Light‐Driven Enantioselective Carbene‐Catalyzed Radical‐Radical Coupling

Angewandte Chemie International Edition, Год журнала: 2023, Номер 62(49)

Опубликована: Окт. 17, 2023

Abstract An enantioselective carbene‐catalyzed radical‐radical coupling of acyl imidazoles and racemi c Hantzsch esters is disclosed. This method involves the an N‐heterocyclic carbene‐derived ketyl radical a secondary sp 3 ‐carbon allows access to chiral α‐aryl aliphatic ketones in moderate‐to‐good yields enantioselectivities without any competitive epimerization. The utility this protocol highlighted by late‐stage functionalization various pharmaceutical compounds further demonstrated transformation enantioenriched products biologically relevant molecules. Computational investigations reveal carbene controls double‐facial selectivity alkyl radicals, respectively.

Язык: Английский

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Hydrolase mimic via second coordination sphere engineering in metal-organic frameworks for environmental remediation

Nature Communications, Год журнала: 2023, Номер 14(1)

Опубликована: Сен. 25, 2023

Enzymes achieve high catalytic activity with their elaborate arrangements of amino acid residues in confined optimized spaces. Nevertheless, when exposed to complicated environmental implementation scenarios, including acidity, organic solvent and ionic strength, enzymes exhibit low operational stability poor activity. Here, we report a metal-organic frameworks (MOFs)-based artificial enzyme system via second coordination sphere engineering hydrolytic under mild conditions. Experiments theoretical calculations reveal that amide cleavage catalyzed by MOFs follows two distinct mechanisms, Lewis acid- hydrogen bonding-mediated processes. The bond formed the secondary exhibits 11-fold higher than acidic zinc ions. satisfactory degradation performance toxins extreme working conditions, fermentation broth ethanol environments, display broad substrate specificity. These findings hold great promise for designing remediation.

Язык: Английский

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Appended Lewis Acids Enable Dioxygen Reactivity and Catalytic Oxidations with Ni(II)

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(18), С. 12375 - 12385

Опубликована: Апрель 25, 2024

We disclose a suite of Ni(II) complexes featuring secondary sphere Lewis acids varied acidity and tether lengths. Several these feature atypical behavior Ni(II): reactivity with O2 that occurs only in the presence tethered acid. In situ UV–vis spectroscopy revealed that, although adducts are stable at −40 °C, containing 9-borabicyclo[3.3.1]nonane (9-BBN) underwent irreversible oxidative deborylation when warmed to room temperature. computationally experimentally identified instability appended 9-BBN moieties can be mitigated using weaker such as pinacolborane (BPin). These insights enabled realization catalytic reactions: hydrogen atom abstraction from phenols temperature oxygen transfer PPh3.

Язык: Английский

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Divergent Reactivity of Azides and Diazoalkanes Toward Ferrous Complexes and Isolation of a Fe^III Carbene Radical Complex

Organometallics, Год журнала: 2025, Номер unknown

Опубликована: Янв. 9, 2025

Treatment of [(tBupyrr2pyr)Fe(OEt2)] (1-OEt2) (tBupyrr2pyr2– = 3,5-tBu2-bis(pyrrolyl)pyridine) with trimethylsilyl azide (N3SiMe3) and subsequent photolysis at 390 nm results in clean formation [(tBupyrrpyrpyrrNHSiMe3)Fe] (2) as the result a nitrene being inserted into tert-butyl C–H bond tBupyrr2pyr ligand. 1-OEt2 azidotrimethyltin (N3SnMe3), however, isolation γ-bound adduct ferrous complex, [(tBupyrr2pyr)Fe(N3SnMe3)] (1-N3SnMe3). When treated diphenyl diazomethane (Ph2CN2), complex converts to iron carbene [(tBupyrr2pyr)FeCPh2] (1-CPh2), X-ray structure revealed Fe–CPh2 length 1.964(3) Å. A room temperature magnetic moment 1-CPh2 indicates an S 2 spin state, consistent high-spin FeIII center antiferromagnetically coupled radical anion (CPh2•–). Zero-field 57Fe Mössbauer spectroscopy Fe K-edge absorption confirm this assignment. In solution, rearranges [{tBupyrrpyrC(═CPh2)-C(CMe3)═CH–C(CMe3)═N}Fe]2 (3) resulting from insertion 1-position pyrrolide arm ligand dimerization. Complex 3 possesses two FeII centers according spectroscopy, antiferromagnetic coupling between centers. Monitoring conversion by UV–vis reveals process be first order highly ordered transition state evidenced activation parameters: ΔS‡ −87.6 ± 25.8 J·mol–1·K–1 ΔH‡ 63.1 8.3 kJ·mol–1.

Язык: Английский

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Cooperative Nitrile Coordination Using Nickel and a Boron‐Containing Secondary Coordination Sphere**

Chemistry - A European Journal, Год журнала: 2022, Номер 29(17)

Опубликована: Дек. 19, 2022

Metal-ligand cooperation has emerged as a versatile tool for substrate activation in chemical reactivity. Herein, we provide the synthesis and characterization of monoboranyl-containing analogue ubiquitous bulky diphosphine ligand, 1,2-bis(di-tert-butylphosphino)ethane, whose reactivity been examined using nickel. Together, pairing nickel boron provides platform that allows cooperative coordination organonitriles, giving unusual examples intermolecularly bound dinickelacycles.

