Oxidative thiocarbonyl compounds

Bis(p-methoxyphenyl) telluroxide (118) and the corresponding tellurone (119) have recently been shown to exhibit mild oxidizing properties towards easily oxidizable substrates. Thus the telluroxide (118) oxidizes thiocarbonyl compounds RR C=S to the corresponding ketone RR C—O364,365 and 3,4-di-f-butylpyrocatechol to 3,4-di-f-butyl-o-quinone.364 The tellurone (119) oxidizes benzyl alcohols to the corresponding carbonyl compounds, a reaction. .which is not observed with (118).366... 

DMSO with proton acids or BF3 oxidizes thiocarbonyl compounds to carbonyl analogues MejS and sulphur are the other products, and are... 

These reactions differ from those of sulfur tetrafluoride with carbonyl compounds in that a formal oxidation-reduction of the sulfur atoms m the thiocarbonyl compound and sulfur tetrafluoride molecule occurs, resulting in the formation of free sulfur and the complete utilization of the fluorine atoms in sulfur tetrafluoride. 

Tc(V) and Re(V) are thiols, thioethers and thiocarbonyl compounds and molecules containing combinations of their functional groups. There exist significant differences in the ability of the various groups to form stable complexes and in the kind of complexes formed. Unlike thiols, a neutral S-donor shows a preference for the metals in oxidation states lower than +5. 

Common synthesis of disulfonium dications involves formation of a S-S bond by oxidative coupling of two sulfide moieties. Involving for oxidative generation of S-S bond, thiocarbonyl compounds can lead to new-type dications containing disulfide moieties between two positively charged fragments. There are several disulfide dications of this type derived from thioureas, thiocarbon-ates and thioketones as well as selenium derivatives.137 148... 

Nitrosonium tetrafluorobprate was used later as oxidant for convertion of dithiolanthione 150 to dication 151.151 This technique was found to be general for oxidation of number of thiocarbonyl compounds (Scheme 56).146... 

Direct oxidation of thiocarbonyl compound by triflic anhydride results in stable dication salts containing disulfide framework. For example, reaction of thiocarbonate 155 with Tf2Q yields the dication salt 156 (Scheme 58).154... 

I.3.4.2.5. Carbonyl and Thiocarbonyl Compounds a-(Hydroxyimino)phenyl-acetonitrile oxide (generated in situ at room temperature from PhC( NOH)C ( NOH)Cl in the presence of NaHC03 or Et3N) reacts with simple aldehydes and ketones R1R2CO to give 1,4,2-dioxazoles 180 (347). Related dioxazoles, formed by cycloaddition of benzonitrile oxide to aromatic aldehydes, upon treatment with I-BuOK, undergo cyclo-reversion, allowing direct conversion to substituted benzoic acids or their esters (348). 

Treatment of Fischer-type carbene complexes with different oxidants can lead to the formation of carbonyl compounds [150,253]. Treatment with sulfur leads to the formation of complexed thiocarbonyl compounds [141]. Conversion of the carbene carbon atom into a methylene or acetal group can be achieved by treatment with reducing agents. Treatment of vinylcarbene complexes with diborane can also lead to demetallation and formation of diols [278]. The conversion of heteroatom-substituted carbene complexes to non-heteroatom-substituted carbene complexes... 

Considering that diaryl tellurides debrominate vic-dibromides, forming diarylteUurium dibromides (see Section 4.1.12.1), which in tnm can be easily hydrolysed to the corresponding tellnroxides by aqueous bases, a catalytic procedure has been provided for the oxidation of thiocarbonyl compounds. 

Thiocarbonyl compounds can be generated thermally in the gas-phase from a variety of precursors. Bock et al. [77JCS(CC)287 82CB492] have shown that pyrolysis of 1,2,4-trithiolane derivatives (81) is especially advantageous for this purpose. The fragmentation reactions were monitored by PE spectroscopy. By this method thioaldehydes including thioformaldehyde and thioketones that polymerize readily were obtained. 1,2,4-Trithiolane 4-oxide (82) yields a mixture of thioformaldehyde and thioformaldehyde oxide. 

