Biphasic toluene/water

A series of eight closely related N,0-based hgands was used to imravel possible steric and electronic influences in the copper-catalyzed polymerization of 2,6-dimethylphenol [248]. Applying a biphasic toluene/water emulsion, with an in situ prepared Cu(Melm)-catalyst (Melm = 1-methylimidazole),... 

Most studies of biocatalysis in ionic liquids have been concerned with the use of isolated enzymes. It should not be overlooked, however, that the first report on biocatalysis and ionic liquids involved a whole-cell preparation Rhodococcus R312 in a biphasic [BMIm][PF(s]-water system [7]. It was shown, using a nitrile hydrolysis test reaction, that the microorganism maintained its activity better in ionic liquid than in a biphasic toluene-water system. 

Sawamoto has described the controlled radical polymerization of MMA using [RuCl2(PPh3)3] as a catalyst [218]. In organic solvents, this ruthenium catalyst [197] necessitates the use of an aluminum-containing co-catalyst, usually A1(O IT), thus affording a very efficient control of the polymerization of methacrylic monomers. As the aluminum compound can not be used in neat water, polymerizations were initially carried out in a biphasic toluene water 1 1 mixture. Polymerizations in this aqueous system were found to be somewhat faster than in neat toluene. In view of these results, the authors have demonstrated that aqueous polymerizations do not necessitate the use of any aluminum co-cata-lyst. Thus, in the absence of an aluminum salt, suspension polymerization of MMA in water at 80°C was found to be efficient and controlled (83% conversion M =9.6xl0 g moT 1.42). 

Bromobenzene was carbonylated in a biphasic toluene/water system in the presence of Pd(tppts)3 giving the expected benzoic acid exclusively with high conversion [79]. 

The catalytic reaction mixtures were refluxed at 353 K in a round bottom flask. They included 10 ml of solvent (methanol or water), 0.5 g catalyst, 0.1 mole substrate and Oxidant/Substrate = 0.2. The monophasic (phencH methanol) or biphasic (toluene + water) system was stirred vigourously at 1000 rpm with a magnetic stirrer. 

Acid catalysts 78 and 84 were both successfully used inacid-catalyzed acetal hydrolyses (Eqs. 33 and 34). However, the reactions did not always strictly turn on and off below and above the LOST of 78 and 84. For example, when 84 was usedin a biphasic toluene/water mixture at 1 °C, hydrolysis of the acetal of acetophenone was about four times slower than at 24 °C. At 48 °C (above 84 s LOST), the hydrolysis rate was ca. half the rate at 24 °C. In this case the reaction... 

Oxidation of alkyl aromatics in a biphasic toluene-water system can give the acid.186 After optimization (reagent concentrations, pH, additional mechanical stirring), toluene is transformed to benzoic acid in 60% yield within 3 h. Xylenes were submitted to the same treatment and gave interesting yields unfortunately the nature of the acid(s) obtained is not mentioned. Nitrotoluenes are also oxidized, in lower yields, only to the acids without dimer formation. 

Water-soluble dicationic palladium(II) complexes [(R.2P(CH2)3PR.2)Pd-(NCMe)2][BF4]2 proved to be highly active in the carbon monox-ide/ethene copolymerization under biphasic conditions (water-toluene). In the presence of an emulsifier and methanol as activator, the catalytic activity increased by a factor of about three. Also higher olefins could be successfully incorporated into the copolymerization with CO and the terpolymerization with ethene and CO.184... 

A diastereomeric guanidine-bisthiourea bifunctional organocatalyst gives high ees (g) and des in nitroaldols in a biphasic system toluene-water at 0°C.146... 

The ACP with Ru Pybox- hm revealed that the use of single organic solvents, such as toluene and tetrahydrofuran (THF), resulted in lower yields and lower enantioselectivity. However, when water was added to THF or toluene solutions, the reaction proceeded smoothly, improving the enantioselectivity and the yields slightly. This phenomenon accounted for the increase of the solubility of the Ru(Pybox-hm)Cl2(vacant or solvent) species. The ACP carried out in toluene/water biphasic media attained 94% ee for the trans form (Scheme 4). As the active Ru Pybox-hm species still remained in the aqueous phase after the reaction, the second run( ) could be carried out by addition of diazoacetate and styrene to give a similar result. Thus, the water-soluble catalyst can be recycled. 

