Hydroformylation catalyzed by rhodium

Hydroformylation catalyzed by rhodium triphenylphospine results in only the 9 and 10 isomers in approximately equal amounts (79). A study of recycling the rhodium catalyst and a cost estimate for a batch process have been made (81). 

On the basis of multiple observations and the generally accepted mechanism of hydroformylation catalyzed by rhodium triarylphosphine complexes, the authors proposed a mechanism consisting of three consecutive steps that they claimed to be analogous to enzyme catalysis (Scheme 2) ... 

Whatever metal is used, homogeneous processes suffer from high cost resulting from the consumption of the catalyst, whether recycled or not. This is why two-phase catalytic processes have been developed such as hydroformylation catalyzed by rhodium complexes, which are dissolved in water thanks to hydrophilic phosphines (cf. Section 3.1.1.1) [17]. Due to the sensitivity of most dimerization catalysts to proton-active or coordinating solvents, the use of non-aqueous ionic liquids (NAILs) as catalyst solvents has been proposed. These media are typically mixtures of quaternary ammonium or phosphonium salts, such as 1,3-dialkylimi-dazolium chloride, with aluminum trichloride (cf. Section 3.1.1.2.2). They prove to be superb solvents for cationic active species such as the cationic nickel complexes which are the active species of olefin dimerization [18, 19]. The dimers. 

A phosphite-modified calixarene with unsubstituted hydroxyl groups was used as a ligand in 1-hexene hydroformylation catalyzed by rhodium complexes [224], The reaction was carried out at a synthesis gas pressure of 6.0 MPa and 160 °C. Rh(acac)(CO)2 was a catalyst precursor. In 3 h, the conversion of the initial alkene virtually reached its theoretically predicted value the yield of aldehydes was 80-85%, and the normal-to-isomeric aldehyde ratio was approximately 1 1. Some similar phosphites 83 were also studied as components of catalytic systems for 1-octene hydroformylation [225]. It was shown that the nature and steric volume of substituent R have no essential effect on the main laws of the process. For example, the conversion was 80-90% at a selectivity with respect to nonanal of about 60% in all cases. The regioselectivity with respect to nonanal was considerably increased to 90-92% by using the chelate biphosphite 84 [220]. 

Botteghi C, Delogu C, Marchetti M, Paganelli S, Sechi B (1999) Aryloxypropanoic herbicides by asymmetric hydroformylation catalyzed by rhodium carbonyl complexes modified with phosphorus ligands. J Mol Catal A 143 311-323... 

Several new water-soluble phosphines were prepared for hydroformylation catalyzed by rhodium(I) complexes. These include the sulfonated derivatives BISBIS (16), BINAS (16,139), BIPHLOPHOS (143), sulfonated XANTPHOS (144), and others (Scheme 15). Rh-BINAS showed an enormously high activity in propene hydroformylation at 125°C and 5.2 MPa syngas, TOF = 10710 h , which was about 12 times higher than that of Rh-TPPTS under the same conditions (143). At the same time, the selectivity also increased to n/iso 98/2 from 95/5. Despite these improvements, the low price and availability still favors the industrial use of [HRh(CO)(TPPTS)3] -I- excess TPPTS. 

Hughes, O.R. and Unruh, J.D. (1981) Hydroformylation catalyzed by rhodium complexes with diphosphine ligands. Journal of Molecular Catalysis, 12,71 Sanger, A.R. (1977) Hydroformylation of 1-hexene catalysed by complexes of rhodium(I) with di- or tritertiary phosphines. Journal of Molecular Catalysis, 3,221 Sanger, A.R. and Schallig, L.R. (1977) The structures and hydroformylation catalytic activities of polyphosphine complexes of rhodium(l), and related complexes immobilised on polymer supports. Journal of Molecular Catalysis, 3, 101 Pittman, C.U. and Hirao, A. (1978) Hydroformylation catalyzed by cis-chelated rhodium complexes - extension to polymer-anchored cis-chelated rhodium catalysts. The Journal of Organic Chemistry, 43, 640. 

