We report that the complex generated from Pd[P(o-tol)3]2 and the alkylbisphosphine CyPF-t-Bu is a highly active and selective catalyst for the coupling of ammonia with aryl chlorides, bromides, iodides, and sulfonates. The couplings of ammonia with this catalyst conducted with a solution of ammonia in dioxane form primary arylamines from a variety of aryl electrophiles in high yields. Catalyst loadings as low as 0.1 mol % were sufficient for reactions of many aryl chlorides and bromides. In the presence of this catalyst, aryl sulfonates also coupled with ammonia for the first time in high yields. A comparison of reactions in the presence of this catalyst versus those in the presence of existing copper and palladium systems revealed a complementary, if not broader substrate scope. The utility of this method to generate amides, imides and carbamates is illustrated by a one-pot synthesis of a small library of these carbonyl compounds from aryl bromides and chlorides. Mechanistic studies show that Pd[P(o-tol)3]2 and CyPF-t-Bu generate a more active and general catalyst than that generated from CyPF-t-Bu and palladiun(II) precursors because of the low concentration of active catalyst that is generated from the combination of palladium(II), ammonia and base.

a-Aryl carbonyl compounds are precursors to many important synthetic intermediates bearing alcohol, imine, amine, olefin, and nitrile functional groups. [1][2][3][4][5] The palladiumcatalyzed a-arylation of carbonyl compounds has evolved into one of the more important methods for the preparation of compounds. [6,7] The a-arylation process now encompasses the couplings of ketones, [8][9][10] amides, [11][12][13] esters, [12,14] malonates, [9,15] and cyanoacetates [15,16] with a broad range of aryl halides and sulfonates. The a-arylation of aldehydes [Eq. (1)], however, has been challenging to develop because of competing aldol condensations under the cross-coupling reaction conditions. Accordingly, only three reports on the a-arylation of aldehydes have been published. The first examples were reported by Miura and co-workers in 2002. [17] Miuras protocols employed high temperatures and high catalyst loadings to give modest yields of the coupled products, and the substrate scope was limited. In 2005 Bertrand and co-workers described the a-arylation of isobutanal with 2-chlorotoluene in the presence of a palladium(II) catalyst ligated by a cyclic(amino)alkyl carbene. [18] Recently, Martín and Buchwald described improved protocols for the a-arylation of aldehydes, but most examples in this work involved the coupling of electron-poor aryl halides; few reactions of haloarenes that could be considered to be electron-neutral or electron-rich were reported, and the one example of the reaction of an electron-rich haloarene was sterically biased. [19] Herein we report a more general system for palladiumcatalyzed coupling of aldehydes with electron-poor and electron-rich aryl bromides. The coupling of linear aldehydes with electron-poor or electron-neutral bromoarenes occurred in good yield when catalyzed by complexes having a bisphosphine ligand. The coupling of branched aldehydes with bromo-and chloroarenes occurred in high yield when catalyzed by complexes bearing monophosphine 1,2,3,4,5-pentaphenyl-1'-(di-tert-butylphosphino)ferrocene (Q-phos) that was developed in our laboratory.[20] One factor that leads to the efficiency of this process is the use of these ligands in combination with a palladium precursor that is known [21] to undergo facile generation of active [L n Pd 0 ] species. Our initial study focused on the identification of a catalyst for a-arylation that reacted with rates that were faster than those of the competing aldol condensations. We examined various combinations of palladium precursors and ligands for the coupling of octanal with 1-bromo-4-tert-butylbenzene in the presence of various bases, and the results of this study are summarized in Table 1. Reactions conducted with either [Pd(dba) 2 ] (dba = trans,trans-dibenzylideneacetone) or Pd-(OAc) 2 as a catalyst precursor and cesium carbonate as a base formed the coupled product in modest yields. Catalysts generated from [Pd(dba) 2 ] or Pd(OAc) 2 and bisphosphine ligands bis[2-(diphenylphosphino)phenyl]ether (dpephos), 4,5-bis(diphenylphosphino)-9,9-dime...

We report the design, synthesis, and physical/ mechanical properties of graft copolymers containing semicrystalline polypropylene side chains and amorphous ethylene/α-olefin copolymer backbones. These materials, a new class of semicrystalline, polyolefin-based thermoplastic elastomers, are made in two steps. First, allyl-terminated syndiotactic or isotactic polypropylene macromonomers are synthesized with controlled microstructure and molecular weight using bis(phenoxyimine)-titanium or chiral ansa-zirconocene catalysts, respectively. Second, a pyridyl-amido hafnium catalyst is used to copolymerize the macromonomer, ethylene, and an α-olefin with precise control of composition and side chain incorporation. With highly crystalline polypropylene side chains and amorphous backbones of low glass-transition temperatures (<−55°C), the samples have strain-to-break values up to 1400% and elastic recovery above 85% at maximum strains up to 1000%. The synthetic method described herein does not require the use of a living polymerization catalyst; in addition, the mechanical properties of these graft copolymers exceed those of the best linear block polyolefins.T hermoplastic elastomers (TPEs) are an important class of industrial materials that are an attractive alternative to vulcanized rubber. 1 TPEs can be melt-processed, do not require vulcanization, and, unlike thermoset rubbers, can be recycled. TPEs are blocky polymers that derive their elastomeric properties from a combination of "hard" segments with high melting points (T m ) or high glass-transition temperatures (T g ) and "soft" segments with low T g . Elastomeric properties can be obtained in structures having at least two hard sequences separated by a soft sequence and are typically linear triblock or multiblock copolymers. In the solid state, the hard segments are dispersed throughout the amorphous matrix and form physical cross-links that produce recoverable elasticity after straininduced deformation. 1 A well-known example of a commercial TPE is a triblock polystyrene-block-poly(ethylene-co-butene)-block-polystyrene copolymer (SEBS). Although many commercial TPEs are prepared via anionic polymerization and contain polystyrene, there has been longstanding interest in the synthesis and properties of TPEs based on other monomers. Bates and co-workers prepared model polyolefin TPEs by anionic polymerization followed by hydrogenation. 2 More recently, bio-derived TPEs have been reported. 3Given the low cost of ethylene, propylene, and α-olefins, considerable academic and industrial efforts have focused on the development of catalysts and reaction conditions to prepare blocky polyolefins. 4 Several approaches are shown in Scheme 1. Early efforts focused on elastomeric polypropylene (Scheme 1A) prepared with nonliving catalysts. Natta reported the first elastomeric polypropylene in 1959 using TiCl 3 /AlR 3 catalyst mixtures, 5 and more recently similar materials were obtained using zirconium and titanium alkyl complexes supported on alumina. 6 In the 1990s, the synth...

