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• 4466-24-4 2-Butylfuran 
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• 623-00-7 4-bromobenzenecarbonitrile 

Relevant academic research and scientific papers

Exploring Green Solvents Associated to Pd/C as Heterogeneous Catalyst for Direct Arylation of Heteroaromatics with Aryl Bromides

Metal residues are certainly one of the major sources of contamination of products in metal-catalyzed direct arylation reactions. We found that the use of only 1 mol% of the heterogeneous catalyst Pd/C promotes very efficiently the direct arylations of most heteroaromatics. In the presence of this catalyst and potassium acetate as the base, the direct arylation of thiophenes, furans, pyrroles, thiazoles, imidazoles or isoxazoles, using aryl bromides as coupling partners, proceeds highly regioselectively and in moderate to very high yields. With several heteroarenes both electron-deficient and electron-rich aryl bromides were tolerated; moreover, with the most reactive heteroarenes, the Pd/C catalyst tolerated green solvents such as diethyl carbonate, 3-methylbutan-1-ol and pentan-1-ol, affording a synthetic scheme with low environmental impact. (Figure presented.).

Functionalized tri- and tetraphosphine ligands as a general approach for controlled implantation of phosphorus donors with a high local density in immobilized molecular catalysts

Supported phosphine ligands are auxiliaries of topical academic and industrial interest in catalysis promoted by transition metals. However, both controlled implantation and controlled conformation of ligands should be achieved to produce immobilized catalysts that are able to structurally "copy" efficient homogeneous systems. We provide herein a general synthetic strategy for assembling a new class of branched tetraand triphosphine ligands with a unique controlled rigid conformation, and thus providing a high local density of phosphorus atoms for extended coordination to the metal center. We prepared new functionalized cyclopentadienyl (Cp) salts to design polyphosphines that were "ready for immobilization". These protected Cp fragments might also be of synthetic utility for generating other supported metallocenes. Tetra- and triphosphines were then formed and diversely functionalized for immobilization on virtually any kind of support. As evidenced by 31P NMR spectroscopy and the strong "through-space" spin- spin TSJ(P,P) coupling observed between P atoms, these modified polyphosphines induce, when immobilized on a support, a high local concentration of phosphorus donors that are spatially very close to each other (3-5 A?). These functionalized ligands have been incorporated into polystyrene to give either soluble or insoluble polymers and on inorganic supports such as silica. We report the catalytic performance at 0.05-0.5 mol% low palladium loading of the resulting immobilized polyphosphine ligands. This study provides proof-of-concept of supported catalytic materials built from modular polyphosphines with a novel approach to structurally controlled polydentate heterogeneous catalysts.

Modular functionalized polyphosphines for supported materials: Previously unobserved 31P-NMR through-space ABCD spin systems and heterogeneous palladium-catalysed C-C and C-H arylation

The modular design of polyphosphines, diversely functionalized for facile immobilization on virtually any kind of support, is reported. Previously unobserved ABCD 31P NMR spin-spin systems evidence the control exercised on the polyphosphines co

Solvent-free palladium-catalyzed direct arylation of heteroaromatics with aryl bromides

Solvent is one of the major sources of waste in the course of catalyzed direct arylations. Some palladium-catalyzed direct arylations of heteroaromatics can be advantageously performed without any solvent. In the presence of palladium catalysts (1 mol%) and potassium acetate as the base, the direct 5-arylation of some thiazoles, thiophenes, furans, or pyrroles with aryl bromides as coupling partners proceeds highly regioselectively and in moderate to high yields. However, the use of these solvent-free conditions is limited to electron-deficient aryl bromides. Copyright

Cyclopentyl methyl ether: An alternative solvent for palladium-catalyzed direct arylation of heteroaromatics

Some ethers, such as cyclopentyl methyl ether and di-n-butyl ether, which can be considered as "greener" solvents than N,N-dimethylacetamide (DMAc) or DMF, can be advantageously employed for the palladium-catalyzed direct arylation of heteroaromatics. In the presence of such ethers and only 0.5-1 mol% of palladium catalysts at 125-150°C, the direct 5-arylation of thiazoles, thiophenes, or furans by using aryl bromides as coupling partners proceeds in moderate to high yields.

