Acid-Promoted Multicomponent Tandem Cyclization to Synthesize Fully Substituted Oxazoles via Robinson-Gabriel-Type Reaction.

An acid-promoted multicomponent reaction for the synthesis of diverse fully substituted oxazole derivatives from simple and readily available arylglyoxal monohydrates, nitriles, and various C-nucleophiles has been developed. This protocol features wide functional group diversity which is capable of installing 4-hydroxycoumarin, 2-naphthol, and 1,3-cyclohexanedione motifs to oxazoles. Mechanistic analysis indicates that a classical Robinson-Gabriel reaction served as the key step for this tandem transformation.

Acid-Catalyzed Multicomponent Tandem Double Cyclization: A One-pot, Metal-free Route to Synthesize Polyfunctional 4,9-Dihydropyrrolo[2,1-b]quinazolines.

An acid-catalyzed multicomponent tandem double cyclization protocol has been developed for the synthesis of polyfunctional 4,9-dihydropyrrolo[2,1-b]quinazolines from simple and readily available arylglyoxal monohydrates, 2-aminobenzylamine, and trans-ß-nitrostyrenes. This practical and metal-free reaction proceeds through an imine formation/cyclization/Michael addition/Henry cyclization protocol, resulting in the construction of four new bonds and two ring moieties directly in one pot.

Improvement of sulfur and water resistance with Fe-modified S-MnCoCe/Ti/Si catalyst for low-temperature selective catalytic reduction of NO with NH3.

The low-temperature SCR of NOx by NH3 is restricted in application since the catalysts is easily poisoned by sulfur and water. The Fe modified Mn-Co-Ce/TiO2/SiO2 catalysts synthesized via impregnation method and sulfating were evaluated for low-temperature NH3-SCR in the presence of SO2 and H2O. The calcination temperature and loading amounts of Mn, Fe, Co and Ce were optimized. Adding of Fe into S-MnCoCe/Ti/Si played an important role in resistance to sulfur and water poisoning. The optimal calcination temperature was 380 °C and the optical mass loading of the catalyst was 10% of Mn, 10% of Fe, 1% of Co and 4% of Ce. The optimal S-MnFeCoCe/Ti/Si catalyst maintained high NOx conversion of 93% at reaction temperature of 160 °C in the presence of 50 ppm SO2 and 10 vol% H2O. The catalytic activity did not continue to fall after two times of repeated used in the temperature range of 100-200 °C, indicating its excellent sulfur and water durability and stability in the presence of SO2 and H2O. The interaction between MnOx and FeOx enhanced sulfur and water durability rather than other bi-metal interactions. Furthermore, the mechanism of Fe improving resistance to SO2 and H2O was discussed.

Estimating Risks of Inapparent Avian Exposure for Human Infection: Avian Influenza Virus A (H7N9) in Zhejiang Province, China.

Inapparent avian exposure was suspected for the sporadic infection of avian influenza A(H7N9) occurring in China. This type of exposure is usually unnoticed and difficult to model and measure. Infected poultry with avian influenza H7N9 virus typically remains asymptomatic, which may facilitate infection through inapparent poultry/bird exposure, especially in a country with widespread practice of backyard poultry. The present study proposed a novel approach that integrated ecological and case-control methods to quantify the risk of inapparent avian exposure on human H7N9 infection. Significant associations of the infection with chicken and goose densities, but not with duck density, were identified after adjusting for spatial clustering effects of the H7N9 cases across multiple geographic scales of neighborhood, community, district and city levels. These exposure risks varied geographically in association with proximity to rivers and lakes that were also proxies for inapparent exposure to avian-related environment. Males, elderly people, and farmers were high-risk subgroups for the virus infection. These findings enable health officials to target educational programs and awareness training in specific locations to reduce the risks of inapparent exposure.

Acid-Catalyzed Multicomponent Tandem Cyclizations: Access to Polyfunctional Dihydroindolizino[8,7-b]indoles.

An acid-catalyzed multicomponent tandem cyclization protocol has been developed for the synthesis of polyfunctional dihydroindolizino[8,7-b]indoles from simple and readily available arylglyoxal monohydrates, tryptamines, and trans-ß-nitrostyrenes or malononitrile. This reaction represents a highly efficient and convenient methodology for the synthesis of diversely substituted heteropolycyclic scaffolds under mild, metal-free conditions.

Expeditious Synthesis of 2-Phenylquinazolin-4-amines via a Fe/Cu Relay-Catalyzed Domino Strategy.

A highly efficient Fe/Cu relay-catalyzed domino protocol has been developed for the synthesis of 2-phenylquinazolin-4-amines from commercially available ortho-halogenated benzonitriles, aldehydes, and sodium azide. This elegant domino process involved consecutive iron-mediated [3 + 2] cycloaddition, copper-catalyzed SNAr, reduction, cyclization, oxidation, and copper-catalyzed denitrogenation sequences. The formed structure is the privileged core in drugs and bioactive molecules.

Consecutive Cycloaddition/S(N)Ar/Reduction/Cyclization/Oxidation Sequences: A Copper-Catalyzed Multicomponent Synthesis of Fused N-Heterocycles.

A highly efficient multicomponent domino protocol has been developed for the synthesis of 5-phenyl-[1,2,3]triazolo[1,5-c]quinazolines from simple and readily available (E)-1-bromo-2-(2-nitrovinyl)benzenes, aldehydes, and sodium azide. This elegant domino process involved consecutive [3 + 2] cycloaddition, copper-catalyzed S(N)Ar, reduction, cyclization, and oxidation sequences. Notably, sodium azide acted as a dual nitrogen source in the construction of this novel fused N-heterocycle.

Intramolecular decarboxylative coupling as the key step in copper-catalyzed domino reaction: facile access to 2-(1,3,4-oxadiazol-2-yl)aniline derivatives.

A copper-catalyzed domino protocol for the synthesis of 2-(1,3,4-oxadiazol-2-yl)aniline derivatives has been developed from simple and available isatins and hydrazides. This domino process integrated consecutive condensation, base-promoted ring-opening and the key copper-catalyzed decarboxylative coupling for intramolecular C-O bond formation.