1
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Reactivity and Selectivity of Azaspirocycles in Radical C-H Functionalization. Org Lett 2024; 26:2784-2789. [PMID: 38032812 DOI: 10.1021/acs.orglett.3c02881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2023]
Abstract
Investigations of saturated spirocycles toward selective C-H functionalization reactions are scarce, despite their potential applications. In this work, we uncovered fundamental reactivity and selectivity differences between saturated heterocycles and their spirocyclic analogues using a model radical C-H xanthylation coupled with computational analysis. Ultimately, this study sheds light on the fundamental, understudied radical reactivity of spirocycles, thereby allowing for a pronounced chemical tunability that will prove to be advantageous in the expansion of their chemical space and applications in medicinal chemistry.
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2
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Antimicrobial resistance in wildlife: detection of antimicrobial resistance genes in Apennine wolves (Canis lupus italicus Altobello, 1921) from Central Italy. Vet Res Commun 2024:10.1007/s11259-024-10354-8. [PMID: 38499909 DOI: 10.1007/s11259-024-10354-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2024] [Accepted: 03/10/2024] [Indexed: 03/20/2024]
Abstract
The aim of this study was to molecularly investigate the presence of antimicrobial resistance genes (ARGs) in organ samples from 11 Apennine wolves (Canis lupus italicus) collected in Central Italy. Samples from lung, liver, spleen, kidney, tongue and intestine were investigated by PCRs targeting the following genes: tet(A), tet(B), tet(C), tet(D), tet(E), tet(G), tet(K), tet(L), tet(M), tet(O), tetA(P), tet(Q), tet(S), tet(X), sul1, sul2, sul3, blaCTX-M, blaSHV, blaTEM and mcr-1. A PCR positivity was highlighted for 13 out of the 21 tested genes; no positive results were obtained for tet(C), tet(D), tet(E), tet(G), sul3, blaCTX, blaSHV and mcr-1 genes. All 11 animals sampled showed positivity for one or more resistance genes. The results confirm the potential role of the wolf as an indicator and/or vector of antimicrobial-resistant bacteria or ARGs.
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3
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Regiodivergent Ring-Expansion of Oxindoles to Quinolinones. J Am Chem Soc 2024; 146:4301-4308. [PMID: 38335924 PMCID: PMC10885155 DOI: 10.1021/jacs.3c12119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2024]
Abstract
The development of divergent methods to expedite structure-activity relationship studies is crucial to streamline discovery processes. We developed a rare example of regiodivergent ring expansion to access two regioisomers from a common starting material. To enable this regiodivergence, we identified two distinct reaction conditions for transforming oxindoles into quinolinone isomers. The presented methods proved to be compatible with a variety of functional groups, which enabled the late-stage diversification of bioactive oxindoles as well as facilitated the synthesis of quinolinone drugs and their derivatives.
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4
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Escaping from directing groups: Enantioselective C-C bond construction from unactivated olefins. Sci Bull (Beijing) 2024; 69:290-292. [PMID: 38101963 DOI: 10.1016/j.scib.2023.11.044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2023]
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5
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Mechanistic Investigation of the Rhodium-Catalyzed Transfer Hydroarylation Reaction Involving Reversible C-C Bond Activation. J Am Chem Soc 2023; 145:26657-26666. [PMID: 38032811 PMCID: PMC10722515 DOI: 10.1021/jacs.3c07780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 10/22/2023] [Accepted: 11/01/2023] [Indexed: 12/02/2023]
Abstract
Carbon-carbon (C-C) bonds are ubiquitous but are among the least reactive bonds in organic chemistry. Recently, catalytic approaches to activate C-C bonds by transition metals have demonstrated the synthetic potential of directly reorganizing the skeleton of small molecules. However, these approaches are usually restricted to strained molecules or rely on directing groups, limiting their broader impact. We report a detailed mechanistic study of a rare example of catalytic C-C bond cleavage of unstrained alcohols that enables reversible ketone transfer hydroarylation under Rh-catalysis. Combined insight from kinetic analysis, in situ nuclear magnetic resonance (NMR) monitoring, and density functional theory (DFT) calculations supports a symmetric catalytic cycle, including a key reversible β-carbon elimination event. In addition, we provide evidence regarding the turnover-limiting step, the catalyst resting state, and the role of the sterically encumbered NHC ligand. The study further led to an improved catalytic system with the discovery of two air-stable precatalysts that showed higher activity for the transformation in comparison to the original conditions.
