Substituted cinnamic acids decarboxylation

Lindsay RF, FG Priest (1975) Decarboxylation of substituted cinnamic acids by enterobacteria the influence on beer flavour. J Appl Bacterial 39 181-187. 

If the original reaction is carried out under more vigorous conditions with malonic acid 67, the decarboxylation occurs during the reaction to give the unsaturated acid in one step. This is a simple way to make11 substituted cinnamic acids 68. 

As a preparative method the direct decarboxylation of olefinic acids is almost limited to the formation of styrenes and stilbenes from substituted cinnamic acids. Thermal decomposition of cinnamic acid gives styrene (41%). The yield is nearly quantitative if the reaction is carried out in quinoline at 220° in the presence of a copper catalyst. The yields of substituted styrenes where the aryl radical contains halo, methoxyl, aldehyde, cyano, and nitro groups are in the range of 30-76%. cis-Stilbene and cis-p-nitrostilbene are prepared in this way from the corresponding a-phenylcinnamic acids (65%). One aliphatic compound worthy of mention is 2-ethoxypropene, prepared by heating -ethoxycro-tonic acid at 165° (91% yield). The mechanism of acid-catalyzed decarboxylations of this type has been studied. Isomerization of the double bond from the a,/5- to the /5, y-position before decarboxylation very likely occurs in many instances. ... 

When a /3-hydroxy acid or its /-butyl ester is heated in quinoline solution with a trace of copper powder, decarboxylation and dehydration occur and the product is an exocyclic olefin. For decarboxylation of substituted cinnamic acids in quinoline. 

Lindsay RF, Priest FG (1975) Decarboxylation of substituted cinnamic acids by enterobacteria the influence on beer flavour. J Appl Bacteriol 39 181-187 Steinhaus M, Schieberle P (2000) Comparison of the most odor-active compounds in Ifesh and dried hop cones (Humulus lupulus L. variety spalter select) based on GC-olfactometry and odor dilution techniques. J Agric Food Chem 48 1776-1783... 

The reaction mechanism involves superoxide anion radicals O, produced from L-cysteine Fe(ll) or L-cysteine Co(ll) complexes, which has an important role to attack on the carbonyl carbon and formed corresponding peroxoacid anions or peroxoacid intermediates which give oxidative, non-oxidative decarboxylated substituted cinnamic acid as well as some cyclized boizofuran. But for ferulic acid, no cyclized product was formed due to positive inductive effect of methoxy group in the benzene ring. 

Decarboxylation for Generation of Substituted Vinylphenols (Canolol) from Substituted Cinnamic Acid... 

In the past few years, microwave-assisted chemical synthesis has been used extensively as an environmental-friendly, rapid and high-yielding technique. Nomura et al. (2005) reported a base-catalysed decarboxylation and amide-forming reaction of substituted cinnamic acids via microwave heating. 

Decarboxylation reaction of aromatic acids (especially substituted cinnamic acid) occurred in the presence of a base and microwave heating by following mechanism (Nomura et al., 2005). Aliphatic amines are used as base for these reaction purposes. Para hydroxyl group produced good yield as compared to the acid group. The progress of the reaction also depends upon the value of the base in the reaction mixture (Schemes 3.20 and 3.21). 

An alternative method for the classical Knoevenagel-type preparation of cinnamic acids has been reported this came to light during a study of the bromine-induced decarboxylation of substituted cinnamic acids. Cinnamic acid derivatives can also be prepared by the palladium-catalysed coupling of methyl acrylate with electron-rich aryl iodidessimilarly 5-arylpenta-2,4-dienoic acids (29) can be synthesized from penta-2,4-dienoic acid and bromo-aryls. A Stobbe-type condensation between aromatic aldehydes and methyl propylidenemalonate leads to the , -unsaturated acids (30), probably via a 5-lactone intermediate. ... 

Baker s yeast-mediated decarboxylation of substituted cinnamic acids. 

Reactions. Heating an aqueous solution of malonic acid above 70°C results in its decomposition to acetic acid and carbon dioxide. Malonic acid is a useful tool for synthesizing a-unsaturated carboxyUc acids because of its abiUty to undergo decarboxylation and condensation with aldehydes or ketones at the methylene group. Cinnamic acids are formed from the reaction of malonic acid and benzaldehyde derivatives (1). If aUphatic aldehydes are used acryhc acids result (2). Similarly this facile decarboxylation combined with the condensation with an activated double bond yields a-substituted acetic acid derivatives. For example, 4-thiazohdine acetic acids (2) are readily prepared from 2,5-dihydro-l,3-thiazoles (3). A further feature of malonic acid is that it does not form an anhydride when heated with phosphorous pentoxide [1314-56-3] but rather carbon suboxide [504-64-3] [0=C=C=0], a toxic gas that reacts with water to reform malonic acid. 

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