- Palladium-catalyzed cross-coupling of benzyltitanium(IV) reagents with aryl fluorides
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The first palladium-catalyzed cross-coupling between benzyltitanium(IV) reagents with aryl fluorides is reported. A variety of diarylmethanes can be prepared in good to excellent yields by the catalyst system of PdCl2(dppf)2 associated with 1-[2-(di-tert-butylphosphanyl)phenyl]-4-methoxypiperidine. This reaction offered a highly efficient approach to diarylmethanes that are commonly found in life-changing drug molecules. Graphical abstract: [Figure not available: see fulltext.]
- Li, Yan
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- Acylation of 2-benzylpyridine N-oxides and subsequent in situ [3,3]-sigamatropic rearrangement reaction
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An effective method for the acylation of 2-benzylpyridine N-oxides and their fast in situ [3,3]-sigmatropic rearrangement was reported. This transformation has a wide substrate scope under mild conditions, giving moderate to excellent yields. The application for the synthesis of chiral phenyl-2-pyridylmethanol products was briefly explored. Furthermore, an interesting example of tandem substitution and in situ [3,3]-sigamatropic rearrangement of 2-benzylpyridine N-oxide with benzenecarboximidoyl chloride was reported.
- Antilla, Jon C.,Jing, Hua-qing,Li, Hong-liang
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- Ligand-Facilitated Reductive Coupling of Benzyl Chlorides with Aryl Chlorides Catalyzed by Well-Defined Heteroleptic Ni (II)-NHC Complexes
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Novel heteroleptic Ni (II) complexes bearing a highly hindered yet flexible IPr* ligand, Ni (IPr*)(PPh3)Br2 (1) and Ni (IPr*)(PCy3)Br2 (2) (IPr* = 1,3-bis(2,6-bis (diphenylmethyl)-4-methylphenyl)imidazol-2-ylidene), were easily prepared in 78percent and 89percent yield, respectively. Both were characterized by elemental analysis and NMR spectroscopy, and 1 was subjected to X-ray crystallography. Compared with 2 and its analogue bearing a less sterically demanding IPr ligand (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), complex 1 exhibited superior catalytic activity in the magnesium-mediated reductive coupling of benzyl chlorides with aryl chlorides, featuring outstanding tolerance of both coupling partners with steric demand. This study discloses a ligand-facilitated reductive coupling of benzyl chlorides with aryl chlorides, which provides a new and practical synthetic tool for the synthesis of diarylmethanes.
- Lu, Gusheng,Li, Ruipeng,Shen, Zhengwang,Wu, Qinjia,Sun, Hongmei
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- Ligand-Free Iridium-Catalyzed Dehydrogenative ortho C?H Borylation of Benzyl-2-Pyridines at Room Temperature
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A convenient and ligand-free iridium-catalyzed dehydrogenative ortho C?H borylation of benzyl-2-pyridines has been developed. The reaction proceeds smoothly at room temperature using pinacolborane as a borylating reagent in the presence of catalytic amount of [IrOMe(COD)]2. The reaction is compatible with many functional groups, providing a vast array of ortho borylated products in moderate to excellent yields with excellent selectivities. (Figure presented.).
- Yang, Yuhuan,Gao, Qian,Xu, Senmiao
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p. 858 - 862
(2019/01/04)
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- Metal-Free Halogen(I) Catalysts for the Oxidation of Aryl(heteroaryl)methanes to Ketones or Esters: Selectivity Control by Halogen Bonding
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Metal-free halogen(I) catalysts were used for the selective oxidation of aryl(heteroaryl)methanes [C(sp3)?H] to ketones [C(sp2)=O] or esters [C(sp3)?O]. The synthesis of ketones was performed with a catalytic amount of NBS in DMSO solvent. Experimental studies and density functional theory (DFT) calculations supported the formation of halogen bonding (XB) between the heteroarene and N-bromosuccinimide, which enabled imine–enamine tautomerism of the substrates. No additional activator was required for this crucial step. Isotope-labeling and other supporting experiments suggested that a Kornblum-type oxidation with DMSO and aerobic oxygenation with molecular oxygen took place simultaneously. A background XB-assisted electron transfer between the heteroarenes and halogen(I) catalysts was responsible for the formation of heterobenzylic radicals and, thus, the aerobic oxygenation. For selective acyloxylation (ester formation), a catalytic amount of iodine was employed with tert-butyl hydroperoxide in aliphatic carboxylic acid solvent. Several control reactions, spectroscopic studies, and Time-Dependent Density Functional Theory (TD–DFT) calculations established the presence of acetyl hypoiodite as an active halogen(I) species in the acetoxylation process. With the help of a selectivity study, for the first time we report that the strength of the XB interaction and the frontier orbital mixing between the substrates and acyl hypoiodites determined the extent of the background electron-transfer process and, thus, the selectivity of the reaction.