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6
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Antimicrobial resistance genes in a golden jackal (Canis aureus L. 1758) from Central Italy. Vet Res Commun 2023; 47:2351-2355. [PMID: 37436553 DOI: 10.1007/s11259-023-10172-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 07/08/2023] [Indexed: 07/13/2023]
Abstract
In recent years an increasing interest has been focused on the contribution of wildlife in ecology and evolution of the antimicrobial resistance (AMR). The aim of this study was to molecularly investigate the presence of antimicrobial resistance genes (ARGs) in organ samples from a golden jackal (Canis aureus) found dead in the Marche region (Central Italy). Samples from lung, liver, spleen, kidney, and intestine were investigated by PCRs targeting the following genes: tet(A), tet(B), tet(C), tet(D), tet(E), tet(G), tet(K), tet(L), tet(M), tet(O), tet(S), tet(P), tet(Q), tet(X), sul1, sul2, sul3, blaCTX-M, blaSHV, blaTEM, and mcr-1 to mcr-10. One or more ARGs were detected in all organs tested, except the spleen. Specifically, the lung and liver were positive for tet(M) and tet(P), the kidney for mcr-1 and the intestine for tet(A), tet(L), tet(M), tet(O), tet(P), sul3 and blaTEM-1. These results, according to the opportunistic foraging strategy of the jackal, confirm its potential role as a good bioindicator of AMR environmental contamination.
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7
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Direct Access to Quinazolines and Pyrimidines from Unprotected Indoles and Pyrroles through Nitrogen Atom Insertion. Org Lett 2023; 25:8419-8423. [PMID: 37983173 DOI: 10.1021/acs.orglett.3c03264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Recent advances in single-atom insertion reactions have opened up new synthetic approaches for molecular diversification. Developing innovative strategies to directly transform biologically relevant molecules, without any prefunctionalization, is key to further expanding the scope and utility of such transformations. Herein, the direct access to quinazolines and pyrimidines from the corresponding unprotected 1H-indoles and 1H-pyrroles is reported, relying on the implementation of lithium bis(trimethylsilyl)amide (LiHMDS) as a novel nitrogen atom source in combination with commercially available hypervalent iodine reagents. Further application of this strategy in late-stage settings demonstrates its potential in lead structure diversification campaigns.
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8
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Nickel-Catalyzed Enantioselective Hydrothiocarbonylation of Cyclopropenes. Org Lett 2023. [PMID: 38014880 DOI: 10.1021/acs.orglett.3c03563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Hydrothiocarbonylation of olefins using carbon monoxide and thiols is a powerful method to synthesize thioesters from simple building blocks. Owing to the intrinsic challenges of catalyst poisoning, transition-metal-catalyzed asymmetric thiocarbonylation, particularly when utilizing earth abundant metals, remains rare in the literature. Herein, we report a nickel-catalyzed enantioselective hydrothiocarbonylation of cyclopropenes for the synthesis of a diverse collection of functionalized thioesters in good to excellent yields with high stereoselectivity. This new method employs an inexpensive, air-stable nickel(II) precursor, which provides enhanced catalyst fidelity against CO poisoning compared to nickel(0) catalysts.
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9
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Nickel(I)-Phenolate Complexes: The Key to Well-Defined Ni(I) Species. Inorg Chem 2023; 62:16661-16668. [PMID: 37782818 DOI: 10.1021/acs.inorgchem.3c01559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
Phosphine-stabilized monovalent nickel complexes play an important role in catalysis, either as catalytically active species or as decomposition products. Most routes to access these complexes are highly ligand specific or rely on strong reducing agents. Our group recently disclosed a path to access nickel(I)-phenolate complexes from bis(1,5-cyclooctadiene)nickel(0) (Ni(cod)2). Herein, we demonstrate this protocol's broad applicability by ligating a wide range of mono- and bidentate phosphine ligands. We further show the versatility of the phenolate fragment as a precursor to nickel(I)-alkyl or aryl species, which are relevant to Ni catalysis or synthetically useful nickel(I)-chloride and hydride complexes. We also demonstrate that the chloride complex can be synthesized in a one-pot procedure starting from Ni(cod)2 in good yield, making this protocol a valuable alternative to current procedures. Single-crystal X-ray diffraction, IR, and EPR (or NMR) spectroscopy were employed to characterize all of the synthesized nickel complexes.
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10
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Direct Synthesis of Unprotected Indolines Through Intramolecular sp 3 C-H Amination Using Nitroarenes as Aryl Nitrene Precursors. Chemistry 2023; 29:e202301978. [PMID: 37404217 DOI: 10.1002/chem.202301978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 07/03/2023] [Accepted: 07/03/2023] [Indexed: 07/06/2023]
Abstract
Given the prevalence of molecules containing nitro groups in organic synthesis, innovative methods to expand the reactivity of this functional group are of interest in both industrial and academic settings. In this report, a metal-free intramolecular benzylic sp3 C-H amination is disclosed using aryl nitro compounds as aryl nitrene precursors. Organosilicon reagent N,N'-bis(trimethylsilyl)-4,4'-bipyridinylidene (Si-DHBP) served as an efficient reductant in the transformation, enabling the in situ generation of aryl nitrene species for the direct, metal-free synthesis of unprotected 2-arylindolines from the corresponding nitroarene compounds.
