Hydroformylation catalytic systems

The recent reviews by Damoense et al. and Kramer et al. give further information on these and related hydroformylation catalytic systems. Stereoselective hydroformylations have been reviewed by Breit. There have been many theoretical studies of these systems and much of this work is described, along with new results, in a series of papers by Jiao and co-workers. ... 

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]. 

Complex 74 as a preformed catalyst, as well as the Rh(acac)(CO)2+2(17b) in an in situ catalytic system were useful in the hydroformylation of styrene and gave the branched aldehyde in regioselectivities of 65-96% [63],... 

The less bulky ligand (71) studied by Gladfelter leads to dimeric complexes [Rh2(71)2(CO)2] and even tetramers.222 Transformations of rhodium carbonyl complexes in alkene hydroformylation are discussed from the standpoint of the catalytic system self-control under the action of reaction... 

The influence of steric and electronic effects of diphosphites (111) and (112) have been studied with regard to their catalytic performance on the hydroformylation of styrene catalyzed by platinum complexes. The highest chemoselectivity to aldehyde (71%) and regioselectivity to branched aldehyde (85%), with an enantiomeric excess of 86%, was obtained with the plat-inum(II)-SnCl2 catalytic system associated with ligand (25, 45)-bis(5)-(lll).340... 

The monosulfonated PPh derivative, Ph2P(m-C6H4S03K) (DPM) and its rhodium complex, HRh(CO)(DPM)3 have been synthesized and characterized by IR and NMR spectroscopic techniques. The data showed that the structure was similar to [HRh(CO)(PPh3)3]. The catalytic activity and selectivity of [HRh(CO)(DPM)3] in styrene hydroformylation were studied in biphasic catalytic systems.420 421 Rh1 complexes [Rh(acac)(CO)(PR3)] with tpa (131), cyep (132), (126), ompp (133), pmpp (134), tmpp (135), PPh2(pyl), PPh(pyl)2, and P(pyl)3 were characterized with NMR and IR spectra. Complexes with (131), (132), and (126) were catalysts for hydrogenation of C—C and C—O bonds, isomerization of alkenes, and hydroformylation of alkenes.422 Asymmetric hydroformylation of styrene was performed using as catalyst precursor [Rh(//-0 Me)(COD)]2 associated with sodium salts of m-sulfonated diarylphosphines.423... 

Highly enantioselective hydroformylation catalyzed by chiral metal complexes has been obtained with only a few catalytic systems. Many chiral phosphorus ligands have been used in Pt(II) and Rh(I) systems in the asymmetric hydroformylation of styrene. The first highly enantioselective examples of the asymmetric hydroformylation of styrene were reported by Consiglio et al. in 1991 and used Pt-Sn systems. ligand 1 achieved an ee of 86% (Fig. 1) [10-12],... 

This chapter mainly focuses on the latest achievements and recent developments in asymmetric hydroformylation. Since several reviews have been made in the last decade [9,14-16], the chapter discusses the contributions reported between 2000-2005 in particular, although the main diphoshites and phosphine-phosphite rhodium catalytic systems discovered since 1995 are also considered because of their significance in the subject. Particular attention is paid to mechanistic aspects and characterization of intermediates in the case of the hydroformylation of vinyl arenes because this is one of the most important breakthroughs in the area. The application of this catalytic reaction to different type of substrates, in particular dihydrofurans and unsaturated nitriles is the other main subject of this chapter because of their interest in organic synthesis and their industrial relevance. 

The homogeneous rhodium catalyzed hydroformylation of isoprene was the first application of SA to spectral reconstruction of a real catalytic system [92]. The MIR... 

Many catalytic reactions require high pressures of reactant gases. Thus, an in-depth understanding of such catalytic systems requires truly in situ NMR and IR measurements and it has been necessary to develop appropriate High Pressure-spectroscopic cells the development and use of HP-NMR and HP-IR cells are reviewed in chapters 2 and 3 respectively. The use of both of these complementary methods/HP-techniques is probably best illustrated in chapters 5 - carbonyla-tion reactions, chapter 6 - hydroformylation and chapter 7 - alkene/CO copolymerisation, which deal with the recent advances in each of these important areas. 

The possible intermediacy of formaldehyde in CO hydrogenation has been addressed above with regard to the cobalt catalytic system. Fahey has observed a small amount of 1,3-dioxolane (the ethylene glycol acetal of formaldehyde) as a product of the rhodium system (43). Thus, there is evidence that formaldehyde or a complexed form of this molecule could be an intermediate in the CO reduction process by this system. Rhodium catalysts are indeed found to be useful for the hydroformylation of formaldehyde to glycolaldehyde (159-161) methanol is a by-product in these reactions. 

Water soluble Rh/tppts and Rh/tppms complexes dissolved in nonaqueous media such as the ionic liquids, l-ethyl-3-methylimidazolium or l-n-butyl-3-methylimidazolium salt have also been used as catalysts in the hydroformylation of 1-pentene employing a two phase system.15,16 The yields obtained were 16-33% (TOF=59-103 h 1) without any leaching of the rhodium from the ionic liquid to the aldehydes/feedstock phase. Rh/PPh3 catalysts exhibited higher rates (TOF=333 h 1) for the same biphasic reaction albeit with leaching of rhodium due to the uncharged nature of the catalytic system.15... 

Thus transition metal complexes capable of effecting cyanation reactions on aromatic nuclei under mild conditions have been discovered Cassar et al. describe such a catalytic system. The past few years have also seen the discovery of asymmetric catalysis. Asymmetric catalysts contain optically active ligands and, like enzymes, can promote catalytic reactions during which substantial levels of optical activity are introduced into the products. This volume contains examples of asymmetric hydrogenation and asymmetric hydroformylation catalysis in the papers, respectively, by Knowles et al. and Pino et al. 

Table VII. Stereoelective Hydroformylation of (R) (S)-3-Methyl-1-pentene with HRh(CO) (PPh3)3/( — )-DIOP Catalytic System...

Industrial problems have, in some instances, been solved either by a proper choice of construction materials and suitable process design or by development of heterogeneous catalytic systems using supported complexes or by generating active complexes in situ on a support material which avoid some of the problems of liquid-phase operation. For example, a number of the problems in liquid-phase vinyl acetate processing have been overcome by development of supported Pd catalysts (106). Vapor-phase hydroformylation has been carried out on supported rhodium complexes (107). 

---