Carbon disulfide is an abundant, inexpensive and readily available material. One of the main challenges in the reaction of epoxides with CS2 is to control the chemoselectivity as a variety of compounds would be formed in the reaction. A simple and convenient method toward selectively synthesis of oxathiolane and trithiocarbonate from epoxides with CS2 catalyzed by NHC/LiCl(Br) under the neat conditions has been developed. This catalytic system exhibits excellent activity and selectivity in cycloaddition reactions of carbon disulfide to terminal epoxides.Download high-res image (201KB)Download full-size image

A series of di-N-heterocyclic carbene (NHC) dipalladium complexes, [PdPyBr2]2(di-NHC) (2a–h), in which di-NHC represents a di-triazolylidene, featuring a 1,4-xylylene spacer between the carbene units, have been prepared from the reactions of the corresponding ditriazolium bromides with PdCl2 and excess NaBr as an additive in the presence of K2CO3 in pyridine. All of the complexes were fully characterized by NMR spectra, IR and elemental analyses. The molecular structure of 2b was determined by X-ray diffraction study, showing the intermolecular hydrogen bonding of Br···H–C. The influences of size of ligands on the catalytic activity have been investigated in the Heck reaction of styrene with bromobenzene. The complex 2g showed the best catalytic activity, and it is active for various aryl bromides with different electronic and steric properties and styrenes with both electron-donating and electron-withdrawing groups.

An effective intramolecular C–H arylation reaction catalyzed by a bimetallic catalytic system Pd(OAc)2/CuI for the synthesis of fluorine-substituted carbazoles from corresponding N-phenyl-2-haloaniline derivatives under ligand free conditions is demonstrated. The established method is effective for both N-phenyl-2-bromoaniline and N-phenyl-2-chloroaniline, and requires the low loading of Pd(OAc)2 (0.5 mol %). A series of new fluorinated carbazoles were synthesized in excellent yields using the protocol (>83%, 19 examples) and were fully characterized by 1H, 13C and 19F NMR spectral data, HRMS and elemental analysis. All compounds were evaluated for their antibacterial activities against four bacteria (Bacillus subtilis, Staphylococcus aureus, Escherichia coli and methicillin-resistant S. aureus with resistance to gentamicin) by serial dilution technique. All tested compounds showed antibacterial activity against three test strains (S. aureus, B. subtilis and MRSA), and most of these compounds displayed pronounced antimicrobial activities against these three strains with low MIC values ranging from 0.39 to 6.25 μg/mL. Among them, compounds 7 and 14 exhibited potent inhibitory activity better than reference drugs meropenem and streptomycin. Three compounds (2, 4 and 5) showed antibacterial activity against E. coli. with MIC values from 12.5 to 25 μg/mL.

Under atmospheric pressure, quinazoline-2,4(1H,3H)-diones were obtained from the reaction of 2-aminobenzonitriles with carbon dioxide (0.1 MPa) with a catalytic amount of N-heterocyclic carbene in DMSO. It was found that various electron-donating and electron-withdrawing groups such as –OMe, –F, –Cl, –Br, –CH3, –CF3 and –CN were well tolerated to give the products in almost quantitative yields.

A simple and effective aromatic nucleophilic monosubstitution reaction for the synthesis of aromatic amines via selective C–F bond cleavage of various fluoroarenes (mono-, di-, tri-, tetra-, penta- and perfluorobenzene) with primary and secondary aromatic amines under transition metal free conditions is demonstrated. The reaction conditions were investigated thoroughly for a wide range of fluoroarene substrates bearing different numbers of fluorine atoms, and the results showed that the solvent and reaction temperature are very crucial for the successful substitution reactions. The established methods enabled the formation of nonfluorinated and partially fluorinated aromatic amines in good to excellent yields. Several functional groups were tolerated under the optimized conditions.

Multicomponent self-assembly, wherein two unique donor precursors are combined with a single metal acceptor instead of the more common two-component assembly, can be achieved by selecting Lewis-basic sites and metal nodes that select for heteroligated coordination spheres. Platinum(II) ions show a thermodynamic preference for mixed pyridyl/carboxylate coordination environments and are thus suitable for such designs. The use of three or more unique building blocks increases the structural complexity of supramolecules. Herein, we describe the synthesis and characterization of rectangular prismatic supramolecular coordination complexes (SCCs) with two faces occupied by porphyrin molecules, motivated by the search for new multichromophore complexes with promising light-harvesting properties. These prisms are obtained from the self-assembly of a 90° Pt(II) acceptor with a meso-substituted tetrapyridylporphyrin (TPyP) and dicarboxylate ligands. The generality of this self-assembly reaction is demonstrated using five dicarboxylate ligands, two based on a rigid central phenyl ring and three alkyl-spaced variants, to form a total of five free-base and five Zn-metallated porphyrin prisms. All 10 SCCs are characterized by 31P and 1H multinuclear NMR spectroscopy and electrospray ionization mass spectrometry, confirming the structure of each self-assembly and the stoichiometry of formation. The photophysical properties of the resulting SCCs were investigated revealing that the absorption and emission properties of the free-base and metallated porphyrin prisms preserve the spectral features associated with free TPyP.