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11
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Late-Stage Molecular Editing Enabled by Ketone Chain-Walking Isomerization. J Am Chem Soc 2023; 145:19496-19502. [PMID: 37640367 PMCID: PMC10510328 DOI: 10.1021/jacs.3c05680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Indexed: 08/31/2023]
Abstract
Herein, a method for the isomerization of ketones in a manner akin to the chain-walking reaction of alkenes is described. Widely available and inexpensive pyrrolidine and elemental sulfur are deployed as catalysts to achieve this reversible transformation. Key to the utility of this approach was the elucidation of a stereochemical model to determine the thermodynamically favored product of the reaction and the kinetic selectivity observed. With the distinct selectivity profile of our ketone chain-walking process, the isomerization of various steroids was demonstrated to rapidly access novel steroids with "unnatural" oxidation patterns.
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12
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Mechanistic Investigation of the Nickel-Catalyzed Transfer Hydrocyanation of Alkynes. ACS Catal 2023; 13:11548-11555. [PMID: 37671177 PMCID: PMC10476158 DOI: 10.1021/acscatal.3c02977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/28/2023] [Indexed: 09/07/2023]
Abstract
The implementation of HCN-free transfer hydrocyanation reactions on laboratory scales has recently been achieved by using HCN donor reagents under nickel- and Lewis acid co-catalysis. More recently, malononitrile-based HCN donor reagents were shown to undergo the C(sp3)-CN bond activation by the nickel catalyst in the absence of Lewis acids. However, there is a lack of detailed mechanistic understanding of the challenging C(sp3)-CN bond cleavage step. In this work, in-depth kinetic and computational studies using alkynes as substrates were used to elucidate the overall reaction mechanism of this transfer hydrocyanation, with a particular focus on the activation of the C(sp3)-CN bond to generate the active H-Ni-CN transfer hydrocyanation catalyst. Comparisons of experimentally and computationally derived 13C kinetic isotope effect data support a direct oxidative addition mechanism of the nickel catalyst into the C(sp3)-CN bond facilitated by the coordination of the second nitrile group to the nickel catalyst.
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13
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Skeletal metalation of lactams through a carbonyl-to-nickel-exchange logic. Nat Commun 2023; 14:5273. [PMID: 37644031 PMCID: PMC10465567 DOI: 10.1038/s41467-023-40979-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 08/17/2023] [Indexed: 08/31/2023] Open
Abstract
Classical metalation reactions such as the metal-halogen exchange have had a transformative impact on organic synthesis owing to their broad applicability in building carbon-carbon bonds from carbon-halogen bonds. Extending the metal-halogen exchange logic to a metal-carbon exchange would enable the direct modification of carbon frameworks with new implications in retrosynthetic analysis. However, such a transformation requires the selective cleavage of highly inert chemical bonds and formation of stable intermediates amenable to further synthetic elaborations, hence its development has remained considerably challenging. Here we introduce a skeletal metalation strategy that allows lactams, a prevalent motif in bioactive molecules, to be readily converted into well-defined, synthetically useful organonickel reagents. The reaction features a selective activation of unstrained amide C-N bonds mediated by an easily prepared Ni(0) reagent, followed by CO deinsertion and dissociation under mild room temperature conditions in a formal carbonyl-to-nickel-exchange process. The underlying principles of this unique reactivity are rationalized by organometallic and computational studies. The skeletal metalation is further applied to a direct CO excision reaction and a carbon isotope exchange reaction of lactams, underscoring the broad potential of metal-carbon exchange logic in organic synthesis.
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14
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Ni-catalyzed mild hydrogenolysis and oxidations of C-O bonds via carbonate redox tags. Nat Commun 2023; 14:2604. [PMID: 37147279 PMCID: PMC10163265 DOI: 10.1038/s41467-023-38305-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 04/20/2023] [Indexed: 05/07/2023] Open
Abstract
Oxygenated molecules are omnipresent in natural as well as artificial settings making the redox transformation of the present C-O bonds a central tool for their processing. However, the required (super)stoichiometric redox agents which traditionally include highly reactive and hazardous reagents pose multiple practical challenges including process safety hazards or special waste management requirements. Here, we report a mild Ni-catalyzed fragmentation strategy based on carbonate redox tags for redox transformations of oxygenated hydrocarbons in the absence of any external redox equivalents or other additives. The purely catalytic process enables the hydrogenolysis of strong C(sp2)-O bonds including that of enol carbonates as well as the catalytic oxidation of C-O bonds under mild conditions down to room temperature. Additionally, we investigated the underlying mechanism and showcased the benefits of carbonate redox tags in multiple applications. More broadly, the work herein demonstrates the potential of redox tags for organic synthesis.
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15
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Azide-Free Synthesis of N-Alkyliminophosphoranes from Phosphines and Hydroxylamine Derivatives. Org Lett 2023; 25:1695-1700. [PMID: 36926926 DOI: 10.1021/acs.orglett.3c00366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
Abstract
A broadly applicable and efficient method for the synthesis of N-alkyliminophosphoranes from phosphines that does not use potentially hazardous alkyl azides is reported. Under iron catalysis, a hydroxylamine-derived triflic acid salt oxidizes phosphines to a wide range of iminophosphorane triflic acid salts. Diphosphines afford phosphine-iminophosphoranes that can serve as ligands in transition metal complexes. The developed method can be employed in the synthesis of mixed diiminophosphoranes and in a traceless Staudinger ligation.