Congested ferrocenyl polyphosphanes bearing electron-donating or electron-withdrawing phosphanyl groups: Assessment of metallocene conformation from NMR spin couplings and use in palladium-catalyzed chloroarenes activation

The synthesis of novel substituted cyclopentadienyl salts that incorporate both a congested branched alkyl group (tert-butyl, (triphenyl)methyl, or tri(4-tert-butyl)phenylmethyl) and a phosphanyl group is reported. The introduction of either electron-withdrawing or electron-donating substituents (furyl, i-propyl, cyclohexyl, tert-butyl) on P atoms was generally achieved in high yield. The modular synthesis of ferrocenyl polyphosphanes from an assembly of these cyclopentadienyl salts was investigated, leading to the formation of new triphosphanes (denoted as 9-12) and diphosphanes (denoted as 14-16). The resulting phosphanes are not sensitive to air or moisture, even when electron-rich substituents are present. This set of polyphosphanes displays varied conformational features, which are discussed in the light of their multinuclear NMR characterization in solution and of the X-ray solid state structure of the representative triphosphane 1,2-bis(diphenylphosphanyl)- 1′-(diisopropylphosphanyl)-3′-(triphenyl)methyl-4-tert-butyl ferrocene, 11. In particular, the existence of a range of significantly different nonbonded ("through-space", TS) spin-spin coupling constants between heteroannular P atoms, for the triphosphanes of this class, allowed their preferred conformation in solution to be appraised. The study evidences an unanticipated flexibility of the ferrocene platform, despite the presence of very congested tert-butyl and trityl groups. Herein, we show that, contrary to our first belief, the preferred conformation for the backbone of ferrocenyl polyphosphanes can not only depend on the hindrance of the groups decorating the cyclopentadienyl rings but is also a function of the substituents of the phosphanyl groups. The interest of these robust phosphanes as ligands was illustrated in palladium catalysis for the arylation of n-butyl furan with chloroarenes, using direct C-H activation of the heteroaromatic in the presence of low metal/ligand loadings (0.5-1.0 mol %). Thus, 4-chlorobenzonitrile, 4-chloronitrobenzene, 4-chloropropiophenone, and 4-(trifluoromethyl) chlorobenzene were efficiently coupled to n-butyl furan, using Pd(OAc) 2 associated to the new diphosphane ligands 1,1′- bis(diisopropylphosphanyl)-3,3′-di(triphenyl)methyl ferrocene (15) or 1,1′-bis(dicyclohexylphosphanyl)-3,3′-di(triphenyl)methylferrocene (16), which respectively hold the electron-rich -Pi-Pr2 and -PCy 2 groups.

Carbonates: Eco-friendly solvents for palladium-catalysed direct arylation of heteroaromatics

The palladium-catalysed direct 2-, 4- or 5-arylation of a wide range of heteroaromatics with aryl halides proceed in moderate to good yields using the eco-friendly solvents carbonates. The best yields were obtained using benzoxazole or thiazole derivatives. The arylation of furan, thiophene, pyrrole, imidazole or isoxazole derivatives was found to require a more elevated reaction temperature. The Royal Society of Chemistry 2010.

Aversatile palladium/triphosphane system for direct arylation of heteroarenes with chloroarenes at low catalyst loading

Put a ring on it: The use of an air-stable, robust palladium/tridentate phosphane catalyst in direct C-H and C-Cl activation reactions is reported (see scheme; DMAc=N,N-dimethylacetamide, TBAB=tetra-n-butylammonium bromide). Electron-rich, electron-poor, and polysubstituted furans (X=O), thiophenes (X=S), pyrroles (X=NR5), and thiazoles were arylated with chloroarenes in the presence of the catalyst.

Low catalyst loading ligand-free palladium-catalyzed direct arylation of furans: An economically and environmentally attractive access to 5-arylfurans

The direct 5-arylation of furans at very low catalyst loading using Pd(OAc)2 as catalyst without added ligand proceed in high yields. Turnover numbers up to 10000 have been obtained for the coupling of several activated aryl bromides. A wide ra