Hydrolysis of thioacetates

When 2-4-0-ethylidene-D-glucofuranurono-6,3-lactone [obtained by the hydrolysis of thioacetal 61 (Ph = Et)] was treated with 5,5-dimethyl-l,3-cyclohexanedione (dimedone), 6-deoxy-6,6-bis(4,4-di-methyl-2,6-dioxocyclohexyl)-3,5-0-ethylidene-L-gulono-1,4-lactone (73) was formed in 71% yield.99... 

Desulfonylation Lithium-Ammonia, 158 Lithium triethylborohydride, 168 Magnesium-Methanol, 170 Sodium dithionite, 281 Sodium naphthalenide, 294 Desulfurization Lithium aluminum hydride-Bis(cyclopentadienyl)nickel, 158 Lithium l-(dimethylamino)naph-thalenide, 165 Lithium-Ethylamine, 158 Dethioacetalization (see Hydrolysis of thioacetals and -ketals)... 

Sulfanylalkanoyl Amino Acids and Peptides by Hydrolysis of Thioacetates... 

According to Panek et al.39 thioacetals are hydrolyzed under the action of Dess-Martin periodinane, being possible to perform a selective hydrolysis without affecting an alcohol present in the same molecule. Reaction conditions optimized for the thioacetal hydrolysis involve the use of Dess-Martin periodinane in a MeCN/CH2Cl2/H20 (8 1 1) solvent mixture. Under these conditions, Dess-Martin periodinane behaves as a very efficient reagent for the hydrolysis of thioacetals in complex substrates. 

Hydrolysis of thioacetals. Exposure of the thioacetal 1 to excess methyl iodide in aqueous acetonitrile at reflux results in formation of the lactam 2, an intermediate in the synthesis of quebrachamine. This transformation invoives initiai hydrolysis of 1 to an aldehyde intermediate (4,341), followed by an Hl-catalyzed Pictet-Spengler... 

Hydrolysis of thioacetals (7, 364). TTN has been used for selective dethioacetalization of the bis thioketal 1 to the mono thioketal 2. The paper includes examples of hydrolysis of simpler thioacetals. ... 

Thioacetals - carbonyl compounds. Hydrolysis of thioacetals to the parent carbonyl compound often presents some difficulty. Fetizon and Jurion have described two new methods for this conversion. In one method, a solution of the thioacetal in moist acetone is heated under reflux for several hours with excess methyl iodide. With... 

Another advantage over other Lewis acids is the thiophilic nature of copper this has led to its utility in the hydrolysis of thioacetals. Copper(II) chloride in conjunction with copper(II) oxide was introduced by Mukaiyama [16] for the deprotection of 1,3-dithianes and this method has found utility in a variety of synthetic protocols (Sch. 6) [17]. This combination, in which copper oxide plays the role of a buffer to prevent the medium from becoming too acidic, has also found application in the hydrolysis of a-heteroatom substituted and vinyl sulfides [18]. Acetals, which are prone to epimerization under acid-catalyzed hydrolysis conditions (21), can be con-... 

A second explanation for mercuric ion s effectiveness in hydrolysis of thioacetals lies in the complex formed between the ion and the two sulfur atoms. This stable complex effectively removes HSCH2CH2SH from the equilibrium, shifting the equilibrium to product. (An example of whose principle His initials are "Le Chatelier".)... 

Silver ions promote the hydrolysis of thioacetals in dilute aqueous solutions (e.g. reaction l)34b c. 

We first ran the reaction with metals conunonly used to catalyze the hydrolysis of thioacetal, including HgCVCdCOs, AgNOs/AgO, and FeCls/CuO. We found that the hydrolysis (oxidatiOTi) proceeded with FeCls/CuO and, alternatively, with CuCla/CuO, but not with Hgaa/CdCOs or AgNOs/AgO. Between FeCls/CuO and CuCla/CuO, the latter exhibited a shorter reaction time thus, we focused on... 

Satchell and Satchell have continued their studies on the mechanisms of reactions of thio compounds. The Ag" -catalyzed hydrolysis of thioacetates occurs by pathways involving one and two silver ions respectively bound to the sulfur of the thioacetal. In the hydrolytic decomposition of disulfides, shown in equation (52), the mechanism can involve a species R2S2Ag2 , with both silver ions... 

Regeneration of carbonyl compounds from 1,3-dithian 1-oxides can be accomplished using triethyloxonium tetrafluoroborate. Nitrosonium salts, and nitronium salts, either preformed or prepared in situ, are effective reagents for the cleavage of dithioacetals. Similarly hydrolysis of thioacetals can be performed with thallium trinitrate, and selective hydrolysis can also be achieved with this reagent [equation (59)]. ... 

Lithium tetrafluoroborate in wet acetonitrile has been described as an effective combination for the hydrolysis of acetals under mild weakly acidic conditions. Dithians were unaffected. Methods for the hydrolysis of thioacetals continue to appear. Reagents that have been described include a polystyryl-mercury(n) trifluoroacetate combination, which retains the metal on the resin, lead(iv) dioxide and boron trifluoride etherate, aqueous hydrochloric acid in dioxan containing dimethyl sulphoxide, methyl-bis(methylthio)sulphonium hexa-chloroantimonate, and iodoxybenzene, catalysed by toluene-p-sulphonic acid. Dithioacetals derived from ethane-1,2-dithiol may be cleaved with dimethyl sulphoxide in combination with either t-butyl or trimethylsilyl bromides and iodides. Regeneration of ketones from ethanediyl-S S -acetals via the lithium-di-isopropylamide-promoted fragmentation to the thioketone and subsequent hydrolytic work-up only gives satisfactory yields for aryl methylketone derivatives. Dithioacetal SS-dioxides are rapidly cleaved in hot methanolic hydrochloric acid solution. ... 

These sulfur derivatives are stable in aqueous add, a medium that hydrolyzes ordinary acetals. The difference in reactivity may be useful in synthesis when it is necessary to differentiate two different carbonyl groups in the same molecule. Hydrolysis of thioacetals is carried out using mercuric chloride in aqueous acetonitrile. The driving force is the formation of insoluble mercuric sulfides. 

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