7,6-unsaturated acids and esters

Hydrogenation of various unsaturated acids and esters catalysed by 1% Pd/Si02 and 10 bar pressure and 293 K... 

Enantioselective Hydrogenation of Unsaturated Acid and Ester Derivatives... 

Enantioselective Hydrogenation of Unsaturated Acids and Esters 26.3.5.1 a,/ -Unsaturated Carboxylic Acids... 

Allyl chlorides and bromides can be carbonylated to afford the respective unsaturated acids and esters with a variety of catalysts under relatively mild conditions such as 30-50 °C and 1 bar CO (Scheme 5.2). Most prominent are the palladium-containing catalysts and both [PdCl2(TPPMS)2] or [PdCl2(TPPTS)2] and [PdCl2(PPh3)2] were used, dissolved in the aqueous and in the organic phases, respectively [14-16]. 

Catalysts suitable specifically for reduction of carbon-oxygen bonds are based on oxides of copper, zinc and chromium Adkins catalysts). The so-called copper chromite (which is not necessarily a stoichiometric compound) is prepared by thermal decomposition of ammonium chromate and copper nitrate [50]. Its activity and stability is improved if barium nitrate is added before the thermal decomposition [57]. Similarly prepared zinc chromite is suitable for reductions of unsaturated acids and esters to unsaturated alcohols [52]. These catalysts are used specifically for reduction of carbonyl- and carboxyl-containing compounds to alcohols. Aldehydes and ketones are reduced at 150-200° and 100-150 atm, whereas esters and acids require temperatures up to 300° and pressures up to 350 atm. Because such conditions require special equipment and because all reductions achievable with copper chromite catalysts can be accomplished by hydrides and complex hydrides the use of Adkins catalyst in the laboratory is very limited. 

Use of BF3 etherate as catalyst was suggested by the report of Yamamoto and Maruyama4 that -C,H(iCu complexed with BF3 undergoes conjugate addition to a,/ -unsaturated acids and esters, a reaction that has not been observed with R CuLi, even in the presence of BFj etherate. 

The syntheses of carboxylic acids and esters are widely studied processes. Since the first examples of carboxylation in the presence of metal carbonyls were reported by Reppe, these reactions are sometimes referred to as the Reppe reactions. In his pioneering work125-127 stoichiometric or catalytic amounts of [Ni(CO)4] and ethylene or acetylene were reacted in the presence of water or alcohols to form saturated and unsaturated acids and esters. Commercial processes are practiced in the manufacture of propionic acid, acrylic acid and acrylates (see Section 7.2.4). 

This reaction type leading to oc,/ -unsaturated acids and esters is exemplified in the Perkin reaction (Section 6.12.3, p. 1036) and the Knoevenagel reaction (Section 5.11.6, p. 681). The Doebner reaction, which is illustrated in this section, is the condensation of an aldehyde with malonic acid in pyridine solution, often in the presence of a trace of piperidine. The reaction mechanism involves the addition of a malonate anion to the aldehydic carbonyl carbon atom followed by the elimination of water accompanied by decarboxylation. 

While the ethenolysis of fatty acids and esters yields a-olefins and oo-unsaturated acids and esters, the use of higher olefins or functionalized olefins as CM partners gives access to a wide spectrum of platform chemicals. The wide availability of ethylene makes ethenolysis particularly attractive however, the associated problems regarding loss of catalyst activity already explained have motivated the search for alternative low molecular weight olefins. In this way, 2-butene (butenolysis) has been used to avoid the mentioned problems. Patel et al. reported the butenolysis of different natural oils in the presence of C5 [63], TONs between... 

The Addition of the NH-Gtroup ofPyrazoles to Activated Double Bonds Pyrazoles undergo Michael addition to a,j3-unsaturated acids and esters,618,736,737,737 acrylonitrile,104,483,738 maleic anhydride, acetylene dicarboxylic ester,282,737 a,j8-unsaturated ketones,736 and quinones.104 Alkaline catalysts667 are not essential in this reaction,104 at least for addition to unsaturated nitriles, maleic anhydride, and quinones. The reaction is reversible, and V-pyrazolyl propionic... 

