Yuecheng Zhang

Deep eutectic solvent supported TEMPO for oxidation of alcohols

A novel deep eutectic solvent supported TEMPO (DES–TEMPO) composed of N,N-dimethyl-(4-(2,2,6,6-tetramethyl-1-oxyl-4-piperidoxyl)butyl)dodecyl ammonium salt ([Quaternium-TEMPO]+Br−) and urea was prepared. An efficient catalytic system for the oxidation of alcohols with molecular oxygen as terminal oxidant has been developed from DES–TEMPO and Fe(NO3)3·9H2O. The DES–TEMPO/Fe(NO3)3 system showed good performances on the selective oxidation of various alcohols to the corresponding aldehydes and ketones under mild and solvent-free conditions. The DES could be recovered easily and recycled up to five times in the oxidation of benzyl alcohol without significant loss of catalytic activity.

Cobalt-Catalyzed Trifluoromethylation–Peroxidation of Unactivated Alkenes with Sodium Trifluoromethanesulfinate and Hydroperoxide

Disclosed herein is an unprecedented cobalt-catalyzed trifluoromethylation-peroxidation of unactivated alkenes. In this process the hydroperoxide acts as a radical initiator as well as a coupling partner. The cheap and readily available sodium trifluoromethanesulfinate serves as the CF3 source in the reaction. Various alkenes are transformed into vicinal trifluoromethyl-peroxide compounds in moderate to good yields.

Synthesis of a polymer–ruthenium complex Ru(pbbp)(pydic) and its catalysis in the oxidation of secondary alcohols with TBHP as oxidant

A polymer–ruthenium complex Ru(pbbp)(pydic) was synthesized from the reaction of poly-2,6-bis(benzimidazolyl)pyridine (pbbp) with RuCl3 and disodium pyridine-2,6-dicarboxylate (pydic). The Ru(pbbp)(pydic) was characterized thoroughly by spectroscopic methods. ICP analysis revealed that the percentage of complexation of 2,6-bis(benzimidazolyl)pyridine unit in pbbp was about 83%. The complex was tested as a heterogeneous catalyst for the oxidation of secondary alcohols to their corresponding carbonyl compounds in solvent-free conditions using aqueous tert-butyl hydroperoxide as oxidant. The developed catalytic system exhibited high activity and broad functional group compatibility, allowing a variety of secondary alcohols, including substituted secondary benzylic alcohols and secondary aliphatic ones, to be oxidized to the corresponding ketones in high yields. This Ru(pbbp)(pydic) could be recycled for several times, but it dissolved in part in the reaction mixture during the catalytic run leading to gradual deactivation of the catalyst with repeated runs.

Liquid-phase oxidation of 2-methoxy-p-cresol to vanillin with oxygen catalyzed by a combination of CoCl2 and N-hydroxyphthalimide

Liquid-phase oxidation of 2-methoxy-p-cresol to vanillin (4-hydroxy-3-methoxybenzaldehyde), in methanol, with molecular oxygen at atmospheric pressure as oxidant and a combination of cobaltous chloride and N-hydroxyphthalimide (NHPI) as catalyst, has been investigated. The effect of reaction conditions on conversion and selectivity for vanillin was studied systematically. Selectivity for vanillin could be enhanced by optimizing the molar ratio of 2-methoxy-p-cresol to NHPI, the amount of sodium hydroxide, reaction time, reaction temperature, and the volume of methanol, which determined the concentration of the reactants. Under the optimized conditions the yield of vanillin was 90.1xa0%.

Activated Carbon Supported Ruthenium Nanoparticles Catalyzed Synthesis of Imines from Aerobic Oxidation of Alcohols with Amines

AbstractImines were synthesized from the cross-coupling of alcohols with amines catalyzed by activated carbon (AC) supported ruthenium nanoparticles under atmospheric molecular oxygen without aid of any additives. The readily prepared catalyst 5%Ru/AC showed good to excellent (yieldu2009>u200990%) performances in the reaction of aromatic and heterocyclic alcohols with various amines, such as aromatic, aliphatic and heterocyclic amines. This protocol is simple, efficient, and environmentally friendly, and the catalyst can be easily recovered without major ruthenium loss.Graphical AbstractImines were synthesized from the cross-coupling of alcohols with amines catalyzed by activated carbon (AC) supported ruthenium nanoparticles under atmospheric molecular oxygen without aid of any additives. This protocol is simple, efficient, and environment friendly, and the readily prepared catalyst 5%Ru/AC showed good to excellent performances in the reaction of aromatic and heterocyclic alcohols with various amines, such as aromatic, and aliphatic amines.n

Aerobic oxidation of p-cresols to 4-hydroxy benzaldehydes catalyzed by cobaltous chloride/NHPI/salen-Cu(II) catalytic system

Oxidation of 2-methoxy-p-cresol, p-cresol, 2-bromo-p-cresol to their corresponding 4-hydroxybenzaldehydes with atmospheric molecular oxygen as oxidant and a combination of cobaltous chloride and N-hydroxyphthalimide (NHPI) as catalyst in methanol has been investigated for the first time. The results indicated that the reaction progress was related to the substituents in the structures of the substrates: the electron-donating group methoxy favors the aerobic reaction but the electron-withdrawing group Br is detrimental to the reaction. The introduction of salen-Cu(II) complexes as the third component into the cobaltous chloride/NHPI catalytic system can considerably improve the aerobic oxidation of p-cresol and 2-brom-p-cresol to the corresponding 4-hydroxybenzaldes.