- Guha, Somraj,Sekar, Govindasamy
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supporting information
p. 14171 - 14182
(2018/09/10)
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- Copper-Catalyzed Base-Controlled Diastereoselective Synthesis of Tetraarylethanes from 2-Benzylpyridines
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A highly efficient and base-controlled diastereoselective synthesis of tetraarylethanes through copper-catalyzed dehydrogenative homocoupling of readily available 2-benzylpyridines is reported. Various dl - and meso -tetraarylethanes were diastereoseletively synthesized by this new protocol, where base plays the role of the principle modulator: Grignard reagents selectively provide the C2 isomers, whereas KO t -Bu promotes the formation of the meso -tetraarylethanes. Interestingly, the presence of excess KO t -Bu generates the (E)-tetraarylethenes as the only product.
- Chandrasekar, Selvaraj,Karthikeyan, Iyyanar,Sekar, Govindasamy
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p. 1275 - 1283
(2017/12/26)
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- Efficient Selenium-Catalyzed Selective C(sp3)?H Oxidation of Benzylpyridines with Molecular Oxygen
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An efficient selenium-catalyzed direct oxidation of benzylpyridines in aqueous DMSO has been successfully developed by using molecular oxygen as the oxidant. A variety of benzoylpyridines with broad functional group tolerance were obtained in modest to excellent yields and with exclusive chemoselectivity. (Figure presented.).
- Jin, Weiwei,Zheng, Poonnapa,Wong, Wing-Tak,Law, Ga-Lai
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p. 1588 - 1593
(2017/05/05)
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- Palladium-Catalyzed Arylation of Benzylic C-H Bonds of Azaarylmethanes with Aryl Sulfides
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Benzylic C-H arylation of azaarylmethanes with aryl sulfides has been developed by using a Pd-NHC catalyst and an amide base. Various azaarylmethanes and aryl sulfides were involved in the reaction to afford the corresponding diarylmethanes in good to excellent yields. Moreover, triarylmethane synthesis was accomplished through iterative arylations of 2- or 4-methylpyridine with two different aryl sulfides.
- Gao, Ke,Yamamoto, Keita,Nogi, Keisuke,Yorimitsu, Hideki
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supporting information
p. 2956 - 2960
(2017/10/06)
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- Triazole Ureas Act as Diacylglycerol Lipase Inhibitors and Prevent Fasting-Induced Refeeding
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Triazole ureas constitute a versatile class of irreversible inhibitors that target serine hydrolases in both cells and animal models. We have previously reported that triazole ureas can act as selective and CNS-active inhibitors for diacylglycerol lipases (DAGLs), enzymes responsible for the biosynthesis of 2-arachidonoylglycerol (2-AG) that activates cannabinoid CB1 receptor. Here, we report the enantio- and diastereoselective synthesis and structure-activity relationship studies. We found that 2,4-substituted triazole ureas with a biphenylmethanol group provided the most optimal scaffold. Introduction of a chiral ether substituent on the 5-position of the piperidine ring provided ultrapotent inhibitor 38 (DH376) with picomolar activity. Compound 38 temporarily reduces fasting-induced refeeding of mice, thereby emulating the effect of cannabinoid CB1-receptor inverse agonists. This was mirrored by 39 (DO34) but also by the negative control compound 40 (DO53) (which does not inhibit DAGL), which indicates the triazole ureas may affect the energy balance in mice through multiple molecular targets.
- Deng, Hui,Kooijman, Sander,Van Den Nieuwendijk, Adrianus M. C. H.,Ogasawara, Daisuke,Van der Wel, Tom,Van Dalen, Floris,Baggelaar, Marc P.,Janssen, Freek J.,Van Den Berg, Richard J. B. H. N.,Den Dulk, Hans,Cravatt, Benjamin F.,Overkleeft, Herman S.,Rensen, Patrick C. N.,Van der Stelt, Mario
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p. 428 - 440
(2017/04/26)
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- Versatile C(sp2)?C(sp3) Ligand Couplings of Sulfoxides for the Enantioselective Synthesis of Diarylalkanes
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The reaction of chiral (hetero)aryl benzyl sulfoxides with Grignard reagents affords enantiomerically pure diarylalkanes in up to 98 % yield and greater than 99.5 % enantiomeric excess. This ligand coupling reaction is tolerant to multiple substitution patterns and provides access to diverse areas of chemical space in three operationally simple steps from commercially available reagents. This strategy provides orthogonal access to electron-deficient heteroaromatic compounds, which are traditionally synthesized by transition metal catalyzed cross-couplings, and circumvents common issues associated with proto-demetalation and β-hydride elimination.
