Biphasic reduction

Table 15.5 Biphasic reduction of 3-methyl-2-butenal. RuCI3 (0.5 mol%)...

The binding of functionalized chiral ligands to water-soluble polymers has also been shown a (diphenylphosphino)pyrrolidine derivative reacts with poly(acrylic acid) to form a macroligand that is useful in biphasic reduction (35). 

Palladium(II) chloride in conjuction with PEG-400 smoothly catalyzes the biphasic reduction of arylalkynes with sodium borohydride [18]. The reaction does not occur in the absence of PdCl2. In contrast to LiAlH, (a well-known reagent for the... 

Respiratory Asthma due to tosylchloramide (Chloramine T) has been reported in a 43-year-old male nurse, who noticed asthmatic reactions after exposure to the disinfectant [25" ]. A skin test with tosylchloramide was positive and an inhalation test with 0.5% caused a significant biphasic reduction in FEVi an inhalation test with glu-taral (glutaraldehyde), to which he had also been exposed, was negative. 

Radiation also reduces the rate of DNA synthesis during the S phase (Fig. 14.4b). There is a dose-de-pendent biphasic reduction, suggesting inhibition of at least two different steps in replication. It is now known that the radiosensitive component reflects inhibition of replicon cluster initiation, whereas the radioresistant component reflects inhibition of DNA chain elongation (Painter and Young 1980). This inhibition is reduced in cells from ataxia telangiectasia (AT) patients, suggesting that it reflects an active cellular response to the... 

Other biphasic reductions using molecular hydrogen or an H-donor molecule include the selective hydrogenation of dienes to monoenes by K3[HCo(CN)5] (4) and reduction of arenes by hydridoruthenium clusters, such as [H4Ru4( -C6H6)4][BF4]2 (106). These reactions represent potentially important chemical transformations however, owing to catalyst instability or low productivity they have not been developed to practical biphasic processes. 

Joo, F. Benyei, A. (1989) Biphasic reduction of unsaturated aldehydes to unsaturated alcohols by ruthenium complex-catalysed hydrogen transfer, J. Organomet. Chem., 363, C19-21. 

Another example for the use of hydrogen as reductant is observed in the reduction of imine [5b]. New imine reductase activity has been discovered in the anaerobic bacterium Acetobacterium woodii by screening a dynamic combinatorial library of virtual imine substrates, using a biphasic water-tetradecane solvent system. 

In a biphasic solid-liquid medium irradiated by power ultrasound, major mechanical effects are the reduction of particles size leading to an increased surface area and the formation of liquid jets at solid surfaces by the asymmetrical inrush of the fluid into the collapsing voids. These liquid jets not only provide surface cleaning but also induce pitting and surface activation effects and increase the rate of phase mixing, mass transfer and catalyst activation. 

Groger, H., Hummel, W., Rollmann, C. et al. (2004) Preparative asymmetric reduction of ketones in a biphasic medium with an (5)-alcohol dehydrogenase under in f/w-cofactor-recycling with a formate dehydrogenase. Tetrahedron, 60 (3), 633-640. 

Octonol is an intermediate for the production of several optically active pharmaceuticals, such as steroids and vitamins. The asymmetric reduction of 2-octanone to (5)-2-octonol by baker s yeast was inhibited severely by substrate and product concentration of 10 him and 6 mM respectively. Whole-cell biotransformation of 2-octanone in a water-ra-dodecane biphasic system yielded a high product concentration of 106him with 89% ee in 96h [37],... 

Li, Y.-N., Shi, X.-A., Zong, M.-H. et al. (2007) Asymmetric reduction of 2-octanone in water/organic solvent biphasic system with baker s yeast FD-12. Enzyme and Microbial Technology, 40, 1305-1311. 

An investigation of different organic solvents, buffer, surfactants, and organorhodium compounds established that the catalytic reduction of tetralin using [ Rh(l,5-hexadiene)Cl 2] proceeds with high efficiency at high substrate-to-catalyst ratios. The reaction occurs at r. t. and 1 atm. pressure in a biphasic mixture of hexane and an aqueous buffer containing a low concentration of a surfactant which stabilizes the catalysts.314... 

Quite new ideas for the reactor design of aqueous multiphase fluid/fluid reactions have been reported by researchers from Oxeno. In packed tubular reactors and under unconventional reaction conditions they observed very high space-time yields which increased the rate compared with conventional operation by a factor of 10 due to a combination of mass transfer area and kinetics [29]. Thus the old question of aqueous-biphase hydroformylation "Where does the reaction takes place " - i.e., at the interphase or the bulk of the liquid phase [23,56h] - is again questionable, at least under the conditions (packed tubular reactors, other hydrodynamic conditions, in mini plants, and in the unusual,and costly presence of ethylene glycol) and not in harsh industrial operation. The considerable reduction of the laminar boundary layer in highly loaded packed tubular reactors increases the mass transfer coefficients, thus Oxeno claim the successful hydroformylation of 1-octene [25a,26,29c,49a,49e,58d,58f], The search for a new reactor design may also include operation in microreactors [59]. 

It has been believed that P-450 reduction by NADPH cytochrome P-450 reductase is a biphasic process, but it was recently shown [7] that some P-450 cytochromes are reduced with single-exponential kinetics and that the presence of substrate is not an obligatory condition for the reduction of all P-450 forms. Thus, the kinetics of reduction of various ferric P-450 cytochromes possibly depends on many factors such as substrate, rate-limiting step, etc. 

Because electrode measurements of O2 uptake can detect intra- and extracellular oxidase activity, this assay can be used to measure the respiratory burst elicited by soluble and particulate stimuli. What is somewhat surprising is that, during stimulation of neutrophils with agonists such as fMet-Leu-Phe, the activated O2 uptake profile is biphasic (Fig. 5.11c). A rapid burst of O2 uptake (which coincides with measurements of cytochrome c reduction) is followed by a more sustained activity of lower magnitude. 

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