Dethioacetalization thioacetals

Dethioacetalization. Thioacetals can be cleaved to the ketones in high yield by treatment with trimethyloxonium tetrafluoroborate (6 equivalents) followed by addition of water (cf. 4, 528-529). 

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)... 

Keywords thioacetal, dethioacetalization, clayfen, microwave irradiation, ketone,... 

Dethioacetalization.1 The combin C6H5OPOCl2, and Nal converts acetals to 1 but has little, if any, effect on thioacetal addition of DMF converts thioketals into at room temperature in 1-17 hours in 70- ... 

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. ... 

Deacetalization and dethioacetalization. Dimethyl acetals, 4-p-methoxy-phenyl-l,3-dioxolanes are cleaved withDDQ in the presence of water. For deprotection of thioacetals under mild conditions photochemical assistance seems advantageous. The same reaction principle of deacetalization can be extended to ether exchange. Thus alcohol protection is possible by mixing with 2,2-dimethoxypropane in the presence of DDQ, and proximal diols are converted to acetonides. Replacement of anomeric arylmethoxyl groups by this method complements other glycosylation procedures. 

Dethioacetttlization, Thioacetals are dethioacetalized to the parent carbonyl compound by thallium(lll) nitrate in methanol at 25° in 5-30 minutes yields are 75-99%. About 2.2 molar equiv. of TTN are required for complete reaction. The present method appears to be preferable to the use of thallium(III) tri-fluoroacetate for this purpose. ... 

Sulphur.—Thioacetals and Thioketals. The widespread utilization of lithiated thio-acetals and thioketals as acyl carbanion equivalents (see Section on Li) renders information about other reactions of such species important in general synthetic methodology. Several methods for dethioacetalization have appeared, and in-clude transthioacetalization using glyoxalic acid in acetic acid, and oxidative hydrolysis using S02Cl2-wet silica gel or Tl nitrate. 

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