Thiocarbonic acid esters

Thiocarbonic acid esters s.a. Mono-thiolcarbonic acid esters Trithio-carbonic - -Thiocarbonyl compds. 

Thiocarbonic acid esters s. (Hydroxythiol)thiono-carbonic acid esters, Thiol-, Trithio-... 

Thiolcarbonic Acid, HS.CO.OH, yields carbon oxysulphide, COS, by decomposition its esters yield alcohols or mereaptans when saponified, according to whether the alkyl group is attached to oxygen or to sulphur by this means the constitutions of the thiocarbonic acids are established. 

The carbonates and thiocarbonates may be classified quite simply into the following types, (i) Mixed Esters. In these esters, the carbonic acid or thiocarbonic acid is esterified with both an alcohol and a carbohydrate, (ii) Acid Esters. Here, a metal salt of a half-ester of a carbohydrate has been formed, (iii) Intermolecular Esters. Here, an ester has been formed between one molecule of the acid and two molecules of carbohydrate, (iv) Cyclic or Intramolecular Esters. Here, one molecule of the acid is di-esterified with one molecule of carbohydrate. 

The present Section is mainly concerned with differences of stability between the two classes of derivatives and any variations within each class. Their stability toward hydrolytic agents has frequently been examined, and, for the thiocarbonates, the thermal stability has also received attention. These studies have, in general, been neither exhaustive nor quantitative, and comparative data are directly available for certain cellulose derivatives only. The progressive replacement of the oxygen atoms in a neutral carbonic ester by sulfur appears to lead to a decrease in the sensitivity to alkali and an increase in the sensitivity toward acids, water, and heat. As expected, the acid esters are less stable than their neutral analogs toward the last-named agents. 

Carbohydrates, allyloxycarbonates, 123 carbonates of, 151 chloroformyl esters of, 102 conformational analysis of, 12 reaction of, with carbon dioxide, 129 with carbon disulfide, 135 with carbonic acid, 129 with phosgene in acetone, 105 thermochemical properties of, 21 thiocarbonates of, 157 Carbonic acid, esters, 91,92,151 bis(methyl 3,4-0-isopropylidene-/3-D-arabinopyranoside), 2,2 -, 96 bis(1,2,3,4 - tetra - O - acetyl -/J - D - glucose), 6,6 -, 104 cyclic, 103... 

Figure 2. GC-MS analysis of thiocarbonic acid O, S-dimethyl ester (4) in Scheurebe wine extract (SP II). GC column DB-Wax...

Carbon disulfide is a valuable synthon (see Chapter 9, p. 147) which can be used for the synthesis of thiocarbonic acid derivatives. Thus, carbon disulfide reacts with ammonium polysulfide or hydrogen sulfide to give trithiocarbonic acid (70) or symmetrical esters (73) after reaction with an alkyl halide. With alkoxides or thiolates, carbon disulfide forms xanthates (77) or S-alkyl trithiocarbonates the latter by further treatment with alkyl, acyl or diazonium halides affords the derivatives (74)-(76) (Scheme 39). 

Although the corresponding thio compounds should be readily available from hydrazidoyl halides and hydrogen sulfide or mercaptans, respectively, these reactions are not reported in the literature. However, Fusco and Musante investigated the reaction of thiocarbonic acid 0-esters with hydrazidoyl bromides. 

Sulfinic acid alkoxymethyl esters Thionocarbonic acid esters Thiocarbonate esters 40... 

Besides acetates and benzoates many other types of carboxylic acid esters can be formed, such as chloroacetates, trifluoroacetates, pivalates, carbonates, and thiocarbonates, by reaction with chloroacetic anhydride, trifluoroacetic anhydride, pivaloyl chloride (2,2-dimethyl propanoyl chloride), phosgene or methylchloro-formate, and carbon disulfide or carbonyl sulfide, respectively. Each of the ester derivatives imparts specific chemical properties to the carbohydrates so they can be used selectively in synthetic schemes. It was found that the sulfonic acid esters... 