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16
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Synthesis and Reversible H
2
Activation by Coordinatively Unsaturated Rhodium NHC Complexes. Helv Chim Acta 2023. [DOI: 10.1002/hlca.202200199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2023]
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17
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Nitrogen atom insertion into indenes to access isoquinolines. Chem Sci 2023; 14:2954-2959. [PMID: 36937579 PMCID: PMC10016357 DOI: 10.1039/d2sc06952k] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Accepted: 02/14/2023] [Indexed: 02/25/2023] Open
Abstract
We report a convenient protocol for a nitrogen atom insertion into indenes to afford isoquinolines. The reaction uses a combination of commercially available phenyliodine(iii) diacetate (PIDA) and ammonium carbamate as the nitrogen source to furnish a wide range of isoquinolines. Various substitution patterns and commonly used functional groups are well tolerated. The operational simplicity renders this protocol broadly applicable and has been successfully extended towards the direct interconversion of cyclopentadienes into the corresponding pyridines. Furthermore, this strategy enables the facile synthesis of 15N labelled isoquinolines, using 15NH4Cl as a commercial 15N source.
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18
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Deaminative coupling of benzylamines and arylboronic acids. Chem Sci 2023; 14:1709-1714. [PMID: 36819866 PMCID: PMC9930926 DOI: 10.1039/d2sc06055h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 12/30/2022] [Indexed: 01/15/2023] Open
Abstract
A metal-free deaminative coupling of non-prefunctionalised benzylamines and arylboronic acids is reported. In this operationally simple reaction, a primary amine in benzylamine is converted into a good leaving group in situ using inexpensive and commercially available isoamyl nitrite as a nitrosating reagent. Lewis-acidic arylboronic acids are shown to replace mineral acids such as HCl or HBF4 that are conventionally used in the preparation of aryl diazonium salts. This unlocked the formation of the corresponding diarylmethanes by forging a new C-C bond in good yields.
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19
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Rhodium-Catalyzed Anti-Markovnikov Transfer Hydroiodination of Terminal Alkynes. Angew Chem Int Ed Engl 2023; 62:e202214071. [PMID: 36336665 PMCID: PMC10107805 DOI: 10.1002/anie.202214071] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 11/01/2022] [Accepted: 11/02/2022] [Indexed: 11/09/2022]
Abstract
A rhodium-catalyzed anti-Markovnikov hydroiodination of aromatic and aliphatic terminal alkynes is reported. Depending on the choice of ligand and substrate, either (E)- or (Z)-configured alkenyl iodides are obtained in high to exclusive isomeric purity. The reaction exhibits a broad substrate scope and high functional group tolerance, employing easily accessible or commercially available aliphatic iodides as HI surrogates through a shuttle process. The synthesized vinyl iodides were applied in several C-C and C-heteroatom bond-forming reactions with full retention of the stereoselectivity. The developed method could be used to significantly shorten the total synthesis of a marine cis-fatty acid. Additionally, initial deuterium-labeling experiments and stoichiometric reactions shed some light on the potential reaction mechanism.
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20
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Controlling Selectivity in Shuttle Hetero-difunctionalization Reactions: Electrochemical Transfer Halo-thiolation of Alkynes. Angew Chem Int Ed Engl 2023; 62:e202213630. [PMID: 36336662 PMCID: PMC10107926 DOI: 10.1002/anie.202213630] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 10/28/2022] [Accepted: 10/31/2022] [Indexed: 11/09/2022]
Abstract
Shuttle hetero-difunctionalization reaction, in which two chemically distinct functional groups are transferred between two molecules, has long been an unmet goal due to the daunting challenges in controlling the chemo-, regio-, and stereoselectivity. Herein, we disclose an electrochemistry enabled shuttle reaction (e-shuttle) to selectively transfer one RS- and one X- group between β-halosulfides and unsaturated hydrocarbons via a consecutive paired electrolysis mechanism. The preferential anodic oxidation of one anion over the other, which is controlled by their distinct redox potentials, plays a pivotal role in controlling the high chemoselectivity of the process. This easily scalable methodology enables the construction of a myriad of densely functionalized β-halo alkenyl sulfides in unprecedented chemo-, regio-, and stereoselectivity using benign surrogates, e.g., 2-bromoethyl sulfide, avoiding the handling of corrosive and oxidative RS-Br reagents. In a broader context, these results open up new strategies for selective shuttle difunctionalization reactions.
