Addition of Carboxylic Acids to Unsaturated Compounds

Nafion resins have been used not only for the opening of epoxides but also for their isomerization to aldehydes or ketones [137]. Various other rearrangements and isomerizations are catalyzed by this solid acid, in some cases with selectivities higher than those obtained with other solid catalysts [138-140]. Other reactions that have been studied include the Peterson methylenation of carbonyl compounds [141], hetero-Michael additions to unsaturated ketones [142], the Koch-type carbon-ylation of alcohols to form carboxylic acids [143], dimerization of a-methylstyrene [144], addition of carboxylic acids to olefins [145] and Diels-Alder reactions [146]. Notably, in most cases, reutilization of the catalyst is considered but only after an appropriate washing protocol to regenerate its acidity/activity. 

A variation on a literature procedure draws attention to a useful method for the synthesis of tetrolic acid. Copper dienolates derived from a,jS-unsatur-ated acids undergo y-alkylation with a regioselectivity of 91%. A full paper has appeared from Mulzer and his co workers on the control of 1,2-/1,4-regioselectivity in the additions of carboxylic acid dianions to a,jS-unsaturated carbonyl compounds. The addition of phenyl acetate dianion (23) (Scheme 20) to a,/3-un aturated aldehydes leads to the f/ireo-unsaturated /S-hydroxy-carboxylic acid (24) the threo and erythro ratio of 5 examples was >9 1. 

Abstract The formation of carbon-oxygen bond upon addition of O-nucleophUes to unsaturated molecules is very attractive as it represents an atom economical strategy to prepare a variety of saturated compounds from olefins and vinylic derivatives from aUcynes. Group 8 metals, especially ruthenium have provided an important contribution in this field. We report here on iron- and ruthenium-catalyzed addition of nucleophiles to unsaturated systems. As additions to alkenes are still scarce with these metals and the use of iron catalysts is limited, the main part of the chapter is dedicated to addition of carbamates, carboxylic acids, alcohols and water to triple bonds with ruthenium catalysts. 

The Michael-type addition, a nucleophilic addition of an anion to the carbon-carbon double bond of an a,(3-unsaturated ketone, aldehyde, nitrile, nitro, sulphonyl, or carboxylic acid derivative, provides a powerful tool for carbon-carbon bond formation. The reaction is most successful with relatively nonbasic ( soft ) nucleophiles such as thiols, cyanide, primary and secondary amines, and P-dicarbonyl compounds. There is often a competition between direct attack on the carbonyl carbon (1,2-addition) and conjugate addition (1,4-addition) when the substrate is an a,(3-unsaturated carbonyl compound. 

Won et al. [19], have reported synthesis of polyesters with valine, leucine, isoleucine, methionine, and phenylalanine (Table 12.1). This three-step process involves synthesis of a diester and a dinitro compound that are copolymerized [19], An amino acid is first coupled with a diol (with 3, 4, or 6 methylene groups) in the presence of tosyl to yield a diester with acid salts of diamine at the terminal ends. The second monomer, di-p-nitrophenyl ester of carboxylic acids, is synthesized by a condensation reaction of adipoyl or se-bacoyl chloride with p-nitro phenol. The final polymerization step involves an arduous condensation reaction in the presence of a strong proton abstractor between acid salt of bis(amino acid-alkyne diester) and di-p-nitrophenyl ester of dicarboxylic acids. Following along the same lines, Chu and Guo [22] have copolymerized a mixture of nitro phenyl ester of succinate, adipate, or sebacate and nitrophenyl fumarate with toluenesulfonic acid salt of phenylalanine butane-1,4-diester. The addition of fumarate derivative to the monomer mixture provides an unsaturated double bond in the polymer backbone that can be functionalized for specific biomedical... 

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