Manganese-Catalyzed Dehydrogenative Silylation of Alkenes Following Two Parallel Inner-Sphere Pathways

Journal of the American Chemical Society, Год журнала: 2021, Номер 143(42), С. 17825 - 17832

Опубликована: Окт. 13, 2021

We report on an additive-free Mn(I)-catalyzed dehydrogenative silylation of terminal alkenes. The most active precatalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. catalytic process initiated by migratory insertion a CO ligand into Mn–alkyl bond to yield acyl intermediate which undergoes rapid Si–H cleavage silane HSiR3 forming 16e– silyl catalyst [Mn(dippe)(CO)2(SiR3)] together with liberated butanal. A broad variety aromatic and aliphatic alkenes was efficiently selectively converted E-vinylsilanes allylsilanes, respectively, at room temperature. Mechanistic insights are provided based experimental data DFT calculations revealing that two parallel reaction pathways operative: acceptorless pathway involving dihydrogen release requiring alkene as sacrificial hydrogen acceptor.

Язык: Английский

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E-Selective Manganese-Catalyzed Semihydrogenation of Alkynes with H₂ Directly Employed or In Situ-Generated

ACS Catalysis, Год журнала: 2022, Номер 12(4), С. 2253 - 2260

Опубликована: Янв. 31, 2022

Selective semihydrogenation of alkynes with the Mn(I) alkyl catalyst fac-[Mn(dippe)(CO)3(CH2CH2CH3)] (dippe = 1,2-bis(di-iso-propylphosphino)ethane) as a precatalyst is described. The required hydrogen gas either directly employed or in situ-generated upon alcoholysis KBH4 methanol. A series aryl-aryl, aryl-alkyl, alkyl-alkyl, and terminal was readily hydrogenated to yield E-alkenes good excellent isolated yields. reaction proceeds at 60 °C for 60-90 loadings 0.5-2 mol %. implemented protocol tolerates variety electron-donating electron-withdrawing functional groups, including halides, phenols, nitriles, unprotected amines, heterocycles. can be upscaled gram scale. Mechanistic investigations, deuterium-labeling studies density theory (DFT) calculations, were undertaken provide reasonable mechanism, showing that initially formed Z-isomer undergoes fast isomerization afford thermodynamically more stable E-isomer.

Язык: Английский

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Manganese Alkyl Carbonyl Complexes: From Iconic Stoichiometric Textbook Reactions to Catalytic Applications

Accounts of Chemical Research, Год журнала: 2022, Номер 55(18), С. 2740 - 2751

Опубликована: Сен. 8, 2022

ConspectusThe activation of weakly polarized bonds represents a challenging, yet highly valuable process. In this context, precious metal catalysts have been used as reliable compounds for the rather inert last several decades. Nevertheless, base-metal complexes including cobalt, iron, or nickel are currently promising candidates substitution noble metals in order to develop more sustainable processes. past few years, manganese(I)-based were heavily employed efficient (de)hydrogenation reactions. However, vast majority these operate via metal–ligand bifunctionality already well implemented decades ago. Although high reactivity can be achieved various reactions, concept is often not applicable certain transformations due outer-sphere mechanisms. Account, we outline potential alkylated Mn(I)-carbonyl nonpolar and moderately polar E–H (E = H, B, C, Si) disclose our successful approach utilization field homogeneous catalysis. This involves rational design manganese hydrogenation reactions involving ketones, nitriles, carbon dioxide, alkynes. addition that, reduction alkenes by dihydrogen could series well-defined which was possible before. Furthermore, elucidate Mn-based hydrofunctionalization carbon–carbon multiple bonds. Our investigations unveiled novel insights into reaction pathways dehydrogenative silylation trans-1,2-diboration terminal alkynes, reported transition metals. Due catalyst design, under mild conditions. Delightfully, all bench-stable compounds. We took advantage fact that Mn(I) alkyl known undergo migratory insertion group CO ligand, yielding an unsaturated acyl intermediate. Hydrogen atom abstraction ligand then paves way active species variety catalytic proceed inner-sphere textbook well-known decades, application still its infancy. A brief historical overview manganese(I)–carbonyl provided, covering synthesis especially iconic stoichiometric transformations, e.g., carbonylation, intensively examined Calderazzo, Moss, others. An future applications defined will given, may inspire researchers development (base-)metal catalysts.

Язык: Английский

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Homogeneous Manganese-Catalyzed Hydrofunctionalizations of Alkenes and Alkynes: Catalytic and Mechanistic Tendencies

ACS Omega, Год журнала: 2022, Номер 7(42), С. 37008 - 37038

Опубликована: Окт. 11, 2022

In recent years, many manganese-based homogeneous catalytic precursors have been developed as powerful alternatives in organic synthesis. Among these, the hydrofunctionalizations of unsaturated C–C bonds correspond to outstanding ways afford compounds with more versatile functional groups, which are commonly used building blocks production fine chemicals and feedstock for industrial field. Herein, we present an account Mn-catalyzed alkenes alkynes main objective finding mechanistic tendencies that could serve a platform works come.

