Thiocarboxylic acids synthesis

Although acylation reactions rank among the best-known methods for the synthesis of thiocarboxylic 5-esters (1), there exist other important and convenient routes, - e.g. the alkylation of thiocarboxylate anions (equation 1) or radical addition of thiocarboxylic acids to carbon-carbon double bonds (equation 2). These methods are not dealt with here (qf. Volume 4, Chapter 1.5). 

Crystalline adducts from thioamides and aromatic acid chlorides ate well known. A very convenient synthesis of diacyl sulfides and thiocarboxylic acids - proceeds via adducts of thio-DMF with acid chlorides. 

A one-pot four-component solution phase procedure has been developed for the synthesis of 2,4,5-trisubstituted thiazoles 25 <05SL79>. The four components, the 3-substituted 3-bromo-2-isocyanoacrylate 18, the ketone or aldehyde 19, the primary amine 20, and the thiocarboxylic acid 21, can vary broadly, thus producing thiazoles with five potential diversity points. Presumably, condensation of 19 with 20 generates imine 22, which reacts regioselectively with 18 and 21 via the Ugi pathway. The intermediate Ugi product 23 is in... 

A copper-catalyzed synthesis of benzo[f)]thiophenes and benzothiazoles using thiocarboxylic acids as sulfur source and coupling partner in the presence of Cul and 1,10-phenanthroline (1-10 phen) was developed this year (13JOC8898). The reaction proceeds by UUmann-type C—S bond coupling followed by Wittig condensation. 

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

An acyl transfer agent which can be used for the synthesis of acid anhydrides is obtained from the reaction of an acid chloride with 4-benzylpyridine (equation 24). In this way benzoic acid anhydride and cinnamic acid anhydride were obtained in 72% and 57% yields, respectively. As the intermediate, 1-acyl-4-benzylidene-l,4-dihydropyridines, can be isolated, Ais procedure should be well suited for the preparation of mixed anhydrides. Mixed aromatic and aliphatic anhydrides can be prepared with 2-ben-zoylthio-l-methylpyridinium chloride and salts of carboxylic acids. These reactions are carried out in aqueous solution. Iliey make use of the high reactivity of esters of thiocarboxylic esters towards nucleophiles. The mixed anhydrides of benzoic acid with 3-phenylpropanoic acid, phenoxyacetic acid, isobu-tyric acid, p-toluic acid and cinnamic acid were formed in 82, 79,61,91 and 66% yields, respectively. 

---