Hydroformylation- -hydrogenation tandem

In 2013, Nozaki s group reported a dual Rh/Ru catalyst based on a combination of Rh(diphosphite), Shvo s catalyst, and Rug(CO)j2 in the isomerization-hydroformylation-hydrogenation tandem reaction [108]. 

One year later, the same research group reported a similar dual Rh/Ru catalyst based on a combination of a Rh(diphosphite), Shvo s catalyst, and Ru3(CO)j2 in the isomerization-hydroformylation-hydrogenation tandem reaction (Scheme 5.41) [21]. With methyl oleate, 53% yield of the terminal alcohol was observed. With unmodified internal olefins (2-decene, 2-tridecene, 4-octene), even higher regioselectivities in favor of the terminal alcohol could be achieved Ub up to 12). 

Over 75 years research into hydroformylation, the concomitant hydrogenation of aldehydes to alcohols by the effect of Co(I), Rh(I), Ir(I), Ru(II), Pd(II), and Pt(II) catalyst has been described repeatedly. These observations finally led to the development of highly efficient hydroformylation-hydrogenation tandem protocols, which almost completely result in formation of the desired alcohols. 

A breakthrough was achieved by Slaugh and MuUineaux at Shell, who discovered the beneficial effect of trialkylphosphines such as PEtj, P( Bu)3, or P(Cy)3 on the cobalt-catalyzed hydroformylation-hydrogenation tandem reaction with several olefins as substrates (1- and 2-pentene, 1-butene, propylene, methyl-pentenes, cyclohexenes, dimethyl-butenes, and higher olefins) [31, 36]. Large substituents at the phosphorus, as present in tris(2-ethylhexyl)phosphine, reduce... 

Scheme 5.57 PPhj-directed syn hydroformylation-hydrogenation tandem reaction.

Scheme 5.58 Hydroformylation-hydrogenation tandem reaction using a supramolecular catalyst and a calculated transition state (A).

Scheme 5.59 Decarboxylative hydroformylation-hydrogenation tandem reaction of a,p-unsaturated carboxylic acids.

Palladium-Catalyzed Hydroformylation-Hydrogenation Tandem Reaction... 

Polymetallic Systems and Other Metal-Based Catalytic Systems for Hydroformylation-Hydrogenation Tandem Reactions... 

During hydroformylation, acetalization of aldehydes can take place as an undesired side reaction when the hydroformylation is conducted in alcohols as solvent and under the influence of a hydroformylation catalyst with acidic properties. Moreover, when alcohols result in a hydroformylation-hydrogenation tandem reaction (see Section 5.2), acetalization has always been taken into consideration. 

Special hydroformylation protocols allow the one-step production of alcohols (hydroformylation-hydrogenation tandem reaction, see also Section 5.2), which are also of crucial importance as aroma compounds. Acetals, which have similar odors like their aldehydic precursors, maybe produced in the hydroformylation in alcohols as solvent under acidic conditions (hydroformylation-acetalization tandem reaction, see also Section 5.3) [15]. The acetal formed protects the aldehyde toward oxidations, reactions with amines, or aldol condensations. Especially in demanding fragrances, these modifications that may affect the scent impression are not desired. 

Scheme 6.107 Hydroformylation-hydrogenation tandem reaction of ethylene oxide.

Scheme 3.14 Tandem hydroformylation-hydrogenation reaction with carbon dioxide.

This principle was extended to the tandem decarboxylative hydroformylation-hydrogenation reaction ofa,P Unsaturated carboxylic acids (Scheme 5.59) [77]. 

Scheme 6.77 Hydroformylation-(aldol condensation)-hydrogenation tandem reaction and...

Scheme 6.125 Cobalt-catalyzed tandem hydroformylation-hydrogenation reaction of paraformaldehyde.

Garbay reported the chemoselective reduction of a a-dehydrophenylala-nine substrate bearing a p-acrylate moiety [105]. Robinson et al. have also used a tandem, one-pot asymmetric hydrogenation-hydroformylation-cyclization approach to generate six- to eight-membered cyclic a-amino acids [136]. 

In almost the same manner, tandem hydroformylation/aldol condensation aldol condensation of ketoolefins, such as p,y-unsaturated ketones, gives a single cyclization product under acid catalysis. Similar to the stepwise reaction, the in situ generated aldehyde preferentially acts as the electrophilic carbonyl component, while the ketone acts as the nucleophilic enol to form the five-membered ring product. Subsequent dehydration and hydrogenation of the resulting enone readily occurs under the reductive reaction conditions used (Scheme 30) [84],... 

Wittig yhdes have been shown to be compatible with hydroformylation conditions, and may thus be used in a domino reaction sequence such as from 16a to 38 (Scheme 5.15) [20]. When an a-unsubstituted ylide is employed, the resulting alkene undergoes in-situ rhodium-catalyzed hydrogenation in a triple tandem reaction to convert 10 a to 39. Several other examples were reported establishing the generality of this domino reaction sequence. 

