Catalytic Electrophilic C−H Borylation Using NHC⋅Boranes and Iodine Forms C2‐, not C3‐, Borylated Indoles

McGough, John S.; Cid, Jessica; Ingleson, Michael J.

doi:10.1002/chem.201702060

Cited by 46 publications

(33 citation statements)

References 44 publications

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“…24 By employing the N-heterocyclic carbene-borane 7 as a boron source, Ingleson and co-workers demonstrated an I 2catalyzed C-H borylation of hetarenes, in which a C2-regioselectivity was observed in contrast to the C3-regioselectivity reported in the previous catalytic electrophilic C-H borylation (Scheme 2). 25 Mechanistic studies supported an S E Ar mechanism and indicated that the C2-regioselectivity might arise as a result of the presence of a competent Brønsted acid, the higher thermodynamic stability of C2isomers, and the ready protodeboronation of C3 isomers.…”

Section: Synpacts Syn Lettmentioning

confidence: 90%

Metal-Free Catalytic Aromatic C–H Borylation

Zhang

Wang

2020

Synlett

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In recent decades, C–H borylation has undergone rapid development and has become one of the most important and efficient methods for the synthesis of organoboron compounds. Although transition-metal catalysis dominates C–H borylation, the metal-free approach has emerged as a promising alternative strategy. This article briefly summarizes the history of metal-free aromatic C–H borylation, including early reports on electrophilic C–H borylation and recent progress in metal-free catalytic intermolecular C–H borylation; it also highlights our recent work on BF3·Et2O-catalyzed C2–H borylation of hetarenes. Despite these recent advances, comprehensive mechanistic studies on various metal-free catalytic aromatic C–H borylations and novel processes with a wider substrate scope are eagerly expected in the near future.

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Section: Synpacts Syn Lettmentioning

confidence: 90%

Metal-Free Catalytic Aromatic C–H Borylation

Zhang

Wang

2020

Synlett

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“…While stoichiometric C-H borylation reactions have been reported with a number of highly Lewis acidic boranes and borenium ions, 61,[149][150][151][152][153][154][155][156][157][158][159]160 these processes employ stoichiometric amounts of highly reactive reagents through a Wheland-like mechanism. In a few cases, Friedel-Crafts-type catalysis could be observed for the TM-free catalytic borylation of arenes, in mechanisms that bear little similarity to TM chemistry.…”

Section: Arene C-h Activationmentioning

confidence: 99%

Metallomimetic Chemistry of Boron

2019

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The study of main-group molecules that behave and react similarly to transition metal (TM) complexes has attracted significant interest in the recent decades. Most notably, the attractive idea of eliminating the all-too-often rare and costly metals from catalysis has motivated efforts to develop main-group-element-mediated reactions. Main-group elements, however, lack the electronic flexibility of many TM complexes that arise from combinations of empty and filled d-orbitals and that seem ideally suited to bind and activate many substrates. In this Review, we look at boron, an element which, despite its non-metal nature, low atomic weight, and relative redox staticity has achieved great milestones in terms of TM-like reactivity. We show how in inter-element cooperative systems, diboron molecules and hypovalent complexes, the fifth element can acquire a truly metallomimetic character. As we discuss, this character is particularly strikingly demonstrated by the reactivity of boron-based molecules with H2, CO, alkynes, alkenes and even with N2.

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“…Employing NHC-boranes and sub-stoichiometric I 2 as catalyst C 2 -borylation of indoles was achieved. 30 Substantial evidence also demonstrates a dramatic impact of I 2 as an additive on hydrogenation of Nheteroarenes. 31 Based on these studies Chang and coworkers have investigated the role of iodine as the catalyst for tandem hydrogenation of N-heteroarenes using HBpin as reducing agent.…”

Section: Hydroboration Of Heteroarenes Catalyzed By Pblock Elementsmentioning

confidence: 99%

Catalytic dearomative hydroboration of heteroaromatic compounds

Chatterjee

Gunanathan

2019

J Chem Sci

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This review offers a comprehensive discussion on literature concerning the development of catalytic protocols for the dearomative hydroboration of heteroaromatic compounds. The importance of selective dearomatization of heteroarenes, their remarkable applications along with the development of different catalytic methods and their synthetic scopes are emphasized. adhana (0123456789().,-volV)FT3](0123456 789().,-volV) Recently, we have developed an efficient method for ruthenium-catalyzed regioselective 1,4-dearomatization of pyridine derivatives using pinacolborane. 16 Scheme 3. Thorium-catalyzed regioselective 1,2-hydroboration of pyridines. Catalytic intermediates involved in this process are isolated, characterized and further used as effective catalysts. Also in situ NMR studies and a detailed mechanistic investigation revealed the active presence of two intermediates [Ru(p-cymene)Cl 2 (Py)(P(Cy) 3 )] 7 and [Ru(p-cymene)(H)Cl(Py)(PCy 3 )] 8 in solutionScheme 4. Lanthanum-catalyzed regioselective 1,2-hydroboration of N-heteroarenes.Scheme 5. Cerium-catalyzed regioselective 1,4-hydroboration of N-heteroarenes.

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Catalytic Electrophilic C−H Borylation Using NHC⋅Boranes and Iodine Forms C2‐, not C3‐, Borylated Indoles

Cited by 46 publications

References 44 publications

Metal-Free Catalytic Aromatic C–H Borylation

Metal-Free Catalytic Aromatic C–H Borylation

Metallomimetic Chemistry of Boron

Catalytic dearomative hydroboration of heteroaromatic compounds

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