Dynamic kinetic Transfer hydrogenation reaction of 2-methyl-2,4-diaryl-2,3-dihydrobenzo[b][1,4]diazepines, using phosphoric acids as catalysts and Hantzsch ester as hydride source, has been studied. A 3,3'-H8-binol derived phosphoric acid has been identified the optimal chiral catalyst for this transformation, affording 1,3-diamine derivatives with up to 8/1 dr, 86% ee and 94% ee for the major ...

Enantioenriched secondary alcohols represent an important class of molecules found in numerous intermediates, chiral building blocks, and biologically active compounds. Asymmetric reduction of prochiral ketones constitutes the most straightforward way to form these important moieties. Traditionally, stoichiometric amounts of chiral ligands were used together with an aluminium or a boron hydride...

the present work concerns on the investigation of the role of polyethylene glycols (pegs) as masking agent for amelioration of extraction-separation of la(iii), eu(iii) and er(iii) ions by the acidic extractant bis(2-ethylhexyl)phosphoric acid (dehpa). the studied solvent extraction system is based on the combination of chelating effect of dehpa in the organic phase on the one hand, and the bin...

statement of problem: in some clinical situations, repair of composite restorations is treatment of choice. improving the bond strength between one new and old composite usually requires increased surface roughness to promote mechanical interlocking since chemical bonding might not be adequate. similarly, the treatment of a laboratory fabricated resin composite restoration involves the same pro...

The aim of this study was to evaluate the effect of conditioners (sodium hypochlorite (NaOCl), Roth's ethylenediaminetetraacetic acid (EDTA), and phosphoric acid) on shear bond strength and morphology of Nd:YAP laser-irradiated dentin. In particular, the key focus was on the bond durability between resin composite and treated dentin after being subjected to thermocycling in artificial saliva be...

After the combustions, the phosphoric acid was, in fact, in aqueous solution, so that a correction for the heat of solution was necessary. These combustions were made in a static bomb, and as a result the concentration of phosphoric acid probably varied considerably in different parts of the bomb, leading to the comparatively large error of ±O·l per cent, associated with the heats of combustion...

This study assessed bonding of orthodontic brackets to porcelain teeth using two different surface preparation techniques and comparing two bonding systems, Fuji Ortho L.C. and Transbond. Four groups of 20 porcelain premolar teeth were bonded with metal orthodontic brackets (0.022 inch Minitwin, 3M Unitek) according to the following protocol: Transbond with a phosphoric acid etch (group 1), Tra...