HP-NMR) and in situ high-pressure infrared (HPIR) characterizations of intermediates on asymmetric hydroformylation catalyzed by rhodium phosphine-phosphite, diphosphites and diphosphines allowed to elucidate mechanistic aspects of the reaction, especially the steps determining the reaction rate and the formation of the intermediates of the reaction [9,12]. 

The mechanism of olefin hydroformylation catalyzed by rhodium complexes has been extensively studied. For TPP as a ligand, it corresponds to Wilkinson s dissociative mechanism, which involves the four-coordinated active intermediate HRh(CO)L2 (L = TPP, Figure 14.2). Coordination of olefin with HRh(CO)L2 yields the 7t-complex 2. The insertion of coordinated olefin to the Rh-H bond leads to the formation of alkyl complexes 3a or 3b, respectively, via the anti-Markovnikov or the Markovnikov path. Subsequently, the alkyl migration to the CO affords the acyl complexes 4a or 4b, which leads to linear or branched aldehyde and HRh(CO)L2 via hydrogenolysis, eventually. The water-soluble catalyst HRh(CO)(TPPTS)3 is considered to react according to the dissociative mechanism [10]. However, the reaction occurs at the liquid phase or the gaseous-Hquid interface [11], and the activity and selectivity are remarkably different from those... 

Although most of the reports that have appeared since 1980 on hydroformylation of alkenes focus on rhodium catalysts, alkene hydroformylation catalyzed by Ptn complexes in the presence of Sn11 halides has been the object of great interest and platinum can be considered as the second metal in hydroformylation.77-79... 

Chiral thioureas have been synthesized and used as ligands for the asymmetric hydroformylation of styrene catalyzed by rhodium(I) complexes. The best results were obtained with /V-phenyl-TV -OS )-(l-phenylethyl)thiourea associated with a cationic rhodium(I) precursor, and asymmetric induction of 40% was then achieved.387,388 Chiral polyether-phosphite ligands derived from (5)-binaphthol were prepared and combined with [Rh(cod)2]BF4. These systems showed high activity, chemo- and regio-selectivity for the catalytic enantioselective hydroformylation of styrene in thermoregulated phase-transfer conditions. Ee values of up to 25% were obtained and recycling was possible without loss of enantioselectivity.389... 

Chauvin, Y., Mussmann, L., and Olivier, H., A novel class of versatile solvents for two-phase catalysis hydrogenation, isomerization, and hydroformylation of alkenes catalyzed by rhodium complexes in liquid 1,3-dialkylimidazolium salts, Angew. Chem. Int. Ed., 34, 2698-2700,1996. 

A sample of the polymer of step 1 product was hydroformylated by reacting it with a mixture of carbon monoxide and hydrogen under 690 kPa for 4 hours catalyzed by rhodium dicarbonyl acetylacetonate (10.2 mg) and tris(2,4-di-/-butylphenyl)pho-sphite (48.2 mg) dissolved in toluene. H-NMR spectrum of this polymer showed the presence of carbonyl functional groups in place of ethylenic unsaturation. 

Industrial Applications. Several large scale industrial processes are based on some of the reactions listed above, and more are under development. Most notable among those currently in use is the already mentioned Wacker process for acetaldehyde production. Similarly, the production of vinyl acetate from ethylene and acetic acid has been commercialized. Major processes nearing commercialization are hydroformylations catalyzed by phosphine-cobalt or phosphine-rhodium complexes and the carbonylation of methanol to acetic acid catalyzed by (< 3P) 2RhCOCl. 

The above results were reviewed in 1974 (5). Since then the main advances in the field have been the achievement of asymmetric hydro-carbalkoxylation (see Scheme I, X = -OR) using palladium catalysts in the presence of (-)DIOP (6), the use of other diphosphines as asymmetric ligands in hydroformylation by rhodium (7), and the achievement of the platinum-catalyzed asymmetric hydroformylation (8, 9). Further work in the field of asymmetric hydroformylation with rhodium catalysts has been directed mainly towards improving optical yields using different asymmetric ligands (10), while only very few efforts were devoted to asymmetric hydroformylation catalyzed by cobalt or other metals (11, 12) and it will be discussed in a modified form in this chapter. 