Enhanced selectivity in the conversion of glycerol to pyridine bases over HZSM-5/11 intergrowth zeolite

A composite co-crystalline zeolite HZSM-5/11(78) was synthesized and tested in the conversion of glycerol with ammonia to pyridine bases (pyridine, 2-methylpyridine, 3-methylpyridine). The HZSM-5/11(78) showed good performance compared to other zeolites with similar Si/Al ratios such as HZSM-5(80), HZSM-11(80) and the physical mixture of HZSM-5(80) and HZSM-11(80). Characterization results from the N2 adsorption–desorption and IR of the adsorbed pyridine indicated that the good performance of HZSM-5/11(78) was related to the higher surface area and co-existence of an appropriate ratio of Lewis and Bronsted sites, which are derived from the intergrowth between zeolites HZSM-5 and HZSM-11. The parameters affecting the catalytic performance of HZSM-5/11(78) were investigated systematically. The optimal conditions for producing pyridine bases from glycerol with ammonia over this catalyst were determined, including a reaction temperature of 520 °C, 0.1 MPa pressure with a molar ratio of ammonia to glycerol of 12u2006:u20061, and a GHSV of 300 h−1.

A Recyclable Organocatalyst for Asymmetric Michael Addition

In this study, a new organocatalyst derived from proline was developed and shown to be an efficient catalyst for asymmetric Michael addition reactions of ketones and aldehydes to nitroolefins with high diastereo- and enantioselectivities. (syn;anti up to 99:1, ee. up to 98xa0%.). Furthermore, the catalyst is easily recovered and could be reused six times without significant loss of its ability to affect the outcome of the asymmetric reactions. In addition, computational studies at the B3LYP/6-311G(d,p)//6-311xa0+xa0G(2dp,f) level was conducted on a model reaction, and confirmed the following hypotheses: first, the hydrogen bonding between carboxyl group and nitro group plays an important role in catalysis, and second, the energy barrier for re-face attack in reactions of ketones to form 2S, 3R products is lower than that for the si-face attack leading to 2S, 3R products.Graphical AbstractStructural modification of a previously reported organocatalyst (lead compound in figure) was used to design an efficient and recyclable organocatalyst for asymmetric Michael addition. The introduced carboxyl group not only enhances the enantioselectivity but also brings convenience to the recovery of the catalyst.

Hydrogen generation from hydrazine catalyzed by a Ni1-(CeO1.8)0.5/carbon-nanotubes catalyst

Well-dispersed Ni-CeOx nanoparticles grown on carbon nanotubes (CNTs) were successfully synthesized via a simple one-step co-reduction method. The structure and properties of the catalysts were investigated by XRD, XPS, SEM, TEM and ICP-OES. Among the prepared catalysts, Ni1-(CeO1.8)0.5/CNTs exhibited the highest catalytic activity, with 100% hydrogen selectivity and 80xa0molH2xa0molNi−1xa0h−1 of hydrogen generation rate (HGR) for hydrogen generation from hydrazine under 1.0xa0M NaOH solution at 343xa0K. This superior catalytic performance might be attributed to the smaller sizes and amorphous states of Ni species in Ni1-(CeO1.8)0.5/CNTs, as well as the close attachment of Ni-CeOx NPs on CNTs.

Ru(OH)x supported on polyethylenimine modified magnetic nanoparticles coated with silica as catalyst for one-pot tandem aerobic oxidation/Knoevenagel condensation of alcohols and active methylene compounds

The immobilization of ruthenium species on polyethylenimine (PEI) modified magnetic nanoparticles coated with silica afford a multifunctional catalyst (Fe3O4@SiO2@PEI@Ru(OH)x) for the aerobic oxidation/Knoevenagel condensation of alcohols and active methylene compounds. A wide scope of alcohols and malononitrile could be converted to their corresponding condensation products in excellent yields under mild conditions. This catalyst has advantages of leaching-free of ruthenium species and ease of recovery by an external magnet. The activity deactivation of the catalyst was investigated and was ascribed to the transformation of surface Ru3+ to Ru4+ in the process of aerobic oxidation of alcohols.