Reduction hydroformylation

Pardey and coworkers—Rh, Cu, and Ir complexes heterogenization and applications of water-gas shift (e.g., nitrobenzene reduction, hydroformylation). 

A typical benchmark system is the Shell catalyst for reductive hydroformylation of 1-dodecene based on the mixture of Phobane-C2o ligands, which operates under a syngas pressure of 85 bar with an excess of H2 in comparison to CO to give 86.9% yield of isomeric tridecanols (Scheme 5.44) [46a]. 1-Tridecanol is used as a lubricant or as an ingredient of surfactants, ink solvents, and pesticides. 

Scheme 5.52 Rh-catalyzed reductive hydroformylation of 1,3-butadiene using two different phosphine ligands.

Scheme 5.54 Rh-catalyzed reductive hydroformylation of mono-olefins using a temperature gradient.

Scheme 5.61 Part of the mechanism of the Pd-catalyzed reductive hydroformylation.

The group of Pakkanen [80] published several examples that show that Ru3(CO)i2/2,2 -bipyrimidine anchored on silica is active in the reductive hydroformylation of alkenes. The outcome and the reproducibility of the reaction are strongly dependent on the impregnation method [81]. The reaction proceeded best in THF. The rate-limiting catalytic step is the hydroformylation of the alkene, whereas the hydrogenation of the intermediate aldehyde proceeds fast and with good yields. By addition of NEtj or the support of rhodium on AljOj, the formation of the alcohol could be improved [82]. 

Scheme 5.63 Ru-catalyzed reductive hydroformylation with a dual hydroformylation-hydrogenation catalyst.

Scheme 5.64 Ru-catalyzed reductive hydroformylation using a nitrogen ligand.

In the patent literature, numerous protocols for the reductive hydroformylation of preferentially short chain olefins, such as ethylene or propylene, with heterogeneous Mo catalysts in the presence of different additives are claimed [95]. Heterogeneous Rh catalysts for the reductive hydroformylation of ethylene benefit from the presence of V, Fe, Zn, or Mo [96]. Also, supported cluster-derived Co catalysts have been successfully used [97]. 

Hexanol has been synthesized by reductive hydroformylation of 1-pentene with a modified Co catalyst [192]. The yield of the desired alcohol was dependent... 

In contrast to triphenylphosphine-modified rhodium catalysis, a high aldehyde product isomer ratio via cobalt-catalyzed hydroformylation requires high CO partial pressures, eg, 9 MPa (1305 psi) and 110°C. Under such conditions alkyl isomerization is almost completely suppressed, and the 4.4 1 isomer ratio reflects the precursor mixture which contains principally the kinetically favored -butyryl to isobutyryl cobalt tetracarbonyl. At lower CO partial pressures, eg, 0.25 MPa (36.25 psi) and 110°C, the rate of isomerization of the -butyryl cobalt intermediate is competitive with butyryl reductive elimination to aldehyde. The product n/iso ratio of 1.6 1 obtained under these conditions reflects the equihbrium isomer ratio of the precursor butyryl cobalt tetracarbonyls (11). 

The most common oxidatiou states and corresponding electronic configurations of rhodium are +1 which is usually square planar although some five coordinate complexes are known, and +3 (t7 ) which is usually octahedral. Dimeric rhodium carboxylates are +2 (t/) complexes. Compounds iu oxidatiou states —1 to +6 (t5 ) exist. Significant iudustrial appHcatious iuclude rhodium-catalyzed carbouylatiou of methanol to acetic acid and acetic anhydride, and hydroformylation of propene to -butyraldehyde. Enantioselective catalytic reduction has also been demonstrated. 

Most ring syntheses of this type are of modern origin. The cobalt or rhodium carbonyl catalyzed hydrocarboxylation of unsaturated alcohols, amines or amides provides access to tetrahydrofuranones, pyrrolidones or succinimides, although appreciable amounts of the corresponding six-membered heterocycle may also be formed (Scheme 55a) (73JOM(47)28l). Hydrocarboxylation of 4-pentyn-2-ol with nickel carbonyl yields 3-methylenetetrahy-drofuranone (Scheme 55b). Carbonylation of Schiff bases yields 2-arylphthalimidines (Scheme 55c). The hydroformylation of o-nitrostyrene, subsequent reduction of the nitro group and cyclization leads to the formation of skatole (Scheme 55d) (81CC82). 

Methyl-l-hexanol has also been prepared by the reaction of 2-hexylmagncsium halides with formaldehyde,3 the reduction of 2-mctliylliexanoic acid or its ester,4 5 and by hydroformylation of 1-hexene6"8 among others. 

When dicobalt octacarbonyl, [Co(CO)4]2, is the catalyst, the species that actually adds to the double bond is tricarbonylhydrocobalt, HCo(CO)3. Carbonylation, RCo(CO)3- -CO—>RCo(CO)4, takes place, followed by a rearrangement and a reduction of the C—Co bond, similar to steps 4 and 5 of the nickel carbonyl mechanism shown in 15-30. The reducing agent in the reduction step is tetra-carbonylhydrocobalt HCo(CO)4, ° or, under some conditions, H2. When HCo(CO)4 was the agent used to hydroformylate styrene, the observation of CIDNP indicated that the mechanism is different, and involves free radicals. Alcohols can be obtained by allowing the reduction to continue after all the carbon monoxide is... 

The hydroformylation reaction strategy has recently been extended, in a novel way, to the manufacture of primary amines by hydroaminomethylation of olefins with ammonia in a two-phase system. Thus, 1-pentene was reacted with ammonia here hydroformylation to an aldehyde, with CO and H2, with subsequent reductive amination occurs in a domino reaction. The catalyst was Rh/Ir/TPPS (Zimmermann et al., 1999). 

The steps in the hydroformylation reaction are closely related to those that occur in the Fischer-Tropsch process, which is the reductive conversion of carbon monoxide to alkanes and occurs by a repetitive series of carbonylation, migration, and reduction... 

Most recently new applications for substrate-controlled branched-selective hydroformylation of alkenes substituted with inductively electron-with drawing substituents have emerged. A recent example is the hydroformylation of acrylamide with a standard rhodium/triphenylphosphine catalyst, which yields the branched aldehyde exclusively (Scheme 4) [40]. Reduction of the aldehyde function furnishes 3-hydroxy-2-methylpropionamide, which is an intermediate en route to methyl methacrylate. 

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