One-dimensional γ-Al2O3 nanofibers were modified with Nb2O5 to be used as an efficient heterogeneous catalyst to catalyze biomass into 5-hydroxymethylfurfural (5-HMF). At low Nb2O5 loading, the niobia species were well dispersed on γ-Al2O3 nanofiber through Nb-O-Al bridge bonds. The interaction between Nb2O5 precursor and γ-Al2O3 nanofiber results in the niobia species with strong Lewis acid si...

Production of 5-hydroxymethylfurfural (HMF) from biomass-derived glucose has great potential for synthesis renewable fuels and chemicals. Selective conversion to requires a balance between Lewis Brønsted acids the cascade isomerization followed by fructose dehydration. A dual Brønsted-Lewis acid, phosphotungstic acid encapsulated MIL-101(Al)–NH2 metal–organic frameworks (MOFs) was developed cat...

Bi(OTf)(3)·nH(2)O was found to be an efficient promoter of the cyclisative hydroamination of unactivated alkenyl sulfonamides, giving rise to the N-protected 2-methyl pyrrolidines in good to excellent yields (up to 95%). Based on control experiments, a joint Lewis acid-Brønsted acid catalysis might be in operation, or triflic acid itself, generated in situ by hydrolysis of metal triflate, could...

Lewis acidic zeolites are used to synthesize unsaturated dicarboxylic acid esters via aldol condensation of keto esters. Hafnium-containing BEA (Hf-BEA) zeolites catalyze the condensation of ethyl pyruvate into diethyl 2methyl-4-oxopent-2-enedioate and diethyl 2-methylene-4oxopentanedioate (an itaconic acid ester analogue) with a selectivity of ca. 80% at ca. 60% conversion in a packed-bed reac...

Three kinds of HZSM-5 nanoparticles with different acidity were tailored by impregnating MgO or varying Si/Al ratios. Both the textural and acidic properties of the as-prepared nanoparticles were characterized by nitrogen adsorption-desorption measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), ammonia temperature-programmed desorption (NH3-TPD) and Fourier transform infr...

A binary catalyst system for the enantioselective bromocycloetherification of 5-arylpentenols is described. The combination of an achiral Lewis base and a chiral Brønsted acid affords good enantioselectivities for the cyclization of Z configured 5-arylpentenols to form bromomethyltetrahydrofurans. The constitutional site selectivity is highly dependent upon the aromatic substituent and the conf...

Asymmetric catalysis is a powerful component of modern synthetic organic chemistry. To further broaden the scope and utility of asymmetric catalysis, new basic concepts for the design of asymmetric catalysts are crucial. Because most chemical reactions involve bond-formation between two substrates or moieties, high enantioselectivity and catalyst activity should be realized if an asymmetric cat...

Ionic liquid with both Lewis and Brønsted acid sites has been synthesized and its catalytic activities for Michael addition were carefully studied. The novel ionic liquid was stable to water and could be used in aqueous solution. The molar ratio of the Lewis and Brønsted acid sites could be adjusted to match different reactions. The results showed that the novel ionic liquid was very efficient ...

A conjugate addition/asymmetric protonation/aza-Prins cascade reaction has been developed for the enantioselective synthesis of fused polycyclic indolines. A catalyst system generated from ZrCl4 and 3,3'-dibromo-BINOL enables the synthesis of a range of polycyclic indolines in good yields and with high enantioselectivity. A key finding is the use of TMSCl and 2,6-dibromophenol as a stoichiometr...

Photocatalytic reactions of enones using metal polypyridyl complexes proceed by very different reaction manifolds in the presence of either Lewis or Brønsted acid additives. Previous work from our lab demonstrated that photocatalytic [2+2] cycloadditions of enones required the presence of a Lewis acidic co-catalyst, presumably to activate the enone and stabilize the key radical anion intermedia...