Water hydroformylation

In a Lewis-acid catalysed Diels-Alder reaction, the first step is coordination of the catalyst to a Lewis-basic site of the reactant. In a typical catalysed Diels-Alder reaction, the carbonyl oxygen of the dienophile coordinates to the Lewis acid. The most common solvents for these processes are inert apolar liquids such as dichloromethane or benzene. Protic solvents, and water in particular, are avoided because of their strong interactions wifti the catalyst and the reacting system. Interestingly, for other catalysed reactions such as hydroformylations the same solvents do not give problems. This paradox is a result of the difference in hardness of the reactants and the catalyst involved... 

A new homogeneous process for hydroformylation of olefins using a water-soluble catalyst has been developed (40). The catalyst is based on a rhodium complex and utilizes a water-soluble phosphine such as tri(M-sulfophenyl)phosphine. The use of an aqueous phase simplifies the separation of the catalyst and products (see Oxo process). 

With Unsaturated Compounds. The reaction of unsaturated organic compounds with carbon monoxide and molecules containing an active hydrogen atom leads to a variety of interesting organic products. The hydroformylation reaction is the most important member of this class of reactions. When the hydroformylation reaction of ethylene takes place in an aqueous medium, diethyl ketone [96-22-0] is obtained as the principal product instead of propionaldehyde [123-38-6] (59). Ethylene, carbon monoxide, and water also yield propionic acid [79-09-4] under mild conditions (448—468 K and 3—7 MPa or 30—70 atm) using cobalt or rhodium catalysts containing bromide or iodide (60,61). 

Cationic phosphine ligands containing guanidiniumphenyl moieties were originally developed in order to make use of their pronounced solubility in water [72, 73]. They were shown to form active catalytic systems in Pd-mediated C-C coupling reactions between aryl iodides and alkynes (Castro-Stephens-Sonogashira reaction) [72, 74] and Rh-catalyzed hydroformylation of olefins in aqueous two-phase systems [75]. 

Since then, water has emerged as a useful solvent for organometallic catalysis. In addition to the hydroformylation reactions, several other industrial processes... 

When water-miscible ionic liquids are used as solvents, and when the products are partly or totally soluble in these ionic liquids, the addition of polar solvents, such as water, in a separation step after the reaction can make the ionic liquid more hydrophilic and facilitate the separation of the products from the ionic liquid/water mixture (Table 5.3-2, case e). This concept has been developed by Union Carbide for the hydroformylation of higher alkenes catalyzed by Rh-sulfonated phosphine ligand in the N-methylpyrrolidone (NMP)/water system. Thanks to the presence of NMP, the reaction is performed in one homogeneous phase. After the reaction. 

Propanediol is a colorless liquid that boils at 210-211°C. It is soluble in water, alcohol, and ether. It is an intermediate for polyester production. It could be produced via the hydroformylation of ethylene oxide which yields 3-hydroxypropionaldehyde. Flydrogenation of the product produces 1,3-propanediol. 

The carbonyl complex [Ru(EDTAH)(CO)] has been reported to be a very good catalyst for reactions like hydroformylation of alkenes, carbonylation of ammonia and ammines as well as a very active catalyst for the water gas shift reaction. The nitrosyl [Ru(EDTA)(NO)] is an oxygen-transfer agent for the oxidation of hex-l-ene to hexan-2-one, and cyclohexane to the corresponding epoxide. 

An example of a large scale application of the aqueous biphasic concept is the Ruhrchemie/Rhone-Poulenc process for the hydroformylation of propylene to n-butanal (Eqn. (15)), which employs a water-soluble rhodium(I) complex of trisulphonated triphenylphosphine (tppts) as the catalyst (Cornils and Wiebus, 1996). 

The adoption of a second liquid phase has also proved useful in the hydroformylation reaction of propylene for which Ruhrchemie and Rhone-Poulenc have used Rh based water... 

An unusual enhancement of catalytic activity in a two-phase system has been reported by Fremy et al. (1998) for the hydroformylation of acrylic esters using Rh complex of TPTS as catalyst. Even though acrylic esters have reasonable solubility in water, rate enhancements in two-phase systems by a factor of 2 to 14 have been reported. It seems that water is not an inert solvent but also acts as a reactant or a co-ordinating solvent which can modify elementary steps of the catalytic cycle (Cornilis, 1997). 

