Cinnamyl alcohol, oxidation cinnamaldehyde

Of particular interest are oxidations of unsaturated alcohols, for example, oxidation of cinnamyl alcohol to cinnamaldehyde,74,75 and special promoters have been added to increase selectivity (Fig. 6.13).75 Although the functions of these promoters are still not fully undestood, some authors attribute their increased selectivity to physical blocking of reaction sites. This blocking reduces the size of the active site ensemble and suppresses the tendency for alcohols to strongly adsorb and dissociate on Pt.75... 

The effect of a surfactant such as do-decylbenzene sulfonate (DBS) has been investigated and the DBS concentration slightly influences the current efficiency [213]. The oxidation of cinnamyl alcohol to cinnamaldehyde with a solid... 

Potassium ferrate, K2Fe04, is isomorphous with chromates and readily oxidizes alcohols to carbonyl compounds in the presence of alkali.286,287 The purple color of ferrate ion fades with the progress of the reaction. Yields as high as 96% have been reported for the oxidation of cinnamyl alcohol to cinnamaldehyde (equation 111).287... 

These results compare well with those reported by Mallat (7) in his studies on the oxidation of cinnamyl alcohol to cinnamaldehyde using a 5% Pt, 3% BPC catalyst in an aqueous solvent. Careful control of the system pH was critical to achieve high selectivities to the aldehyde. In our system using organic solvents rather than the water/base solvent no such control of the pH is necessary and a simpler monometallic catalyst can be used rather than the Bi promoted bimetallic catalyst. 

The copper(II) complex with polyaniline exhibits a higher catalytic capability for the dehydrogenation of cinnamyl alcohol into cinnamaldehyde [18, 20]. The cooperative catalysis of both components is achieved. Iron(lll) chloride is similarly employed instead of copper(II) chloride. The catalytic system is applicable to the decarboxylative dehydrogenation of mandelic acid to benzaldehyde. In these oxidation reactions, a complex catalyst consisting of polyaniline and metal salt forms a reversible redox cycle under molecular oxygen (Scheme 3.10). The copper salt appears to play a role as a metallic dopant, which is monitored spectroscopically. 

When heated in the presence of a carboxyHc acid, cinnamyl alcohol is converted to the corresponding ester. Oxidation to cinnamaldehyde is readily accompHshed under Oppenauer conditions with furfural as a hydrogen acceptor in the presence of aluminum isopropoxide (44). Cinnamic acid is produced directly with strong oxidants such as chromic acid and nickel peroxide. The use of t-butyl hydroperoxide with vanadium pentoxide catalysis offers a selective method for epoxidation of the olefinic double bond of cinnamyl alcohol (45). 

CHROMIUM TRIOXIDE-PYRIDINE COMPLEX, preparation in situ, 55, 84 Chrysene, 58,15, 16 fzans-Cinnamaldehyde, 57, 85 Cinnamaldehyde dimethylacetal, 57, 84 Cinnamyl alcohol, 56,105 58, 9 2-Cinnamylthio-2-thiazoline, 56, 82 Citric acid, 58,43 Citronellal, 58, 107, 112 Cleavage of methyl ethers with iodotri-methylsilane, 59, 35 Cobalt(II) acetylacetonate, 57, 13 Conjugate addition of aryl aldehydes, 59, 53 Copper (I) bromide, 58, 52, 54, 56 59,123 COPPER CATALYZED ARYLATION OF /3-DlCARBONYL COMPOUNDS, 58, 52 Copper (I) chloride, 57, 34 Copper (II) chloride, 56, 10 Copper(I) iodide, 55, 105, 123, 124 Copper(I) oxide, 59, 206 Copper(ll) oxide, 56, 10 Copper salts of carboxylic acids, 59, 127 Copper(l) thiophenoxide, 55, 123 59, 210 Copper(l) trifluoromethanesulfonate, 59, 202... 

Two of the commonest models are benzyl and cinnamyl alcohols - the former because it is easily oxidised beyond benzaldehde to benzoic acid and the latter because its double bond is often attacked, so that oxidation to cinnamaldehyde would show that the oxidant is mild enough to avoid competing double-bond attack. Geraniol is also included as a model substrate as it is in the same category as cinnamyl alcohol. Since there are so many examples of smdies on their oxidations a limited selection only is given. 

Some commercial samples of precipitated manganese dioxide may be active enough for use directly in an oxidation process. To assess the activity of a sample of manganese dioxide, dissolve 0.25 g of pure cinnamyl alcohol in 50 ml of dry light petroleum (b.p. 40-60 °C) and shake the solution at room temperature for 2 hours with 2g of the sample of manganese dioxide (previously dried over phosphoric oxide). Filter, remove the solvent by evaporation and treat the residue with an excess of 2,4-dinitrophenylhydrazine sulphate in methanolt (Section 9.6.13, p. 1257). Collect the cinnamaldehyde 2,4-dinitrophenyl-hydrazone and crystallise it from ethyl acetate. An active dioxide should give a yield of the derivative, m.p. 255 °C (decomp.), in excess of 0.35 g (60%). 

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. 

The partial oxidation of cinnamyl alcohol (Ph-CH—CH-CH2OH) to cinnamalde-hyde was conducted in the presence of a surfactant (sodium dodecylbenzene sulfonate) because reactant and product were insoluble in water [45,50]. Oxidation on Bi-Pt/AljOj catalysts was performed at basic pH obtained by addition of Li2C03, and by controlling the air supply to avoid over-oxidation of the metal. The maximum selectivity for cinnamaldehyde, 98.5 % at 95.5 % conversion, was obtained for a Bi/Pts ratio of 0.5. The high selectivity for cinnamyl aldehyde was attributed to the negligible hydration of the aldehyde because of the conjugation of C—O, C=C, and aromatic nucleus (see Section 9.2.2.1). Under similar conditions the selectivity for oxidation of 1-dodecanol [50] to dodecanal was poor. 

Geraniol is converted into atmospheric pressure phenethyl alcohol gives phenylacetaldehyde cinnamaldehyde is obtained from cinnamyl alcohol in good yield by use of a silver catalyst at 200°/20 mm.429 Bremner et al.43° describe a laboratory method for oxidation of tetrahydrofurfuryl alcohol by air on silver wool. 

Jones reagent (1, 142-143). Primary allylic or benzyUc alcohols are oxidized in high yield with chromic acid in acetone. Thus cinnamyl alcohol is oxidized to cinnamaldehyde in 84% yield, and benzaldehyde is obtained from benzyl alcohol in 76% yield. Manganese dioxide has usually been used in such oxidations. 

A similar type of oxidation was observed when alcohols reacted with DMSO. Traynelis and Hergenrother showed that benzylic and allylic alcohols were converted to the aldehyde in high yield by refluxing them in DMSO with air bubbling through the medium. 5 jjj j is case, air was a reagent and cinnamyl alcohol was oxidized in this manner to cinnamaldehyde in 90% yield. 5 Air is the oxidant and DMSO probably functions as a solvent. 

Oxidation of prim, alocohols to aldehydes with CrOg in graphite is specific, simple, and gives high yields. - E Cinnamyl alcohol refluxed 24 hrs. with CrOg-graphite in toluene -> cinnamaldehyde. Y ca. 100%. F. e. s. J.-M. Lalancette, G. Rollin, and P. Dumas, Can. J. Chem. 50, 3058 (1972). 

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