Hengshan Wang

Ce(OTf)3-Catalyzed [3 + 2] Cycloaddition of Azides with Nitroolefins: Regioselective Synthesis of 1,5-Disubstituted 1,2,3-Triazoles

The first example of rare earth metal-catalyzed [3 + 2] cycloaddition of organic azides with nitroolefins and subsequent elimination reaction is described. In the presence of a catalytic amount of Ce(OTf)3, both benzyl and phenyl azides react with a broad range of aryl nitroolefins containing a range of functionalities selectively producing 1,5-disubstituted 1,2,3-triazoles in good to excellent yields.

Regioselective Synthesis of 1,3,5-Substituted Benzenes via the InCl3/2-Iodophenol-Catalyzed Cyclotrimerization of Alkynes

A novel indium(III)-catalyzed cyclotrimerization of alkynes in the presence of 2-iodophenol gave 1,3,5-substituted benzenes in excellent yields with complete regioselectivity. The reaction condition is tolerant to air, and atom economical, in accordance with the concept of modern green chemistry. This method provides a rapid and efficient access to 1,3,5-substituted benzenes.

Atom-Economical Chemoselective Synthesis of 1,4-Enynes from Terminal Alkenes and Propargylic Alcohols Catalyzed by Cu(OTf)2

A novel and efficient Cu(OTf)2-catalyzed sp(3)-sp(2) C-C bond formation reaction through the direct coupling of propargylic alcohols with terminal alkenes has been realized under mild conditions. The reaction is tolerant to air and is atom-economical, in accordance with the concept of modern green chemistry. The present protocol provides an attractive approach to a diverse range of 1,4-enynes in high to excellent yields.

Antioxidant activity of alcoholic extract of Agrimonia pilosa Ledeb

Ultrasonically assisted extraction and Soxhlet extraction using 95% ethanol were performed to obtain ultrasonically assisted extract of Agrimonia pilosa (UEA) and Soxhlet extract of Agrimonia pilosa (SEA). The effects of the different extracting methods on the total phenolic (TP) and total flavonoid (TF) content of the extracts from Agrimonia pilosa were investigated. The findings showed that UEA contained higher TP and TF content than SEA. To understand better the effect of ultrasonic extraction, the antioxidant activities of UEA and SEA were evaluated with different antioxidant testing systems in vitro to determine reducing power, total antioxidant capacity, and free radical scavenging assays, including 2,2′-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radicals. Both SEA and UEA exhibited satisfied antioxidant activity superior to that of synthetic antioxidant butylated hydroxytoluene (BHT). The antioxidant activity of the tested subjects was in the order of UEAxa0>xa0SEAxa0>xa0BHT. Their high phenolic and flavonoid contents could be responsible for their antioxidant activity and pharmacologic actions.

Regioselective Palladium-Catalyzed Decarboxylative Cross-Coupling Reaction of Alkenyl Acids with Coumarins: Synthesis of 3-Styrylcoumarin Compounds

A novel and efficient protocol for the regioselective synthesis of 3-styrylcoumarins from readily available cinnamic acids and coumarins is presented. The reaction proceeds via a decarboxylative cross-coupling mediated by a catalytic amount of Pd(OAc)2, with Ag2CO3 as an oxidant, and with 1,10-phenanthroline as a ligand. A plausible reaction mechanism for this process is depicted, and the resulting 3-styrylcoumarins show excellent fluorescence quantum yields.

Indium(III) chloride catalyzed conjugate addition reaction of alkynylsilanes to acrylate esters.

A novel and efficient procedure for the synthesis of δ,γ-alkynyl esters by the conjugate addition of alkynylsilanes to acrylate esters in the presence of a catalytic amount of indium(III) chloride has been developed. This method provides a rapid and efficient access to substituted δ,γ-alkynyl esters.

Antioxidant activities of Liquidambar formosana Hance leaf extracts

Leaves of Liquidambar formosana Hance has been be used as a rice dye for festival food by a small group of people in Guangxi province China. This study evaluated the antioxidant activities of extracts of L. formosana Hance leaves, and the effects of different extract solvents on total phenolics (TP), total flavonoids (TF), and antioxidant potential. The antioxidant activity of the extracts was assessed by using the following methods: in vitro: 1,1-diphenyl-2-picrylhydrazyl and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diamonium salt both free radical scavenging assays, reducing, and phosphomolybdenum assays. Antioxidant activity of the synthetic antioxidant butylated hydroxytoluene also was determined in parallel experiments for comparison. All extracts exhibited excellent antioxidant activities and were superior to butylated hydroxytoluene. The antioxidant activity and TP and TF content of various extracts seemed to follow the same trend: ethanolic extractxa0>xa0water extractxa0>xa0acetone extract. This implied that there is a good correlation between antioxidant activities and TP/TF content. In addition, UV/Vis spectra of various extracts were examined to obtain potential antioxidant compounds in assorted extracts.

Cu(OTf)2-catalyzed three-component annulation reaction: one-pot synthesis of 4,5-dihydropyrazole from aldehydes, hydrazines and alkenes

A convenient one-pot three-component annulation process has been developed for the synthesis of 4,5-dihydropyrazole derivatives from aldehydes, hydrazines and alkenes using Cu(OTf)2 as a catalyst. This method provides a flexible and rapid route to 4,5-dihydropyrazole.

Syntheses, characterization and fluorescent properties of two series of dehydroabietic acid C-ring derivatives.

Two series of dehydroabietic acid C-ring derivatives, nitrogen-containing heterocycles (6a-9b) and C-12 substituted compounds (10a-11b), were synthesized and characterized by element analysis, IR, NMR and MS. The UV-vis absorption and fluorescence spectral characteristics of these compounds have been comparatively investigated, and their fluorescence quantum yields were further evaluated. Compared to dehydroabietic acid 1, the absorption and emission spectra of these compounds were bathochromically shifted due to the multiple aromatic rings with rigid planar structures or the larger conjugation of benzene moiety.

Palladium-catalyzed formation of phenolic compounds by reaction of carbonyl compounds with carbon dioxide

The use of carbon dioxide as a renewable and environmentally friendly source of carbon is highly attractive. A novel and efficient protocol for the synthesis of phenolic compounds from carbonyl compounds and carbon dioxide in the presence of a catalytic amount of Pd(OAc)(2) has been developed. This reaction is appealing for industries and is a tool for the sequestration of carbon dioxide.