Conjugate additions of dialkylcuprates to (3-substituted-a,P-unsaturated acids and esters give low yields. Addition of boron trifluoride etherate, BFj-OEtj, to certain dialkylcuprates and higher-order cuprates enhances their reactivity in Michael additions to conjugated acids and esters. 

Principle mechanisms of pyrone formation are summarized in Scheme 2. The probable pathway via Structures 10-11-12 is based on related stoichiometric reactions with model complexes [19] and X-ray structural investigations on precatalysts, and is consistent with the experimental details. In 11, the sp center next to nickel is suitable for the insertion of further alkynes, yielding the intermediate 12. Reductive elimination of the product 9 and addition of a further alkyne molecule closes the cycle. Analogous complexes to the intermediate 11 were shown to be versatile stoichiometric reagents for transformations to unsaturated acids and esters, by the groups of Hoberg, Dinjus, and Walther [20]. 

Fig. 16. Mechanism and hydrogen isotope exchange in the Ru-BINAP-catalyzed hydrogenation of unsaturated acids and esters, reflecting the author s views...

Unsaturated acids and esters including fatty acids derivatives are also selectively hydrogenated over homogeneous catalysts , e.g., Ir(CO)Cl(PPh3)2 catalyzes the hydrogenation of styrene, ethylacrylate at 10 Pa and 80-120°C . ... 

Two ruthenium complexes, binap 3.43-Ru(OCOR)2(R = Me,CF3) [892] and binap 3.43-RuX2 (X = Cl, Br, I) [893, 894], are quite useful. The acetate and trifluoroacetate complexes of 3.43 induce selective asymmetric hydrogenations of classes of prochiral olefins that are poorly selective with rhodium complexes. These classes include a,(3- or fcy-unsaturated acids and esters, ally alcohols, j3-acylaminoacrylates and enamide precursors of isoquinoline alkaloids [752, 853, 859, 881, 883, 895]. 

The fluid dimer polyamides and fatty amido amines also react with phenolic resins (23). These reactions are significantly different from those of epoxy resins. With the heat-reactive phenolic resins, the aminopolyamide portions react with methylol groups. A carbon-nitrogen bond or cross-link is formed and a volatile byproduct, water, is produced. This reaction requires external heat to remove water. At temperatures near 150 °C the reaction proceeds smoothly. Since curing at elevated temperatures is required, the pot life or shelf life at room temperature is relatively long. The liquid dimer polyamide and fatty amido amines also react with alpha, beta unsaturated acids and esters (29) and with polyesters (30). The unsaturated esters reduce viscosity, lengthen useful pot life, and reduce heat of reaction. Thus, they are useful diluents when low viscosity is desired. 

Several analytical and separation techniques are based on the reversible formation of complexes between alkenes and Ag+ ions. Analytical methods for terpenes, unsaturated acids and esters, and other unsaturated nonpolar compounds are based on the use of Ag" -impregnated materials for thin-layer (TLC) and high-pressure (HPLC) as well as gas-liquid (GLC) chromatography. GLC measurements done some years ago suggest that the affinity decreases with additional substituents, but increases with strain. ... 

Although the carboxyl group was unaffected in the hydrogenations of unsaturated acids and esters described above, Sauer and Adkins192a succeeded in... 

In the reaction of <%,/ -unsaturated carboxylic acids and esters with HBr the addition of radical-formers is without effect on the entry of bromine at the / -position, but radical addition to give co-bromo carboxylic acids and esters is possible with co-unsaturated acids and esters that have CH2 groups between the C=C and the COOH groups. 

Claisen methodology for the elaboration of ,6-unsaturated acids and esters continues to be developed. The readily available dibromo-ether (281) is useful in the preparation of vinyl ether functions required for such rearrangements the e-bromine is displaced by an alkoxide derived from an allylic alcohol to give a... 

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