Saponification followed by acidification

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

Recall from Section 14.3C that the hydrolysis of an ester in aqueous sodium hydroxide (saponification), followed by acidification of the reaction mixture with HCl or other mineral acid, converts an ester to a carboxylic acid and an alcohol. Recall also from Section 13.8 that )3-ketoacids and )3-dicarboxylic acids readily undergo decarboxylation (lose CO2) when heated. The following equations illustrate the results of a Claisen condensation, followed by saponification, acidification, and decarboxylation ... 

The product of Claisen and Dieckmann condensation reactions can be treated with aqueous base (saponification) followed by acidification to convert the j8-ketoester group into a )8-ketoacid that is then heated to cause decarboxylation to give a ketone product and CO2. 

The Reeopet process for the ehemical recycling of PETP is described. The three-stage process, which allows the recovery of highly pure terephthalic acid, commences with continuous saponification followed by chromatographic purification with activated carbon and a final acidification step. 

Compounds in this dibenzocycloheptene series also manifest antidepressant activity when the trigonal one-carbon bridge is replaced by tetrahedral carbon. Thus, the reaction of hydrocarbon (24-7) with a metal amide in liquid ammonia leads to the corresponding carbanion (29-1). Treatment of that with the ethyl carbamate from A -methyl-3-chloropropylamine (29-2) leads to the alkylation product. The carbamate protecting group is then removed by sequential saponification with a base followed by acidification. This yields the antidepressant agent protriptyline (29-3) [30]. 

The saponification/acidification route is used for the manufacture of fatty acids that are sensitive to excessive heat. The splitting of castor oil with NaOH at 100-220°C followed by acidification has been used to produce castor fatty acids.12... 

The product formed in this hetero-Diels-Alder reaction of ethyl glyoxylate with a cyclic diene catalyzed by (.S, iS )-t-Bu-box in combination with a copper(II) salt was used in the simple synthetic approach to enantiopure synthons for a class of natural products. Saponification of the bicyclic adduct followed by acidification with aqueous HCl provides the enantiopure (>99% ee) rearrangement product (eq 8). ... 

Acetyl Content. The acetyl content of wood is determined by saponification of the sample in 1 N NaOH, followed by acidification, quantitative distillation of the acetic acid, and titration of the distillate with standard NaOH (47). A modification here (Forest Products Laboratory) enables acetic acid determination by using GC with propanoic acid as an internal standard. This modification eliminates the tedious, time-consuming distillation step. 

Saponification of the diester followed by acidification gives the corresponding malonic acid which is then decarboxylated. The decarboxylation step may require high temperatures (150-250 °C). Treatment of malonic acids with a catalytic amount of Cu(I) oxide in acetonitrile is reported to accelerate the decarboxylation step and affords the monoacid products in good yield under milder conditions. ... 

Each set of compounds undergoes (1,2) Claisen condensation, (3) saponification followed by (4) acidification, and (5) thermal... 

Each compound or set of compounds undergoes a Claisen or Dieckmann condensation followed by acidification, saponification, acidification, and thermal decarboxylation. 

The rDA reaction of 75 giving TBP tetracarboxylic esters was conducted under the similar conditions as the parent TBP precursors, while the rDA reaction required much higher temperatures of >230 and >255 °C in the cases affording TNPs and TAPs, respectively (Table 15.4). Free-base precursor 75b-H2 with eight carboxylic acid was obtained by saponification with NaOH in DMF at room temperature for 12h followed by acidification with 1-M HCl [75]. Ester 75a-Zn and acid 75b-H2 showed similar behaviors in solid. When 75a-Zn was treated with NaOH at 110°C in DMF for 16 h, however, the rDA reaction as well as the saponification took place to afford the corresponding sodium salt of TBP octa-carboxylic acid. This easy rDA reaction may be ascribed to modulation of HOMO and LUMO energy levels of expanded porphyrins by carboxylate anions. 

Saponification and acidification with concentrated hydrochloric acid, followed by decarboxylation, lead to the N-protected 1-oxoethylene Gly dipeptide. 

The recovery of fatty acids from soapstocks by a continuous process has been described soapstocks obtained from degumming and alkali refining operations are subjected to a saponification step followed by controlled acidification for cost efficiency and pollution control.Ila,b... 