Suzuki-type C-C-coupling reactions (cf. Section 2.11) with Pd phosphine complexes as catalysts can also be promoted by amphiphiles in an aqueous biphasic system (toluene/water). The amphiphile should have a phase-transfer function, with the best effect being observed with micelle-forming amphiphiles [27]. 

Toorisaka et al.87 studied the structure of the complex formed between a cobalt ion and alkyl imidazole that catalyses hydrolysis of an amino acid ester. By using HyperChem they calculated the lowest energy structure of the complex in vacuum. Then the complex was placed at the toluene-water interface by replacing 11 toluene molecules with molecules of water (Fig. 6.9). The MD simulation was performed in the (N, V, T) ensemble after MM calculation in the biphase system,... 

Rh(I) complexes such as RhCl(TPPMS)3 4HzO, Rh(cod)Cl(TPPMS) H20, [Rh(cod)(/<2-Ph2P—C6H4-3-S02—0)]2 catalyze oligomerization of alkynes (propynoic acid, arylacetylenes) this has been studied only very recently in terms of biphasic catalysis. The Rh(I) complex Rh(cod)(/<2-Ph2P—C6H4-3-S02—0)]2 already reported by Wilkinson etal. [50] promotes the conversion of phenylacetylene to 1,2,4- and 1,3,5-triphenylbenzene under biphasic conditions (toluene/water) [58],... 

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. 

Hydroformylation of ethylene using a water-soluble Rh-TPPTS catalyst has been investigated [27] using a toluene-water solvent system at 353 K. The effect ofTPPTS concentration on rate shows a maximum at a P/ Rh ratio of 8 1. The rate of reaction first increases with catalyst concentration, and above a certain value it remains constant. The effect of aqueous-phase hold-up shows a maximum in the rate at = 0.4. The apparent reaction orders for the partial pressures of hydrogen and ethylene were found to be one and zero respectively. A strong inhibition in the rate with an increase in Pqq was observed. An interesting example of tandem synthesis of methacrolein in an aqueous biphasic system has been reported by Deshpande et al. [28], in which hydroformylation of ethylene and aldol condensahon reactions occur in two immiscible liquid phases with a high yield of the product Use of a two-phase system prevents contact of the hydroformylation and aldol catalysts, the interaction of which leads to deactivation. 

The reduction of allylic halides or acetates, as well as benzyl halides, can be achieved by the Pd-catalyzed reaction with formate ions in the biphasic system of toluene-water or heptane-water in the presence of hydrophilic phosphine ligands TPPMS, sodium 3-(diphenylphosphino)benzoate, and PEG-modilied trialkylphosphine. The process is accelerated by the addition of PEGJ ... 

In a similar manner, a modified Rh(PPh3) catalyst was able to convert camphene under neat conditions at 200 bar into the aldehydes [77, 78]. This protocol was carried out in a >400 g scale. When the syngas pressure and temperature were lowered (90 bar, 100 °C), the linear aldehydes were formed in nearly quantitative yields [7 6]. In the presence of phosphorus ligands, the formation of the endo isomer was favored (exo/endo 1 1.5), whereas in immodified systems both exo and endo compounds were formed in nearly equal amounts. Neither steric nor electronic parameters of the Ugands were found to influence significantly the diastereose-lectivity of the rhodium-catalyzed hydroformylation. The reaction was likewise performed in a toluene/water biphasic system employing TPPTS to immobilize the rhodium catalyst in the aqueous phase [84]. A mixture of exo and endo isomers of the linear aldehyde (exo/endo 1/1.5) was obtained in nearly 100% chemoselectivity and 71% yield [Rh(COD)(OAc)]2, TPPTS, CO/Hj (1 1, 8 MPa), 80 C, toluene/water (2.5 1 v/v), 48 h. ... 