The following compounds are unaffected by bis(p-methoxyphenyl) telluroxide dithi-olanes, enamines, aldehydes, ketones, alcohols, pyrroles, indoles, amino acids, aromatic amines, monohydroxyarenes, esters, hindered thiocarbonates, isonitriles, oximes, arylhy-drazones, sulphides, and selenides. ... 

Sulfur as Heteroatom. Thiols and sulfides are protonated on sulfur in superacid media and give mono- and dialkylsulfonium ions, respectively.136 Thio-carboxylic acids, 5-alkyl esters, thioesters, dithioesters, and thiocarbonates in similar media also form stable protonated ions541,647 such as cations 348-353. 

In the course of the reactions, the other functional groups are also derivatized. Hydroxyamino acids and Tyr react with alkyl chloroformate with the formation of carbonate esters, Cys and CysH provide thiocarbonates, and the imidazole nitrogen of His is also protected. The indole functional group of Try does not change, Pro forms a stable carbalkoxydithiocarbamate and Arg does not provide any volatile product. The derivatives were separated successfully (except the pair Leu-De) on 5% of QF-1 with temperature programming (94-235°C). The reproducibility of the method was stated to be 5%. Using an FID and ECD, 10-10 and 10-13 mol of amino acids, respectively, can be determined. 

For many years, the carbohydrate esters of carbonic acid and thiocar-bonic acid have found important application as intermediates in the synthesis of otherwise difficultly accessible derivatives. A review of these esters is particularly opportune, because both their preparation and properties are considerably influenced by stereochemical factors which require interpretation in the light of modem concepts of reaction mechanisms and conformational analysis. Although the historical development of the chemistry of the carbonic and thiocarbonic esters of carbohydrates has been independent, it is appropriate to give a comparative treatment of their closely related structures and properties. 

SYNS AI3-25722 CARBONIC ACID, DITHIODI-, o,o -DIMETHYL S,S -(2,3-QUINOXALINEDIYL) ESTER CARBONOTHIOIC ACID, S,S -2,3-QUINOXALINEDIYL o,o -DIMETHYL ESTER CARBONIC ACID, THia, o,o -DIMETHYL S,S -2,3-QUINOXALINEDIYL ESTER CARBONIC ACID, THIO-, o-METHYL ESTER, S,S-DIESTERMTH2,3-QUINOXALINEDITHIOL o,o -DIMETHYL S,S -2,3-QUINOXALINEDIYL THIOCARBONATE SAS2185... 

The di-O-tosylates (prepared by action of tosyl chloride in pyridine) are reduced with zinc (Nal/Zn route e Tipson-Cohen reaction) [13]. Cyclic ortho-esters (prepared by reaction of the diol with ethyl orthoformate) are transformed into olefins by simple heating in the presence of acids (Eastwood reaction, route b) [14]. Cyclic thiocarbonates (obtained by reaction of a diol with thiophosgene or (V,(V -thiocarbonyl-di-imidazole) are reduced to olefin with trimethyl phosphite (Corey-Winter method, route c) [15]. Finally, reduction of vicinal di-xanthates with tri- -butyltin hydride according to the Barton procedure [16] affords olefins via a reductive elimination process route a). The Corey-Winter, Garegg, and Tipson-Cohen methods are most commonly applied for deoxygenation of sugar diols. 

Alkyl(aryl) thiocarbonates (xanthates) are (9-alkyl(aryl) esters of the hypothetical dithiocarbonic acid, HSC(S)OH.174,175 These esters are unknown in the free state and only their alkali metal salts, M[S2COR], are readily available, and stable enough to be used as starting materials for metal complexes. Alkyl(aryl) dithiocarbonates (xanthates) were discussed in CCC (1987) and continued to be used as ligands, with some interesting new results being reported. 

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