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21
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Intermolecular Pauson-Khand-Type Reaction of Vinyl Iodides with Alkynes and a CO Surrogate. J Org Chem 2023; 88:5069-5077. [PMID: 36598125 DOI: 10.1021/acs.joc.2c02465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
A strategy for the palladium-catalyzed intermolecular synthesis of polysubstituted cyclopentenones is reported. The three-component reaction utilizes vinyl iodides and internal alkynes to form the carbon framework of the cyclopentenone with Cr(CO)6 serving as an easy to handle, solid CO surrogate, and a hydrosilane as a hydride source. We demonstrate the scope of the reaction which includes a wide range of functional groups. The reaction is regioselective, with the use of linear or branched vinyl iodides resulting in the α- or β-substituted cyclopentenones, respectively. Further, we show that a two-step sequence from commercially available alkynes can be used to generate cyclopentenone products via formation of the vinyl iodide and subsequent Pauson-Khand-type reaction.
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22
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Structural Evidence for Aromatic Heterocycle N–O Bond Activation via Oxidative Addition. Organometallics 2023. [DOI: 10.1021/acs.organomet.2c00533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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23
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Controlling Selectivity in Shuttle Hetero‐difunctionalization Reactions: Electrochemical Transfer Halo‐thiolation of Alkynes. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/anie.202217110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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24
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Controlling Selectivity in Shuttle Hetero‐difunctionalization Reactions: Electrochemical Transfer Halo‐thiolation of Alkynes. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202217110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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25
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Controlling Selectivity in Shuttle Hetero‐difunctionalization Reactions: Electrochemical Transfer Halo‐thiolation of Alkynes. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202213630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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26
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Rhodium‐catalyzed Anti‐Markovnikov Transfer Hydroiodination of Terminal Alkynes. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202214071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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27
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The advent of electrophilic hydroxylamine-derived reagents for the direct preparation of unprotected amines. Chem Commun (Camb) 2022; 58:9991-10003. [PMID: 35993918 PMCID: PMC9453917 DOI: 10.1039/d2cc02431d] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 07/20/2022] [Indexed: 11/21/2022]
Abstract
Electrophilic aminating reagents have seen a renaissance in recent years as effective nitrogen sources for the synthesis of unprotected amino functionalities. Based on their reactivity, several noble and non-noble transition metal catalysed amination reactions have been developed. These include the aziridination and difunctionalisation of alkenes, the amination of arenes as well as the synthesis of aminated sulfur compounds. In particular, the use of hydroxylamine-derived (N-O) reagents, such as PONT (PivONH3OTf), has enabled the introduction of unprotected amino groups on various different feedstock compounds, such as alkenes, arenes and thiols. This strategy obviates undesired protecting-group manipulations and thus improves step efficiency and atom economy. Overall, this feature article gives a recent update on several reactions that have been unlocked by employing versatile hydroxylamine-derived aminating reagents, which facilitate the generation of unprotected primary, secondary and tertiary amino groups.
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Abstract
Compared with peripheral late-stage transformations mainly focusing on carbon-hydrogen functionalizations, reliable strategies to directly edit the core skeleton of pharmaceutical lead compounds still remain scarce despite the recent flurry of activity in this area. Herein, we report the skeletal editing of indoles through nitrogen atom insertion, accessing the corresponding quinazoline or quinoxaline bioisosteres by trapping of an electrophilic nitrene species generated from ammonium carbamate and hypervalent iodine. This reactivity relies on the strategic use of a silyl group as a labile protecting group that can facilitate subsequent product release. The utility of this highly functional group-compatible methodology in the context of late-stage skeletal editing of several commercial drugs is demonstrated.
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Mechanistic Investigation of the Nickel-Catalyzed Metathesis between Aryl Thioethers and Aryl Nitriles. J Am Chem Soc 2022; 144:13096-13108. [PMID: 35834613 DOI: 10.1021/jacs.2c01595] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Functional group metathesis is an emerging field in organic chemistry with promising synthetic applications. However, no complete mechanistic studies of these reactions have been reported to date, particularly regarding the nature of the key functional group transfer mechanism. Unraveling the mechanism of these transformations would not only allow for their further improvement but would also lead to the design of novel reactions. Herein, we describe our detailed mechanistic studies of the nickel-catalyzed functional group metathesis reaction between aryl methyl sulfides and aryl nitriles, combining experimental and computational results. These studies did not support a mechanism proceeding through reversible migratory insertion of the nitrile into a Ni-Ar bond and provided strong support for an alternative mechanism involving a key transmetalation step between two independently generated oxidative addition complexes. Extensive kinetic analysis, including rate law determination and Eyring analysis, indicated the oxidative addition complex of aryl nitrile as the resting state of the catalytic reaction. Depending on the concentration of aryl methyl sulfide, either the reductive elimination of aryl nitrile or the oxidative addition into the C(sp2)-S bond of aryl methyl sulfide is the turnover-limiting step of the reaction. NMR studies, including an unusual 31P-2H HMBC experiment using deuterium-labeled complexes, unambiguously demonstrated that the sulfide and cyanide groups exchange during the transmetalation step, rather than the two aryl moieties. In addition, Eyring and Hammett analyses of the transmetalation between two Ni(II) complexes revealed that this central step proceeds via an associative mechanism. Organometallic studies involving the synthesis, isolation, and characterization of all putative intermediates and possible deactivation complexes have further shed light on the reaction mechanism, including the identification of a key deactivation pathway, which has led to an improved catalytic protocol.
