Thiocarboxylic acids derivatives

Tominaga et al.1B0 studied the cycloaddition of DMAD to 3-indoledi-thiocarboxylic acid derivatives (278). A 2-substituent was essential for success, and 278 (R1 = R2 = R3 = Me) gave a 90% yield of 279. Similarly, morpholino- and piperidinothioamides 282 formed cycloadducts 283. Treatment of 279 with methanolic hydrochloric acid gave 281 via the ring-cleaved intermediate 280. 

S,3R). Secondly, the t/treo-3-methyl-D-cysteine (25,35) was prepared using the previously described addition of thiocarboxylic acid to threonine-derived aziridines. 62 ... 

TABLE XXXIV. 3-Pyrazolin-o-oneB. Carboxylic Acids and Thiocarboxylic Acids and Derivatives... 

Thiocarboxylic acid arsenic derivatives 107 (E=S x=l-3) have been synthesized by the following four methods (1) R PhAsO+RCOSH [316] (2) R2PhAsS+ RCOBr [317] (3) Ph3 AsClx+M(ArCOS) (M=K, (CH2)4NH2) [305] (4) AS2O3+ RCOSH [to (RCOS)3As] [292]. Among these, the methods (3) and (4) are preferable in terms of yield and simplicity of procedure. A series of selenium isologues... 

Recently, 4-acylthio-5-alkoxypyrazoles have been prepared by the reaction of conjugated azoalkenes with thiocarboxylic acids [95UP2]. The preliminary hydrazone intermediates which arise from the normal 1,4-addition of thioacids to the azo-ene system of conjugated azoalkenes in the presence of trifluoroacetic acid, have provided the above-mentioned derivatives. The reaction pathway proceeds through steps already described in the general presentation of this section. They lead to closure of the heteroring with elimination of a water molecule to give the pyrazole heterocycles (Scheme 11). 

Aryl thiocarboxylic acid chlorides. These compounds can be obtained from reaction of aryl carbodithioic acids with phosgene at 0-35° followed by thermolysis of the S-chlorocarbonyl derivatives below 1 torr. The products are stable for several months in the dark at 0". ... 

Diethylaluminium cyanide is a valuable reagent for the conjugate addition of HCN to o , 3-unsaturated carboxylic acid derivatives [120]. Steroidal conjugate esters are somewhat resistant to HCN addition even with this powerful reagent and optimum yields of only 36-50% were obtained. With aj3-unsaturated acid chlorides and acid cyanides, however, the reaction proceeds smoothly in toluene at room temperature and, after hydrolysis the 0-cyanoacid was obtained in 71—73% yield. Conjugated steroidal thiocarboxylic S-esters react under similar conditions to give the product in yields of 85-87%. 

A review on A-functional derivatives of thiocarboxylic acids, covering the synthesis of thioamides, thioureas, and thiocarbamates, has appeared in Methodicum Chimicum. ... 

Thiocarboxylic acids, sulf(on, in, en)ic acids, and their derivatives are treated analogously if necessary specific positions of esterification must be marked separately by placing an indicative letter locant (in italics) in front of the name of the esterifying group. 

Reaction with Thiocarboxylic Acids, Phosphoric Acids, Sulfonic Acids, and their Derivatives. Thiocarboxylic acids, - dithiocarboxylic acids, and dimethyldithiocarbamic acid zinc salt, as well as various phosphorus oxyacids and phosphorus thioacids, can also be utilized. a,o)-Mercapto alcohols form cyclic thioethers whereas thiols react with both DEAD and TPP-DEAD to form disulfides. 2-Mercaptoazoles also react with alcohols in the presence of DEAD and TPP. Although arenesulfonic acids do not enter into the reaction, a combination of DEAD-TPP with methyl p-toluenesulfonate as a nucleophile carrier gives the corresponding alkyl sulfonates (eq 14). Altema-... 

S-Methyl thiocarboxylates. Ketene S,S-dimethylacetals (1) can be hydrolyzed to S-methyl thiocarboxylates (2) by trifluoroacetic acid in water. Ketene thioacetals derived from 1,3-dithiane are unchanged by this procedure. ... 

The trialkyls R3M (M=A1, Ga, In) undergo insertion reactions with COS to form alkylmetal thiocarboxylates (RCOS)xMR3 x (M=A1, Ga, In x=l-3), which are difficult to separate [327]. Treatment of trimethylaluminum with thioacetic acid, however, leads to a good yield of dimethylaluminum thioacetate 75 as yellow crystals that sublime (Scheme 6) [327]. On the basis of infrared and NMR spectra, the structure of 78 has been deduced to be a dimer [327]. Syntheses of Group 13 metal derivatives of selenocarboxylic acids have not been reported, although the formation of RCOSeAl(CH3)3 has been described as a short-lived intermediate in the reaction of RCOOR with [(CH3)2Al]2Se to form diacyl diselenide [281]. 

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