These are respectively the 5-oxides and 5-dioxides of thiocarbonyl compounds. The lachrymatory factor of onions was shown to be (Z)- ... 

Sulfines are commonly prepared by oxidation of the corresponding thiocarbonyl compounds [187, 188], Monosubstiluted sulfines are not available by such a process, and an indirect route has been proposed [189],... 

The products of the thermolysis of 3-phenyl-5-(arylamino)-l,2,4-oxadiazoles and thiazoles have been accounted for by a radical mechanism.266 Flash vacuum pyrolysis of 1,3-dithiolane-1-oxides has led to thiocarbonyl compounds, but the transformation is not general.267 hi an ongoing study of silacyclobutane pyrolysis, CASSF(4,4), MR-CI and CASSCF(4,4)+MP2 calculations using the 3-21G and 6-31G basis sets have modelled the reaction between silenes and ethylene, suggesting a cyclic transition state from which silacyclobutane or a trcins-biradical are formed.268 An AMI study of the thermolysis of 1,3,3-trinitroazacyclobutane and its derivatives has identified gem-dinitro C—N bond homolysis as the initial reaction.269 Similar AMI analysis has determined the activation energy of die formation of NCh from methyl nitrate.270 Thermal decomposition of nitromethane in a shock tube (1050-1400 K, 0.2-40 atm) was studied spectrophotometrically, allowing determination of rate constants.271... 

Flash vacuum pyrolysis (FVP) of 1,3-dithiolane 1-oxides (88-90), as a possible route to thiocarbonyl compounds, has been studied.57 Thiobenzophenone and thiofenchone are obtained from (88) and (89), respectively, but there was no evidence of heptane-4-thione formation from (90). A stepwise homolytic cleavage has been proposed. 

A cycloreversion mechanism is suggested for the transformation of the nonisolable cycloadduct 90 to the aldehyde 91 and isothiocyanate 92 <1996BCJ719> and for the spiro-1,4,2-oxathiazole intermediates 94 to the dioxothiazoline 95 and the aryl isothiocyanate 92 <2001MOL510>. Both cycloadducts are obtained by cycloaddition reactions of nitrile oxides 88 to thiocarbonyl compounds (Scheme 12). 

Thiocarbonyl compounds (e.g., compound 237) can be oxidized by m-OI-C6H4-COd I to. Y-oxidcs (sulfines, e.g., compound 238) which as 1,3-dipoles react with thioketones yielding 1,2,4-oxadithioles 239-241. The structure of the cross-product 241 was confirmed by X-ray crystallography (Scheme 76) <2005HCA2624>. 

S NMR spectra of thiocarbonyl, thiophosphoryl compounds, and of some sulphonium salts have also been published. Machiguchi et al. have reported the 33S NMR spectrum of tropothione41 2, a thiocarbonyl compound, and of its corresponding S-oxide, 3 and sulphenic acid, 4.42... 

A third method of access to sulfines is the oxidation of thiocarbonyl compounds. When the starting material is available it is an attractive route. There has been some dispute in the past whether enethiolisable thiocarbonyl derivatives would lead to the corresponding sulfines or to divinyl disulfides [101, 102]. It is now clear from our research that, even if the C=S molecules bear highly acidic a-protons, oxidation occurs on C=S and does not touch the a-protons. There are many examples of this behaviour. The most easily enethiolised compounds are thioketones. We have shown that their reaction with a peroxycarboxylic acid, mCPBA, is very fast at 0°C and quantitatively provides the corresponding sulfines [103]. In many examples the aliphatic sulfines are not very stable and have to be used in subsequent reactions that will be faster than their decomposition (t1/2 from some hours to days). 

The oxidation of a large variety of thiocarbonyl compounds to the corresponding S-oxides has been studied by Zwanenburg.40 Like normal thiones, thioacylsilanes... 

Two methods have been utilized for the preparation of 0-[(alkylthio)car-bonyl] derivatives (X—0—CO—S—R). The thiocarbonyl sulfur of an 0-[(alkylthio)thiocarbonyl] compound has been specifically oxidized by silver nitrate. However, the action of (S-alkyl thiochloroformates upon a... 

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