Yanhui Shi

Efficient synthesis of quinazoline-2,4(1H,3H)-diones from CO2 catalyzed by N-heterocyclic carbene at atmospheric pressure

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 urea decorated (3,24)-connected rht-type metal–organic framework exhibiting high gas uptake capability and catalytic activity

A (3,24)-connected rht-type metal organic framework (MOF Cu-UBTA) containing a urea group was readily prepared by the solvothermal reaction between a hexacarboxylate ligand and Cu(NO3)2. Gas sorption investigations demonstrated its high porosity and high uptake capacities for CO2 and H2. Moreover, the MOF can act as an efficient heterogeneous catalyst for Friedel–Crafts alkylation of N-methyl pyrrole or indole with nitroalkenes.

An rht-type metal–organic framework constructed from an unsymmetrical ligand exhibiting high hydrogen uptake capability

An unsymmetrical hexatopic carboxylate acid (H6-1) ligand containing one acrylamide unit and two triazole groups was designed and synthesized, and then used to construct a metal–organic framework (MOF Cu-ABTA) via a solvothermal reaction with Cu(NO3)2. A powder X-ray diffraction investigation indicated that the MOF Cu-ABTA possesses a (3,24)-connected rht-network, as does our previously reported MOF NTU-105 with three triazole groups. The gas sorption measurements revealed that Cu-ABTA shows high porosity and a very high H2-uptake capability with a strong H2 binding affinity as demonstrated by the enhanced isosteric heat of adsorption, which make it a highly promising candidate for clean energy storage.

Effective, transition metal free and selective C–F activation under mild conditions

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.

Synthesis of fluorinated carbazoles via C–H arylation catalyzed by Pd/Cu bimetal system and their antibacterial activities

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 (1)H, (13)C and (19)F 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.

Synthesis of N-aryl-2-oxazolidinones from cyclic carbonates and aromatic amines catalyzed by bio-catalyst

A convenient and effective method of synthesizing 3-aryl-2-oxazolidinones from cyclic carbonates and aryl amines catalyzed by bio-catalyst adenine in the presence of Et3N under solvent-free conditions is described. The protocol is suitable for the wide scope of substrates, e.g. cyclic carbonates with or without substitutes, and aryl amines with either electron-withdrawing or electron-donating group. The products were obtained in good to excellent yields under the optimal conditions, even in steric hindered cases. The effect of reaction time, temperature, loading of catalyst, and amount of starting materials in the reaction were investigated, and the reaction mechanism is discussed.

Synthesis of Oxazolidinones and Derivatives through Three-Component Fixation of Carbon Dioxide

An effective three‐component fixation of atmospheric CO2 with readily available 1,2‐dichloroethane and aromatic amine toward oxazolidinones catalyzed by in situ NHC was developed. The reaction occurred in good to excellent yields with good generality and wide functional group tolerance, including challenging steric hindered substituted‐dichloroethane (e.g. 1,2‐dichloropropane and 2,3‐dichlorobutane). The catalytic system is not sensitive to air and moisture, and high yield of oxazolidinone was achieved even with about 0.3u2005atm of pressure of carbon dioxide. The mechanistic study suggests that the reaction catalyze by in situ NHC via NHC‐CO2 adduct, 1‐butyl‐3‐methylimidazolium‐2‐carboxylate as intermediate and aminochloride involves in reaction pathways. The catalyst can be recycled for at least 3u2005times without obvious loss of catalytic activity. The protocol is also effective to prepare six‐membered 3‐aryl‐1,3‐oxazinan‐2‐one and even seven‐membered 3‐aryl‐1,3‐oxazepan‐2‐one, when 1,3‐dichloropropane and 1,4‐dichlorobutane was employed.

Synthesis, structure and catalytic activity of xylylene-bridged dipalladium complexes with triazolylidene ligands

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.