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A novel class of luminescent dialkynylgold(III) complexes containing various phenylpyridine and phenylisoquinoline-type bidentate ligands has been successfully synthesized and characterized. The structures of some of them have also been determined by X-ray crystallography. Electrochemical studies demonstrate the presence of a ligand-centered reduction originating from the cyclometalating C^N ligand, whereas the first oxidation wave is associated with an alkynyl ligand-centered oxidation. The electronic absorption and photoluminescence properties of the complexes have also been investigated. In dichloromethane solution at room temperature, the low-energy absorption bands are assigned as the metal-perturbed π-π* intraligand (IL) transition of the cyclometalating C^N ligand, with mixing of charge-transfer character from the aryl ring to the pyridine or isoquinoline moieties of the cyclometalating C^N ligand. The low-energy emission bands of the complexes in fluid solution at room temperature are ascribed to originate from the metal-perturbed π-π* IL transition of the cyclometalatng C^N ligand. For complex 4 that contains an electron-rich amino substituent on the alkynyl ligand, a structureless emission band, instead of one with vibronic structures as in the other complexes, was observed, which was assigned as being derived from an excited state of a [π(Ci￡CC6H 4NH2)→π (C^N)] ligand-to-ligand charge-transfer (LLCT) transition. Luminescence enhancement: A novel class of luminescent dialkynylgold(III) complexes containing various phenylpyridine- and phenylisoquinoline-type bidentate ligands has been successfully synthesized and characterized. This class of complexes has been shown to demonstrate rich and tunable photoluminescence properties (see picture).

Heteroaromatic sulfinates are effective nucleophilic reagents in Pd0-catalyzed cross-coupling reactions with aryl halides. However, metal sulfinate salts can be challenging to purify, solubilize in reaction media, and are not tolerant to multi-step transformations. Here we introduce base-activated, latent sulfinate reagents: β-nitrile and β-ester sulfones. We show that under the cross-coupling conditions, these species generate the sulfinate salt in situ, which then undergo efficient palladium-catalyzed desulfinative cross-coupling with (hetero)aryl bromides to deliver a broad range of biaryls. These latent sulfinate reagents have proven to be stable through multi-step substrate elaboration, and amenable to scale-up.

A rhodium-catalyzed C(sp2)-H ethoxycarbonylation of indoles and arylpyridines using diethyl dicarbonate was developed. The catalytic process features an additive-free ethoxycarbonylation reaction, in which only ethanol and CO2 are produced as byproducts, providing a CO-free and operationally simple protocol. The introduced ethoxycarbonyl group is easily transformed into other ester and amide functionalities in a single step. Moreover, the reaction can be successfully applied on gram scale, and allows for the efficient synthesis of indole-2-carboxylic acid esters and isophthalates.

Pyridinium-containing polyheterocycles exhibit distinctive biological properties and interesting electrochemical and optical properties and thus are widely used as drugs, functional materials, and photocatalysts. Here, we describe a unified two-step strategy by merging Rh-catalyzed C-H vinylation with two switchable electrocyclizations, including aza-6π-electrocyclization and all-carbon-6π-electrocyclization, for rapid and divergent access to dihydropyridoisoquinoliniums and dihydrobenzoquinolines. Through computation, the high selectivity of aza-electrocyclization in the presence of an appropriate "HCl"source under either thermal conditions or photochemical conditions is shown to result from the favorable kinetics and symmetries of frontier orbitals. We further demonstrated the value of this protocol by the synthesis of several complex pyridinium-containing polyheterocycles, including the two alkaloids berberine and chelerythrine.

A new set of palladium(II) complexes comprising phenyl(thiazolyl)thiourea ligands have been successfully synthesized and characterized with the aid of analytical as well as spectral (IR, UV–visible and NMR) methods. A distorted square-planar geometry with N^S coordination mode of thiourea ligands in the new palladium complexes was corroborated by single-crystal X-ray diffraction methods. Interestingly, the palladium(II) thiourea complexes showed the highest catalytic activity with 0.1 mol% catalyst loading in Suzuki–Miyaura cross-coupling reactions utilizing a range of aryl bromides/unactivated aryl chlorides with arylboronic acids as coupling partners in aqueous–organic media. Syntheses of diaryl ketones using aryl esters and arylboronic acids as coupling partners were also achieved with low catalyst loading within 20 h. The potential of our catalyst was demonstrated by its wide substrate scope, low catalyst loadings and high isolated yield. Moreover, the influences of key parameters like solvent, base, temperature and catalyst loading were also investigated.

Polystyrene supported N-phenylpiperazine-Pd(II) complex D was synthesized and characterized by various techniques, including Fourier transform infrared spectroscopy (FTIR), scanning electronmicroscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and thermal analysis (TG-DTA). This heterogeneous Pd(II) complex showed high catalytic efficiency for the Suzuki-Miyaura coupling of arylboronic acids with aryl bromides, aryl chlorides to give the corresponding 2-arylpyridines and heteroarenes. The coupled products were formed in excellent yields at low catalyst loadings under mild reaction conditions. Further, this heterogeneous catalyst showed excellent recyclability and reused for four cycles with no significant decrease in its activity.