- Dean, William M.,?iau?iulis, Mindaugas,Storr, Thomas E.,Lewis, William,Stockman, Robert A.
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p. 10013 - 10016
(2016/08/16)
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- Nickel-Catalyzed Reductive Cross-Coupling of Benzyl Chlorides with Aryl Chlorides/Fluorides: A One-Pot Synthesis of Diarylmethanes
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The first nickel-catalyzed, magnesium-mediated reductive cross-coupling between benzyl chlorides and aryl chlorides or fluorides is reported. A variety of diarylmethanes can be prepared in good to excellent yields in a one-pot manner using easy-to-access mixed PPh3/NHC Ni(II) complexes of Ni(PPh3)(NHC)Br2 (NHC = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, IPr, 1a; 1,3-di-tert-butylimidazol-2-ylidene, ItBu, 1b) as catalyst precursors. Activation of polychloroarenes or chemoselective cross-coupling based on the difference in catalytic activity between 1a and 1b is used to construct oligo-diarylmethane motifs.
- Zhang, Jie,Lu, Gusheng,Xu, Jin,Sun, Hongmei,Shen, Qi
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supporting information
p. 2860 - 2863
(2016/07/06)
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- PBr3-mediated unexpected reductive deoxygenation of α-aryl-pyridinemethanols: Synthesis of arylmethylpyridines
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PBr3-mediated reductive deoxygenation of α-aryl-pyridinemethanols to provide arylmethylpyridines is described, the alcohol substrate scope is explored, free radical trap TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) is introduced, and the hydrogen source of the methylene product is defined. The unexpected reaction enabled us to prepare previously inaccessible, novel EP1 antagonists.
- Nishigaya, Yosuke,Umei, Kentaro,Watanabe, Daisuke,Kohno, Yasushi,Seto, Shigeki
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supporting information
p. 1566 - 1572
(2016/03/01)
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- N-heterocyclic carbene-palladium(II)-1-methylimidazole complex-catalyzed Suzuki-Miyaura coupling of benzyl sulfonates with arylboronic acids
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The first example of palladium-catalyzed Suzuki-Miyaura coupling between benzyl sulfonates and arylboronic acids was reported in this paper. In the presence of a well-defined, air-stable and easily available NHC-Pd(ii)-Im complex, all reactions worked well to give the desired products in good to almost quantitative yields under the optimal conditions. Electron-rich, -neutral, -poor and sterically-hindered substituents on both substrates are tolerated in such transformation, providing a convenient, efficient and alternative method for the synthesis of diarylmethanes.
- Wang, Xiao-Xia,Xu, Bin-Bin,Song, Wen-Ting,Sun, Kai-Xin,Lu, Jian-Mei
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p. 4925 - 4930
(2015/05/05)
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- Synergistic H4NI-AcOH Catalyzed Oxidation of the Csp3-H Bonds of Benzylpyridines with Molecular Oxygen
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The oxidation of benzylpyridines forming benzoylpyridines was achieved based on a synergistic H4NI-AcOH catalyst and molecular oxygen in high yield under solvent-free conditions. This is the first nonmetallic catalytic system for this oxidation transformation using molecular oxygen as the oxidant. The catalytic system has a wide scope of substrates and excellent chemoselectivity, and this procedure can also be scaled up. The study of a preliminary reaction mechanism demonstrated that the oxidation of the Csp3-H bonds of benzylpyridines was promoted by the pyridinium salts formed by AcOH and benzylpyridines. The synergistic effect of H4NI-AcOH was also demonstrated by control experiments. (Figure Presented).
- Ren, Lanhui,Wang, Lianyue,Lv, Ying,Li, Guosong,Gao, Shuang
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p. 2078 - 2081
(2015/05/13)
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- Synthesis of heteroaryl compounds through cross-coupling reaction of aryl bromides or benzyl halides with thienyl and pyridyl aluminum reagents
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An efficient method for synthesis of useful biaryl building blocks containing 2-thienyl, 3-thienyl, 2-pyridyl, and 3-pyridyl moieties was provided through cross-coupling reactions of aryl bromides or benzyl halides with heteroaryl aluminum reagents in the presence of Pd(OAc)2 and (o-tolyl)3P. The coupling reaction also worked efficiently with heteroaryl bromides affording series of heterobiaryl compounds. The reaction of phenylbromide with in situ prepared 3-pyridyl aluminum was demonstrated to afford the product 8a in high yield. Additionally, the catalytic system was also suited well for the coupling reaction of benzyl halides with pyridyl aluminum reagents to afford series of pyridyl-arylmethane.
