Chemoselective hydrogenation of α,β-unsaturated aldehydes with modified Pd/C catalyst

Selective hydrogenation of α, β-unsaturated aldehydes with modified Pd/C catalyst was developed.The reduction of C=O bond could be efficiently inhibited by the addition of carbonates,and high selectivity to the corresponding saturated aldehydes was achieved under mild conditions.This protocol provides an alternative for efficient preparation of saturated aldehydes.     

A robust Ru-PNNP catalyst system for the asymmetric hydrogenation of α,β-unsaturated ketones to allylic alcohol

A robust and stable Ru-Biphosphinobioxazoline catalyst system is discovered for the highly enantioselective hydrogenation of enones to allylic alcohols. A series of acyclic α,β-unsaturated ketones react well affording the desired products in high yields (up to 98%) and enantioselectivities (up to 98% ee). Simple manipulation process and tolerance of water and air make this catalysis more practical and appealing.     

One-pot Approach to the Conversion of Alcohols into α-Halo-α,β-unsaturated Esters

α-Halo-α, β-unsaturated esters are important intermediates in organic synthesis. For example, they are used for α-amino acid preparation1 and vinylogous Darzen reactions2, as a versatile fluorinated building block, they are also used for the preparati…     

Self-supported BINOL-Zn catalysts for heterogeneous enantioselective epoxidation of (E)-α,β-unsaturated ketones

A class of chiral self-supported catalysts prepared from bis-BINOL ligands and diethyl zinc were successfully applied in the hetereogeneous enantioselective epoxidation of a range of (E)-α,β-unsaturated ketones, affording the corresponding epoxy ketones in high enantioselectivity. The self-supported catalysts were easily recovered from the reaction mixture and were reusable for several consecutive runs.     

无铬Co-Cu/SBA-15催化剂催化生物质衍生α-,β-不饱和醛加氢制醇（英文）

Cr-free bi-metallic SBA-15-supported Co–Cu catalysts were examined in the conversion of biomass-derived α-, β-unsaturated aldehyde(furfural) to value-added chemical furfuryl alcohol(FOL).Co–Cu/SBA-15 catalysts with a fixed Cu loading of 10 wt% and varying Co loadings(2.5, 5, and 10 wt%) were prepared by the impregnation method. The catalysts were characterized by X-ray diffraction, N2 sorption, H2 temperature-programmed reduction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, CO chemisorption, and inductively coupled plasma mass spectrometry. The influence of different reaction parameters such as temperature, pressure, catalyst dosage, and furfural concentration on the catalyst performance was evaluated. Relative to catalysts supported on amorphous silica, the current SBA-15-supported Co–Cu catalysts displayed higher performance, attaining a furfural conversion of 99% and furfuryl alcohol selectivity of 80%. The catalytic reactions were conducted in a 100-mL autoclave at 170 °C and 2 MPa H2 pressure for 4 h.     

Quantum-dots containing Fe/SBA-15 silica as “green” catalysts for the selective photocatalytic oxidation of alcohol (methanol,under visible light)

Fe/SBA-15 catalysts containing iron oxide nanoparticles confined inside silica pores (replicated, internal, poorly crystalline) and grown outside silica grains (external, mainly crystalline hematite) in different proportions are prepared using a single silica support. Fe-species are deposited by the two-solvent technique with two iron salts precursors (Fe(NO₃)₃·9H₂O, FeCl₃·6H₂O) and two solvents (cyclohexane, hexane) for 11 wt% of iron. Calcination is performed in reproducible conditions (700 °C, 2 °C/min, thin bed, in air). SAXS measurements are used to show that the 2D hexagonal structure of the used silica is maintained after Fe-loading and calcination. Ar sorption measurements show that the pores are partially plugged. The oxidation of pure methanol is used as a test reaction to compare photocatalytic properties. H₂O₂ and visible light both activate the reaction. More active catalysts are formed with hexane associated with FeCl₃·6H₂O than with Fe(NO₃)₃·9H₂O. A reversed situation is observed with cyclohexane. Iron leaching (after 1 h 30 of test, up to 3 mg of Fe by mL) is important. These results are expected to be of interest in the exploration of size and shape “nanocatalysis” and to provide a further understanding for the reactions that take place when porous silicas are used as supports.     

Sulfamic acid as a cost-effective and recyclable solid acid catalyst for Friedel–Crafts alkylation of indole with α,β-unsaturated carbonyl compound and benzyl alcohol

Sulfamic acid was proved to be a cost-effective and recyclable catalyst for Friedel-Crafts type reaction of indole withα,β-unsaturated carbonyl compound and benzyl alcohol.Various indoles,α,β-unsaturated carbonyl compounds and a benzyl alcohol were successfully used in this type of reaction,and the corresponding products were obtained in good to excellent yields.     

Catalytic conjugate addition of indole toα,β-unsaturated ketones by Co（ClO4）-2·6H2O/bis-Schiff base complexes

Co（ClO₄）)₂·6H₂O/bis-Schiff base complexes promoted the conjugate addition of indole toα,β-unsaturated ketones under mild conditions,giving the corresponding addition products with high yields.And the complex has been characterized with XRD and IR.     

TiCl4-mediated olefination of aldehydes with acetic acid and alkyl acetates: a stereoselective approach to (E)-α,β-unsaturated carboxylic acids and esters

A new method has been developed for the preparation of α,β-unsaturated carboxylic acids and corresponding esters with (E)-stereoselectivity via the TiCl₄-mediated olefination of aldehydes. The method, which uses readily available acetic acid or its alkyl esters as active methylene partners, is more flexible and complementary to conventional routes in the preparation of (E)-cinnamic acid derivatives.