Hydroaminomethylation is a promising reaction to functionalize unsaturated compounds with an amino group [13, 48, 49], The tandem reaction was discovered by Reppe in 1949 and has been further developed in recent years by Eilbracht and Beller. Hydroaminomethylation consists of three consecutive reactions which are carried out in the same reaction vessel [48], The first reaction is hydroformylation which is followed by the condensation with an amine. Hydrogenation of the generated enamine/imine to the amine is the last step. The conditions for hydroaminomethylation are related to the hydroformylation reaction but are not similar due to the two other reactions. The reaction is called an auto-tandem reaction because two of the three reactions need the same catalyst [9] (Scheme 16). 

FIGURE 8 Molecular clips equipped with phosphines or phosphites used for host-guest catalysis in rhodium-catalyzed hydrogenation and hydroformylation. At the bottom are depicted the peculiar tandem cyclizations, found only for allyldihydr-oxybenzenes in the host molecule as the catalyst (37,32). (For a color version of this figure, the reader is referred to the Web version of this chapter.)... 

Tandem hydroformylation - Michael addition - hydrogenation - cyclization Scheme 22... 

Hydroformylation of ethylene using a water-soluble Rh-TPPTS catalyst has been investigated [27] using a toluene-water solvent system at 353 K. The effect ofTPPTS concentration on rate shows a maximum at a P/ Rh ratio of 8 1. The rate of reaction first increases with catalyst concentration, and above a certain value it remains constant. The effect of aqueous-phase hold-up shows a maximum in the rate at = 0.4. The apparent reaction orders for the partial pressures of hydrogen and ethylene were found to be one and zero respectively. A strong inhibition in the rate with an increase in Pqq was observed. An interesting example of tandem synthesis of methacrolein in an aqueous biphasic system has been reported by Deshpande et al. [28], in which hydroformylation of ethylene and aldol condensahon reactions occur in two immiscible liquid phases with a high yield of the product Use of a two-phase system prevents contact of the hydroformylation and aldol catalysts, the interaction of which leads to deactivation. 

Several factors are needed to realize the tandem process. First, the catalyst should not be poisioned by the high concentration of amine. Tlie use of bidentate ligands helps to retard catalyst decomposition by this route. Second, the catalyst must be sufficiently electron rich to catalyze hydrogenation of the relatively electron-rich enamine, while not being too electron rich to prevent hydroformylation. These properties have been achieved with a number of systems, many of which have been outlined in a review on tandem processes initiated by hydroformylation. Some of these catalysts lack phosphine ligands, while others contain PPhj or more modern bisphosphine or bisphosphite ligands shown by the examples in the equations above. 

The carbonylation of epoxides and aziridines has been studied for several decades, and two forms of this process are now well established. Highly active catalysts for the ring expansion of epoxides and aziridines to p-lactones and 3-lactams are now known. In addition, conditions have been developed for the hydroformylation of epoxides to a-hydroxy aldehydes (including protected a-hydroxyacetals), and similar conditions have been developed for the tandem hydroformylation and hydrogenation of epoxides to generate... 

The metal present can also catalyse other reactions, giving rise to tandem processes. If hydroformylation is carried out in the presence of a secondary amine, the aldehyde 4.136 produced by hydroformylation will condense to give an enamine 4.137, which will be hydrogenated (but not hydroformylated) under the reaction conditions to give a tertiary amine 4.138 (Scheme 4.52). This chemistry can be extended to dienes to give iV-heterocycles of various kinds (Schemes 4.53 and 4.54). ... 

Nolte suggested the use of rhodium dicarbonyl dipivaloylmethanate (TMHD = 2,2,6,6-tetramethyl 3,5-heptanedionate, (2)) instead of Rh(acac)(CO)2, which has a longer shelf-life in solution (Scheme 1.21) [38]. Alternatively, [Rh(p-OAc)(COD)]2 (3) or [Rh(p-OMe)(COD)]2 (4) has been used for the generation of rhodium precatalysts [39, 40]. Numerous pieces of evidence were given that also [Rh( i-Cl)(COD)]2 (5), representing a typical precatalyst for hydrogenation, is suitable, for example, for several tandem reactions as well as for heterogenization of rhodium catalysts [41-43]. It should be noted that under hydroformylation conditions the formation of the hydrido rhodium catalyst from the precursors can take considerable time especially at ambient temperature (below 40 °C 5-10 h) therefore sometimes an incubation time is recommended [44]. 

Tandem or domino reactions using hydroformylation as the first step allow the immediate transformation of the formed aldehydes into other valuable chemical compounds (see Chapter 5) [41]. As discussed previously, the hydrogenation of olefinic substrates or product aldehydes is a commonly observed side reaction in the hydroformylation with Ru complexes. On the other hand, the reduction of the aldehydes can be desired. 

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