Thiocarbonyl .S -oxides

The present review concentrates on the developments reported in the last few years (1992 to May 1997) and mostly on carbon-carbon bond forming reactions. Other classes of compounds are generally not discussed, including thiocarbo-nates, dithiocarbonates and thiocarbamates. The chemistry of thiocarbonyl S-oxides is presented and compared. 

Cycloaddition of Sulfur Monoxide or Thiocarbonyl S-Oxides to Unsaturated Compounds... 

The simplest, parent thiocarbonyl. S -oxide, CH2SO, prepared in situ by treatment of trimethylsi-lylmethanesulfinyl chloride with cesium fluoride, reacts with cyclopentadiene to give the bi-cyclic sulfoxide 8 as a mixture of two diastereomers in a 9 1 ratio83. 

When chiral thiocarbonyl S-oxides derived from (S)-proline, prepared from the appropriate l-(trimethylsilylalkylsulfonyl)-2-(alkoxymethyl)pyrrolidine, are subjected to Diels-Alder reaction with 2,3-dimcthyl-l,3-butadiene, the 2-substituted 2-[(2-alkoxymethyl-l-pyrrolidinyl)sul-fonyl]-3,6-dihydro-4.5-dimethyl-2/f-thiopyran 1-oxides 10A and 10B are formed as a mixture of diastereomers. Their ratio depends on the nature of the substituents R1 and R2 as well as on the reaction temperature. The diastereomeric excess values, determined by H NMR in the presence of Yb(tfc)3 or by HPLC, vary from 0 to 41 % 84. 

Oxidation of 1-alkenyl 2-alkenyl sulfides to the corresponding sulfoxides leads to a remarkable rate acceleration in the [3,3] sigmatropic process351. Rearrangement of the sulfoxides occurs below 0 °C in some cases (Table 6). The sulfines (thiocarbonyl S-oxides) can be isolated and converted into carbonyl compounds under mild conditions ... 

Thiocarbonyl-Verbindungen konnen auf oxidativem Wege in die entsprechenden Carbonyl-Verbindungen oder in Thiocarbonyl-S-oxide iibergefuhrt werden. 

Diazoalkanes," azides, " partial oxiranes, oxazolidinone, " aziri-dines, trimethylsilyhnethyltriflate salts (TfO TMSM ), and a-aminoac-id ester imines form pentaatomic rings through reactive intermediate ylides. Species like thiocarbonyl S-ylides, " thiocarbonyl S-imides, thiocar-bonyl S-sulfides (thiosulfines), and thiocarbonyl S-oxides (sulfines) containing a three atomic system as central unit with the sulfur atom in the middle position are known as sulfur centred 1,3-dipoles. Oxiranes react opening the ring by L.A. Thiosulfines, " reactive intermediates in the formation of 1,2,4-trithiolanes, are not isolable species since they decompose to thione and sulfur. 

Thiocarbonyl S-Oxides (SulSnes). Cycloaliphatic sulfines such as 2 or 48 react with 1 in chloroform at 80 °C to give the stable 1,2,4-oxadithiolanes of type 49 in a regioselective [2 + 3] cycloaddition (eq 20). 

When =S=0 becomes a ligand to X2C, sulfines (thiocarbonyl-S-oxides) are formed. Their stability increases in the order F < CF3 < CF3S that means F2C=S=0 is less stable than (CF3)2C=S=0 and (CF3S)2C=S=0. Stability and reactivity of perfluorinated ketenes and sulfines compare rather well. With CO as a ligand to XN, isocyanates are obtained. Their chemistry and stability is well known and shows that CF3SNCO is more stable than CF3NCO and FNCO (76). 

Thiocarbonyl ylides (1) belong to tbe family of sulfur-centered 1,3-dipoles cbaracterized by tbe presence of two sp C atoms attached to tbe sulfur atom. Formal replacement of one of the C atoms by heteroatoms such as NR3, O, and S lead to the other representatives of the family, namely, thiocarbonyl S-imides (2), S-oxides (sulfines) (3), and S-sulfides (thiosulfines) (4), respectively. 

