Panliang Zhang

Enantioselective extraction of hydrophilic 2-chloromandelic acid enantiomers by hydroxypropyl-β-cyclodextrin: experiments and modeling

Enantioselective extraction of hydrophilic 2-chloromandelic acid (CMA) enantiomers from organic to aqueous phase with hydroxypropyl-β-cyclodextrin (HP-β-CD) as the selector was investigated. Equilibrium of the extraction system was modeled using a reactive extraction model with a homogeneous aqueous phase reaction. The influence of important process variables on the extraction efficiency, such as the type of the organic solvent and β-cyclodextrin derivatives (β-CDs), concentration of the selector, pH and temperature, was investigated by experiment and modeling. Important parameters of this model were determined experimentally. Results showed that the experimental data agree with the model prediction perfectly and the model was further applied to accurately predict the extraction efficiency influenced simultaneously by pH and the concentration of HP-β-CD. Combining the experiment and the model data, the best extraction conditions were: pH of 2.5, HP-β-CD concentration of 0.05 mol L−1, and temperature of 5°C, providing the enantioselectivity of 1.285 and the performance factor (pf) of 0.011.

Metal-Free Oxidative C–C Bond Functionalization of Methylenecyclopropanes with Ethers Leading to 2-Substituted 3,4-Dihydronaphthalenes

A novel metal-free oxidative ring-opening/cyclization of methylenecyclopropanes with ethers was established for the synthesis of diverse 2-substituted 3,4-dihydronaphthalenes with high selectivity and efficiency. This oxidative cyclization is achieved by C(sp3)-H functionalization, ring-opening, and cyclization, and this method represents a new example of methylenecyclopropane oxidative cyclization with an aromatic carbon and a C(sp3)-H bond by simultaneously forming two new carbon-carbon bonds.

Visible-Light-Mediated Ipso-Carboacylation of Alkynes: Synthesis of 3-Acylspiro[4,5]trienones from N-(p-methoxyaryl)propiolamides and Acyl Chlorides

A novel visible-light-mediated ipso-carboacylation of N-(p-methoxyaryl)propiolamides with acyl chloride has been established for the synthesis of diverse 3-acylspiro[4,5]trienones with high selectivity and efficiency. This method represents a new difunctionalization of alkynes through cross coupling of the acyl chloride C-Cl bonds with an ipso-aromatic carbon by simultaneously forming two new carbon-carbon bonds and one carbon-oxygen double bond.

Kinetic study on reactive extraction of clorprenaline enantiomers with a combined chiral selector

ABSTRACT This paper reports on the kinetic study on reactive extraction of clorprenaline (CPNL) enantiomers with isobutyl (d)-tartrate (DT) and boric acid (BA) as combined chiral selector in a Lewis cell, where exists an interfacial reaction involving three species: BA, DT, and CPNL enantiomers. The important factors that influence the kinetics of reactive extraction are investigated. Through multiple linear regression analysis of the experimental data, the order with respect to BA, CPNL, and DT of the interfacial reaction is 0.6, 0.8, and 0.8, respectively, and the total order of reaction is about 2.2. The forward rate constants have been calculated to be 2.476 × 10–4 L1.53/(mol1.2 s) for (R)-CPNL and 1.349 × 10–4 L1.53/(mol1.2 s) for (S)-CPNL.

