transformations, epoxidations, C(sp 3 )‐H hydroxylations ketonizations, desymmetrizations, kinetic resolutions, etc. Furthermore, past few years Mn based catalysts become major platform studies focused getting insight into molecular mechanisms oxidant activation (stereo)selective oxygen transfer, testing non‐traditional hydroperoxide oxidants, engineering catalytic sites enzyme‐like substrate recognition‐based selectivity, exploration regioselectivity trends oxidation biologically active natural origin. This contribution summarizes progress catalyzed C‐H oxygenative transformations substrates, achieved essentially 5 (late 2018–2023).

Язык: Английский

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Mononuclear Non-Heme Manganese-Catalyzed Enantioselective cis-Dihydroxylation of Alkenes Modeling Rieske Dioxygenases

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(50), С. 27626 - 27638

Опубликована: Дек. 8, 2023

The practical catalytic enantioselective cis-dihydroxylation of olefins that utilize earth-abundant first-row transition metal catalysts under environmentally friendly conditions is an important yet challenging task. Inspired by the reactions catalyzed Rieske dioxygenases and non-heme iron models, we report biologically inspired catalysis employs inexpensive readily available mononuclear manganese complex bearing a tetradentate nitrogen-donor ligand aqueous hydrogen peroxide (H2O2) potassium peroxymonosulfate (KHSO5) as terminal oxidants. A wide range are efficiently oxidized to enantioenriched cis-diols in practically useful yields with excellent selectivity enantioselectivity (up 99% ee). Mechanistic studies, such isotopically 18O-labeled water experiments, density functional theory (DFT) calculations support manganese(V)-oxo-hydroxo (HO–MnV═O) species, which formed via water-assisted heterolytic O–O bond cleavage putative manganese(III)-hydroperoxide manganese(III)-peroxysulfate precursors, active oxidant effects olefins; this reminiscent frequently postulated iron(V)-oxo-hydroxo (HO–FeV═O) species arene alkene synthetic models. Further, DFT for mechanism HO–MnV═O-mediated reveal first oxo attack step controls enantioselectivity, exhibits high preference over epoxidation. In study, able replicate both function key chemical principles manganese-catalyzed olefins.

Язык: Английский

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Dual Kinetic Control of Polycarbonate Sequences via Breaking Catalysis Symmetry Using Dual Biomimetic Organoboron Catalysts

Macromolecules, Год журнала: 2025, Номер unknown

Опубликована: Янв. 17, 2025

Biomimetic catalysis is extensively used in chemical synthesis targeting to achieve satisfactory reactivities. However, artificial catalysts possessing outstanding sequence controllability over macromolecular structures that could be precisely achieved nature remain scarce, especially the preparation of complex macromolecules featuring kinetically trapped structures. Herein, we report a dual biomimetic catalyst design for precise regulation controlled CO2/epoxide copolymerization. The as-synthesized dissymmetric organoboron possess microenvironments, which differentiate transfer rates polymer alkoxy anions between two boron centers, thus enabling regulation. Consequently, high −ABB–/–AB– ratio 92% was achieved, up 3.3 times analogous symmetric (Nat. Synth. 2022, 1, 892–901). Detailed mechanistic studies reveal kinetic modulations are responsible This tactic should inspire effective designs transformations.

Язык: Английский

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Understanding Catalytic Enantioselective C–H Bond Oxidation at Nonactivated Methylenes Through Predictive Statistical Modeling Analysis

ACS Catalysis, Год журнала: 2025, Номер 15(3), С. 2110 - 2123

Опубликована: Янв. 22, 2025

Enantioselective C(sp3)-H bond oxidation is a powerful strategy for installing functionality in rich molecules. Site- and enantioselective of strong C-H bonds monosubstituted cyclohexanes with hydrogen peroxide catalyzed by aminopyridine manganese catalysts combination alkanoic acids has been recently described. Mechanistic uncertainties nonobvious enantioselectivity trends challenge development the full potential this reaction as synthetic tool. Herein, we apply predictive statistical analysis to identify mechanistically informative correlations that provide valuable understanding will guide future optimization reactions.

Язык: Английский

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Chiral phosphoric acid-catalyzed atroposelective oxidative coupling of carbazoles

Science China Chemistry, Год журнала: 2025, Номер unknown

Опубликована: Март 14, 2025

Язык: Английский

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Cluster model study of the mechanism and origins of enantio- and chemoselectivity in non-heme iron enzyme-catalyzed C–H azidation

RSC Advances, Год журнала: 2025, Номер 15(12), С. 8931 - 8937

Опубликована: Янв. 1, 2025

Computational insights reveal the origin of enantio- and chemoselectivity in non-heme iron enzyme-catalyzed C–H azidation.

Язык: Английский

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