Conversion of thiocarbonyl

The conversion of thiocarbonyl compounds into carbonyl compounds, long attracted the interest of organic chemists and a variety of methods allowing this conversion have been developed, recurring to diverse organic and inorganic reagents.84... 

Conversion of thiocarbonyl compounds into carbonyl derivatives... 

The carbonyl group in 241 and 242 can be converted into thiocarbonyl which in turn is attacked by hydroxylamine to form an imine (Scheme 30) <1980JOC4198>. The reverse reaction, that is, conversion of thiocarbonyl to carbonyl, is possible with trifluoroacetic anhydride in dichloromethane <1991TL1195>. 

Bis[4-methoxyphenyl] tellurium oxide was found to be a mild and highly selective oxidizing agent for the conversion of thiocarbonyl groups to carbonyl groups, thiols to disulfides, arylhydrazines to arenes, and 1,2- or 1,4-dihydroxyarenes to quinones. No reaction was observed with simple phenols, alcohols, enamines, amines (including pyrrole, indole, tryptophan, tyrosine, aniline, and dimethylaniline), oximes, dithiolanes, isonitriles, and 2,4-dinitrophenylhydrazones4. 

In all of these reactions, the diaryl tellurium oxide is reduced to the diaryl tellurium. To make the conversion of thiocarbonyl to carbonyl groups catalytic with respect to the diaryl tellurium oxide, the diaryl tellurium must be converted back to the diaryl tellurium oxide. A catalytic cycle was developed with 1,2-dibromotetrachloroethane as the agent oxidizing the diaryl tellurium to the diaryl tellurium dibromide and 20% aqueous potassium carbonate as the base hydrolyzing the tellurium dibromide to the tellurium oxide1. 

A number of conversions of thiocarbonyl compounds into em-difluoro compounds have been described in the literature, e.g. formation of 1. 2, - 3, - 5, 6, 7 (Houben-... 

A number of conversions of thiocarbonyl compounds into gem-difluoro compounds have been described in the literature, e.g. formation of 1.189 2,212 3,213-214 4,216 5,212 6,213 7 (Houben-Weyl. Vol.E4, p668),217 and 8.218 Since these reactions give difluoro compounds bearing heteroatoms in the a-position they are not discussed further here. Pyrolysis of 4 gives 1,1-difluoro-substituted alkenes in good yields.216... 

Two new procedures for the conversion of thiocarbonyl groups into the corresponding carbonyls (C=S to C=0) consist of sodium hydroxide... 

The use of benzeneseleninic anhydride in the conversion of thiocarbonyl compounds into the corresponding oxo-derivatives has been reported in full similar reactions were achieved using diaryl telluroxides. ° Steroidal ketones reacted with tris(phenylseleno)borane or tris(methylseleno)borane to give phenyl or methyl selenoacetals. 

First reports have appeared on preparations of telluroesters (137) and telluroamides (138) both classes of compound are reasonably stable. The telluroxide (139) is useful for the conversion of thiocarbonyl groups into their oxo-analogues. The reagent exhibits considerable selectivity and, for example, does not oxidize phenols, alcohols, or many nitrogen-containing functions. ... 

TeUuride Catalyzed Conversion of Thiocarbonyl Compounds to Oxo Analogues... 

Ley et al. reported a catalytic method for the conversion of thiocarbonyl compounds to their oxo analogues with diaryltellurium oxide. The teUuride is recycled with a halogenating agent like 1,2-dibromotetrachloroethane, water and base (Scheme 7.91) [362, 363]. 

Scheme 7.91 Conversion of thiocarbonyl compounds catalyzed by ditelluiium oxide (generated in situ from 201)...

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