Synthesis of a new family of air stable palladium(ii)benzhydrazone complexes of the general formula [PdCl(PPh3)(L)] (where HL = thiophene aldehyde benzhydrazones) incorporating PPh3 and chloride as co-ligands has been described through a single and convenient step with good yields. All the new complexes have been fully characterized by means of elemental analysis, IR, UV-vis, and NMR spectral methods. The molecular structures of three of the complexes were determined by single crystal X-ray crystallography, which confirm the coordination mode of benzhydrazone and reveal the presence of a distorted square planar geometry around the Pd ion. The complexes 1-5 (0.05 mol%) have been found to be a highly active catalytic system in the mono and double Suzuki-Miyaura cross coupling reaction of deactivated aryl and heteroaryl bromides with different types of aryl boronic acids in neat water and the maximum yield was up to >99%. Notably, these catalysts work well with ultra-low loading of the catalysts and show high turnover numbers in a short time towards different substrates. Moreover, the catalysts could be simply recovered and reused five times without significant loss of efficiency.

This study describes the palladium-catalyzed couplings of iodopyridines, chloropyridines, and chloroquinoline with atom-economic BiAr3 reagents in sub-stoichiometric loadings. Mono-arylations of iodo and chloropyridines produced arylpyridines i

A method for achieving the direct arylation of pyridines with phenylhydrazine hydrochloride was developed in this study. This new reaction proceeds readily at room temperature without the use of any transition metal catalysts. This method allows rapid access to various arylated heterocycles that are more difficult to access through traditional methods.

A highly effective visible light-promoted "radical-type" coupling of N-heteroarenes with aryldiazonium salts in water has been developed. The reaction proceeds at room temperature with [Ru(bpy)3]Cl 2×6 H2O as a photosensit

Pyrimidin-2-yl sulfonates, as a reaction partner, can be easily prepared from inexpensive commercial materials and are efficiently cross-coupled with arylboronic acids and terminal alkynes by using Pd(OAc)2-catalyzed Suzuki and Sonogashira reactions. A wide array of C2-functionalized pyrimidines have been prepared in good to excellent yields. 2-Arylpyridines and 2-(oct-1-ynyl)pyridine were also synthesized. An efficient means to synthesize expanded pyrimidin-2-yl conjugated systems was developed by using Pd(OAc) 2-catalyzed cross-coupling reaction of pyrimidin/pyridin-2-yl sulfonates with arylboronic acids and terminal alkynes. Compared with 2-chloropyrimidines, pyrimidin-2-yl sulfonates can be easily prepared from inexpensive commercial materials and the reactions are more efficient. Copyright

A simple route to synthesise palladium(ii) complexes from the reaction of N-substituted pyridine-2-thiocarboxamide ligands and PdCl2(PPh 3)2 has been developed. The new complexes are very soluble in common solvents and have been fully characterised (elemental analysis, FT-IR, 1H, 31P, 13C-NMR), including an X-ray diffraction analysis. The molecular structures of all the complexes were determined and reveal the presence of square planar geometry around Pd with little distortion. The complexes were tested in the Suzuki coupling of electronically deactivated aryl and heteroaryl bromides and were found to have much greater activity, without using any promoting additives or phase transfer agent under aerobic conditions. Higher reaction rates are obtained by varying R substituents on the aromatic ring of pyridine-2-thiocarboxamide. The effect of other variables on the cross-coupling reaction, such as temperature, solvent and base, is also reported.

Recent advances in the development of the copper facilitated Suzuki-Miyaura reaction are described. Improvements include expansion of substrate scope to include aryl chlorides and polyhalo aryl boronates. It was found that use of S-Phos and X-Phos could a

A general, simple and highly efficient method has been developed for the Pd(OAc)2-catalyzed ligand-free and aerobic Suzuki reaction of N-heteroaryl halides, which is strongly dependent on the molecular structure of solvent. A general, simple and highly efficient method has been developed for the Pd(OAc)2-catalyzed ligand-free and aerobic Suzuki reaction of N-heteroaryl halides including 2-pyridyl bromides, 3-pyridyl bromides, 3-quinolyl bromides, 5-pyrimidyl bromides and 2-pyrazyl chloride, which is strongly dependent on the molecular structure of solvent.

A fast protocol has been developed for the construction of 2-aryl-substituted pyridine derivatives by the oxygen-promoted, ligand-free, Pd(OAc)2-catalyzed Suzuki reaction of 2-halogenated pyridines in aqueous isopropanol.

(Chemical Equation Presented) The palladium-catalyzed Suzuki-Miyaura reaction has been utilized as one of the most powerful methods for C-C bond formation. However, Suzuki reactions of electron-deficient 2-heterocyclic coronates generally give low convers

We have developed a new strategy that uses the Kroehnke synthesis for the preparation of various substituted phenylpyridines in excellent yields (up to 88%). Starting with the appropriate commercially available acetophenone, a variety of phenylpyridines substituted by either electron-donating (i.e. methyl, methoxy) or -withdrawing groups (i.e. bromide, nitro) on the phenyl ring are obtained in a two-step synthesis. The corresponding functionalized cyclometalated ruthenium complexes can be prepared with unusually high yields by using methanol as reaction solvent. The electrochemical data of the complexes demonstrate the strong σ-donating character of the anionic phenylpyridine ligand. X-ray analyses of four complexes show a shortening of the Ru-C bond associated with the elongation of only one of the five Ru-N bonds (trans effect). Wiley-VCH Verlag GmbH & Co, KGaA, 2006.

In this report we describe the synthesis photophysical properties (E)-5-(2-arylvinyl)-2-(hetero)-and of various arylpyridines 7a-f, (E)-2-(2-arylvinyl)-5-methoxycarbonylpyridines 14a,b and (E,E)-2,5-bis(2-arylvinyl)pyridines 13a,b. The fluorescence spectr