Triphasic system

Secondary alcohols ate oxidi2ed to ketones in good yields under mild conditions in a triphasic system using an inert solvent, soHd Ca(OCl)2, and a hypochlorite resin as catalyst (175). 

Should a third solvent be added which is immiscible with the other two, then a triphasic system results. The purpose of a third solvent may be, for example, as a built in cleaning step (see below). 

There are various combinations of solvents that lead to the different biphasic and triphasic systems described in Section 2.1 that have found applications in synthesis and catalysis. For practical purposes, it is essential that the catalyst and product... 

Gas-liquid-solid (G-L-S) where a reagent gas is brought into contact with a liquid solution where the reactant is dissolved and where a heterogeneous catalyst is suspended, that are triphasic systems, can be considered biphasic L-S systems in the context of this review. 

Figure 6.15 shows the triphasic system at rest in order to visualize the different phases, macroscopic amounts of the three components were combined. In... 

Just as for the triphasic system, the dienes and triene (Entries 7-13) undergo selective epoxidation at only one of the double bonds. The selective reactivity of the compound featured in Entry 11 is particularly noteworthy. Monoepoxida-tion of the double bond next to the phenyl-bearing carbonyl group was the only reaction observed, despite extended reaction times and use of excess oxidant. 

Triphasic systems comprising, for example, an ionic liquid, water and an organic phase in which the catalyst resides in the ionic liquid, the substrate... 

The asymmetric epoxidation of several chalcones (39) and other electron-poor olefins in a triphase system (water/organjc solvent/chiral polyamino acid) afford optically active oxirans with optical yields of up to 96%. The influence of the molecular structure of the catalysts and substrates, the solvent, and the temperature on the stereochemistry was investigated by a group of chemists from Italy and Spain 77). 

In the synthesis of optically active aryl glycidic esters, Julia66 type epoxidation (triphasic system of NaOH/aqueous hydrogen peroxide, hexane and a polyamino acid) of an unsaturated ketone gives excellent yields of the required epoxide67. A potent and selective leukotriene antagonist (SK F 104353) has been synthesized by a route where one of the key steps is this type of epoxidation (equation 8)68. 

The role of the solvent is complex polarity, solubility of reactants and products, diffusion and counter-diffusion effects, and also interaction with the active centers [88]. Using a triphase system (solid-liquid-liquid) in the absence of any cosolvent, a considerable increase in the conversion of various water-immiscible organic compounds (toluene, anisole, benzyl alcohol, etc.) can be achieved [89]. 

Although they can extend the substrate scope, these modified systems use more expensive bases and oxidants than the original conditions. In 2004, the triphasic system saw renewed interest when Geller and co-workers found that the addition of a phase-transfer catalyst allows much faster reactions without the induction period otherwise needed for catalyst activation, and far lower quantities of base and... 

Julia, S., Guixer, J., Masana, J., Rocas, J., Colonna, S., Annuziata, R. and Molinari, H. Synthetic enzymes. 2. Catalytic asymmetric epoxidation by means of polyamino-acids in a triphase system, J. Chem. Soc., Perkin Trans. 1, 1982, 1317-1324. 

TBAF. The partition process into the triphasic system allowed the isolation of pure compounds (>85% HPLC) in good yields (average 70%). 

The second area of Weckhuysen s roadmap—extending the operational window from mono-phasic to biphasic and triphasic systems— does not need much discussion here. With the design of specialized cells and appropriate detectors, this methodology is already being applied to the characterization of catalysts by XAFS spectroscopy (see some of the examples in Section 3). 

Rigal, L., Gaset, A., and Gorrichon, J. R, Selective conversion of D-fructose to 5-hydroxymethyl-2-furancar-boxaldehyde using a water-solvent-ion-exchange resin triphasic system. Industrial Eng Chem Product Res Dev 1981, 20(4), 719-721. 

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