- Chen, Xu,Zhou, Lingmin,Li, Yimei,Xie, Tao,Zhou, Shuangliu
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p. 230 - 239
(2014/01/17)
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- Synthesis of aryl(di)azinyl ketones through copper- and iron-catalyzed oxidation of the methylene group of aryl(di)azinylmethanes
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Sustainable Oxidations: An oxidation method to transform aryl(di)azinylmethanes into aryl(di)azinyl ketones is described. Base metals (copper and iron) as catalysts in combination with O2 as the oxidant are used, which makes this method sustainable. The utility of this method is illustrated by the synthesis of 6-(4-methylbenzoyl)pyridine-2-carbaldehyde, which is an intermediate in the preparation of the drug Acrivastine. Copyright
- De Houwer, Johan,Abbaspour Tehrani, Kourosch,Maes, Bert U. W.
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p. 2745 - 2748
(2012/04/10)
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- One-pot synthesis of symmetrical and unsymmetrical diarylmethanes via diborylmethane
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A one-pot synthesis of diarylmethanes from air-stable diborylmethane via the Suzuki-Miyaura cross-coupling reaction is described. The present approach realizes the synthesis of various symmetrical and unsymmetrical diarylmethanes in good to excellent yields.
- Endo, Kohei,Ishioka, Takafumi,Ohkubo, Takahiro,Shibata, Takanori
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p. 7223 - 7231
(2012/10/29)
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- Lewis acid promoted benzylic cross-couplings of pyridines with aryl bromides
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Either ZnCl2, Sc(OTf)3, or BF3OEt 2 can promote the palladium-catalyzed arylation of methylpyridines and related heterocycles (see example). The complexation of the Lewis acid to the nitrogen atom in the heteroc
- Duez, Stephanie,Steib, Andreas K.,Manolikakes, Sophia M.,Knochel, Paul
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supporting information; experimental part
p. 7686 - 7690
(2011/10/17)
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- Palladium-catalyzed decarboxylative couplings of 2-(2-Azaaryl)acetates with aryl halides and triflates
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Pd-catalyzed decarboxylative cross-couplings of 2-(2-azaaryl)acetates with aryl halides and triflates have been discovered. This reaction is potentially useful for the synthesis of some functionalized pyridines, quinolines, pyrazines, benzoxazoles, and benzothiazoles. Theoretical analysis shows that the nitrogen atom at the 2-position of the heteroaromatics directly coordinates to Pd(II) in the decarboxylation transition state.
- Shang, Rui,Yang, Zhi-Wei,Wang, Yan,Zhang, Song-Lin,Liu, Lei
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supporting information; experimental part
p. 14391 - 14393
(2010/12/19)
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- Palladium-catalyzed 2-pyridylmethyl transfer from 2-(2-pyridyl)-ethanol derivatives to organic halides by chelation-assisted cleavage of unstrained Csp3-Csp3 bonds
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(Chemical Equation Presented) Making a break for it: Treatment of 2-(2-pyridyl)ethanol derivatives with aryl chlorides in the presence of a palladium catalyst results in the transfer of the pyridylmethyl moiety of the alcohol to yield the corresponding (2-pyridyl-methyl)arene. The reaction proceeds by chelation-assisted cleavage of an Csp3-C5p3 bond (see scheme) followed by formation of a carbon-carbon bond.
- Niwa, Takashi,Yorimitsu, Hideki,Oshima, Koichiro
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p. 2643 - 2645
(2008/02/13)
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- Convenient, benign and scalable synthesis of 2- and 4-substituted benzylpiperidines
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A short, scalable and environmentally benign synthesis of 2- and 4-substituted benzylpiperidines has been developed. The method is based on the temperature-programmed consecutive deoxygenation and heteroaromatic ring saturation of aryl(pyridin-2-yl)- and aryl(pyridin-4-yl)methanols and aryl(pyridin-4-yl)methanones in the presence of Pd/C catalyst. The crucial roles of the temperature, the acidity and the substrate structure in the change of selectivity have been demonstrated by isolation of several substituted aryl(piperidine)methanols. The carbinols and ketones were prepared from commercially available pyridinecarbaldehydes or 4-cyanopyridine and substituted bromobenzenes via organometallic intermediates. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Agai, Bela,Proszenyak, Agnes,Tarkanyi, Gabor,Vida, Laszlo,Faigl, Ferenc
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p. 3623 - 3632
(2007/10/03)
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