The complexes [PdX2Py]2(di-NHC) (X = Br or Cl) in which di-NHC represents a di-N-heterocyclic carbene, featuring a rigid phenylene spacer between the carbene units, have been prepared from reactions of the corresponding diimidazolium halide salts with PdCl2 in pyridine. The molecular structures of three of the complexes were determined by X-ray diffraction studies. The influences of different substitutions and of the halide ligand (Br or Cl) on the structure and reactivity of the complexes have been studied. The catalytic activity of the binuclear palladium complexes was tested in the Mizoroki–Heck reaction of styrene with bromobenzene.

A series of chelating NHC–palladium complexes with different alkane-bridges of the type Pd[NHC–(CH2)n–NHC]X2 (X = Br or Cl, n = 2–4) were synthesized, where NHC is a triazolyl-N-heterocyclic carbene donor ligand. The bromide complexes with n = 2 and 3 were characterized by X-ray crystallography. The effects of the length of the bridge and halide ligand on the catalytic reactivity in the hydroamination reaction were investigated. The best catalytic performance was observed with the propylene-bridged Pd–NHC bromide complex 2. The hydroamination of phenylacetylene or 4-methylphenylacetylene with various substituted anilines catalyzed by 2 yielded only Markovnikov addition products in good yield. Interestingly, this homogenous catalyst can be reused three times without significant loss in activity.

The first practical and regioselective process for the synthesis of 2,3-disubstituted indoles from the reaction of o-iodoanilines or o-bromoanilines and their derivatives with symmetrical and unsymmetrical internal alkynes catalyzed by a ferrocene-functionalized N-heterocyclic carbene (NHC)–palladium complex has been developed, and the indoles were isolated in good yields with high regioselectivity.

A series of Pd complexes of picoline-functionalized N-heterocyclic carbenes with different substituents were synthesized. The molecular structures of selected complexes were determined by X-ray diffraction studies, showing a pseudo-square-planar structure with a Pd center surrounded by carbene, pyridine, and two chloride ligands. The influence of the different substituents on the structure and reactivity of the complexes has been studied. The catalytic properties of the complexes were investigated in the Mizoroki–Heck reaction for cross-coupling of bromobenzene with a variety of aryl halides. Their performances varied in these reactions but showed good product regioselectivities.

•A ternary catalytic system of ZnBr2/K2CO3/[Bmim]Br was developed.•The catalyst is effective for both internal and terminal epoxides.•The catalytic activity do not be affected by little contamination of water and air.•This catalyst is reusable for at least 5 times.A simple, readily available and recyclable ternary catalytic system of ZnBr2/K2CO3/[Bmim]Br was developed for the efficient conversion of CO2 and epoxides (both internal and terminal epoxides) to cyclic carbonates under very mild conditions (room temperature, 1 atm) with excellent yields (>90% for 18 examples). The catalytic activity would not be affected by CO2 in the presence of small amount of water and air. The reactions would even be carried out under CO2 partial pressure as low as 0.5 atm, giving carbonate in good yield. This process has been repeated 5 times without any obvious decrease in catalytic activity. The influences of the type of catalyst, catalyst loading, CO2 pressure, reaction time, and temperature on the reaction yields have been investigated. The possible reaction mechanism was proposed based on the reaction results.Download high-res image (165KB)Download full-size image

•Amino-functionalized ethylene carbonates were prepared in one-pot reaction using CO2.•High yield of product with good selectivity were achieved under atmospheric pressure of CO2.•The catalytic activity do not be affected by little contamination of water and air.•This catalyst is reusable for at least 5 times.Under atmospheric pressure, 4-(arylamino)methyl substituted ethylene carbonates were synthesized from the reaction of carbon dioxides (1 or 0.5 atm) with aromatic amine and 2-(bromomethyl)oxirane catalyzed by a ternary system of ZnBr2/K2CO3/[Bmim]Br, while [Bmim]Br (1-butyl-3-methyl-1H-imidazol-3-ium bromide) acted as both catalyst and solvent in the reaction. In the catalytic protocol, the products were isolated in good to excellent yields with good selectivity (up to 96%, total 15 examples). Various functional groups, such as -OMe, -F, -Cl, -Br, -I, -Me, -Et, -COMe and -CN were found tolerant in the reaction. The presence of a small amount of water and air in CO2 does not affect the catalytic activity, and the catalyst can be recycled.Download high-res image (80KB)Download full-size image