Betzemeier et al. (1998) have used f-BuOOH, in the presence of a Pd(II) catalyst bearing perfluorinated ligands using a biphasic system of benzene and bromo perfluoro octane to convert a variety of olefins, such as styrene, p-substituted styrenes, vinyl naphthalene, 1-decene etc. to the corresponding ketone via a Wacker type process. Xia and Fell (1997) have used the Li salt of triphenylphosphine monosulphonic acid, which can be solubilized with methanol. A hydroformylation reaction is conducted and catalyst recovery is facilitated by removal of methanol when filtration or extraction with water can be practised. The aqueous solution can be evaporated and the solid salt can be dissolved in methanol and recycled. 

Since it is well known that the higher the olefin, the more difficult it is to hydroformylate, we tried our approach on 1-dodecene. We found that when we used 50 50 ethanol/water (R24) and CTAB only (R33) systems they showed no activity for hydroformylation of 1-dodecene whereas, the addition of surfactant to the 50 50 ethanol/water mixture (R27) dramatically increased the reaction rate, as well as the selectivity. 

Table 28.3. Comparison of water-soluble solvents on biphasic hydroformylation of 1-octene.

In summary, what we have found is that the combination of a thermomorphic system and a surfactant is very effective for the hydroformylation of 1-octene and 1-dodecene. We believe that although a 90 10 ethanol/water and heptane system becomes miscible at 70°C, the additional water in a 50 50 ethanol/water and heptane system raises the miscibility temperature to >100°C. When a surfactant is added, the miscibility temperature is lowered and the biphasic solution becomes monophasic below the reaction temperature, resulting in good reaction rates. In addition, the presence of the surfactant also enhances the selectivity compared to the completely homogeneous system from 1.8 to 5.3 L/B... 

For long chain olefins, the hydroformylation generally proceeds slowly and with low selectivity in two-phase systems due to their poor solubility in water. Monflier et al. recently reported a conversion of up to 100% and a regioselectivity of up to 95% for the Rh-catalyzed hydroformylation of dec-l-ene in water, free of organic solvent, in the presence of partially methylated 6-cyclodextrins (Eq. 3.42).173... 

In another interesting area in the study of hydroformylation, Davis developed the concept of supported aqueous phase (SAP) catalysis.175 A thin, aqueous film containing a water-soluble catalyst adheres to silica gel with a high surface area. The reaction occurs at the liquid-liquid interface. Through SAP catalysis, the hydroformylation of very hydrophobic alkenes, such as octene or dicyclopentadiene, is possible with the water-soluble catalyst [HRh(CO)(tppts)3]. 

The unsubstituted quinazolidine system 5 was constructed from mesylate 173. The key feature in this synthesis is based on a cyclohydrocarbonylation of the protected 4-amino-l,6-heptadiene 169 catalyzed by Rh(acac)(CO)2-BIPHEPHOS. Formation of the hemiamidal-aldehyde 171 took place by hydroformylation of the two olefin moieties and cyclization. Elimination of water gave 172, which, after treatment with NaBFE, subsequent mesylation to 173, and catalytic hydrogenation, afforded 5 (Scheme 29) <1998TL4599>. 

CH ligands, (2) to initiate homogeneous catalytic reactions such as hydrogenation, hydroformylation, and the water gas shift reaction, and (3) to study the mechanism of thermal reactions by the photochemical preparation of possible intermediates. 

Relatively little work has been devoted to the characterization of complexes in water and generally it has been assumed that for Rh-catalyzed hydroformylation similar species are formed in water as inorganic solvents, i.e., [RhH(L)2(CO)2] and [RhH(L)3(CO)] are the major species. Therefore, few references can be mentioned here which contain information about coordination complexes. In addition, a few, more recent, studies will be mentioned which do not report in situ coordination compounds. A HP NMR study of [RhH(TPPTS)3(CO)] has been reported. It was... 

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