Myrcene is a very abundant acyclic monoterpene available from the essential oils of various plants including wild thyme and hops. Recently, an excellent overview on the manufacture and transformation of this natural product was given by Behr and Johnen [125]. Commercially, myrcene is produced by the pyrolysis of pinenes [126]. The rhodium-catalyzed hydroformylation of myrcene gives usually a mixture of fragrance aldehydes in more than 90% combined yields (Scheme 6.37) [127, 128]. The main aldehyde, which accounted for 70 - 80% of the mass balance, results from the reaction with the less substituted C=C bond through the formation of a T) -allyl rhodium intermediate complex [127]. The reaction was also performed in a toluene/water biphasic system using the water-soluble TPPTS ligand and a cationic surfactant [84]. 

Mortretox and colleagues [36] discovered that also the rate of the hydroformylation of methyl acrylate can be greatly enhanced by the reaction in the biphasic system water/toluene in comparison to the reaction in neat toluene (Scheme 7.6). 

Ben2yloxy- and 2-tosyloxystyrene were hydroformylated under various reaction conditions to obtain the corresponding linear aldehydes. The best results (up to 70% linear aldehyde at 80 °C and low pressure) were obtained by using the catalyst precursor Pt(xantphos)Cl2 in toluene or the water-soluble catalytic system Rh (CO)2(acac)/2,7-bis(S03Na)2-xantphos in the biphasic medium water/toluene [72]. 

The authors screened common iridium and ruthenium photoredox catalysts for activity and found that the iridium compounds generated the functionalized phosphonates in higher yields. Irradiating a biphasic solvent mixture (toluene/water) containing 1% of the photocatalyst, secondary phosphite, and tetrahydroisoquinoUne afforded the title compounds. The chemistry was compatible with a range of functional groups and was successful at room temperature. 

Free-radical initiators, like azobisisobutyronitrile (AIBN), and peroxides readily polymerize NVK. Thermal bulk polymerization of NVK is possible [47] but gives rather irreproducible results and coloured products even with purified monomer. An almost colourless polymer of high molecular weight can be achieved by bulk polymerization of NVK initiated with AIBN [88]. Besides bulk polymerization, which is carried out as a technical process, PVK can be obtained by precipitation polymerization [89], suspension polymerization [90,91] and photopolymerization [92]. Biswas and Roy [91] performed the suspension polymerization of NVK in a biphasic system (water and toluene) and obtained a polymer with appreciably higher conductivity (ca 1 x 10 S cm ) than that of conventionally prepared PVK. 

Interfacially active guanidinium-thiourea bifunctional catalyst 190 catalyzes highly enantioselective nitroaldol reactions in the presence of an external base such as KOH in toluene/water biphasic conditions. Although the retro-nitroaldol reactions generally proceed under basic conditions, addition of KI inhibits the retro-process. A cooperative reaction mode between guanidinium and thiourea moieties is supported by experiments using structural variants of 190. A positive nonlinear effect is observed between the enantiomeric excess of 190 and the product 191. These results support the hypothesis that self-a egation of 190 is necessary for catalysis (Scheme 28.22) (96, 97). Catalyst 190 has been used in the synthesis of chiral tertiary alcohol products obtained in nitroaldol reactions of nitroalkanes and a-ketoesters [98],... 

In 2006, Ooi conducted an asymmetric Strecker reaction under phase-transfer conditions (PTC) employing a chiral quaternary ammonium salt 76 with a tetrana-phthyl backbone (Scheme 30.18) [43]. Under biphasic conditions, aqueous KCN could be used as an inexpensive and safe surrogate for HCN. With lmol% of catalyst 76 the reaction in toluene-water at 0°C proceeded smoothly in relatively short reaction times (2-8h). In doing so, a-branched and a-unbranched aUphatic N-mesitylenesulfonyl imines 75 were transformed in high yields and good to high... 

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