Hydrogenation of cinnamic acid

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). 

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.. 

Copper-catalyzed Suzuki cross-coupling reactions using mixed nanocluster catalysts have been studied recently. Copper-based catalysts were shown to be effective as reagents that can present an inexpensive and environmentally friendly alternative to noble metal catalysts. In the hydrogenation of cinnamic acid to corresponding alcohol, the selectivity can be varied by doping Sn with Rh colloid catalysts. A selectivity of 86% was achieved using a colloidal Rh/Sn (Rh/Sn = 1.5 1) catalyst on... 

The asymmetric hydrogenation of cinnamic acid derivatives has been developed by Knowles at Monsanto [4], The synthesis of L-dopa (Figure 4.3), a drug for the treatment of Parkinson s disease, has been developed and is applied on an industrial scale. Knowles received the Nobel Prize for Chemistry in 2001 together with Noyori (see below, BINAP ) and Sharpless (asymmetric epoxidation). 

Scheme 6.12 Asymmetric hydrogenation of cinnamic acid acetamidates.

Thus, G. Oehme et al. employed two types of polysoaps in the micellar catalytic asymmetric hydrogenation of cinnamic acid acetamidates as amino acid precursors [81, 82]. 

C12H20O2, Mr 196.29, bpo.nkPa. 91 °C, has not yet been found in nature. It is a colorless liquid with a sweet-fruity odor, reminiscent of pineapples. The ester is prepared by esterification of 3-cyclohexylpropionic acid (obtained by hydrogenation of cinnamic acid) with allyl alcohol. It is used in perfumery to obtain fruity top notes as well as pineapple and chamomile nuances. 

The apparatus may be tested and the activity of the catalyst assessed by carrying out a hydrogenation of cinnamic acid (Expt 6.138) or maleic acid. The procedure for the latter is described below. 

The first industrially interesting production of a chiral pharmaceutical with a chiral metal complex catalyst is the asymmetric hydrogenation of cinnamic acid derivatives to give L-DOPA, see Fig. 6.21. 

Detailed studies of the hydrogenation of cinnamic acid derivatives (Fig. 6.22) by Halpern [53] and Brown [54] have revealed that the most stable intermediate of the two alkene adducts is not the one that leads to the major observed enantiomeric product, see Fig. 6.24. This means that the least stable intermediate alkene-rhodium complex reacts faster in the subsequent reaction step involving... 

Detailed studies of the hydrogenation of cinnamic acid derivatives (Fig. 6.25) by Halpern [72] and Brown [73] have revealed that the most stable intermediate... 

Reaction of [ HCo(CN )5 with activated alkenes, such as ,/i-unsaturated acids, produces free-radical intermediates (see also Section 6.2.2.3), and therefore hydrogenation of these substrates is often characterized by low yields and numerous side-products. In the presence of j3-CD the yield of acrylic acid hydrogenation increased to 81% [73]. Both neutral (Brij 35) and ionic (SDS, CTAB) micellar agents were shown to increase the rate of hydrogenation of cinnamic acid as a result of an increased local concentration of the substrate within the micelles [74] (cf. Section 4.5). 

The catalyst performances were measured in the hydrogenation of cinnamic acid to dihydrocinnamic acid and the catalyst activity given in ml H2/g catalyst/min. The reaction time for the hydrogenation reaction was 5 min in all experiments, and measured between the 3rd and 8th minute starting from the beginning of the H2-supply (Ref. 5). 

Different lots of commercially available, steam-activated and HNO3 washed carbons from beechtree wood were used as catalyst support. Tremendous catalytic activity variations were still found after impregnation with a H2PdCl6-solution using the low pressure hydrogenation of cinnamic acid to dihydrocinnamic acid as a model reaction /5/. 

Surface concentration of nitrogen compounds, determined by integration of the Nls XPS signal group and catalyst activity (A) measured in the hydrogenation of cinnamic acid... 

Quantum mechanical calculation of the enantiose-lective hydrogenation of cinnamic acid derivatives. 

A Rh-colloid/C-catalysts doped with Sn (Rh/Sn = 1.5/1) exhibits 86 % selectivity in the hydrogenation of cinnamic acid to cinnamic alcohol. 

The Kast building block is conveniendy available by hydrogenation of cinnamic acid ester TM 8.2g, a commodity produced on the large scale. An old technology is... 

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