An-Jiang Zhang

Asymmetric Friedel-Crafts Reaction of 4,7-Dihydroindoles with Nitroolefins by Chiral Bronsted Acids under Low Catalyst Loading

Slowly does it! By adding the substrate by a syringe pump, a highly efficient Friedel-Crafts reaction of 4,7-dihydroindoles with nitroolefins was realized with 0.5 mol % of a chiral phosphoric acid. The Friedel-Crafts alkylation, together with a subsequent oxidation of the product, led to 2-substituted indoles in excellent enantiomeric excesses, which can be easily transformed to enantioenriched tetrahydro-gamma-carbolines.

Chiral Bro̷nsted Acid-Catalyzed Asymmetric Friedel−Crafts Alkylation of Pyrroles with Nitroolefins

A highly efficient Friedel-Crafts reaction of pyrroles with nitroolefins by a chiral phosphoric acid was realized. With 5 mol % of catalyst, reactions conducted at rt afforded the 2-substituted or 2,5-disubstituted pyrroles in up to 94% ee for a wide range of substrates.

Synthesis and Biological Activity of 3-(2-Furanyl)-6-Aryl-1,2,4-Triazolo[3,4-b]-1,3,4 –Thiadiazoles

3-(2-Furanyl)-4-amino-5-mercapto-1,2,4-triazole (1) was prepared from 2-furoic acid through a multi-step reaction sequence. Compound 1 reacted with aromatic acids in the presence of phosphorus oxychloride to give 3-(2-furanyl)-6-aryl-1,2,4- triazolo[3,4-b]-1,3,4-thiadiazoles (2). The structures of all the newly synthesized compounds have been confirmed by elemental analysis, IR, 1H-NMR, 13C-NMR and mass spectra. The bioassay indicated most of the title compounds possess significant growth promoting effects on mung bean radicles.

Synthesis and Biological Activity of Some Novel Derivatives of 4-Amino-3-(D-galactopentitol-1-yl)-5-mercapto-1,2,4-triazole

To discover new 1,2,4-triazole derivatives which may possess significant biological activities, we synthesized a series of novel 6-aryl-3-(D-galactopentitol-1-yl)-7H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazines and 4-(arylmethylidene)amino-5-(D-galactopentitol-1-yl)-3-mercapto-4H-1,2,4-triazoles from 4-amino-3-(D-galactopentitol-1-yl)-5-mercapto-1,2,4-triazole. All the title compounds were characterized by elemental analysis, IR, 1H- and 13C-NMR. Plant growth-regulating activity tests showed that these compounds have remarkable effects on the growth of radish and wheat.

pattern-based recognition for determination of enantiomeric excess, using chiral auxiliary induced chemical shift perturbation nmr

A protocol for the determination of enantiomeric excess of chiral carboxylic acid, using the subtle frequency shifts (chemical shift perturbation) in NMR spectra induced by chiral auxiliary, is described. The spectra were analyzed with two pattern recognition protocols. Principal component analysis demonstrated good enantioselective separation of the analytes, and partial least-squares was used to analyze ee values of unknown samples.

Chemical composition of the green alga Codium Divaricatum Holmes

A new sterol, 24-R-stigmasta-4,25-diene-3β,6β-diol (1), along with three known compounds (2-3), was isolated from the green alga Codium divaricatum Holmes, a traditional Chinese medicine, which is efficacious against cancer. All structures were determined by spectroscopic methods and comparison with related known compounds. Single-crystal X-ray crystallography allowed us to confirm the structure of 1. To our knowledge, the compound 1 is reported as the first from natural source, and compounds 2, 4 have not been isolated from green algae before.

A review of preparation of binderless fiberboards and its self-bonding mechanism

The demand for fiberboards has been growing in recent years. However, emission of formaldehyde, which was the main component of adhesives in fiberboards, has caused environmental and health concerns. Industries are therefore pursuing green chemistry technologies to eliminate these concerns. Binderless fiberboards appeared to be such candidates since the manufacturing process involved no resin addition. Several potential mechanisms of the formation of binderless fiberboards have been proposed. Chemical changes of components in lignocellulosic materials were expected to occur, and self-bonding achieved during hot pressing provided main bonding strength. This review summarized various aspects of binderless fiberboard production, particularly feasibility of different raw materials, chemical and enzymatic pretreatments of raw materials, manufacturing process, as well as the potential mechanism of self-bonding. Furthermore, further work that may benefit the elucidation of self-bonding mechanism was discussed.

Synthesis and Biological Evaluation of Some Novel Schiff’s Bases from 1,2,4-Triazole

We have synthesized a number of novel Schiffs bases from 4-amino-3-(D-glucoheptonic-hexitol-1-yl)-1H-1,2,4-triazole-5-thione. By attaching D-glucoheptonic-hexitol-1-yl residues to 1,2,4-triazole at the 3-position, the solubility of the title compounds has been improved greatly. All the products have been characterized by elemental analysis, IR, 1H-NMR, 13C-NMR and MS. The plant-growth regulating effects of the title compounds were examined. From the biological activity results, we found that most compounds showed weak to moderate activities.

Synthesis of Novel 3,5-Dichloro-2-arylpyridines by Palladium Acetate-Catalyzed Ligand-Free Suzuki Reactions in Aqueous Media

A highly efficient palladium acetate-catalyzed ligand-free Suzuki reaction of 2,3,5-trichloropyridine with arylboronic acids in aqueous phase was developed. High yields of 3,5-dichloro-2-arylpyridines, a simple Pd source, absence of ligands, and environmentally benign as well as mild reaction conditions are important features of this method.

Regioselective Synthesis of 1-(2,6-Dichloro-4-Trifluoromethylphenyl)- 4-Alkyl-1H-[1,2,3]-Triazoles

A new and efficient method for the synthesis of 1-(2,6-dichloro-4-trifluoro-methylphenyl)-4-alkyl-1H-[1,2,3]-triazoles by the room temperature 1,3-dipolar cycloaddition of (2-azido-1,3-dichloro-5-trifluoromethyl)benzene with terminal alkynes in the presence of Cu (I) salt as catalyst is reported. All the reactions gave 1,4-disubstituted products with high regioselectivity, as no 1,5-disubstituted product was formed. The structures of all the title compounds have been confirmed by elemental analysis, 1H- and 13C-NMR and in addition, the structure of compound 5a was investigated by X-ray crystallography.