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Nickel-catalysed diversification of phosphine ligands by formal substitution at phosphorus. Chem Sci 2022; 13:7914-7919. [PMID: 35865908 PMCID: PMC9258342 DOI: 10.1039/d2sc02496a] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 06/13/2022] [Indexed: 12/12/2022] Open
Abstract
We report a diversification strategy that enables the direct substituent exchange of tertiary phosphines. Alkylated phosphonium salts, prepared by standard alkylation of phosphines, are selectively dearylated in a nickel-catalysed process to access alkylphosphine products via a formal substitution at the phosphorus center. The reaction can be used to introduce a wide range of alkyl substituents into both mono- and bisphosphines. We also show that the alkylation and dearylation steps can be conducted in a one-pot sequence, enabling accelerated access to derivatives of the parent ligand. The phosphine products of the reaction are converted in situ to air-stable borane adducts for isolation, and versatile derivatisation reactions of these adducts are demonstrated. Phosphine substituents can be exchanged by standard alkylation of a phosphine and a subsequent dearylation of the resulting phosphonium salt. A wide variety of alkyl groups can be introduced into both mono- and bidentate ligands using this method.![]()
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Pd-Catalyzed Direct Deoxygenative Arylation of Non-π-Extended Benzyl Alcohols with Boronic Acids via Transient Formation of Non-Innocent Isoureas. ACS Catal 2022. [DOI: 10.1021/acscatal.2c01858] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Palladium-Catalyzed Carbothiolation of Alkenes and Alkynes for the Synthesis of Heterocycles. ACS Catal 2022. [DOI: 10.1021/acscatal.2c01178] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Abstract
Carbon dioxide (CO2) impacts every aspect of life, and numerous sensing technologies have been established to detect and monitor this ubiquitous molecule. However, its selective sensing at the molecular level remains an unmet challenge, despite the tremendous potential of such an approach for understanding this molecule's role in complex environments. In this work, we introduce a unique class of selective fluorescent carbon dioxide molecular sensors (CarboSen) that addresses these existing challenges through an activity-based approach. Besides the design, synthesis, and evaluation of these small molecules as CO2 sensors, we demonstrate their utility by tailoring their reactivity and optical properties, allowing their use in a broad spectrum of multidisciplinary applications, including atmospheric sensing, chemical reaction monitoring, enzymology, and live-cell imaging. Collectively, these results showcase the potential of CarboSen sensors as broadly applicable tools to monitor and visualize carbon dioxide across multiple disciplines.
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Development of an Operationally Simple, Scalable, and HCN-Free Transfer Hydrocyanation Protocol Using an Air-Stable Nickel Precatalyst. Org Process Res Dev 2022. [DOI: 10.1021/acs.oprd.1c00442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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A Combined Spectroscopic and Computational Study on the Mechanism of Iron-Catalyzed Aminofunctionalization of Olefins Using Hydroxylamine Derived N-O Reagent as the "Amino" Source and "Oxidant". J Am Chem Soc 2022; 144:2637-2656. [PMID: 35119853 PMCID: PMC8855425 DOI: 10.1021/jacs.1c11083] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
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Herein, we study
the mechanism of iron-catalyzed direct synthesis
of unprotected aminoethers from olefins by a hydroxyl amine derived
reagent using a wide range of analytical and spectroscopic techniques
(Mössbauer, Electron Paramagnetic Resonance, Ultra-Violet Visible
Spectroscopy, X-ray Absorption, Nuclear Resonance Vibrational Spectroscopy,
and resonance Raman) along with high-level quantum chemical calculations.
The hydroxyl amine derived triflic acid salt acts as the “oxidant”
as well as “amino” group donor. It activates the high-spin
Fe(II) (St = 2) catalyst [Fe(acac)2(H2O)2] (1) to generate
a high-spin (St = 5/2) intermediate (Int I), which decays to a second intermediate (Int II) with St = 2. The analysis of spectroscopic
and computational data leads to the formulation of Int I as [Fe(III)(acac)2-N-acyloxy] (an alkyl-peroxo-Fe(III)
analogue). Furthermore, Int II is formed by N–O
bond homolysis. However, it does not generate a high-valent
Fe(IV)(NH) species (a Fe(IV)(O) analogue), but instead a high-spin
Fe(III) center which is strongly antiferromagnetically coupled (J = −524 cm–1) to an iminyl radical,
[Fe(III)(acac)2-NH·], giving St = 2. Though Fe(NH) complexes as isoelectronic surrogates
to Fe(O) functionalities are known, detection of a high-spin Fe(III)-N-acyloxy intermediate (Int I), which undergoes
N–O bond cleavage to generate the active iron–nitrogen
intermediate (Int II), is unprecedented. Relative to
Fe(IV)(O) centers, Int II features a weak elongated Fe–N
bond which, together with the unpaired electron density along the
Fe–N bond vector, helps to rationalize its propensity for N-transfer reactions onto styrenyl olefins, resulting in
the overall formation of aminoethers. This study thus demonstrates
the potential of utilizing the iron-coordinated nitrogen-centered
radicals as powerful reactive intermediates in catalysis.
