Zhi-Cai Shang

Room-Temperature Synthesis of Pyrazoles, Diazepines, β-Enaminones, and β-Enamino Esters Using Silica-Supported Sulfuric Acid as a Reusable Catalyst Under Solvent-Free Conditions

Abstract Silica-supported sulfuric acid (H2SO4·SiO2) has been utilized as a heterogeneous recyclable catalyst for a highly efficient regio- and chemoselective condensation of hydrazines/hydrazides, diamines, and primary amines with various β-dicarbonyl compounds at room temperature to afford pyrazoles, diazepines, and β-enaminones/β-enamino esters under solvent-free conditions within 5–15 min.

Binding interactions of pefloxacin mesylate with bovine lactoferrin and human serum albumin

The binding of pefloxacin mesylate (PFLX) to bovine lactoferrin (BLf) and human serum albumin (HSA) in dilute aqueous solution was studied using fluorescence spectra and absorbance spectra. The binding constant K and the binding sites n were obtained by fluorescence quenching method. The binding distance r and energy-transfer efficiency E between pefloxacin mesylate and bovine lactoferrin as well as human serum albumin were also obtained according to the mechanism of Förster-type dipole-dipole nonradiative energy-transfer. The effects of pefloxacin mesylate on the conformations of bovine lactoferrin and human serum albumin were also analyzed using synchronous fluorescence spectroscopy.

Polyethylene Glycol as a Nonionic Liquid Solvent for the Synthesis of N-Alkyl and N-Arylimides

Abstract Polyethylene glycol (PEG) an inexpensive, nontoxic, environmentally friendly reaction medium for the synthesis of N-alkyl and N-arylphthalimides to afford the corresponding adducts in excellent yields under mild reaction conditions. The use of PEG avoids the use of acidic or basic catalysts, and moreover PEG could be recovered and reused.

3D-QSAR studies on 4-Hydroxyphenylpyruvate Dioxygenase inhibitors by comparative molecular field analysis (CoMFA)

A comparative molecular field analysis (CoMFA) of alkanoic acid 3-oxo-cyclohex-1-enyl ester and 2-acylcyclohexane-1,3-dione derivatives of 4-hydroxyphenylpyruvate dioxygenase inhibitors has been performed to determine the factors required for the activity of these compounds. The substrates conformation abstracted from dynamic modeling of the enzyme-substrate complex was used to build the initial structures of the inhibitors. Satisfactory results were obtained after an all-space searching procedure, performing a leave-one out (LOO) cross-validation study with cross-validation q(2) and conventional r(2) values of 0.779 and 0.989, respectively. The results provide the tools for predicting the affinity of related compounds, and for guiding the design and synthesis of new HPPD ligands with predetermined affinities.

Theoretical studies on tautomerism of benzoylcyclohexane-1,3-dione and its derivatives

Abstract In the present paper, geometry optimizations were performed at HF/6-31G ∗ level for all of the possible tautomers of benzoylcyclohexanedione. For one triketone and two cis -endocyclic double bond enol tautomers that have lowest energies, extensive calculations were performed. The effect of calculation method and the size of the basis set on the relative stability of the tautomers were investigated. In addition, the tautomeric equilibrium constants and the energy barrier of the benzoylcyclohexane-1,3-diones were calculated. The solvent effect was fully considered when calculating the equilibrium constants and the results were analyzed by comparing with the experimental results. Finally, calculations were performed on representative 2-substituted benzoylcyclohexane-1,3-dione derivatives. It appears that the free energy of tautomerization and their HPPD inhibitive activity correlated closely.

L-Proline as an efficient and reusable promoter for the synthesis of coumarins in ionic liquid

The effect of L-proline as a promoter on the condensation reaction of salicylaldehyde or its derivatives with ethyl acetoacetate in neutral ionic liquid [emim]BF4 was studied. All reactions were carried out under mild reaction conditions and achieved high yields. Moreover, the ionic liquid containing L-proline could be recycled and reused for several times without noticeably decreasing in productivity. The results show that the L-proline-[emim]BF4 system has a potential in contribution to the development of environmentally friendly and inexpensive processes in organic syntheses.

Correlation between empirical solvent polarity scales and computed quantities derived from molecular surface electrostatic potentials

Analysis of five empirical solvent polarity scales ETN, π*, Py, S′ and SPP is carried out by correlating them with Π and σ2tot, two computed quantities derived from molecular surface electrostatic potentials. Our results indicate (i) that the S′ scale should be a good global solvent polarity scale, (ii) that it would be inappropriate to use the ETN and Py scales to describe non-specific solute–solvent interactions for protic solvents, and (iii) that the π* and SPP scales are probably contaminated with charge-transfer effects for aromatic and polychlorinated solvents. The differences between our results and those obtained by the correlation of empirical scales with a theoretical thermodynamic analysis result (EPNA) are discussed in the context of intermolecular interactions between the probe solutes and the solvent considered.

Room-Temperature Synthesis of Diindolylmethanes Using Silica-Supported Sulfuric Acid as a Reusable Catalyst Under Solvent-Free Conditions

Abstract Efficient electrophilic substitution reactions of indoles with various aromatic and aliphatic aldehydes were carried out using a catalytic amount of H2SO4 · SiO2 under solvent-free conditions to afford the corresponding bis(indolyl)methanes in excellent yields.

Efficient Dimeric Esterification of Alcohols with NBS in Water Using L-Proline as Catalyst

Abstract The L-proline-catalyzed oxidation of aliphatic primary alcohols with N-bromosuccimide (NBS) in water at room temperature to afford the corresponding dimeric esters in good to excellent yields was described. This pathway of dimeric esterification was proved to be very simple and environmentally friendly. GRAPHICAL ABSTRACT

Finding new elicitors that induce resistance in rice to the white-backed planthopper Sogatella furcifera.

Herein we report a new way to identify chemical elicitors that induce resistance in rice to herbivores. Using this method, by quantifying the induction of chemicals for GUS activity in a specific screening system that we established previously, 5 candidate elicitors were selected from the 29 designed and synthesized phenoxyalkanoic acid derivatives. Bioassays confirmed that these candidate elicitors could induce plant defense and then repel feeding of white-backed planthopper Sogatella furcifera.