Cinnamic acid hydrogenation

Cinnamic alcohol can be dehydrogenated to give cinnamaldehyde and oxidized to give cinnamic acid. Hydrogenation yields 3-phenylpropanol and/or 3-cyclo-hexylpropanol. Reaction with carboxylic acids or carboxylic acid derivatives results in the formation of cinnamyl esters, some of which are used as fragrance materials. 

Keywords cinnamic acid, hydrogenation, gas-solid reaction, 3-phenylpropionic acid... 

Cyanophenyl) cinnamic acid hydrogenated in N K-carbonate soln. with 5%-Pd-on-carbon catalyst at room temp, and 20 Ibs./sq. in., until 1.07 moles of H2 have been absorbed after 20 min. —> / -[2-(2 -cyanophenyl)]phenylpropionic acid. Y 84%. (H. Rapo-port and A. R. Williams, Am. Soc. 71, 1774 (1949).)... 

Fig. 67. The dependence of the catalytic activity of metals on the heat of their sublimation, Ak for the reactions (a) benzene hydrogenation (b) cinnamic acid hydrogenation (c) oxygen hydrogenation (d) cthylamine hydrogenolysis 477).

Figure 15.19 Parity plot of activity in cinnamic acid hydrogenation at 1 bar determined in a 300-mL reactor (y-axes) and in a 20-mL reactor (x-axes) using different Pt/C and Pd/C catalysts.

Cinnamic acid can be readily esterified by the Fischer-Speier method without any risk of the addition of hydrogen chloride at the double bond. Proceed precisely as for the preparation of ethyl benzoate (p. 104), using 20 g. of cinnamic acid and 20 ml. of rectified spirit. When the crude product is poured into water, a sharp separation of the ester is not readily obtained, and hence the addition of about 10 ml. of carbon tetrachloride is particularly desirable. Finally distil off the carbon... 

Use 01 g. of the platinum oxide catalyst and 11 4 g, of pure cinnamic acid dissolved in 100 ml. of absolute alcohol. The theoretical volume of hydrogen is absorbed after 7-8 hours. Filter off the platinum, and evaporate the filtrate on a water bath. The resulting oil solidifies on cooling to a colourless acid, m.p. 47-48° (11-2 g.). Upon recrystallisation from light petroleum, b.p. 60-80°, pure dihydrocinnamic acid, m.p. 48-49°, is obtained. 

Hydrocinnamic acid may also be prepared by the reduction of cinnamic acid with sodium and alcohol or with sodium amalgam or with hydrogen in the presence of Adams platinum oxide catalyst (Section 111,150) ... 

Pyrolytic Decomposition. The pyrolytic decomposition at 350—460°C of castor oil or the methyl ester of ricinoleic acid spHts the ricinoleate molecule at the hydroxyl group forming heptaldehyde and undecylenic acids. Heptaldehyde, used in the manufacture of synthetic flavors and fragrances (see Elavors and spices Perfumes) may also be converted to heptanoic acid by various oxidation techniques and to heptyl alcohol by catalytic hydrogenation. When heptaldehyde reacts with benzaldehyde, amyl cinnamic aldehyde is produced (see Cinnamic acid, cinnamaldehyde, and cinnamyl... 

Cinnamic acid undergoes reactions that are typical of an aromatic carboxyhc acid. Using standard methodology, simple esters are easily prepared and salts are formed upon neutrali2ation with the appropriate base. Hydrogenation of cinnamic acid under mild conditions leads to 3-phenylpropanoic acid [501-52-0] whereas under forcing conditions, such as under high pressure in presence of a nickel catalyst, complete saturation to 3-cyclohexylpropanoic acid [701-97-3] is readily accompHshed (8). 

Selective oxidation of either the aromatic ring or the side chain can also be accompHshed. For example, epoxidation of the double bond of cinnamic acid is effected in excellent yield by treatment with potassium hydrogen persulfate (10). 

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). 

Cinnamic Acid.—The reaction, which takes place when an aldehyde (aliphatic or aromatic) acts on the sodium salt of an aliphatic acid in presence of the anhychide, is known as Perkin s reaction, and has a ery wide application. Accoid-ing to the result of Fittig s researches on the properties of the unsaturated acids described below, the reaction occurs in two steps. The aldeh) de forms first an additive compound with the acid, the aldehyde caibon attaching itself to the n-carbon ii.e.i nevt the carbovyl) of the acid. A saturated hydiOKy-acid is formed, which is stable, if the a-carbon is attached to only one atom of hydrogen, as in the case of isobutync acid,... 

As shown in Schemes 10-44 and 10-45, two products may be formed in a Meerwein reaction Scheme 10-44 shows a simple aryl-de-hydrogenation of cinnamic aldehyde, whereas Scheme 10-45 shows an aryl-de-hydrogenation combined with the addition of HC1 to the double bond of the methyl ester of cinnamic acid. No systematic studies have been made as to which of the two products will be formed in a given reaction, what experimental conditions will favor one or the other product, and what substituents or other structural characteristics of the alkene influence the ratio of the two types of product. The addition product can, in most cases, easily be converted... 

N-chlorosuccinimide, reaction+PhOH, 92 chrysene, bromination of, 405 —, hydrogen exchange with, 258 —, nitration of, 39 cinnamic acid, nitration of, 39 cinnanyl p-totyl ethers, Ciaisen rearrangement of, 472... 

The trans cinnamic acid and phenyl propiolic acid data involve fits of essentially the same precision at o-, m-, and p- positions (SD =. 05 . 02). However, the RMS of these sets is quite low, and consequently, / values of. 200 prevail. The interpretation of these results is therefore uncertain. To the extent that the results of Table VII are meaningful, it is of particular interest that Kj =p°Ip =. 68 for the phenyl propiolic acid, whereas for the tram cinnamic acids, K° = 1.02. These results suggest that in contrast to the ortho substituted benzoic acids, the lines of field forces in the ortho substituted phenyl propiolic acids do (partly at least) penetrate regions of hi dielectric solvent. The results for the tram cinnamic acids would then indicate some (but not complete) exclusion of solvent resulting from the presence of the vinyl hydrogens. These interesting results from the application of eq. (1) clearly need to be confirmed by additional studies. 

In recent years, the catalytic asymmetric hydrogenation of a-acylamino acrylic or cinnamic acid derivatives has been widely investigated as a method for preparing chiral a-amino acids, and considerable efforts have been devoted for developing new chiral ligands and complexes to this end. In this context, simple chiral phosphinous amides as well as chiral bis(aminophosphanes) have found notorious applications as ligands in Rh(I) complexes, which have been used in the asymmetric hydrogenation of a-acylamino acrylic acid derivatives (Scheme 43). 

Simandi and Nagy studied the kinetics of the catalyzed hydrogenation of cinnamic acid (S) to dihydrocinnamic acid (SHj) under steady-state conditions 166). They concluded that the kinetically important reactions were the two successive transfers of hydrogen atoms, viz.. 

A few data exist on the oxidation by ferricyanide. This is simple second-order (in oxidant and neutral hydrazine), and leads to quantitative production of nitrogen in accordance with scheme (71)-(74) with A 4 k and A i. No scrambling occurs during oxidation of N-labelled N2H4 indicating that all N2 is formed via di-imine" Di-imine so prepared is capable of hydrogenating added unsaturated compounds, for example, phenylpropiolic acid gives m-cinnamic acid" " . 

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