Main Group Catalyzed Arene Borylation: Challenges and Opportunities

Ingleson, Michael J.

doi:10.1021/acscatal.3c01668

Cited by 8 publications

(3 citation statements)

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“…Non-catalytic C–H borylation facilitated by directing groups is also an important addition to the synthetic toolkit. 7 16…”

Section: C–h Borylation Via Boron-based Catalystsmentioning

confidence: 99%

“…It will examine the underlying mechanisms by which main group systems can cleave C–H bonds and focus on two approaches using boron- and phosphorus-based systems. 7 A discussion will also draw an analogy between the concerted metalation–deprotonation-type mechanism for C–H bond cleavage in late-transition-metal-catalyzed reactions and those involving main group elements.…”

Section: Introductionmentioning

confidence: 99%

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Towards Catalytic C–H Activation Using Main Group Elements

McNally

2024

Synlett

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Catalytic C–H activation reactions are now established as a means to directly transform organic molecules and are commonly associated with metals such as palladium, rhodium, ruthenium and iridium. This Account will describe a short number of reports demonstrating that structures containing main group elements can facilitate C–H activation processes. In particular, boron-based catalysts can promote catalytic arene C–H borylation reaction, and an emerging approach using phosphenium ions can also cleave sp2 C–H bonds. These processes use a Lewis acidic main group atom combined with a pendant base to cleave C–H bonds, which compares with metal-catalyzed reactions that proceed via concerted metalation deprotonation mechanisms.

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“…Non-catalytic C–H borylation facilitated by directing groups is also an important addition to the synthetic toolkit. 7 16…”

Section: C–h Borylation Via Boron-based Catalystsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Towards Catalytic C–H Activation Using Main Group Elements

McNally

2024

Synlett

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“…Thus, remote C–H functionalization methods for the selective formation of one constitutional isomer are transformative. Site-selective C(sp 2 )–H borylation represents one of the most impactful C–H functionalization methods in organic synthesis because the C–B bond installed is readily and selectively transformed to a variety of other substituents using robust and well-established chemistry ( 3 – 7 ).…”

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confidence: 99%

Kinetic and thermodynamic control of C(sp ² )–H activation enables site-selective borylation

Roque,

Shimozono,

Pabst

et al. 2023

Science

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Catalysts that distinguish between electronically distinct carbon-hydrogen (C–H) bonds without relying on steric effects or directing groups are challenging to design. In this work, cobalt precatalysts supported by N -alkyl-imidazole–substituted pyridine dicarbene (ACNC) pincer ligands are described that enable undirected, remote borylation of fluoroaromatics and expansion of scope to include electron-rich arenes, pyridines, and tri- and difluoromethoxylated arenes, thereby addressing one of the major limitations of first-row transition metal C–H functionalization catalysts. Mechanistic studies established a kinetic preference for C–H bond activation at the meta -position despite cobalt-aryl complexes resulting from ortho C–H activation being thermodynamically preferred. Switchable site selectivity in C–H borylation as a function of the boron reagent was thereby preliminarily demonstrated using a single precatalyst.

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Transition Metal‐Free Catalytic C−H Zincation and Alumination

Kumar Bisai,

Łosiewicz,

Sotorrios

et al. 2024

Angewandte Chemie

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C−H metalation is the most efficient method to prepare aryl–zinc and –aluminium complexes that are ubiquitous nucleophiles. Virtually all C–H metalation routes to form Al/Zn organometallics require stoichiometric, strong Brønsted bases with no base‐catalyzed reactions reported. Herein we present a catalytic in amine/ammonium salt (Et3N/[(Et3N)H]+) C–H metalation process to form aryl‐zinc and aryl‐aluminium complexes. Key to this approach is coupling an endergonic C–H metalation step with a sufficiently exergonic dehydrocoupling step between the ammonium salt by‐product of C–H metalation ([(Et3N)H]+) and a Zn–H or Al–Me containing complex. This step, forming H2/MeH, makes the overall cycle exergonic while generating more of the reactive metal electrophile. Mechanistic studies supported by DFT calculations revealed metal‐specific dehydrocoupling pathways, with the divergent reactivity due to the different metal valency (which impacts the accessibility of amine‐free cationic metal complexes) and steric environment. Notably, dehydrocoupling in the zinc system proceeds through a ligand‐mediated pathway involving protonation of the b‐diketiminate Cg position. Given this process is applicable to two disparate metals (Zn and Al), other main group metals and ligand sets are expected to be amenable to this transition metal‐free, catalytic C−H metalation.

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Main Group Catalyzed Arene Borylation: Challenges and Opportunities

Cited by 8 publications

References 50 publications

Towards Catalytic C–H Activation Using Main Group Elements

Towards Catalytic C–H Activation Using Main Group Elements

Kinetic and thermodynamic control of C(sp ² )–H activation enables site-selective borylation

Transition Metal‐Free Catalytic C−H Zincation and Alumination

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Main Group Catalyzed Arene Borylation: Challenges and Opportunities

Cited by 8 publications

References 50 publications

Towards Catalytic C–H Activation Using Main Group Elements

Towards Catalytic C–H Activation Using Main Group Elements

Kinetic and thermodynamic control of C(sp 2 )–H activation enables site-selective borylation

Transition Metal‐Free Catalytic C−H Zincation and Alumination

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Product

Resources

About

Kinetic and thermodynamic control of C(sp ² )–H activation enables site-selective borylation