Yuanchen Cui

Chitosan-Based Heterogeneous Catalysts for Enantioselective Michael Reaction

Novel chitosan-supported cinchona alkaloids have been developed as heterogeneous catalysts for enantioselective Michael reaction. As-synthesized products as organocatalysts for asymmetric Michael reaction have a high efficiency, providing highly functionalized products (containing adjacent quaternary and tertiary stereocenters) with good stereoselectivity (up to 93% enantiomeric excess) in high yields and recyclability (up to five runs).

Preparation of Immobilized L-Prolinamide Via Enzymatic Polymerization of Phenolic L-Prolinamide and Evaluation of Its Catalytic Performance for Direct Asymmetric Aldol Reaction

Phenolic L-prolinamide was allowed to participate in enzymatic polymerization with horseradish peroxidase as the catalyst, generating immobilized L-prolinamide. The catalytic performance of the resultant polymer-supported L-prolinamide for direct asymmetric aldol reaction between aromatic aldehyde and cyclohexanone was studied. The results show that as prepared L-prolinamide can catalyze the aldol reaction at room temperature in the presence of H2O. Relevant aldol addition products are obtained with good yields (up to 91%), high diastereoselectivities (up to 6:94 dr), and medium enantioselectivities (up to 87% ee). Moreover, the title polymer-supported catalyst can be recovered and reused for at least five cycles while the activity remains almost unchanged.

Enzymatic synthesis of polyguaiacol and its thermal antioxidant behavior in polypropylene

Polyguaiacol was successfully synthesized by enzyme-catalyzed polymerization in an aqueous micelle system with horseradish peroxidase (HRP) as the catalyst. As-synthesized polyguaiacol was characterized by infrared spectrometry and gel permeation chromatography, and its thermal stability was evaluated by thermogravimetric analysis. Besides, the thermal antioxidant behavior of the as-synthesized phenolic polymer as an antioxidant in polypropylene was evaluated by differential scanning calorimetry and accelerated aging test, and the apparent activation energies of thermal decomposition of polypropylene (PP) were calculated by Friedman method. Results show that the as-synthesized polyguaiacol as an antioxidant is able to significantly increase the oxidation induction time of virgin PP, and it exhibits better antioxidative performance than corresponding monomer. Moreover, polyguaiacol, the as-synthesized phenolic polymer, exhibits good resistance against aging of polypropylene.

Chitosan-supported cinchonine as an efficient organocatalyst for direct asymmetric aldol reaction in water

Abstract Chitosan-supported succinic anhydride-cinchonine (CTS-SA-CN) was synthesized via a two-step route with succinic anhydride as the linker. The catalyst was used to promote the direct asymmetric aldol reaction between cyclohexanone and a variety of aromatic aldehydes in aqueous medium. Aldol adducts were obtained in excellent yields (up to 99%) and good enantioselectivities (up to 96% ee). The CTS-SA-CN catalyst was successfully recycled simply by filtration after use, and was reused 5 times without any significant loss of activity.

Synthesis of polyaspartic acid/2-amino-2-methyl-1,3-propanediol graft copolymer and evaluation of its scale inhibition and corrosion inhibition performance

AbstractPolyaspartic acid/2-amino-2-methyl-1,3-propanediol graft copolymer, a novel non-phosphorus scale and corrosion inhibitor, was synthesized and characterized by infrared spectroscopy. Its performance was evaluated by static scale inhibition method and dynamic corrosion testing. It was found that the graft copolymer showed excellent inhibition ability against CaCO3, CaSO4, and Ca3(PO4)2 scales and a definite inhibition corrosion performance as well. The inhibition efficiency was close to 99.9% against CaCO3, CaSO4, and Ca3(PO4)2 when the inhibitor was at an appropriate concentration. The inhibitor had still possessed higher antiscale efficiency against CaCO3 with increasing concentration of Ca2+ and heating time. In addition, The graft copolymer could change the structure of crystals CaCO3, CaSO4, and Ca3(PO4)2 by observation of scanning electron microscopy.

Effect of Tetrabutylammonium Bromide on Enzymatic Polymerization of Phenol Catalyzed by Horseradish Peroxidase

In this article tetrabutylammonium bromide (TBAB) was first added in buffer to compose a convenient and environmentally friendly system, and enzymatic polymerization of phenol catalyzed by horseradish peroxidase (HRP) could proceed efficiently in this system. When TBAB was added, the most conversion of phenol could reach 99.1%. The phenol polymer was considered to consist of a mixture of phenylene (Ph) and oxyphenylene (Ox) units by IR analysis, and the ratio of phenylene to oxyphenylene units (Ph/Ox) was measured by titration. Moreover, the effects of the dosage of horseradish peroxidase (HRP) and pH value on the conversion of phenol were investigated. The reaction performed very effectively in this novel system when the addition of HRP was only 0.2 mg. In all cases, the weight-average molecular weight calculated by GPC-SLS was in a range from 12000 Da to 30000 Da. The phenol polymer prepared in the present research possessed good thermal stability shown by TG analysis.