Hydrogenation of cinnamaldehyde

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]. 

Hydrogenation of cinnamaldehyde Pt-Co/C or Pt-Ru/C Cinnamyl alcohol Fine chemicals, perfumery... 

In some ca.ses the use of a two-phase system may allow a change in the selectivity. Thus, Joo et al. (1998) have shown that water-soluble Ru hydrides (sulphanatophenylphosphine Ru complexes) give different products in the hydrogenation of cinnamaldehyde with variation in the pH of the aqueous media. At a pH greater than 7.2, cinnamyl alcohol is formed and at a pH less than 5 saturated aldehyde is formed. 

In continuation of a previous work (1), catalytic hydrogenation of cinnamaldehyde has been studied in slurry phase using a high-pressure autoclave. A series of carbon powder (CP)-supported Pt catalysts with widely varying Pt dispersion and Pt location on the support has been used in the study. The purpose has been to find out how the location of the metal on the support and its dispersion affect the two parallel reaction paths, namely the hydrogenation of the C=0 and C=C bonds. 

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... 

Table 3 Hydrogenation of cinnamaldehyde using various catalyst systems. ...

In a somewhat different approach, supported-aqueous-phase-catalysts (SAPC, see Chapter 5, Section 5.2.5 of this book) have been combined with supercritical CO2 in catalytic hydrogenation [55], Ruthenium was supported on silica and combined with the ligand TPPTS in water, after which a scC02/H2 phase was applied together with the substrate. Better levels of conversion were obtained using scC02 than the equivalent system with toluene for the hydrogenation of cinnamaldehyde. 

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). 

The Osmium cluster Os3(CO)12 and clusters in the presence of various phosphines and triphenylphosphite have been utilized for the hydrogenation of cinnamaldehyde and crotonaldehyde (Table 15.7) [36]. The results show that good yields of unsaturated alcohols can be obtained by using a large excess of phosphine at elevated hydrogenation temperatures. 

In another example, undecanal was hydrogenated to undecanol with a water-soluble catalyst in the presence of chemically modified yS-cyclodextrins, which facilitated the mass transfer between the aqueous and the organic phase [134]. Hydrogenation of cinnamaldehyde with very high (99%) selectivity to cinnamyl alcohol was also performed in water scC02 biphasic systems [135] which al-... 

Fig. 44.6 Product inhibition in the ruthenium-catalyzed hydrogenation of cinnamaldehyde. Reaction conditions 0.1 mmol RuCI3, 0.5 mmol TPPTS, H20 Toluene ratio 5 mL 5 mL.

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.

Fig. 4 Regioselectivity in the hydrogenation of cinnamaldehyde with Ru(II)-TPPMS as a function of pH...

Hajek, Jan Murzin, Dmitry Yu. Liquid-Phase Hydrogenation of Cinnamaldehyde over a Ru-Sn Sol-Gel Catalyst. E Evaluation of Mass Transfer via a Combined ExperimentaFTheoretical Approach, Industrial Engineering Chemistry Research 2004), 43(9), 2030-2038... 

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... 

Hydrogenation of cinnamaldehyde Ru/TPPTS Gas miscibility Enhanced separations Bhanage et al. (1999a)... 

Hydrogenation of cinnamaldehyde to 3-phenylpropionaldehyde over palladium catalyst may be accompanied by the formation of 3-phenyl-1-propanol and propyl-benzene,218 although the formation of 3-phenylpropionaldehyde usually predominates.219,220 The composition of the products are widely affected by the nature of palladium catalysts, solvents, supports, and additives.216,221 The hydrogenation over Pd-Al203 in ethanol or over Pd-kieselguhr in acetic acid gave 3-phenylpropionalde-hyde quantitatively at room temperature and atmospheric pressure. The addition of a 1 1 ratio of ferrous chloride to palladium also resulted in quantitative formation of 3-phenylpropionaldehyde in the hydrogenation over 5% Pd-C in methanol.221 This result was contrasted with those obtained with platinum oxide where iron additives led... 

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