Mechanistic Details of Asymmetric Bromocyclization with BINAP Monoxide: Identification of Chiral Proton-Bridged Bisphosphine Oxide Complex and Its Application to Parallel Kinetic Resolution

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(9), С. 3913 - 3924

Опубликована: Фев. 28, 2022

The mechanism of our previously reported catalytic asymmetric bromocyclization reactions using 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP) monoxide was examined in detail by the means control experiments, NMR studies, X-ray structure analysis, and CryoSpray electrospray ionization mass spectrometry (ESI-MS) analysis. chiral BINAP transformed to a key catalyst precursor, proton-bridged bisphosphine oxide complex (POHOP·Br), presence N-bromosuccinimide (NBS) contaminating water. thus-formed POHOP further reacts with NBS afford dioxide molecular bromine (Br2) simultaneously equimolar amounts. While resulting Br2 is activated form more reactive brominating reagent (Br2─NBS), serves as bifunctional catalyst, acting both Lewis base that Br2─NBS agent (P═O+─Br) also Brønsted for activation substrate. By taking advantage this novel concerted Lewis/Brønsted catalysis dioxide, we achieved first regio- chemodivergent parallel kinetic resolutions (PKRs) racemic unsymmetrical bisallylic amides via bromocyclization.

Язык: Английский

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Silyl Esters as Reactive Intermediates in Organic Synthesis

Synthesis, Год журнала: 2023, Номер 55(20), С. 3209 - 3238

Опубликована: Апрель 28, 2023

Abstract Silyl esters have been exploited as metastable reaction intermediates, both purposefully and unintentionally, since at least the 1960s. Their reactivity is broadly related to substituents on silicon, in this way their properties can be readily modulated. unique profiles that used generate downstream products of a range functionalities, because many excellent methods for synthesis variety value-added chemicals developed. Furthermore, frequent use hydrosilanes terminal reductants catalytic processes, silyl ester intermediates are likely more commonly utilized by synthetic chemists than currently realized. This review comprehensively summarizes reactions known take advantage reactive discusses examples proceed an unanticipated manner through intermediates. 1 Introduction 2 Synthesis Esters 3 Making Amides from 3.1 Amidation Using Chlorosilanes 3.2 Azasilanes 3.3 Oxysilanes 3.4 Hydrosilanes 3.5 Amine Formation via Amidation/Reduction 3.6 Miscellaneous 4 Mechanistic Investigations 4.1 Mechanism 4.2 4.3 Oxy- or 5 6 Aldehydes, Alcohols, Amines, Alkanes Reduction 6.1 Aldehyde Metal-Free 6.2 Metal-Mediated 6.3 Alcohol 6.4 6.5 Alkane 7 Acid Chlorides 8 In Situ Generated Ramifications Catalysis 9 Conclusion

Язык: Английский

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Ligand‐Enabled Disproportionation of 1,2‐Diphenylhydrazine at a P^V‐Center**

Angewandte Chemie International Edition, Год журнала: 2022, Номер 61(35)

Опубликована: Июнь 17, 2022

We present herein the synthesis of a nearly square-pyramidal chlorophosphorane supported by tetradentate bis(amidophenolate) ligand, N,N'-bis(3,5-di-tert-butyl-2-phenoxy)-1,2-phenylenediamide. After chloride abstraction resulting phosphonium cation efficiently promotes disproportionation 1,2-diphenylhydrazine to aniline and azobenzene. Mechanistic studies, spectroscopic analyses theoretical calculations suggest that this unprecedented reactivity mode for P

Язык: Английский

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Combined Computational and Experimental Study Reveals Complex Mechanistic Landscape of Brønsted Acid-Catalyzed Silane-Dependent P═O Reduction

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(20), С. 13983 - 13999

Опубликована: Май 13, 2024

The reaction mechanism of Brønsted acid-catalyzed silane-dependent P═O reduction has been elucidated through combined computational and experimental methods. Due to its remarkable chemo- stereoselective nature, the acid/silane system widely employed in organophosphine-catalyzed transformations involving P(V)/P(III) redox cycle. However, full mechanistic profile this type yet be clearly established date. Supported by both DFT studies, our research reveals that likely proceeds mechanisms other than accepted "dual activation mode silyl ester" or "acid-mediated direct activation" mechanism. We propose although may vary with substitution patterns silane species, acid generally activates rather group transition structures. proposed differs significantly from associated traditional C═O reduction. uniqueness originates dominant Si/O═P orbital interactions structures P/H–Si interactions. comprehensive landscape provided us will serve as a guidance for rational design development more efficient systems well novel reactions

Язык: Английский

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Organophosphorus-Catalyzed “Dual-Substrate Deoxygenation” Strategy for C–S Bond Formation from Sulfonyl Chlorides and Alcohols/Acids

The Journal of Organic Chemistry, Год журнала: 2023, Номер 88(13), С. 8628 - 8635

Опубликована: Июнь 9, 2023

A green method to construct C-S bonds using sulfonyl chlorides and alcohols/acids via a PIII/PV═O catalytic system is reported. The organophosphorus-catalyzed umpolung reaction promotes us propose the "dual-substrate deoxygenation" strategy. Herein, we adopt strategy, which achieves deoxygenation of synthesize thioethers/thioesters driven by redox cycling. represents an operationally simple approach stable phosphine oxide as precatalyst shows broad functional group tolerance. potential application this protocol demonstrated late-stage diversification drug analogues.

