A-Methyl cinnamic acid

Acrylic acid (AA) and methacrylic acid (MAA) (purchased from Merck) are freed from inhibitor on a neutral aluminium oxid column and distilled. Acrylamide (AM) from Kebo, Stockholm, is recrystallized once from chloroform solution before use. Other monomers of analytical grade were purchased from Merck and used as received crotonic acid (CA), tiglic acid (TA), 3-methyl crotonic acid (3-MCA), and a-methyl cinnamic acid (oi-MCia) (Table 1). Benzophenone (analytical grade, Kebo) and acetone (spectroscope grade, Merck) were used as supplied. 

Cinnamic acids. A soln. of triethyl phosphate in THF added to an ethereal soln. of ethyllithium in the same solvent at —78° under N2, allowed to warm slowly to 0°, stirred for 30 min, re-cooled to — 78°, LDA in THF added followed after a few min by /er/-butyl fluoroformate in the same solvent, allowed to warm slowly to room temp., heated to 35-40°, an excess of benzaldehyde in THF added with efficient stirring, heated at 40° for 4-5 h, left one night at room temp., the crude /cr/-butyl ester dissolved in trifluoroacetic acid, and the precipitated acid worked up - (E)-a-methyl-cinnamic acid. Y 81%. F.e.s. M.-P. Teuladeet al., Synth. Commun. 19, 71-81 (1989). 

Phenylpropyne-1 a-Methyl cinnamic acid -f a-phenyl crotonic acid 54 [345]... 

An alternative approach is the modification of heterogeneous catalysts by the addition of naturally occuring chiral molecules. The first example (H2) by Lipkin [17] might not be a real modified Pt catalyst because a stoichiometric amount of hydrocinchonine as salt of P-methyl-cinnamic acid was used. Nakamura [18] and later Isoda [22] and Izumi [4] chose chiral acids to... 

Heterogeneisation of chiral rhodium complex of 1,2-diphosphines already known as very efficient catalysts for enantioselective hydrogenation32 was achieved through amine functionality borne by pyrrolidine molecule. The supported Rh complex revealed as its homogeneous counterpart very high enantioselectivity (<90%) in hydrogenation of a-(acetylamino)cinnamic acid and its methyl ester. 

Franke, A., Mattem, G., and Traber. W.. Synthetical juvenile hormone. Part 1. para-Substituted 2-methyl-cinnamic acid derivatives, Helv. Chim. Acta, 58, 268, 1975. 

Scheme 7.13. (a) Morrison s asymmetric reduction of P-methyl cinnamic acid [116]. (b) Kagan s asymmetric reduction of Al-acetyl dehydrophenylalanine and the debut of the DIOP ligand [117]. 

In another example de Souza and Dupont studied the asymmetric hydrogenation of a-acetamido cinnamic acid and the kinetic resolution of ( )-methyl-3-hydroxy-2-methylenebutanoate with chiral Rh(I) and Ru(ii) complexes in [BMIM][BF4] and [BMIM][PFs] [106]. A special focus oftheir work was on the influence of H2 pressure on conversion. They determined the hydrogen solubility in the ionic liquid using... 

Biemer et al. reported the enantioselective behaviors of a Pd catalysts supported on specially prepared silica gels, which have been precipitated from Na silicate wiA HCl in the presence of optically active alkaloids sulfates of quinine (Q), quinidine (Qd ), cinchonine (Cn), or cinchonidine (Cnd). These catalysts proved to be active in the asymmetric hydrogenation of 2-methyl-cinnamic acid (Scheme 3.1.) . 

Modification of the previously reported ligand (li ,2i )-bis(diphenyl-phosphinamino)cyclohexane (3,323) by N-methylation results in the preferential production of (S)-a-amino-acid derivatives from Z-a-(acylamino)cinnamic acids whereas the original ligand leads to the (i )-acids. Such inversions of product configuration have also been observed when the hydrogen pressure is... 

Fig. 2—(a) Schematic representation of the phase diagram of the homologous series of 4-ethoxybenzol-4-amino-n-alkyl-a-methyl cinnamates (after Ref. [3], data of Ref. [12]). (b) Schematic representation of the phase diagram of the homologous series of cholesteryl esters of saturated aliphatic acids (after Ref. [3], data of Ref. [13]). 

In the asymmetric hydrogenation of the methyl ester of a-acetamido cinnamic acid, 3.24 cannot be observed by conventional NMR techniques. In situ PHIP-NMR studies in contrast do show two hydride signals at -19 and -2 ppm. Using a C-enriched substrate, the coupling between the asterisk-labeled carbon and the hydride at -2 ppm can also be observed. Based on the NMR data, the actual structure is concluded to be more like 3.25 than 3.24. 

Phenyl-2-propenoic acid [621 -82-9] commonly referred to as cinnamic acid, is a white crystalline soHd having a low intensity sweet, honeylike aroma. It has been identified as a principal constituent in the botanical exudates from Styrax IJquidamber orientalis) Benzoin Styrax ben in Pern Balsam [Myroxylon pereirae and Tolu Balsam (]Ayro>ylon balsamum) (4,5). In these, as well as numerous other natural products, it exists both as the free acid and in the form of one or more of its esters, as for example, methyl cinnamate, ben2yl cinnamate [103 1 -3] and cinnamyl cinnamate. 

Esters can be obtained from halogenated olefins using a metal carbonyl catalyst (87), eg, /n j -l-bromo-2-phenylethylene is treated with nickel carbonyl in the presence of methanol to afford the corresponding methyl cinnamate (see Cinnamic acid). 

The add is obtained by the reduction of cinnamic acid by means of sodium amalgam. The acid is then esterified by the condensing action of a mineral acid in methyl alcohol solution. The ester is an oil of very sweet odour, and is very useful for flower bouquets. 

Methyl cinnamate (16 parts) is dissolved in methyl alcohol (20 parts) and treated with bromine (20 parts). The mixture solidifies in the cold. It is shaken with a solution of caustic soda (12 parts) in water (24 parts), the temperature being kept down to 40°. After two hours the mixture is neutralised with dilute sulphuric acid, and an oily layer separates. This is mixed with water (to 250 parts) and sodium carbonate (5-5 parts) added, and the aldehyde distilled in a current of steam, and extracted with ether, and the ether evaporated. The yield is about 75 per cent, of the theoretical. 

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... 

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