Homogeneous catalytic hydrogenation aldehydes

This chapter aims to provide an overview of the current state of the art in homogeneous catalytic hydrogenation of C=0 and C=N bonds. Diastereoselec-tive or enantioselective processes are discussed elsewhere. The chapter is divided into sections detailing the hydrogenation of aldehydes, the hydrogenation of ketones, domino-hydroformylation-reduction, reductive amination, domino hydroformylation-reductive amination, and ester, acid and anhydride hydrogenation. 

Hydroformylation is the most successful application of a homogeneous catalytic reaction to industrial processes [1], Aldehydes are conveniently produced by hydroformylation, in which CO and hydrogen are simultaneously added to an alkene (Figure 1). 

Reduction of the double bond only was achieved by catalytic hydrogenation over palladium prepared by reduction with sodium borohydride. This catalyst does not catalyze hydrogenation of the aldehyde group [31]. Also sodium borohydride-reduced nickel was used for conversion of cinnamaldehyde to hydrocinnamaldehyde [31]. Homogeneous hydrogenation over tris(triphenylphosphine)rhodium chloride gave 60% of hydrocinnamaldehyde and 40% of ethylbenzene [5(5]. Raney nickel, by contrast, catalyzes total reduction to hydrocinnamyl alcohol [4S. Total reduction of both the double... 

One of the most interesting catalytic reactions to be discovered is the so-called oxo reaction. The oxo reaction consists of the catalytic addition of carbon monoxide and hydrogen to olefins to form, primarily, aldehydes possessing one carbon atom more than the original olefin. This hy-droformylation reaction was developed during World War II by Roelen and co-workers (22) in Germany. While they utilized solid Fischer-Tropsch cobalt-thoria catalyst, it became apparent to them that the hydroformylation reaction was probably a homogeneous catalytic process with either dicobalt octaearbonyl or cobalt hydrocarbonyl as the catalyst. 

Aldehydes can be obtained homogeneously from ozonides by reductive cleavage, which can be effected either by zinc in glacial acetic acid or by catalytic hydrogenation of the ozonide118,119 in the presence of a 1 19 palladium-calcium carbonate catalyst.120 Adipdialdehyde has thus been obtained from cyclohexene in 60-70% yield 121... 

Hydroformylation (Equation (14)) is one of the very largest homogeneous catalytic reactions carried out by industry making over 15 billion pounds of aldehyde products each year. These are subsequently hydrogenated to alcohols or oxidized to carboxylic acids. There are several recent excellent reviews on hydroformylation catalysis (cf. Refs 7,7a-7c). Industry is generally more interested in the linear aldehyde product, and much of hydroformylation catalyst development work has been directed at increasing the linear to branched regioselectivity (L B, also referred to as normal to iso), reaction rates, and catalyst stability (lifetime). There are three main hydroformylation catalysis... 

Hydroformylation involves the reaction of carbon monoxide and hydrogen with an alkene to produce aldehydes, which does not proceed in the absence of a catalyst [25]. It is the widely used homogeneous catalytic reaction of alkenes. Although the catalysis is well established, catalyst separation is still a challenge and is the focus of intense research. Thus, significant efibrts have been focused on the immobilization of organometaUic species for the catalytic hydroformylation [26]. 

Oxo Synthesis. Ad of the synthesis gas reactions discussed to this point are heterogeneous catalytic reactions. The oxo process (qv) is an example of an industriady important class of reactions cataly2ed by homogeneous metal complexes. In the oxo reaction, carbon monoxide and hydrogen add to an olefin to produce an aldehyde with one more carbon atom than the original olefin, eg, for propjiene ... 

Homogeneous Hydrogenation of Aldehydes, Ketones, Imines and Carboxylic Acid Derivatives Chemoselectivity and Catalytic Activity 413... 

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