Dicarboxylic acids, reaction with thiol

Reactions of 4,7-phenanthroline-5,6-dione have been the subject of considerable study. It is reduced to 5,6-dihydroxy-4,7-phenanthroline by Raney nickel hydrogenation226,249 or by aromatic thiols in benzene,262 and oxidized by permanganate to 3,3 -bipyridyl-2,2 -dicarboxylic acid.263 It forms bishemiketals with alcohols226 and diepoxides with diazomethane.226 The diepoxides by reaction with hydrochloric acid form diols of type 57, R = Cl, which on oxidation with lead tetraacetate give 3,3 -bipyridyl diketones of type 58, R = Cl. Methyl ketones of type 58, R = H, are also obtained by lead(IV) acetate oxidation of the diol 57, R = H, obtained by lithium aluminum hydride reduction of 57, R = Cl. With phenyldiazomethane and diphenyldiazomethane the dione forms 1,3-dioxole derivatives,264,265 which readily hydrolyze back to the dione with concomitant formation of benzaldehyde and benzophenone, respectively. 

A carboxyl group can be introduced in almost any compound by various methods. In cases where a free thiol is present, the carboxyl group can be introduced easily by reaction with bromo- or iodoacetic acid. This reaction is very mild and is usually performed at pH around 8-9. When the hapten contains a hydroxyl group, carboxylic acid may be introduced by one of the following methods (a) carboxymethylation of the hydroxyl group with bromo- or iodoacetic acid (b) esterification with dicarboxylic acid anhydrides, such as succinic anhydride, to yield hemi-succinates, which are unstable above pH 9 (c) reaction with phosgene, which results in the formation of chlorocarbonates. ... 

Some of the most familiar reactions falling into the polycondensation class are those leading to polyamides derived from dicarboxylic acids and diamines, polyesters from glycols and dicarboxylic acids, polyurethanes from polyols and polyisocyanates, and polyureas from diamines and diisocyanates. Similar polymer formations utilizing bifunctional acid chlorides with polyols or polyamines also fall into this class. The condensations of aldehydes or ketones with a variety of active hydrogen compounds such as phenols and diamines are in this group. Some of the less familar polycondensation reactions include the formation of polyethers from bifunctional halogen compounds and the sodium salts of bis-phenols, and the addition of bis-thiols to diolefins under certain conditions. 

Thioesters, Selenoesters, and Thioamides.—Commercially available phenyl dichlorophosphate has been reported to be a superior reagent to MV-dimethyl-phosphoramidic dichloride (4, 244) for the preparation of thioesters directly from carboxylic acids and thiols. Carboxylic acid chlorides can be efficiently converted into thioesters by reaction with adducts formed between thiols and l-methylpyridine-3,5-dicarboxylates. Alternatively, copper(i) mercaptides, formed from thiols and CuaO, or thallous thiophenoxide can be used. The latter method can also be used to prepare selenoesters as well as a-phenylthio-and a-phenylseleno-acids and esters from a-halo-acids and a-halo-esters, respectively. 

The details of carbon metabolism in the citric acid cycle are beyond the scope of this article. In brief, pyruvate is first oxidatively decarboxylated to yield CO2, NADH, and an acetyl group attached in an ester linkage to a thiol on a large molecule, known as coenzyme A, or CoA. (See Fig. 2.) Acetyl CoA condenses with a four-carbon dicar-boxy lie acid to form the tricarboxylic acid citrate. Free CoA is also a product (Fig. 6). A total of four oxidation-reduction reactions, two of which are oxidative decarboxylations, take place, which results in the generation of the three remaining NADH molecules and one molecule of FADH2. The citric acid cycle is a true cycle. For each two-carbon acetyl moiety oxidized in the cycle, two CO2 molecules are produced and the four-carbon dicarboxylic acid with which acetyl CoA condenses is regenerated. 

The aldehyde (0.38 mmol, 1.5 equiv), the catalyst (10 mol%), and benzoic acid (10 mol%) were stirred in toluene and cooled to —15 °C. The thiol (1 equiv) was added and the reaction mixture stirred for 30 min. Diazo dicarboxylate derivative (1.3 equiv) was added and the reaction progress monitored by TLC (3-24 h). The crude reaction mixture was diluted with MeOH (2 mL) and cooled to 0 °C, followed by the addition of NaBH4 (2 equiv). After 10 min, 2 M NaOH (2 mL) and THF (2 mL) were added and the crude reaction mixture was stirred for 2 h. After standard aqueous work-up, the product was purified by FC on silica gel. 

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