In addition to the classic sequence of saponification-acidification followed by heating, the decarboxylation of (3-keto esters can be effected by more direct methods such as decarbalkoxylation. For example, heating (3-keto esters in the presence of lithium halides in H2O-DMSO25 or in H20-collidine produces ketone products in one-pot transformations, as shown below. 

O-Dechloroacetylation of IV.61 by treatment with thiomea gave IV.62, which was subsequently reprotected as the hydrogenolyzable 4-methoxybenzyl ether with 4-methoxybenzyl trichloroacetimidate and triflic acid under phase transfer catalysis conditions [104]. Saponification of the benzoate and methyl esters with lithium hydroperoxide followed by methanolic sodium hydroxide and acidification then gave the acid IV.63. O-Sulfonation of IV.63 was achieved with the sulfur trioxide-tri-methylamine complex to give the disulfate IV.64 as the sodium salt. Finally, hydro-genolysis of IV.64 with Pd/C in aqueous methanol afforded the target disaccharide IV.51. 

Decarboxylation of 10 with HCl led to clean formation of the a-free pyrrole 16. Vilsmeier formylation followed by saponification of the ethyl ester moiety and acidification led to the acid aldehyde 9. Time constraints dnring the early stages of onr work forced ns to make 9 in-honse because vendors quoted rather long lead times for delivery of this material. However, this componnd is now commercially available and can be pnrchased from several vendors. 

The final step in the synthesis of 9 is the saponification of the ester in 16, followed by precipitation by acidification, and filtration (Scheme 4.3). Although HCl was used for this purpose when 9 was made in-house, the vendor utilized acetic acid. The by-product of this transformation is potassium acetate and could be a potential contaminant in 9. Further support for this hypothesis was garnered by analysis of the filtrate obtained after washing the implicated batch of 9 with water and methanol, which revealed the presence of potassium (by qualitative elemental x-ray microanalysis) and acetate (by Fourier transform infrared [FT-IR] spectroscopy). ICP (inductively coupled plasma) tests did not show the presence of any other ionic impurities at significant levels. 

Pectin Most standard procedmres for pectin analysis in vegetables and legumes involve extraction of the pectin as pectic acid followed by precipitation. Aqueous extraction of the pectin is followed by saponification with cold alkali, acidification, and the quantification of the precipitate. The pectic acid can be precipitated as calcium pectate or, as in the AOAC procedure, using ethanol. 

Claisen condensation between diethyl phthalate and ethyl acetate, followed by saponification, acidification, and decarboxylation, forms a diketone, C9H6O2. Propose structural formulas for compounds A, B, and the diketone (See Example 15.9)... 

Quantitative recoveries of endogenously labeled bile acids in homogenized human feces can be obtained by continuous extraction for 48 hr with hot chloroform-methanol, 1 1 (18). After saponification, acidification, and continuous diethyl ether extraction, the bile acids are purified on silicic acid (Section IIIB 4 and Ref. 18) to give one mono- and disubstituted, and one trisubstituted bile acid fraction. For identification purposes further subfractionation can be made [see Table V (69, 77, 126, 127)]. The subfrac-ticns are subsequently subjected to small-scale preparative thin-layer chromatography of methylated bile acids. The fractions eluted from the thin-layer plates are next subjected to peak-shift analyses followed by final identification by gas chromatography-mass spectrometry. When the fecal bile acid composition has been elucidated in this way the mono-, di- and trisubstituted bile acids from the first silicic acid column may be quantitated after methyla-tion and by analysis on QF-1. These results are then compared with those obtained after trifluoroacetylation of the bile acid methyl esters. (18). 

The general case of a Claisen condensation followed by saponification, acidification, and decarboxylation gives a symmetrical ketone product. 

Acidify the aqueous phase D, remaining after the removal of alcohols (see above) with concentrated hydrochloric acid and extract the liberated thioacid with diethyl ether. Liquid - liquid extraction for 4 hours produces more material, but shaking with 50 cm of diethyl ether for about 1 min normally gives enough extract for identification. Because of partial decomposition of the thioacid during the foregoing saponification, sulphides are produced and the above acidification and extraction should be carried out in a fiime cupboard. The ether extract can be evaporated to dryness on a water bath md examined by infrared or nuclear magnetic resonance spectroscopy or by both techniques, but, because of partial decomposition a better way of identification at least for the thioacid, is as follows ... 

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