Cinnamaldehyde, hydrogenation selective

Hydrogenation of cinnamaldehyde has been studied extensively since selectivity has often been an issue. Under mild conditions the carbonyl group is reduced giving cinnamyl alcohol, whereas at elevated temperatures complete reduction to 3-phenylpropanol [122-97 ] results. It is possible to saturate the double bond without concomitant reduction of the carbonyl group through selective hydrogenation with a ferrous chloride-activated palladium catalyst (30), thereby producing 3-phenylpropanol [104-53-0]. 

Hajek J, Maki-Arvela P, Toukoniitty E, Kumar N, Salmi T, Muizin DY (2004) The effect of chemical reducing agents in the synthesis of sol-gel Ru-Sn catalysts selective hydrogenation of cinnamaldehyde. J Sol-Gel Sci Technol 30 187-195... 

In 1996, Liu et al. reported the selective hydrogenation of cinnamaldehyde, an a,/ -unsaturated aldehyde, to cinnamyl alcohol, an a,/ -unsaturated alcohol, by means of PVP-protected Pt/Co bimetallic colloids prepared by the polyol process [111]. The colloids were obtained as a dark-brown homogeneous dispersion in a mixture of ethylene glycol and diethylene glycol, and characterized by TEM and XRD. These authors prepared different samples of nanoparticles with Pt Co ratios of 3 1 and 1 1, the mean diameters of which measured 1.7 and 2.2 nm, respectively. These colloidal systems were also compared with the single metal-... 

The catalytic system of [Ir(COD)Cl]2 with an excess of the bulky phosphine P(o-MeOPh)3 under transfer hydrogenation conditions of propan-2-ol and KOH was used successfully in the selective hydrogenation of cinnamaldehyde (Scheme 15.4) [4]. Selectivity and activity were found to increase with increasing P/Ir ratios, and complete conversion was achieved in as little as 5 minutes (turnover frequency (TOF) 6000 IT1). 

Tessonnier JP, Pesant L, Ehret G, Ledoux MJ, Pham-Huu C (2005) Pd nanoparticles introduced inside multi-walled carbon nanotubes for selective hydrogenation of cinnamaldehyde into hydiocinnamaldehyde. Applied Catalysis A General 288 203-210. 

A typical probe reaction for estimating catalytic properties in selective hydrogenations is the hydrogenation of cinnamaldehyde. This molecule contains both a C=C and a C=0 double bond, thus the formation of hydrocinnamaldehyde and/or cinnamyl alcohol by reduction of the one or the other, or the formation of phenyl propanol in the case of complete reduction may indicate the potential of the catalyst for other fine chemical transformations. Indeed, this reaction was one of the first to be tested by CNT-supported catalysts [120]. Noble metals show a high activity in this reaction and... 

Fig. 15.15 Cinnamyl alcohol selectivity as a function of conversion in the selective hydrogenation of cinnamaldehyde over differently supported Ru catalysts. Reactions conditions as listed in Tab. 15.4. Data compiled from literature [120,122,123,126], HSAG high-surface area graphite AC activated carbon.

A 95% yield of cinnamic alcohol is obtained by selective hydrogenation of the carbonyl group in cinnamaldehyde with, for example, an osmium-carbon catalyst [145]. 

Dihydrocinnamaldehyde can be obtained with scarcely any byproducts by selective hydrogenation of cinnamaldehyde. It is used in perfumery for hyacinth and lilac compositions. 

Osmium complexes modified with tppts and tppms also catalyse the selective hydrogenation of cinnamaldehyde to cinnamylalcohol (Figure 14, II) in an aqueous/organic two phase system.493 The selectivity towards the unsaturated alcohol II with Os/tppts was lower than with Ru/tppts but both Ru and Os/tppts... 

The selective hydrogenation of cinnamaldehyde to produce cinnamyl alcohol is an important reaction and it represents an often encountered selectivity problem, namely the selective hydrogenation of aldehydes in the presence of a carbon-carbon double bond. The major application of cinnamyl alcohol is as a base for perfumes, and therefore high selectivities and conversions are vital. Ir and Pt catalysts (Fig. 3.4) seem to give the best results [18,19]. Alternatively a homogeneous catalyst can be applied (see below). 