Язык: Английский

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Electrophilic C(sp2)–H Cyanation with Inorganic Cyanate (OCN–) by PIII/PV=O‐Catalyzed Phase Transfer Activation

Angewandte Chemie International Edition, Год журнала: 2024, Номер unknown

Опубликована: Июль 1, 2024

An organophosphorus -catalyzed method for the direct electrophilic cyanation of C(sp

Язык: Английский

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(3+2) Annulation of 4‐Acetoxy Allenoate with Aldimine Enabled by AgF‐Assisted P(III)/P(V) Catalysis

Angewandte Chemie International Edition, Год журнала: 2023, Номер 63(1)

Опубликована: Ноя. 21, 2023

Abstract A phosphine‐catalyzed (3+2) annulation of 4‐acetoxy allenoate and aldimine with the assistance AgF is described. The success this reaction hinges on metathesis between enolate‐phosphonium zwitterion AgF, leading to a key intermediate comprising silver enolate fluorophosphorane P(V)‐moiety. former able undergo Mannich aldimine, whereas latter initiates cascade sequence AcO‐elimination/aza‐addition, thus furnishing P(III)/P(V) catalysis. By taking advantage enolate, preliminary attempt at an asymmetric variant was conducted combination achiral phosphine catalyst chiral bis(oxazolinyl)pyridine ligand (PyBox), giving moderate enantioselectivity.

Язык: Английский

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Generation of Oxyphosphonium Ions by Photoredox/Cobaloxime Catalysis for Scalable Amide and Peptide Synthesis in Batch and Continuous‐Flow

Angewandte Chemie, Год журнала: 2021, Номер 134(5)

Опубликована: Ноя. 16, 2021

Abstract Phosphine‐mediated deoxygenative nucleophilic substitutions, such as the Mitsunobu reaction, are of great importance in organic synthesis. However, conventional protocols require stoichiometric oxidants to trigger formation oxyphosphonium intermediates for subsequent additions. Through dual catalysis photoredox and cobaloxime, we realized a radical strategy catalytic acyloxyphosphonium ions that enables direct amidation. The protocol exhibits broad scope has been used late‐stage amidation drug molecules. In addition batch reactions, continuous‐flow reactor was developed, enabling rapid peptide synthesis on gram scale. successful assembly tetrapeptide solid support further demonstrated versatility this photocatalytic system. Moreover, experimental computational studies consistent with hypothesis being formed key intermediates.

Язык: Английский

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P^III/P^V-Catalyzed Beckmann Reaction and Sequential [2,3]-Sigmatropic Rearrangement to Construct 2-Amidopyridines

Organic Letters, Год журнала: 2024, Номер 26(17), С. 3536 - 3540

Опубликована: Апрель 24, 2024

An organophosphorus catalytic method for the synthesis of substituted 2-amidopyridines is reported. The employs a small-ring organophosphorus-based catalyst and hydrosilane reductant to drive conversion ketoximes pyridine-N-oxides into through sequential Beckmann rearrangement followed by [2,3]-sigmatropic rearrangement. readily available could be activated nitrilium ions in PIII/PV redox catalysis efficiently participate domino reaction pyridine-N-oxides, thus providing various moderate excellent yields. This presented strategy features functional group tolerance broad substrate scope.

Язык: Английский

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Nickel‐Catalyzed Highly Selective Radical C−C Coupling from Carboxylic Acids with Photoredox Catalysis

Angewandte Chemie, Год журнала: 2024, Номер 136(32)

Опубликована: Май 24, 2024

Abstract Controlling the cross‐coupling reaction between two different radicals is a long‐standing challenge due to process occurring statistically, which would lead three products, including homocoupling products and one product. Generally, selectivity achieved by persistent radical effect (PRE) that requires presence of transient radical, thus resulting in limited precursors. In this paper, highly selective alkyl with acyl construct C(sp 2 )−C(sp 3 ) bonds, or bonds have been readily available carboxylic acids their derivatives (NHPI ester) as coupling partners. The success originates from use tridentate ligand (2,2′ : 6′,2′′‐terpyridine) enable Ni‐mediated organometallic mechanism. This protocol offers facile flexible access structurally diverse ketones (up 90 % yield), also new solution for challenging double decarboxylative coupling. broad utility functional group tolerance are further illustrated late‐stage functionalization natural‐occurring drugs.

Язык: Английский

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