Thiocarboxylic acid esters

N,N -Thiocarbonyldiimidazole as reactant 24, 362, 431 Thiocarbonyl dichloiide s. Thiophosgene Thiocarboxylic acid esters s. Thiolic acid esters, Thionocarboxylic - -Thiocyanates... 

Thiocarboxylic acid esters from a-chlorimmonium chlorides -e- s. 19, 628 ... 

Prepn. from N,N-disubst. carboxylic acid amides—Thiocarboxylic acid esters Dithiocarboxylic, thiolic, and thionocarboxylic acid esters—Ring closures to heterocyclics s. 19, 628 a-chlorimmonium chlorides cf. M. Grdini6 and V. Hahn, J. Org. Chem. 30, 2381 (1965)... 

Thiocarboxylic acid esters s. Dithiocarboxylic acid esters, Thiolic —, Thionocarboxylic — Thiochromenes... 

Thiocarboxylic acid esters from a-chlorimmonium chlorides... 

S-Alkylation of a thiocarboxylic acid with an a-halogenated carbonyl compound gives a thiol ester in which the two carbons to be connected... 

Other successful sulfuration agents are (di)thiocarboxylic acids or dithiophosphoric acid esters (87JAP62-10081). 

The esters of phenothiazine-lO-thiocarboxylic acid undergo a similar thermal decomposition yielding 10-dialkylaminoalkylpheno-thiazines and COS however, they are more stable than their oxygen analogs, and the reaction therefore needs more severe conditions, so that the yields are lower owing to the formation of resinous by-products. ... 

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). 

Unlike carboxylic esters, open-chained S-alkyl thiocarboxylates cannot be obtained by direct proton-catalyzed esterification. Whereas thiocarboxylic acids react with alcohols to form esters as expected, thiol esters are formed on reaction of carboxylic acids with thiols, but the equilibrium is shifted towards the educts and the reaction is not useful for synthetic purposes. Therefore, activation is necessary and several methods have been developed to meet this requirement. 

The open-chained thioacetamide, on the other hand, yields iminium salts (34) on acylation. Reaction of (34) with alkyl halides and subsequent hydrolysis results in the formation of thiocarboxylic esters (1). This reaction is actually performed in one step under phase transfer catalysis (equation 21). No unpleasant smelling thiols or thiocarboxylic acids are required as educts, the yields are high and a large variety of substituents R and R are possible. ... 

By addition of thiols to isonitriles thioformimidates (274 equation 147) are accessible. 2-Methyl-propaneisonitrile inserts into the thietane system to give triiminothiolanes (275 Scheme 42). A related insertion of isonitriles into a C—S bond was observed in the reaction of alkylmercaptocyanoacetic acid esters, labile thioimidates (276) are the products. - The addition of thiocarboxylic acids to isonitriles, giving mixed anhydrides of thioformimidic acids and carboxylic acids has been studied. ... 

Thiols and sulfides are protonated on sulfur in superacid media and give mono- and dialkylsulfonium ions, respectively49. Thiocarboxylic acids, S-alkyl esters, thio-esters, dithioesters and thiocarbonates in similar media also form stable protonated ions179 such as... 

The l,3,5-thiadiazinedione-3-thiocarboxylic acid 0-ethyl ester (107) on treatment with DBU in chloroform undergoes loss of COS and rearrangement to yield 2,6-diethoxy-1,3,5-thiadiazin-4-one (108) (Equation (5)) <82CB1252>. 

Alkoxythiocarbonyl isothiocyanates (172 X = S) are also useful 47t components and with imines at room temperature furnish 6-alkoxy-2//-l,3,5-thiadiazine-4(3//)-thiones (173) albeit in variable yields <83CB2044>. In a similar manner ethoxythiocarbonyl isocyanate (172 R = Et, X = O) and benzylideneaniline produce 2,3-diphenyl-6-ethoxy-2/f-l,3,5-thiadiazin-4(3//)-one (174) <82CB1252>. In warm toluene the ethoxythiocarbonyl isocyanate dimerizes to give the 0-ethyl ester (175) of 6-ethoxy-3,4-dihydro-2,4-dioxo-2//-l,3,5-thiadiazine-3-thiocarboxylic acid (Scheme 24). 

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