- Palladium-Catalyzed Methylation of Aryl, Heteroaryl, and Vinyl Boronate Esters
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A method for the direct methylation of aryl, heteroaryl, and vinyl boronate esters is reported, involving the reaction of iodomethane with aryl-, heteroaryl-, and vinylboronate esters catalyzed by palladium and PtBu2Me. This transformation occurs with a remarkably broad scope and is suitable for late-stage derivatization of biologically active compounds via the boronate esters. The unique capabilities of this method are demonstrated by combining carbon-boron bond-forming reactions with palladium-catalyzed methylation in a tandem transformation.
- Haydl, Alexander M.,Hartwig, John F.
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supporting information
p. 1337 - 1341
(2019/02/26)
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- Trimethylphosphate as a Methylating Agent for Cross Coupling: A Slow-Release Mechanism for the Methylation of Arylboronic Esters
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A methyl group on an arene, despite its small size, can have a profound influence on biologically active molecules. Typical methods to form a methylarene involve strong nucleophiles or strong and often toxic electrophiles. We report a strategy for a new, highly efficient, copper and iodide co-catalyzed methylation of aryl- and heteroarylboronic esters with the mild, nontoxic reagent trimethylphosphate, which has not been used previously in coupling reactions. We show that it reacts in all cases tested in yields that are higher than those of analogous copper-catalyzed reactions of MeOTs or MeI. The combination of C-H borylation and this methylation with trimethylphosphate provides a new approach to the functionalization of inert C-H bonds and is illustrated by late-stage methylation of four medicinally active compounds. In addition, reaction on a 200 mmol scale demonstrates reliability of this method. Mechanistic studies show that the reaction occurs by a slow release of methyl iodide by reaction of PO(OMe)3 with iodide catalyst, rather than the typical direct oxidative addition to a metal center. The low concentration of the reactive electrophile enables selective reaction with an arylcopper intermediate, rather than nucleophilic groups on the arylboronate, and binding of tert-butoxide to the boronate inhibits reaction of the electrophile with the tert-butoxide activator to form methyl ether.
- He, Zhi-Tao,Li, Haoquan,Haydl, Alexander M.,Whiteker, Gregory T.,Hartwig, John F.
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supporting information
p. 17197 - 17202
(2018/12/14)
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- A One-Pot Synthesis of Dibenzofurans from 6-Diazo-2-cyclohexenones
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A novel and efficient protocol for the rapid construction of dibenzofuran motifs from 6-diazo-2-cyclohexenone and ortho-haloiodobenzene has been developed. The process involves one-pot Pd-catalyzed cross-coupling/aromatization and Cu-catalyzed Ullmann coupling.
- Zhao, Hua,Yang, Ke,Zheng, Hongyan,Ding, Ruichao,Yin, Fangjie,Wang, Ning,Li, Yun,Cheng, Bin,Wang, Huifei,Zhai, Hongbin
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supporting information
p. 5744 - 5747
(2015/12/11)
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- Palladium-catalyzed intra-and intermolecular C-H arylation using mesylates: Synthetic scope and mechanistic studies
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This paper describes the development of Pd-catalyzed inter-and intramolecular direct arylation using mesylates. Furthermore, a sequential mesylation/arylation protocol using phenols as substrates is described. These transformations are general with respect to the electronics of the C-H substrates and allow for the synthesis of diverse heterocyclic motifs in good yields. Both arenes and heteroarenes efficiently participate in these reactions. Preliminary mechanistic studies are presented for both inter-and intramolecular arylations.
- Ferguson, Devin M.,Rudolph, Stacey R.,Kalyani, Dipannita
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p. 2395 - 2401
(2014/07/21)
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- Rhodium-catalyzed decarbonylative C-H arylation of 2-aryloxybenzoic acids leading to dibenzofuran derivatives
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Rhodium-catalyzed intramolecular C-H arylation of 2-aryloxybenzoic acids proceeded accompanied by decarbonylation to give dibenzofuran derivatives in high yields. The present reaction is widely applicable to substrates bearing various functionalities.
- Maetani, Shinji,Fukuyama, Takahide,Ryu, Ilhyong
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supporting information
p. 2754 - 2757
(2013/07/19)
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- Efficient synthesis of dibenzoxaborininols from diaryl ethers and their application to dibenzofuran synthesis
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A convenient and efficient method for the borylation of diaryl ethers leading to dibenzoxaborininols and the synthesis of dibenzofuran derivatives has been developed. The borylation involves the sequential three-step process: lithiation, borylation and hydrolysis. The synthesized dibenzoxaborininols could be readily transformed into dibenzofuran derivatives in good to excellent yields under palladium catalysis in the presence of iodine, and this is the first example for the formation of an aryl C-C bond from diarylborinic acids. Copyright
- Niu, Liting,Yang, Haijun,Jiang, Yuyang,Fu, Hua
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p. 3625 - 3632
(2014/01/06)
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- Nickel-catalyzed intramolecular C-H arylation using aryl pivalates as electrophiles
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This paper describes a method for nickel catalyzed intramolecular C-H arylation using aryl pivalates as electrophiles. The transformation is efficient for the synthesis of diverse electronically and sterically differentiated dibenzofurans. Additionally, the method could be expanded toward the synthesis of carbazoles. Preliminary mechanistic studies of the transformation are also described.
- Wang, Jiayi,Ferguson, Devin M.,Kalyani, Dipannita
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p. 5780 - 5790
(2013/07/19)
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- Competitive pathways in Pd-catalyzed synthesis of arylphenols
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Novel developments are described, which have been achieved in the framework of the studies of sequential palladium-catalyzed reactions, involving palladacycle formation with norbornene or norbornadiene via aromatic C-H activation. The use of o-bromophenols as partners of iodobenzenes has led to ring formation after norbornene deinsertion, or to arylphenols, containing a pendant norbornenyl or norbornadienyl group or to vinylarylphenols. The availability of a reductive elimination step drives the reaction course toward a preferential product.
