Saponification, ester

In base the tetrahedral intermediate is formed m a manner analogous to that pro posed for ester saponification Steps 1 and 2 m Figure 20 8 show the formation of the tetrahedral intermediate m the basic hydrolysis of amides In step 3 the basic ammo group of the tetrahedral intermediate abstracts a proton from water and m step 4 the derived ammonium ion dissociates Conversion of the carboxylic acid to its corresponding carboxylate anion m step 5 completes the process and renders the overall reaction irreversible... 

The major application of p keto esters to organic synthesis employs a similar pat tern of ester saponification and decarboxylation as its final sfage as described m fhe fol lowing secfion... 

Claisen ester condensation, 6, 279 Thiazolecarboxylic acid chlorides reactions, 6, 279-280 Thiazolecarboxylic acid hydrazides synthesis, 6, 280 Thiazolecarboxylic acids acidity, 6, 279 decarboxylation, 6, 279 reactions, S, 92 6, 274 Thiazole-2-carboxylic acids decarboxylation, S, 92 Thiazole-4-carboxylic acids stability, S, 92 Thiazole-5-carboxylic acids decarboxylation, S, 92 Thiazole-4,5-dicarboxylic acid, 2-amino-diethyl ester reduction, 6, 279 Thiazole-4,5-dicarboxylic acids diethyl ester saponification, 6, 279 Thiazolediones diazo coupling, 5, 59 Thiazoles, 6, 235-331 ab initio calculations, 6, 236 acidity, S, 49 acylation, 6, 256 alkylation, S, 58, 73 6, 253, 256 analytical uses, 6, 328 antifogging agents... 

Ester-lack, m. ester varnish, -saure, /. ester acid, -verseifung, /, ester saponification, -lahl,/, ester number. 

In an effort to make productive use of the undesired C-13 epimer, 100-/ , a process was developed to convert it into the desired isomer 100. To this end, reaction of the lactone enolate derived from 100-) with phenylselenenyl bromide produces an a-selenated lactone which can subsequently be converted to a,) -unsaturated lactone 148 through oxidative syn elimination (91 % overall yield). Interestingly, when 148 is treated sequentially with lithium bis(trimethylsilyl)amide and methanol, the double bond of the unsaturated lactone is shifted, the lactone ring is cleaved, and ) ,y-unsaturated methyl ester alcohol 149 is formed in 94% yield. In light of the constitution of compound 149, we were hopeful that a hydroxyl-directed hydrogenation52 of the trisubstituted double bond might proceed diastereoselectively in the desired direction In the event, however, hydrogenation of 149 in the presence of [Ir(COD)(py)P(Cy)3](PF6)53 produces an equimolar mixture of C-13 epimers in 80 % yield. Sequential methyl ester saponification and lactonization reactions then furnish a separable 1 1 mixture of lactones 100 and 100-) (72% overall yield from 149). 

The ionization of benzoic acids in water at 25° was used by Hammett as the standard reaction for the original qp treatment (2a). This reaction and several analogous reactions, e.g., ionization and ester saponification rates of benzoic acids, cinnamic acids, and phenylpropiolic acids, gives ap correlations of relatively high precision. Taft and Lewis classified such reactions in an A category (2f). Reexamination of these A reactions, as well as additional analogous data which have become available subsequently, provided eight reaction series of data of apparently comparable reliability. In the para position, each of these sets of data meets the necessary condition of a minimal basis set... 

C. Bao, Y. Zhou and Y. Wu, Kinetics of alcohol ester saponification in impinging stream reactor, a paper to be published. 

Menger and Portnoy (1967) developed a quantitative treatment which adequately described inhibition of ester saponification by anionic micelles. Micelles bound hydrophobic esters, and anionic micelles excluded hydroxide ion, and so inhibited the reaction, whereas cationic micelles speeded saponification by attracting hydroxide ion (Menger, 1979b). 

The classes of compounds which are conveniently considered together as derivatives of carboxylic acids include the carboxylic acid anhydrides, acyl chlorides, esters, and amides. In the case of simple aliphatic and aromatic acids, synthetic transformations among these derivatives are usually a straightforward matter involving such fundamental reactions as ester saponification, formation of acyl chlorides, and the reactions of amines with acid anhydrides or acyl chlorides ... 