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Swiss Summer School 2021: Catalysis and Sustainable Chemistry. Chimia (Aarau) 2021; 75:1071-1072. [PMID: 34920783 DOI: 10.2533/chimia.2021.1071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Preparation of Recyclable and Versatile Porous Poly(aryl thioether)s by Reversible Pd-Catalyzed C-S/C-S Metathesis. J Am Chem Soc 2021; 143:21331-21339. [PMID: 34871503 PMCID: PMC8704200 DOI: 10.1021/jacs.1c09884] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
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Porous organic materials
(polymers and COFs) have shown a number
of promising properties; however, the lability of their linkages often
limits their robustness and can hamper downstream industrial application.
Inspired by the outstanding chemical, mechanical, and thermal resistance
of the 1D polymer poly(phenylene sulfide) (PPS), we have designed
a new family of porous poly(aryl thioether)s, synthesized via a mild
Pd-catalyzed C–S/C–S metathesis-based method, that merges
the attractive features common to porous polymers and PPS in a single
material. In addition, the method is highly modular, allowing to easily
introduce application-oriented functionalities in the materials for
a series of environmentally relevant applications including metal
capture, metal sensing, and heterogeneous catalysis. Moreover, despite
their extreme chemical resistance, the polymers can be easily recycled
to recover the original monomers, offering an attractive perspective
for their sustainable use. In a broader context, these results clearly
demonstrate the untapped potential of emerging single-bond metathesis
reactions in the preparation of new, recyclable materials.
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Katalytische Carbochlorocarbonylierung von ungesättigten Kohlenwasserstoffen durch C‐COCl‐Bindungsspaltung**. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202108818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Catalytic Carbochlorocarbonylation of Unsaturated Hydrocarbons via C-COCl Bond Cleavage*. Angew Chem Int Ed Engl 2021; 60:23435-23443. [PMID: 34432940 PMCID: PMC8596603 DOI: 10.1002/anie.202108818] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Indexed: 12/04/2022]
Abstract
Here we report a palladium‐catalysed difunctionalisation of unsaturated C−C bonds with acid chlorides. Formally, the C−COCl bond of an acid chloride is cleaved and added, with complete atom economy, across either strained alkenes or a tethered alkyne to generate new acid chlorides. The transformation does not require exogenous carbon monoxide, operates under mild conditions, shows a good functional group tolerance, and gives the isolated products with excellent stereoselectivity. The intermolecular reaction tolerates both aryl‐ and alkenyl‐substituted acid chlorides and is successful when carboxylic acids are transformed to the acid chloride in situ. The reaction also shows an example of temperature‐dependent stereodivergence which, together with plausible mechanistic pathways, is investigated by DFT calculations. Moreover, we show that benzofurans can be formed in an intramolecular variant of the reaction. Finally, derivatisation of the products from the intermolecular reaction provides a highly stereoselective approach for the synthesis of tetrasubstituted cyclopentanes.
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Abstract
A nickel-catalyzed cyanation of aryl thioethers using Zn(CN)2 as a cyanide source has been developed to access functionalized aryl nitriles. The ligand dcype (1,2-bis(dicyclohexylphosphino)ethane) in combination with the base KOAc (potassium acetate) is essential for achieving this transformation efficiently. This reaction involves both a C-S bond activation and a C-C bond formation. The scalability, low catalyst and reagents loadings, and high functional group tolerance have enabled both late-stage derivatization and polymer recycling, demonstrating the reaction's utility across organic chemistry.
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Abstract
A nickel-catalyzed thiolation of aryl nitriles has been developed to access functionalized aryl thioethers. The ligand dcype (1,2-bis(dicyclohexylphosphino)ethane) as well as the base KOt Bu (potassium tert-butoxide) are essential to achieve this transformation. This scalable and practical process involves both a C-C bond activation and a C-S bond formation. Furthermore, this reaction shows a high functional-group tolerance and enables the late-stage functionalization of important molecules.