Язык: Английский

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A Bidentate Ligand Featuring Ditopic Lewis Acids in the Second Sphere for Selective Substrate Capture and Activation

Angewandte Chemie International Edition, Год журнала: 2023, Номер 62(13)

Опубликована: Фев. 1, 2023

We present a ligand platform featuring appended ditopic Lewis acids to facilitate capture/activation of diatomic substrates. show that incorporation two 9-borabicyclo[3.3.1]nonane (9-BBN) units on single carbon tethered pyridine pyrazole scaffold maintains set unquenched nitrogen donors available coordinate Fe

Язык: Английский

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Secondary Coordination Sphere Alkylation Promotes Cyclometalation

Inorganic Chemistry, Год журнала: 2023, Номер 62(18), С. 7053 - 7060

Опубликована: Апрель 25, 2023

Diphosphines have taken on a dominant role as supporting ligands in transition-metal chemistry. Here, we describe complexes of the type [Cp*Fe(diphosphine)(X)] (X = Cl, H) where for diphosphine 1,2-bis(di-allylphosphino)ethane (tape), Lewis-acidic secondary coordination sphere (SCS) was installed via allyl group hydroboration using dicyclohexylborane (HBCy2). The resulting chloride complex, [Cp*Fe(P2BCy4)(Cl)] (P2BCy4 1,2-bis(di(3-cyclohexylboranyl)propylphosphino)ethane), treated with n-butyllithium (1-10 equiv), incyclometalation at iron. This reactivity is contrasted [Cp*Fe(dnppe)(Cl)] (dnppe 1,2-bis(di-n-propylphosphino)ethane), whereby addition provides mixture products. Overall, cyclometalation common elementary transformation organometallic chemistry; here how this outcome accessed response to Lewis acid SCS incorporation.

Язык: Английский

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Enabling Nucleophilic Reactivity in High-Spin Fe(II) Imido Complexes: From Elementary Steps to Cooperative Catalysis

Accounts of Chemical Research, Год журнала: 2023, Номер 56(23), С. 3392 - 3403

Опубликована: Ноя. 13, 2023

ConspectusTransition metal complexes featuring an M═NR bond have received great attention as critical intermediates in the synthesis of nitrogen-containing compounds. In general, properties imido ligand these are dependent on nature center. Thus, tends to be nucleophilic early transition and electrophilic late complexes. Nonetheless, supporting can a dramatic effect its reactivity. For example, there sporadic examples complexes, often based strongly donating ligands. Building earlier works, this Article, we show that low-coordinate high-spin bis(carbene)borate Fe(II) complex is able access previously unknown reaction pathways, ultimately leading new catalytic transformations. We first focus synthesis, characterization, stoichiometric reactivity highly complex. The entry point for system intermediate-spin three-coordinate Fe(III) complex, which generated from Fe(I) synthon with organic azide. Alkali reduction leads series M+ (M = Li, Na, K) coordinated charge-separated K(18-C-6)) all been isolated fully characterized. Combined electronic structure calculations, results reveal alkali ions moderately polarize Fe═N according K+ ≈ Na+ < Li+. As result, basicity increases charged separated K+, Na+, Li+ validated by intermolecular proton transfer equilibria. impact counterion demonstrated through protonation, alkylation, hydrogen atom abstraction reactions. also directs outcome [2 + 2] reactions benzophenone, where coordination facilitates double metathesis. here, describe how unusual nucleophilicity revealed extended cycloaddition serves basis guanylation carbodiimides under mild conditions. More interestingly, exhibits ene-like alkynes, nitriles, alkenes. These transformations form alkyne nitrile α-deuteration pKa-dictated alkene transposition reactions, respectively. Mechanistic studies role metal-ligand cooperativity facilitating suggest avenues catalysis extend beyond classical nitrene chemistry.

Язык: Английский

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Bis(bicyclo[1.1.1]pentyl)chlorophosphine as a Precursor for the Preparation of Bis(bicyclo[1.1.1]pentyl)phosphines

Organic Letters, Год журнала: 2024, Номер 26(29), С. 6071 - 6075

Опубликована: Май 12, 2024

Dialkylchlorophosphines are among the most versatile building blocks for tertiary phosphine ligands, but their synthesis relies on nucleophilic substitution of PCl3, leaving substituents that require P–H precursors largely inaccessible. The primary reagent iPr2NPH2·BH3 can serve as a doubly protected PH2Cl proxy, enabling bis(bicyclo[1.1.1]pentyl)chlorophosphine (Bcp2PCl) first time. Bcp2PCl serves general preparation family bis(bicyclo[1.1.1]pentyl) alkyl- and arylphosphines, including new members privileged ligand scaffolds.

Язык: Английский

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Facile Synthesis of Uranium Complexes with a Pendant Borane Lewis Acid and 1,2‐Insertion of CO into a U−N Bond

Angewandte Chemie International Edition, Год журнала: 2022, Номер 61(51)

Опубликована: Окт. 18, 2022

In this contribution, we illustrate uranium complexes bearing a pendant borate (i.e. 1 and 2) or borane 3 4) moiety via reaction of the highly strained uranacycle I with various 3-coordinate boranes. Complexes 4 represent first examples Lewis acid. Moreover, complex was capable activation CO, delivering new CO mode, an abnormal 1,2-insertion pathway into U-N bond. The importance confirmed by controlled experiments.

Язык: Английский

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