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Chiral Ph-dbfox (Ph-dbfox = (R,R)-4,6-dibenzofurandiyl-2,2′-bis(4-phenyloxazoline))/Zn(NTf2)2catalyzed enantioselective Friedel–Crafts reactions of β-CF3acrylates with pyrroles and indoles have been investigated, which afforded the corresponding chiral trifluoromethyl pyrrole and indole derivatives in high yields (90–99%) with a range of 66–99% ee values. With the aid of the chiral adduct of the asymmetric Friedel–Crafts reaction, the chiral trifluoromethylated heliotridane has been successfully constructed in good total yield. [ABSTRACT FROM AUTHOR]

Selective oxidation of tetralin by molecular oxygen over mesoporous CrMCM-41 molecular sieve catalyst using supercritical carbon dioxide (scCO2) solvent has been investigated. CrMCM-41 catalyst gave high selectivity (96.2%) and good yield (63.4%) of 1-tetralone. The presence of scCO2medium improves 1-tetralone selectivity and suppresses leaching of chromium from the CrMCM-41. The activity over recycled CrMCM-41 remains nearly the same under the present experimental conditions. The effect of the reaction parameters on CrMCM-41 was also studied in detail along with comparison of its catalytic activities with other mesoporous catalysts, viz.MnMCM-41, CoMCM-41, microporous CrAPO-5, CoMFI, and macroporous Cr/SiO2catalyst, respectively. In addition this catalytic system was also applied for the oxidation of other benzylic compounds such as indane, fluorene, acenaphthene and diphenylmethane. [ABSTRACT FROM AUTHOR]

Controlled individual and partial nanofibrous polyethylenes with high second melting point (Tm2) were obtained through ethylene-confined polymerization. Cp2TiCl2 catalysts were loaded into porous polymer microspheres (PPMs) with different average nanopore diameters through a chemical reaction. Subsequently, controlled confined polymerization occurred inside the PPM-supported Cp2TiCl2 catalysts by changing the pore structure of the PPMs. SEM, FTIR, XPS, XRD, 13C NMR, and SAXS were performed to confirm the loading of Cp2TiCl2 catalysts inside PPM supports and the structure of polyethylene. PPM-supported Cp2TiCl2 catalysts with the smallest average pore diameter exhibited the highest polymerization activity. Different original polyethylene morphologies, such as individual and partial nanofibers, were obtained. PPMs with small pore diameters increased the possibility of obtaining individual polyethylene nanofibers. Moreover, after removing residues through physical treatment, the polyethylene obtained by using the PPM-supported Cp2TiCl2 catalysts revealed a high Tm2 (up to 142.9 °C), whereas the polyethylene obtained by using homogeneous Cp2TiCl2 catalysts showed a Tm2 of 137.9 °C. SAXS analysis indicated that the high Tm2 was due to the entanglement of polyethylene chains in amorphous layers caused by the unique cross-linked multimodal pore structure of the PPM supports. In addition, the high Tm2 showed good stability even after storage for 1 year or dissolution in good solvents for 80 h at 150 °C. [ABSTRACT FROM AUTHOR]

In the present work, palladium nanoparticles supported on hierarchical ZSM-5 zeolite (Pd/H-hierarchical ZSM-5) were evaluated as a novel acid–metal bi-functional heterogeneous catalyst for direct one-pot reductive amination of nitroarenes, using aldehyde in the presence of NaBH4 and water as a mild reducing agent and green solvent, respectively. The structural and morphological properties of the prepared catalyst were investigated by XRD, BET, FT-IR, NH3-TPD, SEM, TEM, XPS, DRS-UV, and ICP-AES techniques. The reaction was carried out at room temperature, in a short reaction time, without producing any by-products. The stability of the catalyst was good, and it could be reused six times without much loss of activity in the reductive amination reaction. [ABSTRACT FROM AUTHOR]

High-performance Pd(0) on the surface of hollow magnetic mesoporous spheres (HMMS), with Fe3O4 nanoparticles embedded in the mesoporous shell was prepared. The catalyst was characterized by TEM, XRD, VSM and ICP. It showed high activity for selective hydrogenation of alkynes to alkenes and the Heck coupling reaction. The catalyst could be recovered in a facile manner from the reaction mixture and recycled six times without loss in activity. [ABSTRACT FROM AUTHOR]

A highly efficient and green protocol has been developed for the synthesis of a new class of tertiary α-amino phosphonates (TAPs) via the Kabachnik–Fields reactions of substituted salicylaldehydes and 2-hydroxy naphthaldehyde, di-n-butylamine, and di-or tri-alkylphosphites in water under ultrasound irradiation as well as under conventional conditions. These multi-component reactions were performed at room temperature without using any catalysts in water. The TAPs were obtained in higher yields (84% to 94%) within shorter reaction times (6 min to 35 min) than those of conventional reactions after simple workup and purification procedures. [ABSTRACT FROM AUTHOR]

The Biginelli-type reaction of 5-amino-3-arylpyrazole-4-carbonitriles with aldehydes and 1,3-dicarbonyl compounds was studied in detail. We found that the reaction requires no catalysts and proceeds in boiling DMF to give 2-aryl-6-RC(O)-4,7-dihydropyrazolo[1,5-a]pyrimidin-3-carbonitriles in good yields. The reaction of aminopyrazoles with dicarbonyls leading to 6-unsubstituted pyrazolo[1,5-a]pyrimidines proceeds competitively and becomes the dominant process under acid-promoted conditions. 2-Aryl-8-oxo-4,5,6,7,8,9-hexahydropyrazolo[5,1-b]quinazolin-3-carbonitriles were obtained under catalyst-free conditions in up to 80% yields starting from 5-amino-3-arylpyrazole-4-carbonitriles, aldehydes and 1,3-cyclohexanedione. [ABSTRACT FROM AUTHOR]

The article discusses a study that investigated the different types of N-heterocyclic carbenes in the benzoin reaction to assess their characteristics as umpolung catalysts. Topics discussed include trends contributing to an increase in the number of nitrogen atoms in the heterocycles and reduction in the free energies for the intermediates and the transition structures.

Catalysts for the asymmetric Henry reaction involving copper(ii) complexes of the chiral Schiff bases N,N′-(1R,2R)-(−)-1,2-cyclohexylenebis(3-hydroxysalicylideneamine) (H21) and N,N′-(1R,2R)-(−)-1,2-cyclohexylenebis(3-ethoxysalicylideneamine) (H22), and H23, which is the reduced analogue of H21, have been studied. Whereas [Cu(1)] and [Cu(2)] give poor yields and enantioselectivity, [Cu(3)] produced moderate to high yields and enantioselectivities were optimal when reactions were carried out in toluene rather than a polar solvent. A significant finding is that both yield and enantioselectivity are enhanced when a second equivalent of Cu(OAc)2is added to the catalyst. The single-crystal structures of [Cu(3)] and [Cu(1)(H2O)] are presented, and the host–guest interactions and molecular packing in the latter are compared with those in [Cu(2)(H2O)]. [ABSTRACT FROM AUTHOR]