Potassium thioacetate

The reverse reaction in which thioacetamide is initially alkylated and then reacted under phase-transfer catalytic conditions with the acyl halide results in the formation of A-acylthioamidates (Scheme 4.15), with only trace amounts of the S-alkyl thioesters [35], S-Alkyl thioacetates have also been obtained from trifluoro-methylsulphonyloxy compounds upon reaction with potassium thioacetate in the presence of TDA-1 [61]. It is probable that tetraalkylammonium salts would be equally good catalysts. 

The first syntheses of 1,2-cfs-thioglycoses (a-D-gluco- and )3-D-manno- derivatives) have been achieved by the reaction in acetone of alkyl or benzyl xanthate or potassium thioacetate with the corresponding l,2-tra s-glycosyl halides [13]. More recently, tetra-O-acetyl-l-S-acetyl-l-thio-a-D-glucopyranose (10a) (Scheme 3) has been obtained i) by reaction of -acetochloroglucose (9 a) with either potassium thioacetate in HMPA or the tetrabutylammonium salt of thio-acetic acid in toluene [14] ii) by peroxide-induced addition of thioacetic acid to the pseudo-glucal (11) [15]. 

The Pd-catalyzed allylic alkylation of thiocarboxylate ions was carried out with potassium thioacetate (KSAc) and potassium thiobenzoate (KSBz) and the racemic cyclic and acyclic carbonates rac-3aa, rac-3ba, rac-lda, rac-laa, rac-lba, and rac-lca, respectively (Scheme 2.1.4.21). The carbonates rac-3aa, rac-3ba, rac-lda, rac-laa, and rac-lba were treated with KSAc (1.4 equiv) or KSBz (2.0 equiv) in the presence of Pd(0)/L (2 mol%) and BPA (8 mol%) in CH2CI2/H2O. Under these conditions the acyclic carbonates rac-3aa and rac-3ba gave the thioesters 18aa, 18ab and 18ba, respectively (Table 2.1.4.14, entries 1-3), with high enantioselec-tivities in high yields [26]. 

Poly(vinyl alcohol) was tosylated in anhydrous pyridine at 85°C and then reacted with dithiothreitol potassium thioacetate and stirred overnight. The mixture was then reacted with dithiothreitol at ambient temperature to form poly(vinyl alcohol)-g-dithiothreitol. It was hydrolyzed by methanolysis and the thiol macromer isolated. 2... 

The reaction of sucrose 2,3-manno-epoxide with potassium thioacetate and ammonium chloride in aqueous ethanol gave the expected 3-5>-acetyl-3-thio-altropyranoside (101). Treatment of 6,6,-dibromo-6,6,-dideoxysucrose hexaacetate with potassium thioacetate and A/, Ak dimethyl thiocarbamate gave the corresponding derivatives of 6,6,-dithiosucrose. The air oxidation of 6,6,-dithiolsucrose gave the bridged 6,6,-episulfide. A detailed conformational study of sucrose 6,6,-dithiol and sucrose 6,6 -episulfide revealed that they are similar but distinguishable (102). 

Some strategies used for the preparation of support-bound thiols are listed in Table 8.1. Oxidative thiolation of lithiated polystyrene has been used to prepare polymeric thiophenol (Entry 1, Table 8.1). Polystyrene functionalized with 2-mercaptoethyl groups has been prepared by radical addition of thioacetic acid to cross-linked vinyl-polystyrene followed by hydrolysis of the intermediate thiol ester (Entry 2, Table 8.1). A more controllable introduction of thiol groups, suitable also for the selective transformation of support-bound substrates, is based on nucleophilic substitution with thiourea or potassium thioacetate. The resulting isothiouronium salts and thiol acetates can be saponified, preferably under reductive conditions, to yield thiols (Table 8.1). Thiol acetates have been saponified on insoluble supports with mercaptoethanol [1], propylamine [2], lithium aluminum hydride [3], sodium or lithium borohydride, alcoholates, or hydrochloric acid (Table 8.1). 

Pivaloylation of 86 using pivaloyl chloride and silver triflate afforded the unstable 1-pivaloyloxypyrazolium salt 178 in quantitative yield. When the salt was treated with potassium thioacetate only products resulting from attack at the ring positions were detected. No details are given (1992JCS(P1)2555) (Scheme 52). 

