Single Electron Transfer to Diazomethane–Borane Adducts Prompts C−H Bond Activations

Cao, Levy L.; Zhou, Jiafeng; Qu, Zheng‐Wang; Stephan, Douglas W.

doi:10.1002/ange.201912338

Cited by 5 publications

(4 citation statements)

References 86 publications

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“…A single electron transfer from Co II to the diazomethane-borane adduct Ph 2 CN 2 B(C 6 F 5 ) 3 was proposed to account for the formation of [Cp*Co(C 5 Me 4 CH 2 B(C 6 F 5 ) 3 )]. 13 Furthermore, in 2020, Stephan and co-workers disclosed that a stoichiometric reaction between Ph 2 CN 2 and the oxygen-linked geminal FLP complexes R 2 POBcat (R = t -Bu, mesityl) (derived from the reaction between phosphine oxides t- Bu 2 P(O)H/Mes 2 P(O)H and ClBcat) afforded Ph 2 C(N 2 )BcatOPR 2 . 14 Formation of these BOPN 2 five-membered heterocyclic compounds was confirmed by single crystal X-ray diffraction.…”

Section: Activation Of Diazo Compounds Using Stoichiometric B(ar F )mentioning

confidence: 99%

“…However, in 2017, Stephan and co-workers demonstrated that B(C 6 F 5 ) 3 can activate diphenydiazomethane as Lewis acidic boranes readily interact with the nitrogen functionality of diazo compounds, leading to the formation of Lewis acid−base adducts. 12 The stoichiometric reaction between Ph 2 CN 2 and B(C 6 13 Furthermore, in 2020, Stephan and co-workers disclosed that a stoichiometric reaction between Ph 2 CN 2 and the oxygen-linked geminal FLP complexes R 2 POBcat (R = t-Bu, mesityl) (derived from the reaction between phosphine oxides t-Bu 2 P(O)H/ Mes 2 P(O)H and ClBcat) afforded Ph 2 C(N 2 )BcatOPR 2 . 14 Formation of these BOPN 2 five-membered heterocyclic compounds was confirmed by single crystal X-ray diffraction.…”

Section: ■ Activation Of Diazo Compounds Using Stoichiometric B(ar F )mentioning

confidence: 99%

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Triarylborane Catalyzed Carbene Transfer Reactions Using Diazo Precursors

2021

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Reactive carbenes generated from diazo compounds are key intermediates for a range of organic reactions to afford synthetically useful organic compounds. The majority of these reactions have been carried out using transition metal catalysts. However, the formation of carbene intermediates using main group elements has not been widely investigated for synthetic purposes. Recent studies have demonstrated that triarylboranes can be used for the in situ generation of reactive carbene intermediates in both stoichiometric and catalytic reactions. These new reactivities of triarylboranes have gained significant attention in synthetic chemistry particularly in catalytic studies. The range of organic compounds that have been synthesized through these reactions are important as pharmaceuticals or agrochemicals. In this perspective, we highlight the recent progress and ongoing challenges of carbene transfer reactions generated from their corresponding diazo precursors using triarylboranes as catalysts. We also highlight the stoichiometric use of triarylboranes in which the boranes not only activate the diazo functionality to afford a carbene intermediate but also actively participate in the reactions as a reagent. The different mechanisms for activation and carbene transfer are described along with the mechanistic and computational studies that have aided the elucidation of these reaction pathways. Potential opportunities for the use of boranes as a catalyst toward different carbene transfer reactions and their future prospects are discussed.

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Section: Activation Of Diazo Compounds Using Stoichiometric B(ar F )mentioning

confidence: 99%

Section: ■ Activation Of Diazo Compounds Using Stoichiometric B(ar F )mentioning

confidence: 99%

Triarylborane Catalyzed Carbene Transfer Reactions Using Diazo Precursors

2021

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“…Attempts to replace the transition metals resulted in the first boron‐based bimolecular catalysts within the framework of frustrated Lewis pairs (FLP) or by exploiting the ambiphilic nature of the boron atom having empty and filled orbitals under certain conditions (being in the B (I) instead of the common B (III) state, Scheme 1). [26–37] A recent computational study employed 2,3’‐bipyridine to mediate intra‐molecular tetraboration of dinitrogen [36] . In a conceptual density functional theory (DFT) study on a peri ‐substituted bond activator molecule, we could recently show that N 2 ‐splitting could potentially also be conducted intra‐molecularly by tripodal light atom molecules containing only earth abundant C, H, P, and Si atoms [38] .…”

