Thioglycolic acid derivatives

Mercaptides are unchallenged as the ligand of choice for the other entities bonded to the tin, but carboxylates can also be used. Whereas a variety of mercaptans are used, the thioglycolic acid derivatives remain the largest single mercaptan. Dibutyltin bis(isooctyl thioglycolate) [25168-24-5] and butyltin tris(isooctyl thioglycolate) [25852-70A] are two common examples. These materials are produced by the reaction of the appropriate alkyl tin chloride or oxide, and the mercaptan. 

The Fiesselmann thiophene synthesis involves the condensation reaction of thioglycolic acid derivatives with a,P-acetylenic esters, which upon treatment with base results in the formation of 3-hydroxy-2-thiophenecarboxyIic acid derivatives. 

Significantly faster is the solid-state racemization of the thioglycolic acid derivative 95 (Scheme 9). A solid sample lost its specific rotation upon standing from -42.3° to -36.9° in 2 months and to -13.9° after 14 months. It is noted that such racemization was more rapid when the acid was exposed to light [57]. A heterolytic dissociation/recombination mechanism appears suitable. 

An analogous approach was employed in the synthesis of benzo[Z)]thieno[3,2- )]thiophene-2-carboxylic acid (56) and naphtho[2,3-Z)]thieno[3,2-/ ]thiophene-2-car-boxylic acid (59) from substituted benzo[Z)]thiophene-2-carbaldehyde 57 (77MI1) (through thioglycolic acid derivative 58) and naphtha[2,3-Z)]thiophene-2-carbalde-hyde 60, respectively (71G774). 

The kinetics have been studied and show that with thioglycollic acid derivatives between pH 1 5 and 2-5 the RS ion and RSH react, but at pH >2-5 the RS anion is the reactive entity. A reaction mechanism has been derived . 

Since its development in cosmetics in the 1940s, thioglycolic acid has become a widespread thiochemical, used all over the world as the acid or in the form of its salts or esters. Because of the several derivatives of thioglycolic acid used, the market size for this chemical is often expressed in terms of thioglycolic acid equivalents. In 1994 the total world market was estimated at around 15,000 to 20,000 metric tons of thioglycolic acid equivalents. Some mercaptocarboxyhc acid and esters available are compiled in Table 2. 

Manufacturing plants for thioglycolic acid and derivatives are found in Europe, the United States, and Asia. Producers in Europe are B. Bock (Germany), Elf Atochem (Erance), and Merck (Germany) in the United States Elf Atochem, Hampshire, and Witco and in Japan, Daicel. Production capacity is expected to be sufficient to supply world demand for five years. 

Table 3. Specifications for Thioglycolic Acid and Some Derivatives...

Soon after the 1946 report by Woodward on the condensation of thioglycolic acid and a,P-unsaturated esters in the presence of base to produce structures like 2-carbomethoxy-3-ketotetrahydrothiophene 4, Fiesselmann extended this reaction to a,p-acetylenic esters for the direct preparation of 3-hydroxy-2-thiophenecarboxyIic acid derivatives. ... 

The Fiesselmann reaction has been extensively used with p-halovinyl esters, ketones,aldehydes and nitriles as reaction partners for thioglycolic acid and its derivatives. This reaction with P-halovinyl aldehydes has been extensively explored as a result of the availability of P-chloro-a,P-unsaturated aldehydes via the Vilsmeier... 

While the majority of examples of the Fiesselmann reactions found in the literature involve thioglycolic acid or the corresponding thioglycolates, the scope of this reaction has been expanded to a variety of other a-mercaptocarbonyl derivatives. Some examples include a-mercapto aldehydes, ketones,and amides. Notably, when compound 33 is treated with 2-mercaptoacetamide, compound 34 was produced in 48% yield. ... 

The cyclized analog of meralluride is prepared by a similar synthesis. Thus, condensation of camphoric acid (42) (obtained by oxidation of camphor) with ammonia gives the bicyclic succinimide (44). Reaction with allyl isocyanate followed by ring opening and then reaction with mercuric acetate affords the mercury derivative (45) as the acetate rather than the hydroxide as above. Reaction with sodium chloride converts that acetate to the halide (46). Displacement on mercury with the disodium salt of thioglycollic acid affords the diuretic mercaptomerine (47). ... 

Mono- and polyl dric phenols and enols frequently form characteristically colored complexes with Fe + ions [4, 28, 29]. Here monohydric phenols usually produce reddish-violet colors, while pyrocatechol derivatives yield green chelates [4]. Detection of acetone using Legal s test is based on the formation of an iron complex [4]. The same applies to the thioglycolic acid reaction of the German Pharmacopoeia (DAB 9) [4, 30]. 

Reeder and Rieger6 used ESR spectra to identify complex ions and to estimate formation constants for aqueous oxovanadium(iv) complexes with lactic acid, thiolactic acid, glycolic acid, and thioglycolic acid. Through the use of second-harmonic detection, which produces second-derivative spectra, the resolution was good enough that several of the individual species could be separately... 

Similarly l-phenyl-3-methyl-4-formyl-5-chloropyrazole reacts with thioglycollic acid in the presence of alkali to yield a mercaptopyrazole derivative that could be cyclized to thieno[2,3-c]pyrazole in the presence of alkali (69KGS760, 69ZOR1498). Similar to this is the reported formation, via 311, of 312 from 310 and mercaptoacetanilide (73ZOR2416). 

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