Extraction triphasic

Seddon s group described the option of carrying out Heck reactions in ionic liquids that do not completely mix with water. These authors studied different Heck reactions in the triphasic [BMIM][PFg]/water/hexane system [91]. While the [BMIM]2[PdCl4] catalyst used remains in the ionic liquid, the products dissolve in the organic layer, with the salt formed as a by-product of the reaction ([H-base]X) being extracted into the aqueous phase. 

As with classical multiphase catalysis, the organometallic catalyst is retained here in a liquid phase that is immiscible with the second phase containing substrates and/or products. For hydrogenation, the liquid/SCF system is always biphasic, whereas conventional systems are usually triphasic (liquid-1 /liquid-2/ H2). The liquid phase must provide a stable environment for the organometallic catalyst and should be insoluble in the SCF phase. Water, ILs and PEG have been used successfully for this purpose, together with scC02 as the mobile phase. Again, the products must not be too polar in order to be effectively extracted if C02 is used as the SCF. 

The use of a triphasic extraction system, where an organic solvent, an aqueous phase and FC-72 [163] were used, allowed after any reaction step the isolation of the pure intermediates and eventually of the clean reaction products. The switch caused by the fluorous tag allowed the total partition of the library intermediates in the fluorous phase, where any other component of the reaction mixture was not dissolved, while after final deprotection the products were cleanly recovered from the organic phase and the tag moiety remained trapped by the fluorous phase. The eight isoxazoline alcohols were recovered with extremely high GC purities (> 91 %, average > 95%) and with moderate to good yields (from 29% to 99%). The low yields were probably due to the volatility of some of the final products. 

C6)3C14P]C1 [(C4)3CiP] [various] Pd2(dba)3 Pd(OAc)2 Et3N NaOAc 50-100 °C. Coupling of activated and deactivated iodides and activated bromides anion effects studied triphasic aqueous workup catalyst recycling possible product extracted with hexane. [10]... 

A number of ILs are hydrophobic, yet they readily dissolve many organic molecules—with the exception of alkanes and alkylated aromatic compounds (e.g., toluene). Among such ILs we find [bmim][PFg], which forms triphasic mixtures with alkanes and water. This multiphasic behavior has decisive implications for clean synthesis. For example, transition-metal catalysts can be exclusively dissolved in the ionic liquid, thus allowing products and by-products to be separated from the ionic liquid by solvent extraction with either water or an organic solvent. This is advantageous when using expensive metal catalysts, as it enables both the ionic liquid and the catalyst to be recycled and reused. Alternatively, some volatile products can be separated from the IL by distillation, as it has negligible vapor pressure. 

Figure 8.20 Liquid-liquid triphase extractions aqueous/organic/fluorous mixtures.

The synthesis of array L7 is reported in Fig. 8.22. Compound 8.38 was reacted simultaneously with amines (Mi, two representatives), aldehydes (Mi, five representatives), and isonitriles (Ms, two representatives) to give 10 compounds (not all the combinations were reacted). The reaction was performed in trifluoroethanol (TFE), another hybrid fluorous-organic solvent (step a. Fig. 8.22), and after evaporation of the TFE, the crude product 8.39 was purified by two-phase extraction between fluorous solvents and benzene (step b). After evaporation of the solvent, the fluorous tag was cleaved with TBAF (step c) and a triphasic extraction (step d, Eig. 8.22) was performed to remove the fluorosilane tag and acid 8.38-related impurities extracted into the fluorous layer. Excess TBAE and TBAE-related impurities partitioned into the acidic aqueous layer. Yields and purities of the synthetic protocol are reported together with the structures of the library members L7a-j in Table 8.2. 

Synthesis of the array L8 is reported in Eig. 8.23. Bromide 8.37 was esterified with a urea alcohol (step a, Eig. 8.23) and purified by triphasic extraction (step b), giving pure 8.40 in the fluorous phase. Compound 8.40 was reacted with Mi ( 3-keto esters, four examples) and with Mi (aldehydes, three examples), as shown in step c, and then intermediates 8.41 were purified by two-phase fluorous/organic extraction (step d). 

After removal of the solvent, the silyl tag was cleaved (step e) and the final triphasic extraction (step b, Fig. 8.23) gave the array L8 in the organic phase, removing TBAF-related impurities and the fluorous tag by extraction into the aqueous and fluorous phases, respectively. Yields and purities are reported together with the structures of the library individuals L8a-j in Table 8.3. A few compounds were obtained as mixtures, probably due to lower reactivity of corresponding monomers and occurrence of side reactions. 

After administration, vincristine is rapidly distributed to ksues and bound to formed blood elements. Elimination is triphasic, with more than half of the drug cleared within 20 ainulcs. The primary mode of elimination is hepatic extraction with secretion into bile. 

Disposition of paditaxel from plasma follows a biphasic elimination pattern. Approximately 97.5% of it is bound to plasma proteins. Clearance is triphasic and results mainly from hepatic extraction and biliary excretion. Eleven metabolites have been delected in plasma, but not identified. " ... 

The use of a triphasic extraction system, where an organic solvent, an aqueous phase, and FC-72 [101] were used, allowed after any reaction step the isolation of the pure intermediates and eventually of the clean reaction products. The switch caused by the fluorous tag allowed the total partition of the library intermediates in the fluorous phase, where any other component of the reaction... 

In the near future, we expect extraction studies with the help of ILs to develop. Studies of M /HX/ZL/IL systems will grow in number, but it is our hope that pragmatic studies, contenting themselves to the measurements of (possibly high) extraction ratios, will be replaced by mechanistic (and kinetic) studies of more fundamental interest. It is our opinion that the most fascinating studies and results will come from M /HX/ZIL and M /HX// (L + IL)/Org systems. Other fascinating results may also arise from triphasic systems, as recently illustrated (Takata and Hirayama, 2009). 

The ideal 2D nano-reactors of the interfaces between immiscible fluids in stratified flows (Fig. 7b) have been used for chemical synthesis, triphase hydrogenation, and biological enzymatic degradation for extraction and separation and for kinetic smdies. 

Perosa, A, Tundo, P., Selva, M., Zinovyev, S. Testa, A. (2004). Heck reaction catalyzed by Pd/ C, in a triphasic-organic/ AUquat 336/ aqueous-solvent system. Organic Biomolecular Chemistry, 2,15,2249-2252, ISSN 1477-0520 PehUvanoglu, N., Uslu, H. Kirba lar, S. I. (2010). Extractive separation of glutaric acid by AUquat 336 in different solvents. Journal of Chemical Engineering Data, 55,9, 2970-2973, ISSN 0021-9568... 

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