Water 1 Biphasic Systems

On the other hand, 3-phenylpropionitrile was synthesized from Z-3-phenyl-propionaldoxime (0.75 M) in a quantitative yield (98gP ) by the use of cells of E. coli JM 109/pOxD-9OF, a transformant harboring a gene for a new enzyme, phenylacetaldoxime dehydratase, from Bacillus sp. strain OxB-1. Other arylalkyl- and alkyl-nitriles were also synthesized in high yields from the corresponding aldoximes. Moreover, 3-phenylpropionitrile was successfully synthesized by the recombinant cells in 70 and 100% yields from 0.1 M unpurified P/Z-3-phenylpropionaldoxime, which is spontaneously formed from 3-phenylpropionaldehyde and hydroxylamine in a butyl acetate/water biphasic system and aqueous phase, respectively. 

The Witting reaction has been investigated in aqueous conditions.305 Wittig olefination reactions with stabilized ylides (known as the Wittig-Homer or Homer-Wadsworth-Emmons reaction) are sometimes performed in an organic/water biphase system.306 Very often, a phase-transfer catalyst is used. Recently, the use of water alone as solvent... 

Fig. 39.2 Enantioselective hydrogenation of polar substrates in an inverted scC02/water biphasic system.

A mass-transfer model was proposed to account for the function of the [BMIM]PF6/water biphasic system in the reaction (Scheme 19). According to this model, a small quantity of [BMIM]PF6 dissolved in water exchanged its anion with H2O2 to form Q OOH , which was transferred into the [BMIM]PF6 phase to initiate the epoxidation reaction. In this reaction system, the ring-opening... 

The surface-active diphosphane 12 was applied in the hydrogenation of methyl a-acetamidocinnamate [Eq. (10)] with [RhCl(COD)]2 as the catalyst precursor in homogeneous methanolic solution and, alternatively, in ethyl acetate-water biphasic systems (96). 

Synthesis of Microporous Silicoaluminophosphates in Hexanol—Water Biphasic Systems... 

Besides ruthenium tetroxide, other ruthenium salts, such as ruthenium trichloride hydrate, may be used for oxidation of carbon-carbon double bonds. Addition of acetonitrile as a cosolvent to the carbon tetrachloride-water biphase system markedly improves the effectiveness and reliability of ruthenium-catalyzed oxidations. For example, RuCl3 H20 in conjunction with NaI04 in acetonitrile-CCl4-H20 oxidizes (Ej-S-decene to pentanoic acid in 88% yield. Ruthenium salts may also be employed for oxidations of primary alcohols to carboxylic acids, secondary alcohols to ketones, and 1,2-diols to carboxylic acids under mild conditions at room temperature, as exemplified below. However, in the absence of such readily oxidized functional groups, even aromatic rings are oxidized. 

The same 43/water biphasic system efficiently works for the Michael addition of indoles to a,P-unsaturated enones, the Mannich reaction in its one-pot three-component version, the allyl stannylation of carbonyl compounds and the asymmetric hydroxymethylation of silylenolethers. The last reaction (Figure 45) is carried out in the presence of the chiral bipyridine 45. ... 

Fig. 10.9 Enzyme catalysis in ILs/water biphasic system (Reproduced from Ref. [23], with kind permission of The American Chemical Society)...

Several modifications of the water-soluble catalysts using co-solvents (cf. Section 4.3 and [14]), micelle forming reagents (Section 4.5 and [15]), super-critical C02-water biphasic system (cf. Section 7.4 and [16]), SAPC (Section 4.7 and [17]), and catalyst binding ligands (interfacial catalysis) [18, 24] have been proposed to overcome the lower rates observed in biphasic catalysis due to poor solubilites of reactants in water. So far endeavors were centered on innovating novel catalyst and development of the existing systems. However, limited information is available on the kinetics of biphasic hydroformylation. 

In benzene/water biphasic systems a variety of dienes were hydrogenated in the presence of /l-cyclodcxtrin (/i-CD) and La, Ce, and Yb salts [72]. 2,3-Dimethyl-l,3-butadiene gave 2,3-dimethyl-l-butene with 100% yield and 97% selectivity, representing a reduction with 1,2-addition of hydrogen (Eq. 29). In this /3-cyclodextrin acted as a reverse-phase transfer agent, assisting the diene to enter the aqueous phase equally selective reactions could be achieved by using poly (ethylene gly-col)s, such as PEG-400. 

Ni(0) complexes of TPPTS have been employed as catalysts for the hydrocyanation of dienes and unsaturated nitriles. Product linearity and catalyst lifetimes can be improved if the catalysis is performed in a xylene/water biphasic system by using TPPTS as co-catalyst [33]. The Ni(0)/TPPTS complexes employed may be obtained by electrochemical reduction of Ni(CN)2 in water in presence of TPPTS [34]. 

Suzuki-type C-C coupling reactions with palladium-phosphine complexes as catalysts can also be promoted by surfactants [21] in a toluene/water biphasic system. 

The carbon dioxide/water biphasic system is an example of binary mixtures consisting of components with widely separated critical temperatures. The critical properties of the pure compounds are given in Table 1. The typical phase diagram for such mixtures can be complex, including the possibility for areas of three-phase coexistence (LEV). For applications in biphasic catalysis, however, the key parameters to be discussed are solubility and cross-contamination, mass transfer, and chemical changes. 

Since some ionic liquids are insoluble in water, they can replace traditional organic solvents in liquid-liquid extractions. In a [bmim][PF6]/water biphasic system, neutral substances dissolve preferentially in the ionic Uquid phase, and charged molecules are recovered mainly in the aqueous layer. This behavior can easily be seen in the case of the partitioning of thymol blue 39 in a mixture of [bmimJPFg] (lower phase) and water (upper phase. Figure 2.6), as a function of the pH. At low pH, the thymol blue exists in its neutral zwitterionic red form and is exclusively soluble in the ionic liquid phase. At pH 7, the yellow monoanion partitions into both phases, and at a basic pH, the blue dianion is found exclusively in the aqueous layer. ... 

Conversion (o) ee (ee of substrate). Reaction was performed in a 2 L bioreactor at 30 °C and 200 rpm using an isopropyl ether-water biphasic system with 100 mM ( )-MPGM and 900 U of chitosan-SmL. The pH was automatically controlled at 8.0-8.3 hy titrating 2% ammonia. The immobilized lipase was reused in new reactions after ee of the last run reached 99.9%. From the 7 batch of reaction, 15 g of fresh immobilized lipase (corresponding to io% of the initial amount, ca. 90 U) was supplemented at the beginning of each reaction cycle. After the 12 batch of reaction, 15 g of used immobilized lipase was substituted by 15 g of fresh lipase (ca. 90 U). The partial renewal of the immobilized biocatalyst was continued for 10 cycles (12 -21 ). 

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