Addition reactions carboxylate

However, the term saturated is often applied to compounds containing double or triple bonds which do not easily undergo addition reactions. Thus ethanoic acid is termed a saturated carboxylic acid and acetonitrile a saturated nitrile, whereas a Schiff base is considered to be unsaturated. 

The organotin maleate and maleate half-ester derivatives also exhibit this bleaching effect reportedly by a Diels-Alder addition reaction (18). The reaction is specific to the organotin maleates other organotin carboxylates containing normal dieneopltiles fail to produce similar results (19). 

Because the integrity of the dihydrothiazine ring and its C-4 carboxyl substituent is crucial to useful antimicrobial activity, reactions involving this part of the cephalosporin molecule are usually undesirable. The possibilities for sulfur oxidation or alkylation, substitution at C-2 which is adjacent to both sulfur and a double bond, double bond isomerization and addition reactions, and the influence of a free carboxylic acid must all be considered in designing reactions to selectively modify other cephalosporin functionalities. 

H-Chromene, 2-ethyl-3-phenyl-synthesis, 3, 764 4H-Chromene, 2-phenyl-synthesis, 3, 763 4H-Chromene, 2,4,4-trimethyl-addition reactions, 3, 669 2 H-Chromene-3-carboxamide reduction, 3, 675 2H-Chromene-3-carboxylic acid methyl ester alcoholysis, 3, 668... 

Michael addition reactions, 4, 302 reactions with ally halides, 4, 301 Pyrrole-2-carboxylic acid, 1-methyl-conformation, 4, 194 esters... 

The second fundamental reaction of carbonyl compounds, nucleophilic acyl substitution, is related to the nucleophilic addition reaction just discussed but occurs only with carboxylic acid derivatives rather than with aldehydes and ketones. When the carbonyl group of a carboxylic acid derivative reacts with a nucleophile, addition occurs in the usual way, but the initially formed tetra-... 

As a general rule, nucleophilic addition reactions are characteristic only of aldehydes and ketones, not of carboxylic acid derivatives. The reason for the difference is structural. As discussed previously in A Preview of Carbonyl Compounds and shown in Figure 19.14, the tetrahedral intermediate produced by addition of a nucleophile to a carboxylic acid derivative can eliminate a leaving group, leading to a net nucleophilic acyl substitution reaction. The tetrahedral intermediate... 

Carbon-centered radicals have been shown to undergo addition reactions with azirine-3-carboxylates. Methyl 2-(2,6-dichlorophenyl)azirine-2-carboxylate thus reacts with alkyl and aryl iodides in the presence of triethylborane to give aziridines in good yields. The radical approaches from the opposite face to the aryl substituent, giving the cis products as single diastereoisomers (Scheme 4.43) [63],... 

Results of nucleophilic addition reactions to various a-oxo 4,5-dihydrooxazoles are summarized in Table 24. In general, the diastereoselectivity of these reactions is low to moderate, although an increased selectivity is found in the presence of triethylamine or N,N,N, N -te-tramethylethylenediamine, which slow down the rate of reaction. Nevertheless, enantiomerical-ly pure 2-hydroxy carboxylic acids can be prepared by this method, since the diastereomeric addition products are separable either by recrystallization or HPLC21. 

Besides simple alkyl-substituted sulfoxides, (a-chloroalkyl)sulfoxides have been used as reagents for diastereoselective addition reactions. Thus, a synthesis of enantiomerically pure 2-hydroxy carboxylates is based on the addition of (-)-l-[(l-chlorobutyl)sulfinyl]-4-methyl-benzene (10) to aldehydes433. The sulfoxide, optically pure with respect to the sulfoxide chirality but a mixture of diastereomers with respect to the a-sulfinyl carbon, can be readily deprotonated at — 55 °C. Subsequent addition to aldehydes afforded a mixture of the diastereomers 11A and 11B. Although the diastereoselectivity of the addition reaction is very low, the diastereomers are easily separated by flash chromatography. Thermal elimination of the sulfinyl group in refluxing xylene cleanly afforded the vinyl chlorides 12 A/12B in high chemical yield as a mixture of E- and Z-isomers. After ozonolysis in ethanol, followed by reductive workup, enantiomerically pure ethyl a-hydroxycarboxylates were obtained. 

The configuration at sulfur is mainly responsible for the sense of asymmetric induction. It is of interest to note that butylcopper and lithium dibutylcuprate undergo addition reactions in the opposite stereochemical sense. The adducts can be converted to chiral /i-disubstituted carboxylic acids1. 

Carboxylic esters are produced by the addition of carboxylic acids to alkenes, a reaction that is usually acid catalyzed (by proton or Lewis acids ) and similar in mechanism to 15-5. Since Markovnikov s rule is followed, hard-to-get esters of... 

Choi and Sakakura et al. reported that iron(III) triflate, in situ formed from FeCls and triflic acid, efficiently catalyzes the intermolecular addition of carboxylic acids to various alkenes to yield carboxylic esters. The reaction is applicable to the synthesis of unstable esters, such as acrylates (Scheme 40) [50]. 

Both CO and C02 are reduced by eh. The immediate product of the first reaction is CO-, which reacts with water, giving OH and the formyl radical the latter has been identified by pulse radiolysis. The product of carbon dioxide reduction, C02-, is stable in the condensed phase with an absorption at 260 nm. It reacts with various organic radicals in addition reactions, giving carboxylates with rates that are competitive with ion-ion or radical-radical combination rates. 

The most characteristic and useful reaction is the dimerization with incorporation of certain nucleophiles. It is well-known that simple olefins coordinated by Pd2+ compounds undergo nucleophilic substitutions [Eq. (9)] or addition reactions [Eq. (10)] (16, 17). Water, alcohols, and carboxylic acids are typical nucleophiles which attack olefins to form aldehydes, ketones, vinyl ethers, and vinyl esters. 

The literature presents a large number of examples concerning the use of known oxazolidinones as chiral auxiliaries in many kinds of reactions. Rare is the use of A-amino derivatives of oxazolidinones, which were used to synthesise new A-acylhydrazones 207. Radical addition reactions occurred with high diastereoselectivity <00JA8329>. The use of glycolate oxazolidinones 210 proved to be efficient for the enantioselective preparation of a-alkoxy carboxylic acid derivatives . Photochemical reaction of vinyl... 

In recent years, the use of a-substituted phosphoryl compounds has mushroomed as they have become recognized as useful analogues of a-substituted carboxyl compounds (including the a-amino acids), as well as materials with their own applications. We will begin here by reviewing the well-established approaches toward such materials, specifically the Abramov and Pudovik reactions, including the associated conjugate addition reactions, and then consider the newer approaches toward such compounds. 

Addition reactions, 20 243. See also Electrophilic addition reactions aldehydes, 2 63-64 allyl alcohol, 2 234-239 butadiene, 4 368—370 carboxylic acids, 5 44-45 ethylene, 10 597—598 quinoline, 21 184 quinone, 21 246-261 toluene, 25 165... 

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