Regiospecific Metalation of Oligobromobenzenes

Luliński, Sergiusz; Serwatowski, Janusz

doi:10.1021/jo0340511

Cited by 58 publications

(52 citation statements)

References 24 publications

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“…Ortho lithiation of 1,3-dibromobenzene by using the protocol of Servatovski et al and subsequent www.chemeurj.org quenching with DMF resulted in 1,6-dibromobenzaldehyde, [74] which was protected as an acetal [75] and treated with nBuLi, followed by quenching the lithiated intermediate with methyliodide to yield the desired deprotected 1-bromo-6-methylbenzaldehyde in nearly quantitative yield. The Suzuki coupling of the bromo-aldehyde with 3,5-dimethylphenylboronic acid [76] afforded 3,3',5'-trimethylbiphenylcarbaldehyde, which was converted into the respective carboxylic acid with H 2 O 2 /NaClO 2 by using the method of Dalcanale.…”

Section: Resultsmentioning

confidence: 99%

9‐Fluorenylphosphines for the Pd‐Catalyzed Sonogashira, Suzuki, and Buchwald–Hartwig Coupling Reactions in Organic Solvents and Water

Fleckenstein

Plenio

2007

Chemistry A European J

173

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The lithiation/alkylation of fluorene leads to various 9-alkyl-fluorenes (alkyl=Me, Et, iPr, -Pr, -C18H25) in>95% yields, for which lithiation and reaction with R2PCl (R=Cy, iPr, tBu) generates 9-alkyl, 9-PR2-fluorenes which constitute electron-rich and bulky phosphine ligands. The in-situ-formed palladium-phosphine complexes ([Na2PdCl4], phosphonium salt, base, substrates) were tested in the Sonogashira, Suzuki, and Buchwald-Hartwig reactions of aryl chlorides and aryl bromides in organic solvents. The Sonogashira coupling of aryl chlorides at 100-120 degrees C leads to>90% yields with 1 mol% of Pd catalyst. The Suzuki coupling of aryl chlorides typically requires 0.05 mol% of Pd catalyst at 100 degrees C in dioxane for quantitative product formation. To carry out "green" cross-coupling reactions in water, 9-ethylfluorenyldicyclohexylphosphine was reacted in sulphuric acid to generate the respective 2-sulfonated phosphonium salt. The Suzuki coupling of activated aryl chlorides by using this water-soluble catalyst requires only 0.01 mol% of Pd catalyst, while a wide range of aryl chlorides can be quantitatively converted into the respective coupling products by using 0.1-0.5 mol% of catalyst in pure water at 100 degrees C. Difficult substrate combinations, such as naphthylboronic acid or 3-pyridylboronic acid and aryl chlorides are coupled at 100 degrees C by using 0.1-0.5 mol% of catalyst in pure water to obtain the respective N-heterocycles in quantitative yields. The copper-free aqueous Sonogashira coupling of aryl bromides generates the respective tolane derivatives in>95% yield.

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Section: Resultsmentioning

confidence: 99%

9‐Fluorenylphosphines for the Pd‐Catalyzed Sonogashira, Suzuki, and Buchwald–Hartwig Coupling Reactions in Organic Solvents and Water

Fleckenstein

Plenio

2007

Chemistry A European J

173

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“…It should be noted that intermediate ortho-halogenated aryllithium compounds are thermally labile. On the other hand, at the safe temperature of -78°C, (2,6-dibromophenyl)lithium [12] reacted rapidly only with the least-hindered borate B(OMe) 3 . Similarly, (2-fluoro-6-iodophenyl)lithium reacted effectively with B(OiPr) 3 only at ca.…”

Section: Resultsmentioning

confidence: 99%

Tandem Synthesis of 9,10‐Dihydro‐9,10‐diboraanthracenes via Elusive ortho‐Lithiated Phenylboronates

et al. 2013

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A simple general protocol is reported for the synthesis of functionalised 9,10-dihydroxy-9,10-dihydro-9,10-diboraanthracenes by treatment of the appropriate substituted (2-halophenyl)boronates with tBuLi. The reaction apparently occurs through the formation of ortho-lithiated phenylboronates. These elusive species possess a trivalent Lewisacidic boron atom in the vicinity of a strongly nucleophilic lithiated carbon atom. The results of DFT calculations indicate that Br/Li exchange is kinetically favored over nucleophilic alkylation of the boron atom, which contrasts with the

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“…Column chromatography was carried out on a column packed with silica gel 60N (spherical neutral size 63-210 μm). 1 H and ( 1 H-decoupled) 13 C NMR spectra were recorded at 400 or 300 and 101 or 75 MHz, 1,2-Dibromo-3-methoxybenzene (2e) [22b] and 2,3-dibromo-1,4-bis-(trimethylsilyl)benzene (6b) [30] were synthesized as described in the literature.…”

Section: Methodsmentioning

confidence: 99%

Efficient and Complementary Methods Offering Access to Synthetically Valuable 1,2‐Dibromobenzenes

2010

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1,2‐Dibromobenzenes are highly valuable precursors for various organic transformations, in particular, reactions based on the intermediate formation of benzynes. This report describes short sequences for the synthesis of various derivatives based on regioselective bromination, ortho‐metalation, and halogen/metal permutations. 1,2‐Dibromo‐3‐iodobenzene (2f), 1,2‐dibromo‐4‐iodobenzene (4c), and 2,3‐dibromo‐1,4‐diiodobenzene (5e) act as intermediates in these syntheses.

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Regiospecific Metalation of Oligobromobenzenes

Cited by 58 publications

References 24 publications

9‐Fluorenylphosphines for the Pd‐Catalyzed Sonogashira, Suzuki, and Buchwald–Hartwig Coupling Reactions in Organic Solvents and Water

9‐Fluorenylphosphines for the Pd‐Catalyzed Sonogashira, Suzuki, and Buchwald–Hartwig Coupling Reactions in Organic Solvents and Water

Tandem Synthesis of 9,10‐Dihydro‐9,10‐diboraanthracenes via Elusive ortho‐Lithiated Phenylboronates

Efficient and Complementary Methods Offering Access to Synthetically Valuable 1,2‐Dibromobenzenes

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