- N-Heterocyclic Carbene Ligand-Controlled Chemodivergent Suzuki-Miyaura Cross Coupling
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Two N-heterocyclic carbene ligands provide orthogonal chemoselectivity during the Pd-catalyzed Suzuki-Miyaura (SM) cross-coupling of chloroaryl triflates. The use of SIPr [SIPr = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene] leads to selective cross-coupling at chloride, while the use of SIMes [SIMes = 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene] provides selective coupling at triflate. With most chloroaryl triflates and arylboronic acids, ligand-controlled selectivity is high (≥10:1). The scope of this methodology is significantly more general than previously reported methods for selective SM coupling of chloroaryl triflates using phosphine ligands. Density functional theory studies suggest that palladium's ligation state during oxidative addition is different with SIMes compared to SIPr.
- Reeves, Emily K.,Humke, Jenna N.,Neufeldt, Sharon R.
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p. 11799 - 11812
(2019/10/11)
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- Copper-Catalyzed Coupling of Triaryl- and Trialkylindium Reagents with Aryl Iodides and Bromides through Consecutive Transmetalations
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An efficient copper(I)-catalyzed coupling of triaryl and trialkylindium reagents with aryl iodides and bromides is reported. The reaction proceeds at low catalyst loadings (2 mol %) and generally only requires 0.33 equivalents of the triorganoindium reagent with respect to the aryl halide as all three organic nucleophilic moieties of the reagent are transferred to the products through consecutive transmetalations. The reaction tolerates a variety of functional groups and sterically hindered substrates. Furthermore, preliminary mechanistic studies that entailed the synthesis and characterization of potential reaction intermediates offered a glimpse of the elementary steps that constitute the catalytic cycle.
- Thapa, Surendra,Gurung, Santosh K.,Dickie, Diane A.,Giri, Ramesh
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supporting information
p. 11620 - 11624
(2016/02/19)
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- 3-ARYL-6-ARYL-[1,2,4]TRIAZOLO[4,3-a]PYRIDINES AS INHIBITORS OF CELL PROLIFERATION AND THE USE THEREOF
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Disclosed are 3-aryl-6-aryl-[1,2,4]triazolo[4,3-a]pyridines thereof, represented by the Formula (I) wherein Ar1, Ar2, R1-R3 are defined herein. Compounds having Formula (I) are inhibitors of cell proliferation.
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Page/Page column 34
(2012/06/01)
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- 3-ARYL-6-ARYL-[1,2,4]TRIAZOLO[4,3-a]PYRIDINES AS INHIBITORS OF CELL PROLIFERATION AND THE USE THEREOF
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Disclosed are 3-aryl-6-aryl-[1,2,4]triazolo[4,3-a]pyridines thereof, represented by the Formula (I) wherein Ar1, Ar2, R1-R3 are defined herein. Compounds having Formula (I) are inhibitors of cell proliferation.
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Page/Page column 34
(2012/06/01)
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- Preparation of polyfunctional arylmagnesium, arylzinc, and benzylic zinc reagents by using magnesium in the presence of LiCl
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The presence of LiCl considerably facilitates the insertion of magnesium into various aromatic and heterocyclic bromides. Several functional groups, such as -OBoc, -OTs, -Cl, -F, -CF3, -OMe, -NMe2, and -N 2NR2, are well tolerated. The presence of a cyano group leads in some cases to competitive reduction of the organic halide to the corresponding ArH compound. The presence of sensitive groups such as methyl or ethyl ester is tolerated upon in situ trapping of the intermediate magnesium reagent with ZnCl2. This method can also be applied to the preparation of functionalized benzylic zinc reagents from benzylic chlorides. In the case of di- or tribromoaryl derivatives, directing groups such as -OPiv, -OTs, -N2NR2, or -OAc orient the zinc insertion (Zn/LiCl) to the ortho-position, while the reaction with Mg/LiCl or Mg/LiCl/ZnCl 2 leads to regioselective insertion into the para-carbon-bromine bond. Large-scale experiments (20-100 mmol) for all of the metalation procedures are described.
- Piller, Fabian M.,Metzger, Albrecht,Schade, Matthias A.,Haag, Benjamin A.,Gavryushin, Andrei,Knochel, Paul
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supporting information; experimental part
p. 7192 - 7202
(2010/03/05)
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- The influence of different spacer lengths on the selectivity of self-assembly processes of bis(bipyridine)-BINOL helicates
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The synthesis and self-assembly behaviour of a series of en-antiomerically pure bis(chelating) ligands is reported. The li-gands differ in the spacer unit between a BINOL core and. two bipyridyl groups as the chelating entities and were found to undergo completely diastereoselective self-assembly to di-nuclear double-stranded helicates with silver(I) salts, as dem-onstrated by NMR and CD spectroscopy and ESI mass spec-trometry. Upon coordination to iron(II) or zinc(II) ions, however, a dramatic loss in the diastereoselectivity of the self-assembly of dinuclear triple-stranded helicates was observed, as a result: of increasing spacer length. In the case of zinc(II), the self-assembly processes were even found, to be nonselec-tive with regard to the composition of the helicates.
- Bunzen, Jens,Hapke, Marko,Luetzen, Arne
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scheme or table
p. 3885 - 3894
(2010/01/18)
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- Convenient preparation of polyfunctional aryl magnesium reagents by a direct magnesium insertion in the presence of LiCl
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(Chemical Equation Presented) In the footsteps of Victor Grignard: The simple LiCl-mediated insertion of magnesium into aryl chlorides and bromides at moderate temperatures leads to functionalized organomagnesium reagents (see scheme). An unprecedented range of functional groups may be present in the substrates (e.g. CN, CO2R, OTs, OBoc; Ts=p-toluenesulfonyl, Boc=tert-butylcarbonyloxy).
- Piller, Fabian M.,Appukkuttan, Prasad,Gavryushin, Andrei,Helm, Matthew,Knochel, Paul
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supporting information; experimental part
p. 6802 - 6806
(2009/04/06)
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- Synthesis of Differently Disubstituted 2,2′-Bipyridines by a Modified Negishi Cross-Coupling Reaction
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A general practical approach to a number of differently disubstituted 2,2′-bipyridines from substituted 2-bromo- and 2-chloropyridines by application of modified Negishi cross-coupling conditions has been developed. These 2,2′-bipyridines carry versatile functional groups that can be elaborated further, as demonstrated for some examples. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Luetzen, Arne,Hapke, Marko,Staats, Holger,Bunzen, Jens
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p. 3948 - 3957
(2007/10/03)
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- Synthesis of multifunctional ligands: A 2,9-diaryl-1,10-phenanthroline/2,2′:6′,2″-terpyridine conjugate
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The synthesis of a ligand including a 1,10-phenanthroline and a 2,2′:6′,2″-terpyridine separated by a 1,3-phenylene spacer is presented. The different aromatic carbon-carbon bonds have been generated by reactions with organolithium compounds, and by Stille and Suzuki couplings.
- Belfrekh, Nicolas,Dietrich-Buchecker, Christiane,Sauvage, Jean-Pierre
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p. 2779 - 2781
(2007/10/03)
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- Substituted 6-phenyl-1,2,4-triazolo[4,3-a]pyridines
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This disclosure describes novel 6-(substituted-phenyl)-1,2,4-triazolo[4,3-a]pyridines useful as hypotensive agents.
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- Substituted 3-alkyl-6-phenyl-1,2,4-triazolo-[4,3-a]pyridines
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This disclosure describes novel 3-alkyl-6-(substituted-phenyl)-1,2,4-triazolo[4,3-a]pyridines useful as anxiolytic agents.
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