Язык: Английский

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Manganese catalysed reduction of nitriles with amine boranes

Catalysis Science & Technology, Год журнала: 2024, Номер 14(17), С. 4843 - 4847

Опубликована: Янв. 1, 2024

The room temperature reduction of various nitriles using amine boranes catalysed by a manganese( i ) alkyl complex is described. Based on experimental findings, plausible mechanistic scenario presented.

Язык: Английский

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Selective Transfer Semihydrogenation of Alkynes Catalyzed by an Iron PCP Pincer Alkyl Complex

ACS Catalysis, Год журнала: 2023, Номер 13(21), С. 14012 - 14022

Опубликована: Окт. 17, 2023

Two bench-stable Fe(II) alkyl complexes [Fe(κ3PCP-PCP-iPr)(CO)2(R)] (R = CH2CH2CH3, CH3) were obtained by the treatment of [Fe(κ3PCP-PCP-iPr)(CO)2(H)] with NaNH2 and subsequent addition CH3CH2CH2Br CH3I, respectively. The reaction proceeds via anionic Fe(0) intermediate Na[Fe(κ3PCP-PCP-iPr)(CO)2]. catalytic performance both was investigated for transfer hydrogenation terminal internal alkynes utilizing PhSiH3 iPrOH as a hydrogen source. Precatalyst activation is initiated migration ligand to carbonyl C atom an adjacent CO ligand. In agreement previous findings, rate follows order nPr > Me. Accordingly, [Fe(κ3PCP-PCP-iPr)(CO)2(CH2CH2CH3)] more active catalyst. takes place at 25 °C catalyst loading 0.5 mol%. There no overhydrogenation, in case alkynes, exclusively, Z-alkenes are formed. implemented protocol tolerates variety electron-donating electron-withdrawing functional groups including halides, nitriles, unprotected amines, heterocycles. Mechanistic investigations deuterium labeling studies DFT calculations undertaken provide reasonable mechanism.

Язык: Английский

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Base- and Additive-Free Carbon Dioxide Hydroboration to Methoxyboranes Catalyzed by Non-Pincer-Type Mn(I) Complexes

ACS Catalysis, Год журнала: 2023, Номер 13(8), С. 5236 - 5244

Опубликована: Март 31, 2023

Well-defined, bench stable Mn(I) non-pincer-type complexes were tested as earth-abundant transition metal catalysts for the selective reduction of CO2 to boryl-protected MeOH in presence pinacolborane (HBpin). Essentially, quantitative yields obtained under mild reaction conditions (1 bar CO2, 60 °C), without need any base or additives, alkylcarbonyl bis(phosphine) fac-[Mn(CH2CH2CH3)(dippe)(CO)3] [Mn1, dippe = 1,2-bis(diisopropylphosphino)ethane] and [Mn(dippe)(CO)2{(μ-H)2(Bpin)}] (Mn4), that is by bench-stable precatalyst Mn1 with HBpin via elimination butanal. Preliminary mechanistic details a combination NMR experiments monitoring catalytic reactions.

Язык: Английский

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Tandem manganese catalysis for the chemo-, regio-, and stereoselective hydroboration of terminal alkynes: in situ precatalyst activation as a key to enhanced chemoselectivity

RSC Advances, Год журнала: 2024, Номер 14(8), С. 5514 - 5523

Опубликована: Янв. 1, 2024

The manganese( ii ) complex [Mn( iPr PNP)Cl 2 ] ( PNP = 2,6-bis(diisopropylphosphinomethyl)pyridine) was found to catalyze the stereo- and regioselective hydroboration of terminal alkynes employing HBPin (pinacolborane).

Язык: Английский

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Monomeric Magnesium Catalyzed Alkene and Alkyne Hydroboration

Chemistry - A European Journal, Год журнала: 2022, Номер 28(56)

Опубликована: Июль 21, 2022

Abstract In this work, two monomeric magnesium alkyl complexes ( 1 and 2 ) were prepared using bis(phosphino)carbazole framework among them has been used as a catalyst for hydroboration of alkenes alkynes with pinacolborane (HBpin). A broad variety aromatic aliphatic efficiently reduced. Anti‐Markovnikov regioselective was achieved, which confirmed by deuterium‐labelling experiments. The work represents the first example use in homogeneous catalytic alkene substrate scope. Experimental mechanistic investigations DFT calculations provided insights into reaction mechanism. Finally, protocol extended to terpenes.

Язык: Английский

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Hydroboration of Terminal Alkenes and trans‐1,2‐Diboration of Terminal Alkynes Catalyzed by a Manganese(I) Alkyl Complex

Angewandte Chemie, Год журнала: 2021, Номер 133(46), С. 24693 - 24697

Опубликована: Авг. 26, 2021

A Mn

Язык: Английский

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