Palladium-Catalyzed Hydroformylation

Structure (43) (QPCH2CH2PQ) (Q = mixture of 1,4- and 1,5-cyclooctanediyl) was reported to be a very effective ligand for the palladium catalyzed hydroformylation of internal and terminal alkenes using small amounts of NaCl or HC1 as an additive in PhOMe or diglyme as the solvent.138-141... 

Also, palladium-catalyzed hydroformylation of alkynes is known [98]. Particularly, Beller s group showed that a wide range of symmetrically and unsymmet-rically substituted alkynes can be converted into the unsaturated aldehydes by the effect of a palladium complex modified with a bidentate 2-pyrrolyl phosphine (Scheme 4.20) [103]. 

Scheme 5.29 Crucial steps of palladium-catalyzed hydroformylation.

Figure 5.9 Diphosphine ligands for n-regioselective palladium-catalyzed hydroformylation.

Scheme 5.30 Palladium-catalyzed hydroformylation of 1-octene under varying conditions.

Palladium-Catalyzed Hydroformylation-Hydrogenation Tandem Reaction... 

In 2014, Beller s group [50] used a palladium-catalyzed hydroformylation-amination-(Diels-Alder) reaction for the construction of cyclohexenes. 

Highly selective halide anion-promoted palladium-catalyzed hydroformylation of internal alkenes to linear alcohols was studied. A (bcope)Pd(OTf)2 complex (bcope) = bis(cydooctyl)phosphinoethane with substoichiometrically added halide anion was found to be a highly efficient homogeneous catalyst to selectively convert internal linear... 

Kotsuki, H., Datta, P.K. and Suenaga, H. (1996) An efficient procedure for palladium-catalyzed hydroformylation of aryl/enol triflates. Synthesis, 470-472. 

Thus, [HRh(C0)(TPPTS)3]/H20/silica (TPPTS = sodium salt of tri(m-sulfophenyl)phopshine) catalyzes the hydroformylation of heavy and functionalized olefins,118-122 the selective hydrogenation of a,/3-unsaturated aldehydes,84 and the asymmetric hydrogenation of 2-(6 -methoxy-2 -naphthyl)acrylic add (a precursor of naproxen).123,124 More recently, this methodology was tested for the palladium-catalyzed Trost Tsuji (allylic substitution) and Heck (olefin arylation) reactions.125-127... 

Another route to the diol monomer is provided by hydroformylation of allyl alcohol or allyl acetate. Allyl acetate can be produced easily by the palladium-catalyzed oxidation of propylene in the presence of acetic acid in a process similar to commercial vinyl acetate production. Both cobalt-and rhodium-catalyzed hydroformylations have received much attention in recent patent literature (83-86). Hydroformylation with cobalt carbonyl at 140°C and 180-200 atm H2/CO (83) gave a mixture of three aldehydes in 85-99% total yield. 

Triphenylphosphine-Functionalized Amphiphiles for Rhodium-Catalyzed Hydroformylation and Palladium-Catalyzed Heck Coupling Reaction... 

Initial studies showed that the encapsulated palladium catalyst based on the assembly outperformed its non-encapsulated analogue by far in the Heck coupling of iodobenzene with styrene [7]. This was attributed to the fact that the active species consist of a monophosphine-palladium complex. The product distribution was not changed by encapsulation of the catalyst. A similar rate enhancement was observed in the rhodium-catalyzed hydroformylation of 1-octene (Scheme 8.1). At room temperature, the catalyst was 10 times more active. For this reaction a completely different product distribution was observed. The encapsulated rhodium catalyst formed preferentially the branched aldehyde (L/B ratio 0.6), whereas usually the linear aldehyde is formed as the main product (L/B > 2 in control experiments). These effects are partly attributed to geometry around the metal complex monophosphine coordinated rhodium complexes are the active species, which was also confirmed by high-pressure IR and NMR techniques. 

The other common elimination is the /3-elimination (equation 7). This is a vital step in many palladium-catalyzed reactions, such as alkene arylation, and occurs as a side reaction leading to isomerization in other alkene reactions such as hydrogenation and hydroformylation. 