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... 

Thiocarbonyl oxides are a subject of active investigation. The natural occurrence of sulfines and related compounds in plants of the genus Allium (onion, garlic, etc.) is included in a superb and extensive review by Block [91]. Two detailed papers [92, 93] report the isolation of zwiebelanes from onions and their chemical synthesis involving intermediate sulfines produced by oxidation of di-l-propenyl disulfide, subsequent sulfoxide accelerated [3.3] sigmatropic shift and the [2+2] cycloaddition of the C=S and C=S=0 moieties. A further article [94] provides a great deal of information on the mechanism of formation of (Z)-propanethial S-oxide, the lachrymatory factor of the onion, as well as its chemical synthesis and reactions. Techniques of analysis of the volatiles of onions have been further improved [95]. 

A precursor of a thiocarbonyl ylid, a dihydrothiadiazole, was reacted [259] with a sulfine, thiobenzophenone S-oxide, to lead mainly to a dithiolane S-oxide, the formation of which was rationalised through a 1,3-dipolar cycloaddition of the ylid with the C=S bond of the sulfine. It is interesting to note that an opposite regioselectivity was observed for thiofluorenone S-oxide. 

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

In contrast, the cycloaddition reaction of ( )- or (Z)-lO-chloro-lO-thioformylcamphor S-oxide with 2,3-dimethyl-1,3-butadiene proceeds with complete asymmetric induction and affords in each case a single diastereomer 12 or 13 only differing in the reaction rate the (L)-thiocarbonyl 5-oxide reacts faster than the (Z)-isomer85. 

Similarly, the cycloaddition of chiral thiocarbonyl 5-oxides, derived From optically active TV-substituted 5-phenyl- or S-(4-methylphenyl)-5-(l-trimethylsilylethyl)sulfoximides with 2,3-di-methyl-1,3-butadiene, is completely stereoselective affording TV-substituted 3,6-dihydro-2,4,5-tri-methyl-2-[(5)-5-phenyl- or 5-(4-methylphenyl)sulfonimidoyl)]-2//-thiopyran 1-oxides as single diastereomers, determined by 1H-NMR spectroscopy using shift reagents and analytical reverse-phase HPLC85,87. 

The thiocarbonyl group in compounds such as thioamides is biotransformed by oxidative attack on sulfur. Sulfoxidation of the thioamide occurs first and is followed by further S-oxidation to give an unstable... 

Sulfines, which are thiocarbonyl mono-S-oxides, represent another type of reactive C=S heterodienophile.48 This functional group is nonlinear and can exist as (Z)-21 or ( >-22 isomers which have good configura-... 

An der Thiocarbonyl-Gruppe sind die Thiocarbonsaure-halogenide oxidationsempfindlich (-> S-Oxide bzw. Carbonyl-Verbindungen) und Additionsreaktionen zuganglich. 

High-level quantum-chemical calculations on the 3 + 2-cycloadditions of thioformaldehyde 5 -imides, S -methylide, S-oxide, and 5-sulfide have been reviewed. Theoretical studies on the 1,3-dipolar cycloaddition between thioketene 5-oxide and methyleneimine show that this reaction is concerted but non-synchronous. Adamantanethione 5-methylide reacts with thiocarbonyl compounds to produce 1,3-dithiolanes. A density-functional-theory study of the cycloaddition of the sulfine H2CSO predicts the 2 + 3-mechanism having the lowest pathway, with an activation barrier of 12.3kcalmoP. R The thermal and photochemical reactions of fluorenethione 5-oxide (69) with cyclooctyne (70) involves an initial 1,3-dipolar cycloaddition to produce the adduct (71), followed by an efficient sulfur transfer to cyclooctyne to produce the enone (72) and the dithiin (73) (Scheme 26). ° ... 

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... 

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