Mono(hydrosilylation) of N-Heterocycles Catalyzed by B(C6F5)3 and Silylium Ion

Petrushko, William D.; Nikonov, Georgii I.

doi:10.1021/acs.organomet.0c00697

Cited by 14 publications

(7 citation statements)

References 52 publications

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“…Harrod and co-workers have reported the first homogeneous catalytic hydrosilylation of pyridines using titanium catalyst with moderate regioselectivity . The groups of Nikonov and Oestreich have independently developed ruthenium-catalyzed 1,4-selective hydrosilylation of N -heteroarenes. , In contrast, 1,2-selective hydrosilylation of N -heteroarenes was less developed, and there are only three notable reports known in the literature. Harder and co-workers developed a calcium complex for catalytic regioselective dearomatization of pyridines with a limited substrate scope .…”

Section: Introductionmentioning

confidence: 99%

Ruthenium(II)-Catalyzed Regioselective 1,2-Hydrosilylation of N-Heteroarenes and Tetrel Bonding Mechanism

et al. 2021

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An efficient regioselective dearomatization of N-heteroarenes using a ruthenium precatalyst [Ru-(p-cymene)(PCy 3 )Cl 2 ] 1 is achieved. Reactions were performed under mild and neat conditions. A wide variety of N-heteroarenes undergo the addition of silanes in the presence of precatalyst 1, leading to exclusive N-silyl-1,2-dihydroheteroarene products. This catalytic method displays a broad substrate scope; quinolines, isoquinolines, benzimidazoles, quinoxalines, pyrazines, pyrimidines, and pyridines undergo highly selective 1,2-dearomatization. Both electron-donating and electronwithdrawing substituents on N-heteroaromatics are well tolerated in this protocol. Mechanistic studies indicate the presence of [Ru-(p-cymene) (PCy 3 )HCl] 4 in the reaction mixture, which may be the resting state of the catalyst. The complete catalytic cycle as revealed from density functional theory (DFT) studies show that the product formation is governed by N → Si tetrel bonding. Initially, PCy 3 dissociates from 1, and further reaction of [(p-cymene)RuCl 2 ] 20 with silane generates the catalytically active intermediate [(p-cymene)RuHCl] 7. Heteroarene coordinates with 7, and subsequent dearomative 1,3-hydride transfer to the C2 position of the heteroaryl ligand generates an amide-ligated intermediate in which the reaction of silane occurs through a tetrel bonding and provides a selective pathway for 1,2-addition. DFT studies also revealed that ruthenium-catalyzed 1,4-hydroboration of pyridines is a facile process with a free energy barrier of 3.2 kcal/mol, whereas a pathway for the 1,2-hydroboration product is not observed due to the steric effects exerted by methyl groups on pinacolborane (HBpin) and p-cymene. Notably, enabled by the amine−amide inter-conversion of the coordinated heteroarene ligand, the +2 oxidation state of ruthenium intermediates remains unchanged throughout the catalytic cycle.

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Section: Introductionmentioning

confidence: 99%

Ruthenium(II)-Catalyzed Regioselective 1,2-Hydrosilylation of N-Heteroarenes and Tetrel Bonding Mechanism

et al. 2021

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“…Since the first results on hydroboration by Hill, numerous reports demonstrated that hydroboration is the most selective hydroelementation system of N -heteroarenes. Indeed, it is possible to reach the desired 1,2- or 1,4-isomer of DHPs and DHQs. − On the other hand, for hydrosilylation, since the nonselective report by Harrod and except for the reports from Oestreich and Nikonov on 1,4-selective ruthenium catalyzed hydrosilylation, , examples of selective 1,2-hydrosilylation of both pyridines and quinolines remain scarce. Indeed, few reports using non-noble metals such as Ca and Zn , are described with a narrow scope.…”

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confidence: 99%

Hydrido-Cobalt Complexes for the Chemo- and Regioselective 1,2-Silylative Dearomatization of N-Heteroarenes

et al. 2023

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We describe an efficient regio-and chemoselective dearomatization of N-heteroarenes using hydrido-cobalt catalysts. Reactions were performed under mild conditions on a wide range of N-heteroarenes leading exclusively to the silyl-1,2-dihydroheteroarene. Various quinolines and pyridines bearing electron-donating and electron-withdrawing substituents are compatible with this methodology. DFT calculations, NMR spectroscopic studies, and X-ray diffraction analysis underlined the importance of a second silane for the final step of the reaction.

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“…Nikonov and co-workers compared the hydrosilylation of quinolines catalyzed by B(C 6 F 5 ) 3 to the same reaction catalyzed directly by the silylinium ion R 3 Si + (Scheme 34). 67 This silylinium ion was generated by hydride abstraction with catalytic amounts of Ph 3 C + B(C 6 F 5 ) 4…”

Section: Metal-free Hydroborations Hydrosilylations Andmentioning

confidence: 99%

Recent Strategies in the Nucleophilic Dearomatization of Pyridines, Quinolines, and Isoquinolines

Escolano,

Gaviña,

Alzuet-Piña

et al. 2024

Chem. Rev.

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Dearomatization reactions have become fundamental chemical transformations in organic synthesis since they allow for the generation of three-dimensional complexity from two-dimensional precursors, bridging arene feedstocks with alicyclic structures. When those processes are applied to pyridines, quinolines, and isoquinolines, partially or fully saturated nitrogen heterocycles are formed, which are among the most significant structural components of pharmaceuticals and natural products. The inherent challenge of those transformations lies in the low reactivity of heteroaromatic substrates, which makes the dearomatization process thermodynamically unfavorable. Usually, connecting the dearomatization event to the irreversible formation of a strong C−C, C− H, or C−heteroatom bond compensates the energy required to disrupt the aromaticity. This aromaticity breakup normally results in a 1,2-or 1,4-functionalization of the heterocycle. Moreover, the combination of these dearomatization processes with subsequent transformations in tandem or stepwise protocols allows for multiple heterocycle functionalizations, giving access to complex molecular skeletons. The aim of this review, which covers the period from 2016 to 2022, is to update the state of the art of nucleophilic dearomatizations of pyridines, quinolines, and isoquinolines, showing the extraordinary ability of the dearomative methodology in organic synthesis and indicating their limitations and future trends.

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Mono(hydrosilylation) of N-Heterocycles Catalyzed by B(C₆F₅)₃ and Silylium Ion

Cited by 14 publications

References 52 publications

Ruthenium(II)-Catalyzed Regioselective 1,2-Hydrosilylation of N-Heteroarenes and Tetrel Bonding Mechanism

Ruthenium(II)-Catalyzed Regioselective 1,2-Hydrosilylation of N-Heteroarenes and Tetrel Bonding Mechanism

Hydrido-Cobalt Complexes for the Chemo- and Regioselective 1,2-Silylative Dearomatization of N-Heteroarenes

Recent Strategies in the Nucleophilic Dearomatization of Pyridines, Quinolines, and Isoquinolines

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