While a nickel boride catalyst preferentially saturates the carbon-carbon double bond of a,p-unsaturated aldehydes, the cobalt borides have a tendency to favor carbonyl group hydrogenation. Cinnamaldehyde was hydrogenated to cinnamoyl alcohol in 97% selectivity at 50% conversion and 86% selectivity at 74% conversion over a P-2 cobalt boride (Eqn. 12.7).5 With a P-2W cobalt boride the unsaturated alcohol was produced in 97% selectivity at 73% conversion. The presence of the aromatic ring enhances selectivity in this reaction since the hydrogenation of crotonaldehyde to 2-buten-l-ol occurred with only about a 25% selectivity at under 20% conversion over either catalyst (Eqn. 12.8).54... 

Selective hydrogenation. Although reduction of an unsaturated aldehyde to the unsaturated alcohol is usually a formidable problem, Tuley and Adams " reported reduction of cinnamaldehyde to cinnamyl alcohol in high yield using a mixture... 

A new method of synthesis of selective platinum catalysts for the hydrogenation of unsaturated carbonyl compounds is presented. Platinum was deposited on the supports tailored with the monolayer of transition metal oxide. Selectivity of these catalysts strongly depended on the type of inorganic support as well as on the type of transition metal in the monolayer. Catalysts were tested in the hydrogenation of furfural, crotonaldehyde and cinnamaldehyde. Selectivity of the synthesis of the appropriate unsaturated alcohols was enhanced when compared with the reactions performed over classical Pt-metal oxide catalysts. 

Reduced osmium on carbon is an excellent catalyst for selective hydrogenation of aj3-unsaturated aldehydes to unsaturated alcohols.1 Cinnamaldehyde — cinnamyl alcohol (95% yield). Reduced rates are observed with alumina as the support. This selective reduction is not applicable to a,/3-unsaturated ketones thus hydrogenation of mesityl oxide afforded methyl isobutyl ketone. 

Aromatic unsaturated aldehydes behave differently, since they are vinylogues of benzaldehydes. In cinnamaldehydes, reduction of the C=0 group and C=C bond are almost equally competitive. However, the selective hydrogenation to hydrocinnamalde-hydes or cynnamyl alcohols is controlled depending on the metal, on the support, on additives and on solvent. Hydrocinnamaldehydes form selectively over Pd catalysts modified with potassium salts of weak acids or FeSO/. Cobalt carbonyl catalysts under 0X0 conditions, or CojfCOlg in the presence of amines, efficiently (96.4% yield) catalyze selective reduction " ... 

At the reactant concentrations used, the rs remained virtually constant and no dependence on reactant concentration became observable. However concentration dependent changes in the adsorption mode were recently reported in selective hydrogenation of a, 3 unsaturated aldehyde [2]. It was supposed that the adsorption mode of cinnamaldehyde at high concentrations differs from that at lower concentrations, more precisely, cinnamaldehyde adsorbs perpendicular to the catalyst surface with the aromatic rings in parallel arrangements at high coverage. However, in om case the competitive adsorption of the modifier and the reactant complicates the situation. 

Electron Spectroscopy for Chemical Analysis (ESCA) studies on some selected catalysts indicate that higher concentration of Pt on the support surface is more conducive to the selective hydrogenation of the terminal C=0 bond of cinnamaldehyde to the corresponding unsaturated alcohol. 

Figure 4.24. Selectivity vs conversion in cinnamaldehyde hydrogenation- mechanism over Ru/Y zeolite. (J. Hajek, N.Kumar, P. Maki-Arvela, T.Salmi, D.Yu.Murzin, Selective hydrogenation of cinnamaldehyde over Ru/Y zeolite, J. Molecular Catal. A. 217 (2004) 145).

SELECTIVE HYDROGENATION OF CINNAMALDEHYDE TO CINNAMYL ALCOHOL USING AN Ir/C CATALYST INFLUENCE OF REACTION CONDITIONS... 

In this paper we will report on the selective hydrogenation of o /3 unsaturated aldehydes using a supported palladium catalyst in a range of ionic liquids. We will also compare their reactivity and selectivity to conventionally used organic solvents. Two systems have been investigated, cinnamaldehyde to form hydrocinnamaldehyde and citral... 

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