Some of these tests cover very broadly the general chemical makeup of waxes. Constants such as acid, ester, saponification and iodine numbers can be used to identify, differentiate or classify waxes chemically (Ref 59). Specific tests are used to determine the values of these numbers for waxes. The saponification number generally indicates the total quantity of both esters and free acids in a wax. The acid value is an indication of the quantity of free fatty acids. The ester value is the relative quantity of esters... 

The formal total synthesis of the novel /3-lactam antibiotic thienamycin has been accomplished from an isoxazoline derivative generated by [3 + 2] dipolar cycloaddition <79H(l2)l 183). Reaction of the nitrile oxide derived from 3-nitropropanal dimethyl acetal with methyl crotonate gave the isoxazoline (477) regio- and stereo-selectively. The isoxazoline was converted to amino ester (478) by hydrogenation and then to /3-lactam (479) by ester saponification and ring closure with DCC. Treatment of (479) with p-nitrobenzyl chloroformate and reaction of the derived acetal (480) with excess N-p-nitrobenzyloxycar-bonylcysteamine gave thioacetal (481), a compound which has previously been converted into ( )-(8S )-thienamycin (Scheme 106). 

The four-membered azetidine ring remains unaffected by sodium in liquid ammonia, 94 methanolic ammonia, 95 5M barium hydroxide at 100 °C for 24 hours, 87 sodium hydroxide under ester saponification conditions, 87 HC1 at room temperature, 96,97 catalytic hydrogenation under normal conditions, 87,95 and ozonolysisJ87 Correspondingly, as observed for proline, the azetidine-2-carboxylic acid (2) raises no particular difficulties in the synthesis of related peptides. 

Most of these procedures are incompatible with common linkers, and are therefore unsuitable for the transformation of support-bound substrates into carboxylic acids. A more versatile approach for this purpose is the saponification of carboxylic esters. Saponifications with KOH or NaOH usually proceed smoothly on hydrophilic supports, such as Tentagel [19] or polyacrylamides, but not on cross-linked polystyrene. Esters linked to hydrophobic supports are more conveniently saponified with LiOH [45] or KOSiMe3 in THF or dioxane (Table 13.11). Alternatively, palladium(O)-mediated saponification of allyl esters [94] can be used to prepare acids on cross-linked polystyrene (Entries 9 and 10, Table 13.11). Fmoc-protected amines are not deprotected under these conditions [160],... 

Step 6 is ester saponification. It yields a 16-carbon chain having a carboxylic acid function at one end and an alcohol at the other. 

In the second step of the synthesis, compound A is subjected to ester saponification. Following acidification, the corresponding diacid (compound B) is isolated. 

Step 3 Ester saponification and acidification, which also cleaves the acid-sensitive THP group. 

Step 2 Ester saponification followed by acidification (-CC Na to -CO2H) and decarboxylation of the (3-keto acids. 

At this point, this mechanism deviates slightly from the ester saponification mechanism. Because amide ion (NHj-) is a poor leaving group, the nitrogen is first protonated by the solvent to convert it to a better leaving group. 

Esters and amides, on the other hand, require the presence of an acid or base catalysis to react with water. These reactions are not instantaneous but require rather strongly acidic or basic conditions and heat to proceed at a reasonable rate. For example, a typical ester saponification is usually conducted with 10% NaOH in water, and the solution is refluxed until the ester layer disappears. (Most esters are not soluble in water.) This may require from 15 minutes up to several hours of reflux. Similarly, a typical amide hydrolysis is often conducted by refluxing the amide in concentrated hydrochloric acid for a period ranging from 15 minutes up to several hours. Esters and amides are relatively stable to the near-neutral conditions found in living organisms, which is one reason why they are important functional groups in biochemistry. 

The mechanism for this reaction, shown in Figure 20.4, has similarities to those of both an aldol condensation (see Figure 20.3) and an ester saponification (see Figure 19.4). As was the case with the aldol condensation, the presence of both the enolate ion and the... 

Substituted sulfonamide 386 (prepared from 2-methoxycarbonylbenzenesulfonyl chloride and the sodium salt of pyrrole followed by ester saponification) under relatively vigorous conditions was smoothly converted into the 5A°-pyrrolo[l,2- ][l,2]benzothiazine-5,5,10-trione 387, in 78% isolated yield (Equation 90) <2004TL9573>. 

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