Section: Introductionmentioning

confidence: 99%

In Silico Partial N₂ to NH₃ Conversion with a Light Atom Molecule

Mebs

2022

ChemPhysChem

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N2 can be stepwise converted in silico into one molecule NH3 and a secondary amide with a bond activator molecule consisting only of light main group elements. The proposed N2‐activating pincer‐related compound carries a silyl ion (Si(+)) center as well as three Lewis acidic (−BF2) and three Lewis basic (−PMe2) sites, providing an efficient binding pocket for gaseous N2 within the framework of intramolecular frustrated Lewis pairs (FLP). In addition, it exhibits supportive secondary P−B and F⋅⋅⋅B contacts, which stabilize the structure. In the PSi(+)−N−N−BP environment the N≡N triple bond is extended from 1.09 Å to remarkable 1.43 Å, resembling a N−N single bond. The strongly activated N−N‐fragment is prone to subsequent hydride addition and protonation steps, resulting in the energy efficient transfer of two hydrogen equivalents. The next hydride added causes the release of one molecule NH3, but leaves the ligand system as poisoned R3Si(+)−NH2−PMe2 or R3Si(+)−NH3 dead‐end states behind. The study indicates that approximately tetrahedral constrained SiBP2‐pockets are capable to activate N2, whereas the acid‐rich SiB3‐ and SiB2P‐pocktes, as well as the base‐rich SiP3‐pockets fail, hinting towards the high relevance of the acid‐base proportion and relative orientation. The electronic structure of the N2‐activated state is compared to the corresponding state of a recently published peri‐substituted bond activator molecule featuring a PSi(+)−N−N−Si(+)P site (S. Mebs, J. Beckmann, Physical Chemistry Chemical Physics 2022, 24, 20953–20967).

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“…However, a single electron transfer (SET) process was assumed to be operative from Cp*2Co to Ph2CN2B(C6F5)3 for the formation of [Cp*Co(C5Me4CH2B(C6F5)3)] (Scheme 1). 27 In 2020, Stephan also examined that frustrated Lewis pairs (FLPs) R2POBcat (R = t Bu, mesityl, cat = catechol) derived from phosphine oxides and ClBcat reacted with Ph2CN2 to form the compound Ph2C(N2)BcatOPR2 (R = t Bu) with 87% yield (Scheme 1). 28 Unfortunately, a problem with isolation prevented the purification of the compound Ph2C(N2)BcatOPR2 (R = mesityl), nevertheless single crystal X-ray analysis helped to assign the structure of the compound.…”

Section: Template For Synthesis Thiemementioning

confidence: 99%

Activation of Diazo Compounds by Fluorinated Triarylborane Catalysts

Pramanik

Melen

2023

Synthesis

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The diverse applicability of diazo compounds as versatile reagents has enlarged the chemical toolbox in organic synthesis. Over the past few decades, transition metal-catalyzed diazo compound activation has ignited the classical synthetic methodology via utilizing highly reactive metal carbenoid species. Many reviews have also appeared in the literature which discloses the advantage and disadvantages of metal-catalyzed activation of the diazo compound. Recently, tris(pentafluorophenyl) borane-mediated diazo activation reactions have reconciled this research area due to the potential for mild, environmentally-friendly, metal-free, non-toxic reaction conditions, and the diverse reactivity patterns of boranes towards diazo compounds. In this review, we have discussed the reactivity of the boron-diazo precursor adduct with compounds using catalytic and stoichiometric halogenated triarylboranes and, the mechanism of N2 release from the diazo reagent. This generates the reactive carbene species as a key intermediate which can further be exploited for O−H, N−H, S‒H, and C−H insertions, azide insertion, carbonate transfer, C‒C and C=C bond forming reactions, [2+2] or [2+4] cascade cyclization reactions, annulation reactions, etc. This review is classified by the following themes: 1. Introduction 2. Diazo Activation Using Stoichiometric Boranes 3. Diazo Activation Using Catalytic B(C6F5)3 4. B(C6F5)3 Catalyzed Diazo Activation Reactions 5. Conclusions

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Single Electron Transfer to Diazomethane–Borane Adducts Prompts C−H Bond Activations

Cited by 5 publications

References 86 publications

Triarylborane Catalyzed Carbene Transfer Reactions Using Diazo Precursors

Triarylborane Catalyzed Carbene Transfer Reactions Using Diazo Precursors

In Silico Partial N₂ to NH₃ Conversion with a Light Atom Molecule

Activation of Diazo Compounds by Fluorinated Triarylborane Catalysts

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Single Electron Transfer to Diazomethane–Borane Adducts Prompts C−H Bond Activations

Cited by 5 publications

References 86 publications

Triarylborane Catalyzed Carbene Transfer Reactions Using Diazo Precursors

Triarylborane Catalyzed Carbene Transfer Reactions Using Diazo Precursors

In Silico Partial N2 to NH3 Conversion with a Light Atom Molecule

Activation of Diazo Compounds by Fluorinated Triarylborane Catalysts

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In Silico Partial N₂ to NH₃ Conversion with a Light Atom Molecule