Oxirane taxol derivatives have also been found to be convenient starting materials for the synthesis of taxols fused with a thietane ring. The oxirane-derived taxine B derivatives 118 and 119 have undergone reaction with potassium thioacetate in dimethylformamide (DMF) at 60°C <2000TL4891, 2001JOC5058>, leading to the formation of thietane-derived taxine B derivatives 57 and 121. In the case of the bromine derivative 118, the thietane-taxol 57 was not the exclusive product and the 1,2-dithiolane derivative 120 occurred as the major product (Equations 35 and 36). 

Two routes for the synthesis of a four-terminal wire compound based on a central porphyrin unit are presented in Scheme 10.25 [13b], In one route, the tetrabro-mide 75 was treated with potassium thioacetate, which resulted in the substitution product 76. Alternatively, reaction of aldehyde 77 with pyrrole 78 at room temperature using mixed acid catalysis conditions provided 76 after oxidation with DDQ. 

Photoinduced nucleophilic substitution of aryl halides with potassium thioacetate. A one-pot approach to aryl methyl and diaryl sulfides. European Journal of Organic Chemistry, 2210-2214. 

The treatment of the derivatives (517) with potassium thioacetate affords the 1,3,4-thiadiazine derivatives (518) which when heated in alkali loses sulfur to give compounds (519) which are formed most likely via the intermediates (520) (Scheme 52) <84CPB4437, 84H(22)479>. Compounds (519) are also formed by irradiation of the hydrazones (521) <84JHC1249,85CPB982,90AHC(48)223>. 

The Step 1 product (2.22 x 10 mol) was dissolved in 30 ml of acetone and treated with potassium thioacetate (6.67 x 10 mol), it was stirred overnight at ambient temperature. The mixture was filtered, concentrated, and precipitated in cold diethyl ether. The residue was dissolved in CH2CI2, extracted with water, dried using Na2S04, and the product was isolated after re-precipitation in cold diethyl ether. 

Thio-D-xylopyranose has been the sugar of this type most thoroughly investigated. Its synthesis was reported in 1961, independently and simultaneously from three different laboratories. With sodium thiocyanate, l,2-0-isopropylidene-5-0-p-tolylsulfonyl-a-D-xylofuranose (211) gives a thiocyanate that reacts with sodium sulfide to give l,2-0-isopropylidene-5-thio-a-D-xylofuranose (212). A better synthesis is the treatment of 211 with sodium thiosulfate, followed by reduction of the resultant Bunte salt with sodium boro-hydride. The same compound 212 is obtained by nucleophilic replacement of the 5-sulfonyloxy group in 211 by treatment with potassium thioacetate followed by deacetylation to 212, or by the reaction of 211 with sodium a-toluenethioxide, followed by scission of the resultant S-benzyl compound with sodium in liquid ammonia. 

Deoxy-6-thio-D-a yfo-hexose forms a 1,6-anhydro compound analogous to 270. S-Acetyl-5-deoxy-l,2-0-isopropylidene-6-thio-a-D-xyZo-hexofuranose is obtained either by nucleophilic displacement on the corresponding 6-p-tolylsulfonyloxy compound with potassium thioacetate or by the photochemical addition of thioacetic acid to... 

A sulfur-containing, septanose form is only obtainable as a result of the protection of the C-5 and C-4 hydroxyl groups in such a way that the pyranose or furanose rings cannot be formed. 2,3,4,5-Tetra-O-acetyl-S-acetyl-6-thio-D-galactose diethyl dithioacetal (273), obtained from the corresponding 6-p-toluenesulfonate with potassium thioacet-ate, undergoes hydrolysis in the presence of mercuric chloride and... 

As to the nucleophiles that can be applied in the nucleophilic reactions, ammonia and amines, water and alcohols, and mercaptans have been mentioned already. Sulfide and thiourea have been used only with the achiral ferrocenylmethylium ion [97]. To obtain chiral derivatives of 1-ferrocenyl-ethylmercaptan, substitution of the acetate with potassium thioacetate in acetic acid, followed by reduction with LiAlH4, was found appropriate [98, 99]. Reaction of (R)-l-ferrocenylethanol with NaH and... 

SCHEME 6.45 Potassium thioacetate is useful for the introduction of sulfur-based functionalities. 

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