The asymmetric hydroformylation of //-substituted 4-vinyl (3-lactams, catalyzed by rhodium(I) complexes, leading to l-(3-methylcarbapenem precursors (VI, Fig. 16) has been reported [285]. 

The hydroformylation of 1-hexene catalyzed by rhodium carbonyl has recently been studied by Lazzaroni and coworkers [21]. They were particularly interested in the influence of reaction parameters on the regioselectivity and the chemoselectivity (to aldehyde and 2-hexene). To understand their results we have to extend Scheme 6.1 by taking account of the formation of linear and branched aldehydes, as well as of isomerization. This is shown in Scheme 6.2. 

Hydroformylation of terpenes, catalyzed by rhodium complexes (see Chapter 5), is an important route to aldehydes of interest in the perfume industry [215]. Some examples are shown in Fig. 8.45. 

Asymmetric hydroformylation of N-protected 2,5-dihydro-l/7-pyrroles 1190 catalyzed by rhodium(l) complexes of chiral phosphine-phosphite ligands 1189 afforded the corresponding optically active aldehydes 1191 as single products with ee 47-92% (R = BOG, 98%, 47% ee (R) and R = Ac, 92%, 66% ee (-)) (Equation 270) <1997MI175>. 

A plausible mechanism was reported for the catalytic formation of benzene resulting from phosphorus-carbon bond cleavage which occurs during propylene hydroformylation catalyzed by triphenylphos-phine-substituted rhodium carbonyls under higher H2 partial pressures (Scheme 37). " ... 

The hydroformylation of alkenes is commonly run using soluble metal carbonyl complexes as catalysts but there are some reports of heterogeneously catalyzed reactions of olefins with hydrogen and carbon monoxide. Almost all of these are vapor phase reactions of ethylene or propylene with hydrogen and carbon monoxide catalyzed by rhodium, " 20 ruthenium,nickel, 22,123 cobalt, 23,124 and cobalt-molybdenum 23 catalysts as well as various sulfided metal catalysts. 23,125,126... 

Summary The hydroformylation of alkenylalkoxysilanes catalyzed by rhodium complexes allows the preparation of aldehyde-fiinctlonalized silanes. It is possible to improve the regioselectivity of this reaction by adding an excess of triphenylphoshine and by temperature variation. 

The reaction was successfully extended to the hydroformylation of propargyl-type alcohols [154] and propargylamine [155], the silylative cyclocarbonylation of alkynes [156], silylcarbocyclization of alkenynes and diynes [157-160], and other transformations of C=C bonds in the presence of HSiRa and CO (e. g., [161]). A generalized catalytic cycle for the silylformylation of 1-alkynes catalyzed by rhodium-cobalt clusters is illustrated in Scheme 6. 

The hydroformylation of 1-hexene catalyzed by rhodium carbonyl has been studied by Lazzaroni and coworkers [31]. They were particularly interested in... 

The use of ionic liquids in combination with CO2 has the potential to produce cleaner processes with improved selectivity. The negligible miscibility of the ionic liquid in CO2 compared with appreciable amounts of CO2 that can be found in the liquid phase make the use of CO2 as a green solvent attractive for continuous reaction processes. Sellin, Webb, and Cole-Hamilton conducted a hydroformylation of hex-l-ene and 1-octene catalyzed by rhodium based catalyst in l-butyl-3-methylimidazolium hexafluoro-phosphate (BMIMHF) in contact with CO2. Improved n iso product selectivity was obtained, compared with that using toluene with similar selectivity, but substantially lower yield (40% compared to >99%). Using 1-octene as a substrate and [Rh2(OAc)4]/[1-propyl-3-methylimidazolium] [PhP(C6H4S03)2] as catalyst, over 20 hr of continuous operation was achieved with minimal catalyst leaching at 373 K. 

---