- Motti, Elena,Della Ca, Nicola,Xu, Di,Armani, Simone,Aresta, Brunella Maria,Catellani, Marta
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p. 4421 - 4428
(2013/06/27)
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- Novel heteroleptic iridium complexes
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Novel phosphorescent heteroleptic iridium complexes with phenylpyridine and dibenzo-containing ligands are provided. The disclosed compounds have low sublimation temperatures that allow for ease of purification and fabrication into a variety of OLED devices.
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Paragraph 0106
(2013/06/05)
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- HETEROLEPTIC IRIDIUM COMPLEX
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Novel phosphorescent heteroleptic iridium complexes with phenylpyridine and dibenzo-containing ligands are provided. The disclosed compounds have low sublimation temperatures that allow for ease of purification and fabrication into a variety of OLED devices.
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Page/Page column
(2013/05/22)
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- Nickel-catalyzed hydrogenolysis of unactivated carbon-cyano bonds
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Selective hydrogenolysis of C-CN bonds can allow chemists to take advantage of ortho-directing ability, α-C-H acidity and electron withdrawing ability of the cyano group for synthetic manipulations. We have discovered hydrogenolysis of aryl and aliphatic cyanides under just 1 bar of hydrogen by using a nickel catalyst. This protocol was applied in the aryl cyanide directed functionalization reaction and α-substitution of benzyl cyanides.
- Patra, Tuhin,Agasti, Soumitra,Modak, Atanu,Maiti, Debabrata
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supporting information
p. 8362 - 8364
(2013/09/23)
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- Palladium-catalyzed intramolecular C-H arylation of arenes using tosylates and mesylates as electrophiles
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This paper describes a method for the palladium catalyzed intramolecular C-H arylation using tosylates and mesylates as electrophiles. The transformation is efficient for the synthesis of various heterocyclic motifs including furans, carbazoles, indoles, and lactams. Additionally, a protocol for the one-pot sequential tosylation/arylation of phenol derivatives is presented.
- Nervig, Christine S.,Waller, Peter J.,Kalyani, Dipannita
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p. 4838 - 4841,4
(2020/09/16)
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- Synthesis of dibenzofurans by palladium-catalysed tandem denitrification/C-H activation
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A palladium-catalysed method for intramolecular cyclisation of ortho-diazonium salts of diaryl ethers to give dibenzofurans is described. The protocol uses 3 mol% palladium acetate as the catalyst in refluxing ethanol in the absence of base. Georg Thieme Verlag Stuttgart · New York.
- Du, Zhenting,Zhou, Jing,Si, Changmei,Ma, Weili
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scheme or table
p. 3023 - 3025
(2012/01/05)
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- Formation of dibenzofurans by flash vacuum pyrolysis of aryl 2-(allyloxy)benzoates and related reactions
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Flash vacuum pyrolysis (FVP) of aryl 2-(allyloxy)benzoates 5 and of the corresponding aryl 2-(allylthio)benzoates 6 at 650°C, gives dibenzofurans 19 and dibenzothiophenes 20, respectively. The mechanism involves generation of phenoxyl (or thiophenoxyl) radicals by homolysis of the O-allyl (or S-allyl) bond, followed by ipso attack at the ester group, loss of CO2 and cyclisation of the resulting aryl radical. Synthetically, the procedure works well for p-substituted substrates, which lead to 2-substituted dibenzofurans 19b-f (73-90%) and dibenzothiophenes 20b-c (90-94%). Little selectivity is shown in the cyclisation of m-substituted substrates and competing interactions of the radical with the substituent - and ipso-attack - complicate the pyrolyses of o-substituted substrates. FVP of related radical precursors including 2-(allyloxy)phenyl benzoates 43 gave no dibenzofurans, whereas 2-(allyloxy-5-methyl)azobenzene 44 gave a much reduced yield. No carbazoles were obtained by FVP of 4-methylphenyl 2-(allylamino)benzoate 42.
- Black, Michael,Cadogan,McNab, Hamish
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experimental part
p. 2961 - 2967
(2010/09/06)
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- Heterocyclic compounds
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The present invention relates to heterocyclic compounds which have been found to have anti-tumour activity. More specifically, the invention concerns Pyrrolo ?3,2-b! carbazoles, 1H-Benzofuro ?3,2-f! indoles and 1H-?1! Benzothieno ?2,3-f! indoles, methods for their preparation, pharmaceutical formulations containing them and their use as anti-tumour agents.
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- Gas phase generation and cyclisation reactions of some o-substituted phenyl radicals
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Flash vacuum pyrolysis of the allyl esters 2 (X=O, S, CH2, CO) at 900°C (10-2 Torr) gives dibenzofurans, dibenzothiophenes, fluorenes, and fluorenones respectively as the major products. The mechanism involves the phenyl radical intermediates 1 which equilibrate by intramolecular hydrogen transfer via six-membered transition states, prior to cyclisation.
- Cadogan,Hutchison,McNab
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p. 7747 - 7762
(2007/10/02)
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- A Short Synthesis of Dibenzofurans and Dibenzothiophenes
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An afficient synthesis of dibenzofurans and dibenzothiophenes from aryl salicylates is described, which involves a novel rearrangement-extrusion-cyclisation sequence of o-substituted phenoxyl and thiophenoxyl radicals.
- Black, Michael,Cadogan, J. I. G.,McNab, Hamish
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p. 395 - 396
(2007/10/02)
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