Much less is known concerning the platinum-catalyzed hydroformylations. However, a reasonable catalytic cycle can be constructed (Scheme 3) from the available information on the generation and reactions of many of the intermediate complexes shown.6,8,9,15 The ability of platinum to catalyze hydroformylation reactions while palladium is not a good catalyst could be due to the ability of platinum to achieve the +4 oxidation state more readily. 

Considering isomeric and stereoisomeric composition of the products obtained in the asymmetric hydrocarbalkoxylation investigated using the palladium-(-)DIOP catalytic system, some interesting regularities are apparent. This is also true of the rhodium-(-)DIOP-catalyzed hydroformylation using the same substrates (13). 

Catalytic formation of carbon-carbon bonds is a powerful tool for construction of complex molecular architectures, and has been developed extensively for applications in organic synthesis. Three main classes of carbon-carbon bond forming reactions have been studied in sc C02 carbonylation (with particular attention paid to the hydroformylation of a-olefins), palladium-catalyzed coupling reactions involving aromatic halides, and olefin metathesis. 

The same regularities observed in hydroformylation seem to exist also in hydroalkoxycarbonylation, the prevailing chiralities in the rhodium-catalyzed hydroformylation being opposite to those in the palladium-catalyzed hydroalkoxycarbonylation. These regularities show that the model used to interpret the experimental hydroformylation data might also be applied to other hydrocarbonylation reactions. 

The group of Van Leeuwen has reported the synthesis of a series of functionalized diphenylphosphines using carbosilane dendrimers as supports. These were applied as ligands for palladium-catalyzed allylic substitution and amination, as well as for rhodium-catalyzed hydroformylation reactions [20,21,44,45]. Carbosilane dendrimers containing two and three carbon atoms between the silicon branching points were used as models in order to investigate the effect of compactness and flexibility of the dendritic ligands on the catalytic performance of their metal complexes. Peripherally phosphine-functionalized carbosilane dendrimers (with both monodentate... 

The C5 aldehyde intermediate is produced from butadiene via catalytic oxidative acetoxylation followed by rhodium-catalyzed hydroformylation (see Fig. 2.30). Two variations on this theme have been described. In the Hoffmann-La-Roche process a mixture of butadiene, acetic acid and air is passed over a palladium/tellurium catalyst. The product is a mixture of cis- and frans-l,4-diacetoxy-2-butene. The latter is then subjected to hydroformylation with a conventional catalyst, RhH(CO)(Ph3P)3, that has been pretreated with sodium borohydride. When the aldehyde product is heated with a catalytic amount of p-toluenesulphonic acid, acetic acid is eliminated to form an unsaturated aldehyde. Treatment with a palladium-on-charcoal catalyst causes the double bond to isomerize, forming the desired Cs-aldehyde intermediate. 

Ionic liquids can be used as replacements for many volatile conventional solvents in chemical processes see Table A-14 in the Appendix. Because of their extraordinary properties, room temperature ionic liquids have already found application as solvents for many synthetic and catalytic reactions, for example nucleophilic substitution reactions [899], Diels-Alder cycloaddition reactions [900, 901], Friedel-Crafts alkylation and acylation reactions [902, 903], as well as palladium-catalyzed Heck vinylations of haloarenes [904]. They are also solvents of choice for homogeneous transition metal complex catalyzed hydrogenation, isomerization, and hydroformylation [905], as well as dimerization and oligomerization reactions of alkenes [906, 907]. The ions of liquid salts are often poorly coordinating, which prevents deactivation of the catalysts. 

Support for the involvement of HPdCl(PPh3)2 as the active species in palladium-catalyzed hydroesterifications comes from the isolation of frans-Pd-(COPr)Cl(PPh3)2 from propene hydroformylation [5], while Pd(CO)(PPh3)3 is inactive as a catalyst in the absence of HCI [6]. In the case of PdX2L2/SnX2 catalyst systems olefins seem to be the hydrogen source for the formation of the active Pd-H species [7],... 

Another advantage of dendrimer-based catalysts concerns their easy recovery by stabilization at the surface of a polymer. The principal activities in dendritic catalysis lie in homogeneous catalysis, including Kharash addition of CC14 to methacrylate, palladium-catalyzed allylic alkylation, hydrogenation of olefins, hydroformylation, cyclopropanation, and oxidation.258 Dendrimers with redox-active cores have been proposed as promising materials for miniaturized information-storage circuits.259... 

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