Stoichiometric and Catalytic B−C Bond Formation from Unactivated Hydrocarbons and Boranes

Iverson, Carl N.; Smith, Milton R.

doi:10.1021/ja991258w

Cited by 353 publications

(155 citation statements)

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“…26 Recognizing that this transformation's simplicity could offer advantages over traditional routes to arylboron compounds, we explored the generality of this reaction with arenes, including the first extensions to heterocyclic substrates. [27][28][29] Despite improvements in catalyst generation, 28,30 application of this methodology to substituted thiophenes is limited to five substrates: 2-methylthiophene, [31][32][33] 2-cyanothiophene, 32 2-bromothiophene, 32 2-methoxythiophene, 33 and 2-trifluoromethylthiophene.…”

Section: Resultsmentioning

confidence: 99%

Iridium-catalyzed borylation of thiophenes: versatile, synthetic elaboration founded on selective C–H functionalization

et al. 2008

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Iridium-catalyzed borylation has been applied to various substituted thiophenes to synthesize polyfunctionalized thiophenes in good to excellent yields. Apart from common functionalities compatible with iridium-catalyzed borylations, additional functional group tolerance to acyl (COMe), and trimethylsilyl (TMS) groups was also observed. High regioselectivities were observed in borylation of 3-and 2,5-di-substituted thiophenes. Electrophilic aromatic C-H/C-Si bromination on thiophene boronate esters is shown to take place without breaking the C-B bond, and one-pot C-H borylation/Suzuki-Miyaura cross-coupling has been accomplished on 2-and 3-borylated thiophenes.

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Section: Resultsmentioning

confidence: 99%

Iridium-catalyzed borylation of thiophenes: versatile, synthetic elaboration founded on selective C–H functionalization

et al. 2008

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“…The metal-mediated stoichiometric and catalytic borylation of alkanes and arenes had far-reaching implications for synthetic chemistry [30][31][32][33][34][35][36] . The final steps of this reaction include B-C bond formation on the metal centre and ejection of the formed organoborane molecule.…”

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Unsupported boron–carbon σ-coordination to platinum as an isolable snapshot of σ-bond activation

et al. 2012

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σ-Complexes of transition metals-key intermediates in metal-mediated bond activation and homogeneous catalysis-have traditionally been isolable only when chelating or when one of the participating atoms is hydrogen. Here, by treating the Lewis-basic transition metal complex [Pt(PEt 3 ) 4 ] with an electron-poor borirene, we isolate a complex with an unsupported borirene ligand bound, not through the unsaturated C = C bond, but exclusively via a B-C single bond. using nmR spectroscopy, X-ray crystallography and density functional theory calculations, we show, herein, that coordination of the borirene ligand is based on electron donation from the B-C σ bond to the metal, aided by a strong Pt-to-B dative interaction. The complex is the first isolable non-agostic σ-complex featuring two p-block elements and has broad implications as a model for the metal-mediated activation of strong p-block-p-block σ-bonds.

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“…[5][6][7][8][9][10][11] Most of these studies have been conducted with excess of substrate, and the resulting methods have required the use of pin 2 B 2 instead of pinBH to obtain high yields. No reactions of a 1:1 ratio of substrate and the readily accessible and inexpensive pinBH, instead of the expensive pin 2 B 2 , have been reported.…”

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Room Temperature Borylation of Arenes and Heteroarenes Using Stoichiometric Amounts of Pinacolborane Catalyzed by Iridium Complexes in an Inert Solvent.

et al. 2004

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Aromatic C-H borylation of arenes and heteroarenes by stoichiometric amounts of pinacolborane was catalyzed by an iridium complex generated from 1/2[Ir(OMe)(COD)] 2 and 4,4'-di-tert-butyl-2,2'-bipyridine at room temperature in hexane and afforded the corresponding aryl-and heteroarylboronates in high yields with excellent regioselectivities.Aryl-and heteroarylboron derivatives have been applied to various fields of chemistry.1 Traditional methods for their synthesis are based on the reactions of trialkylborates with arylmagnesium or -lithium reagents derived from haloarenes, which are most common and convenient for large-scale preparations. Previous work has demonstrated the reaction of arenes and heteroarenes with bis(pinacolato)diboron (pin 2 B 2 , pin = Me 4 C 2 O 2 ) or pinacolborane (pinBH) in the presence of various transition metal complexes to form arylboronates. [5][6][7][8][9][10][11] Most of these studies have been conducted with excess of substrate, and the resulting methods have required the use of pin 2 B 2 instead of pinBH to obtain high yields. No reactions of a 1:1 ratio of substrate and the readily accessible and inexpensive pinBH, instead of the expensive pin 2 B 2 , have been reported. We disclose the culmination of several steps toward the development of such an aromatic C-H borylation process. With modest loadings of 1/2[Ir(OMe)(COD)] 2 (COD = 1,5-cyclooctadiene) and 4,4'-ditert-butyl-2,2'-bipyridine (dtbpy), the reaction of pinBH with many arenes and heteroarenes in a 1:1 ratio occurs in an inert solvent at room temperature (Scheme 1). To achieve the borylation of arenes and heteroarenes at room temperature with equimolar amounts of pinBH and substrate, several combinations of Ir(I) precursors (0.03 mmol of Ir) and ligands (0.03 mmol) were investigated as catalysts for the reaction of pinBH (1.1 mmol) with 1,3-dichlorobenzene (1.0 mmol) in hexane (6 mL) at 25 °C for 8 h. Of the precursors and ligands examined, the combination of 1/2[Ir(OMe)(COD)] 2 and dtbpy 12 efficiently catalyzed the borylation to form isomerically pure 5-boryl-1,3-dichlorobenzene in 86% yield.The choice of catalyst precursor was crucial to observe room temperature reactions. Although the combination of 1/2[Ir(OAc)(COD)] 2 and dtbpy produced the borylated product in 42% yield after 8 h, the combination of dtbpy and either 1/2[IrCl(COD)] 2 or [Ir(COD) 2 ]BF 4 formed no borylated product.The effects of steric and electronic properties of bipyridine ligands were evaluated with 1/2[Ir(OMe)(COD)] 2 as a catalyst precursor. Catalysts bearing 2,2'-bipyridine (bpy), 4,4'-di-Mebpy, and 5,5'-di-Me-bpy displayed moderate or good reactivity, but catalysts bearing 3,3'-di-Me-bpy or 6,6'-di-Me-bpy displayed little activity. These results indicated the importance of a parallel arrangement of two pyridine rings and a relatively unhindered coordination sphere at iridium. Reactions catalyzed by complexes containing electron-rich derivatives of bpy generated more active catalysts than those containing electronpoor derivatives. Catalysts c...

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Stoichiometric and Catalytic B−C Bond Formation from Unactivated Hydrocarbons and Boranes

Cited by 353 publications

References 22 publications

Iridium-catalyzed borylation of thiophenes: versatile, synthetic elaboration founded on selective C–H functionalization

Iridium-catalyzed borylation of thiophenes: versatile, synthetic elaboration founded on selective C–H functionalization

Unsupported boron–carbon σ-coordination to platinum as an isolable snapshot of σ-bond activation

Room Temperature Borylation of Arenes and Heteroarenes Using Stoichiometric Amounts of Pinacolborane Catalyzed by Iridium Complexes in an Inert Solvent.

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