Ir(III) complexes of cyclometalated 5-aryl-1H-1,2,4triazole ligands are highly efficient, phosphorescent emitters. We describe herein a series of fac-IrL 3 complexes, in which the nature of aryl substituents are shown to strongly affect emission wavelength over the range 453−499 nm. Computational and structural studies indicate that for aryl groups the point of attachment and dihedral angle with respect to the cyclometalated ring influence emission color. Significantly, this degree of color tuning may be achieved without resorting to electron-withdrawing or -donating groups. Photo-and electroluminescence device studies of the different emitters indicate that they are generally highly efficient: photoluminescent efficiencies >90% and external quantum efficiencies of up to 22% are observed.

a-Aryl carbonyl compounds are precursors to many important synthetic intermediates bearing alcohol, imine, amine, olefin, and nitrile functional groups. [1][2][3][4][5] The palladiumcatalyzed a-arylation of carbonyl compounds has evolved into one of the more important methods for the preparation of compounds. [6,7] The a-arylation process now encompasses the couplings of ketones, [8][9][10] amides, [11][12][13] esters, [12,14] malonates, [9,15] and cyanoacetates [15,16] with a broad range of aryl halides and sulfonates. The a-arylation of aldehydes [Eq. (1)], however, has been challenging to develop because of competing aldol condensations under the cross-coupling reaction conditions. Accordingly, only three reports on the a-arylation of aldehydes have been published. The first examples were reported by Miura and co-workers in 2002. [17] Miuras protocols employed high temperatures and high catalyst loadings to give modest yields of the coupled products, and the substrate scope was limited. In 2005 Bertrand and co-workers described the a-arylation of isobutanal with 2-chlorotoluene in the presence of a palladium(II) catalyst ligated by a cyclic(amino)alkyl carbene. [18] Recently, Martín and Buchwald described improved protocols for the a-arylation of aldehydes, but most examples in this work involved the coupling of electron-poor aryl halides; few reactions of haloarenes that could be considered to be electron-neutral or electron-rich were reported, and the one example of the reaction of an electron-rich haloarene was sterically biased. [19] Herein we report a more general system for palladiumcatalyzed coupling of aldehydes with electron-poor and electron-rich aryl bromides. The coupling of linear aldehydes with electron-poor or electron-neutral bromoarenes occurred in good yield when catalyzed by complexes having a bisphosphine ligand. The coupling of branched aldehydes with bromo-and chloroarenes occurred in high yield when catalyzed by complexes bearing monophosphine 1,2,3,4,5-pentaphenyl-1'-(di-tert-butylphosphino)ferrocene (Q-phos) that was developed in our laboratory.[20] One factor that leads to the efficiency of this process is the use of these ligands in combination with a palladium precursor that is known [21] to undergo facile generation of active [L n Pd 0 ] species. Our initial study focused on the identification of a catalyst for a-arylation that reacted with rates that were faster than those of the competing aldol condensations. We examined various combinations of palladium precursors and ligands for the coupling of octanal with 1-bromo-4-tert-butylbenzene in the presence of various bases, and the results of this study are summarized in Table 1. Reactions conducted with either [Pd(dba) 2 ] (dba = trans,trans-dibenzylideneacetone) or Pd-(OAc) 2 as a catalyst precursor and cesium carbonate as a base formed the coupled product in modest yields. Catalysts generated from [Pd(dba) 2 ] or Pd(OAc) 2 and bisphosphine ligands bis[2-(diphenylphosphino)phenyl]ether (dpephos), 4,5-bis(diphenylphosphino)-9,9-dime...

Homoleptic fac-IrIIIL3 complexes of 5-aryl-4H-1,2,4-triazole ligands are sky blue emitters. When unsymmetrically substituted, the triazole ligands exhibit atropisomerism, and upon cyclometalation to Ir­(III) a mixture of diastereomers is formed. We have isolated and structurally characterized all four possible diastereomers of the fac-IrIIIL3 complex formed upon cyclometalation of an atropisomeric 5-aryl-4H-1,2,4-triazole ligand onto Ir­(III). The phosphorescent blue emitting materials reported herein are among the most efficient to date, with quantum efficiencies above 95%.

No abstract

Amination O 0268Palladium-Catalyzed Coupling of Ammonia with Aryl Chlorides, Bromides, Iodides, and Sulfonates: A General Method for the Preparation of Primary Arylamines. -The complex derived from Pd[P(o-tolyl)3]2 and bisphosphine FDP is highly active and selective for the title reaction. Loadings as low as 0.1 mol% are sufficient for the reactions of many aryl bromides and chlorides. The catalyst exhibits a complementary, if not broader, substrate scope compared to known copper and palladium systems. Amides, imides and carbamates are prepared by two-step one-pot sequences involving the amination as first step (to be continued). -(VO, G. D.; HARTWIG*, J. F.; J.