Visible-Light-Controlled Oxidation of Glucose using Titania-Supported Silver Photocatalysts.

The visible-light-mediated photo-catalytic selective valorisation of glucose using TiO2-supported Ag nanoparticles is shown for the first time. The optimisation of the catalyst composition, substrate-to-catalyst ratio and reaction medium proved that a near total suppression of the mineralisation pathway could be achieved with a selectivity to partial oxidation products and small-chain monosaccharides as high as 98 %. The primary products were determined to be gluconic acid, arabinose, erythrose, glyceraldehyde and formic acid. Under UVA light, the selectivity to organics decreases because of the production of CO2 from mineralisation. A reaction mechanism is proposed based on an α-scission process combined with the Ruff degradation reaction, which explains the presence of the oxidation products, the smaller carbohydrates and formic acid. X-ray photoelectron spectroscopy, UV/Vis spectroscopy and microscopy studies showed the presence of plasmonic 4 nm particles of silver that were oxidised to silver oxide over the course of the reaction, and recycling studies revealed that this was not detrimental to activity.

Samarium diiodide-catalyzed diastereoselective pinacol couplings.

A complex of samarium diiodide (SmI(2)) with tetraglyme catalyzes the intermolecular pinacol coupling of aromatic or aliphatic aldehydes at loadings of 10 mol % in the presence of Me(2)SiCl(2) and Mg. Diastereoselectivity of up to 95/5 (+/-/meso) has been achieved for aliphatic aldehydes and up to 19/81 (+/-/meso) for aromatic aldehydes. De values of up to 99% have been achieved in intramolecular pinacol coupling reactions using the SmI(2)/tetraglyme/Mg/Me(2)SiCl(2) catalytic system.

Adding the right (or left) twist to tris-chelate complexes--coordination chemistry of chiral oxazolylphenolates with M3+ ions (M = Al or lanthanide).

A series of homoleptic tris-chelate complexes ML3 (M = Al or rare earth; L = chiral or achiral oxazolyl phenolate or -naphtholate) is reported. In all cases, complexes crystallize as mer-isomers and complete diastereoselectivity is observed on crystallization of the complexes: ML3 crystallize with Λ-helicity at the metal where L = (S)-oxazolylphenolate. Complexes have been characterized in solution by NMR spectroscopy, demonstrating rapid ligand exchange at ambient temperature for rare earth complexes, and slow exchange on the NMR timescale for complexes of Al; in all cases the mer-isomer is observed exclusively. Crystal structures are reported for [YL3]2 (L = (S)-2-(4-isopropyl-4,5-dihydrooxazol-2-yl)-phenolate), mer-[YbL3] (L = (S)-2-(4-isopropyl-4,5-dihydrooxazol-2-yl)-6-methylphenolate) and mer-[AlL3] (L = (S)-2-(4-isopropyl-4,5-dihydrooxazol-2-yl)-6-methylphenolate, L = (S)-2-(4-isopropyl-4,5-dihydrooxazol-2-yl)-6-cyanophenolate), L = (S)-1-(4-isopropyl-4,5-dihydrooxazol-2-yl)naphthalen-2-olate, L = 1-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)naphthalen-2-olate).