Preparative enantioseparation of 2-(4-hydroxyphenyl)propionic acid by high speed counter-current chromatography with hydroxyethyl-β-cyclodextrin as chiral selector

ABSTRACT Enantiomers of 2-(4-hydroxyphenyl)propionic acid (HPPA) were successfully separated by high-speed counter-current chromatography (HSCCC) using hydroxyethyl-β-cyclodextrin (HE-β-CD) as chiral selector. Liquid–liquid extraction was applied to optimization of the two-phase solvent system used in HSCCC separation. A two-phase solvent system composed of isobutyl acetate and 0.1 mol L−1 phosphate buffer solution containing HE-β-CD (1:1, v/v) was selected. Factors affecting the distribution behavior of HPPA in the two-phase solvent system were studied separately, including pH of aqueous solution, concentration of HE-β-CD and equilibrium temperature. The optimum conditions containing pH of 2.50, 0.1 mol L−1 of HE-β-CD concentration, 5°C of temperature were obtained. Under the optimum conditions, 20 mg of HPPA enantiomers could be completely separated by HSCCC in a head-to-tail mode. Purities of the separated enantiomers were over 99.5% as determined by HPLC.

Bu4NI-Catalyzed Dehydrogenative Coupling of Diaryl Phosphinic Acids with C(sp3)–H Bonds of Arenes

An efficient phosphorylation of C(sp3)-H bonds of arenes with diaryl phosphinic acids via Bu4NI-catalyzed dehydrogenative coupling has been developed. This transformation proceeds efficiently under transition-metal-free reaction conditions and represents a straightforward method to prepare valuable organophosphorus compounds from readily available arenes and diaryl phosphinic acids.

Oxidative C–C Bond Functionalization of Methylenecyclopropanes with Aldehydes for the Formation of 2-Acyl-3,4-dihydronaphthalenes

A new FeCl2- and DTBP (di- tert-butyl peroxide)-promoted oxidative ring-opening and cyclization of methylenecyclopropanes with aldehydes for the synthesis of 2-acyl-3,4-dihydronaphthalenes is presented. This oxidative cyclization reaction proceeds via a radical addition, ring-opening, and cyclization sequence facilitated by a Lewis acid, and it offers a practical and straightforward route for the oxidative cyclization of methylenecyclopropanes with an aromatic carbon and a C(sp2)-H bond by simultaneously forming two new carbon-carbon bonds.

Kinetic study on extractive resolution of tropic acid by hydroxyethyl-β-cyclodextrin

Reactive extraction is proposed as a promising approach to the resolution of tropic acid (TA), where hydroxyethyl-β-cyclodextrin (HE-β-CD) is used as a selective extractant. The reaction between tropic acid and extractant occurred in the aqueous phase, and kinetic studies of reactive extraction have been investigated in a Lewis-type stirred cell. The batch experiments have been performed to study the process parameters affecting the extraction rate including agitation speed, interfacial area, pH value of aqueous phase, initial concentration of tropic acid enantiomers and initial concentration of extractant on the initial extraction rate. The kinetic equation of the forward rate was deduced at the experiment condition: rTA+xa0=xa0(4.041xa0×xa010−3)[TA+][CD]2; rTA−xa0=xa0(3.1234xa0×xa010−3)[TA−][CD]2.

Efficient adsorption toward precious metal from aqueous solution by zeolitic imidazolate framework-8

The recycling of precious metal ions is highly desirable to the environment and economy. In this work, zeolitic imidazolate framework-8 (ZIF-8), a porous and relatively stable adsorption material, was explored for the adsorption of Au from water. Important conditions affecting the adsorption performance were investigated, including pH, adsorption time, initial concentration, and temperature. In consequence, the ZIF-8 adsorbent exhibits excellent adsorption performance toward Au(III) with high adsorption capacity of 1192xa0mgxa0g−1 at pH 2.5 and 298xa0K. In addition, the study of recycling use indicated that the stable adsorption performance being maintained after recycle twice. The adsorption process of Au(III) onto ZIF-8 undergoes a spontaneous endothermic process and fits well with the Freundlich isotherm model. Kinetics studies indicated that the kinetics follows pseudo-second-order model and the intraparticle diffusion is the adsorption rate-determining step. Mechanism studies suggested that the electrostatic interaction and partial reduction of Au(III) play vital roles in the adsorption process. This work introduces a promising adsorbent for Au separation due to its considerable adsorption capacity, outstanding stability, and facile regeneration.