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Palladium-Catalyzed Decarbonylative Iodination of Aryl Carboxylic Acids Enabled by Ligand-Assisted Halide Exchange. Angew Chem Int Ed Engl 2021; 60:17211-17217. [PMID: 34013616 PMCID: PMC8362116 DOI: 10.1002/anie.202103269] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 05/05/2021] [Indexed: 11/08/2022]
Abstract
We report an efficient and broadly applicable palladium-catalyzed iodination of inexpensive and abundant aryl and vinyl carboxylic acids via in situ activation to the acid chloride and formation of a phosphonium salt. The use of 1-iodobutane as iodide source in combination with a base and a deoxychlorinating reagent gives access to a wide range of aryl and vinyl iodides under Pd/Xantphos catalysis, including complex drug-like scaffolds. Stoichiometric experiments and kinetic analysis suggest a unique mechanism involving C-P reductive elimination to form the Xantphos phosphonium chloride, which subsequently initiates an unusual halogen exchange by outer sphere nucleophilic substitution.
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Palladium‐katalysierte decarbonylierende Iodierung von Carbonsäuren, ermöglicht durch Ligand‐unterstützten Halogenaustausch. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202103269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Abstract
The past 20 years have seen an extensive implementation of nickel in homogeneous catalysis through the development of unique reactivity not easily achievable by using noble transition metals. Many catalytic cycles propose Ni(I) complexes as potential reactive intermediates, yet the scarcity of nickel(I) precursors and the lack of a general, non-ligand-specific protocol for their synthesis have hampered progress in this field of research. This has in turn also limited the access to novel, well-defined Ni(I) species for the development of new catalytic reactions. Herein, we report a simple, general route to access a wide variety of Ni(I)-phenolate complexes via an unusual example of an olefinic Ni(I) complex, [Ni(COD)(OPh*)] (COD = 1,5-cyclooctadiene, OPh* = O(tBu)3C6H2). This route has proven to be highly efficient for several coordination numbers and ligand classes enabling access to the following complexes: [Ni(IPr)(OPh*)] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), [Ni(dcype)(OPh*)] (dcype = 1,2-bis(dicyclohexylphosphino)ethane), [Ni(dppe)(OPh*)] (dppe = 1,2-bis(diphenylphosphino)ethane), and [Ni(terpy)(OPh*)] (terpy = 2,2':6',2″-terpyridine). Moreover, reacting [Ni(dcype)(OPh*)] with trimethylsilyl triflate has led to the isolation of a unique example of a cationic binuclear Ni(I)-arene complex. All these complexes have been characterized by single-crystal X-ray, DFT, and EPR analyses, thus providing crucial experimental and theoretical information about their coordination environment and confirming a d9 electronic structure for all complexes involved. Overall, this new synthetic approach offers exciting opportunities for the discovery of new stoichiometric and catalytic reactivity as well as the mechanistic elucidation of Ni-based catalytic cycles.
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Microsurgical endodontic treatment of the upper molar teeth and their relationship with the maxillary sinus: a retrospective multicentric clinical study. BMC Oral Health 2021; 21:252. [PMID: 33980213 PMCID: PMC8114693 DOI: 10.1186/s12903-021-01610-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 04/27/2021] [Indexed: 11/10/2022] Open
Abstract
PURPOSE To assess the clinical and radiographic success rate of microsurgical endodontic treatment of upper molar teeth in relationship with the maxillary sinus, with 12 months follow-up. METHODS Patients treated with microsurgical endodontic treatment of upper molar teeth in the period between 2017 and 2019 were recruited from two dental clinics according to specific selection criteria. The outcomes were determined based on clinical and radiographic results taken three, six and 12 months post-operatively, compared with those taken immediately before and after surgery. Clinical and radiographic outcomes were recorded. The distance between the most apical part of the root and of the lesion to the maxillary sinus was measured on CBCT images before the surgery. Patient-related outcomes were recorded. RESULTS Out of 35 patients evaluated, 21 were selected according with the selection criteria for a total of 27 roots and 29 canals treated. After 12 months, 18 patients showed a complete healing whereas three demonstrated incomplete healing. Consequently, the success rate in this study was 85.7% after one year. In 28.5% (6 patients) there was a perforation of the Schneiderian membrane that didn't seem to affect the outcome. All patients kept the molar one year later. The pain level decreased significantly over the time during the first week after surgery. CONCLUSION Microsurgical Endodontic treatment of the upper molar teeth should be considered a valid and predictable treatment option even in case of Schneiderian membrane perforation. Future clinical studies with a larger sample size are needed to compare the results obtained.
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A site-selective and stereospecific cascade Suzuki-Miyaura annulation of alkyl 1,2-bisboronic esters and 2,2'-dihalo 1,1'-biaryls. Chem Commun (Camb) 2021; 57:3909-3912. [PMID: 33871510 DOI: 10.1039/d1cc00648g] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A cascade Suzuki-Miyaura cross-coupling giving rise to 9,10-dihydrophenanthrenes has been developed. Using biaryls with unsymmetrical substitution-pattern full site-selectivity was observed. Furthermore, this cross-coupling of an alkyl 1,2-bisboronic pinacol ester proceeds through the challenging coupling of a secondary boronate with complete stereoretention.
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Ruthenium‐Catalyzed Dehydrogenation Through an Intermolecular Hydrogen Atom Transfer Mechanism. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202015837] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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