Dithiolane S-oxides

The corresponding 1,3-dithiolane S -oxides were prepared by oxidation of the thioacetals with m-chloroperbenzoic acid (mCPBA) and, notably, this approach has proven successful in the obtention of both thioaldehydes and thioketones. 

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. 

Treatment of the 1,3-dithiolane S-oxide (149) with iodotrimethylsilane and ethyldiisopropyl amine results in an efficient dehydration and yields the corresponding dithioles (150) (Equation... 

Advances in synthesis and research of oligomeric tetrathiafulvalenes 97MI9. Enantioselective oxidation of 1,3-dithiolanes to corresponding S-oxides and S,S-dioxides by designer yeast 99JHC1533. 

Oxidation of a thiiraneradialene with equimolar amounts of MCPBA in CH2C12 at about 0°C gave the corresponding thiiraneradialene S-oxide 26 in a quantitative yield47 (equation 11). 5-Membered heterocyclic sulphoxides such as 1,3-benzoxathiolane sulphoxide 27, 1,3-benzdithiolane sulphoxide 28 and 1,3-dithiolane sulphoxide 29 were readily obtained from their sulphide precursors by oxidation with MCPBA in dich-loromethane solution48. 

Analogous ring enlargements of S-oxides of benzothiazolium compounds on heating with acetic anhydride have been described elsewhere [19 a] (cf. also Section 8.1.4). S-Oxides of thioketals such as 1189 are converted to the unsaturated 1,3-dithiolanes such as 1190 [21] (Scheme 8.6). 

The formation of S-oxides has also been observed when oxidizing a variety of 5-substituted 2-tert-butyl-l,3-dithianes in wet acetonitrile. In an undivided cell, 4-substituted 1,2-dithiolane-l-oxides were oblained (Scheme 25) [113]. A coupled cathodic process, in this case, was the reduction of protons formed in the anodic reaction. 

V(V), Mo(VI) and Ti(IV) derivatives proved to be both effective and selective in the oxidation of snlfides with alkyl hydroperoxides. As for H2O2, vanadium is at least twofold more efficient than molybdenum in oxidation and much more selective, as proved by the data obtained with the cyclic disulfide 2-aryl-l,3-dithiolane 80. A large predominance of the frawi-S-oxide 81 over the cw-derivative 82 is obtained for all the systems investigated (eqnation 46). However, the diastereoselectivity exhibited by V(V)/TBHP is remarkable . ... 

Although some examples have previously shown the feasibility of this reaction, very few studies have been reported recently. The isolation of a new antibiotic, leinamycin, featuring a novel dithioperoxyester S-oxide moiety, led Pattenden and Shuker [249] to a strategy based upon the [2+2] cycloaddition of a thioketone and a ketene. The expected 4-membered ring thio-lactone was obtained, albeit in modest yield, very probably due to the low thermal stability of thioacetone. The product could be transformed into a model dithiolane oxide. 

The sulfur in 1,2-dithiolanes is nucleophilic and can be alkylated to form 1,2-dithiolanium salts (527 528). S-Oxidation and/or formation of sulfones of thiazolidines results in certain situations, for example, with penams <2001BMC2113>. Pyrolysis of thiazolidin-2-one 1,1-dioxides results in loss of SO2 and the formation of -lactams < 1997J (P 1)2139 >. 

Single and double alkylation of the 1,3-dithiane S-oxide 104 followed by acid hydrolysis results in ring-contraction to form 1,2-dithiolanes 105 and 106 (13RSCA21911). A new method for synthesis of trithiaazapentalene derivatives has allowed examination of the relative contribution of the... 

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). ° ... 

The modified Sharpless reagent was also successfully applied288 for the asymmetric oxidation of a series of 1,3-dithiolanes 248 to their S-monooxides 249 (equation 134). It was observed that the optical induction on sulphur (e.e. from 68 to 83%) is not significantly affected by the substituents R1 and R2. Asymmetric oxidation of a few aryl methyl sulphides by organic hydroperoxides in the presence of a catalytic amount of the optically active Schiff base-oxovanadium(IV) complexes gave the corresponding sulphoxides with e.e. lower than 40%289. 

Heterocycles of this type occur widely. The benzo[l,3]dioxole ring system is often found in natural products and their degradation products, e.g., sesamol 38 lipoic acid 39 is a naturally occurring 1,2-dithiolane derivative. The 1,3-dithiolanes 40 are commonly known as 1,3-dithioacetals and have been extensively used in carbonyl group chemistry. In the absence of cyclic conjugation, ring sulfur atoms can readily exist in higher oxidation states as, for example, in the oxathiole S, -dioxide 41. 1,3,2-Dioxathiolane A-oxides 42 (cyclic sulfites) and 1,3,2-dioxathiolane A,A-dioxides (cyclic sulfates) are useful as synthetic equivalents of epoxides. 

S c s c c Bis-1,3-dithiol-2-yl f 4,5-dioxo-2-thioxo-l,3-dithiolane f l,3-dithiolane-2-thione 5-oxide f tetrathiafulvalenes (TTl, s)ax... 

Fig. 31 Mechanical actuation of a gold-coated microcantilever by molecular muscles [227]. (a) Structural formula of a palindromic, bistable [3]rotaxane with gold-binding dithiolane groups attached to the cyclophanes. (b) Reversible bending up and down of a cantilever by actuation of a monolayer ( 8 billion molecules) of the rotaxanes on its surface. The gold surface bends when the rotaxanes contract under the influence of an electrochemical oxidation that causes the cyclophanes to shuttle inward from the periphery of the molecule, (c) Electrochemical cell (Ag/AgCl, Pt, and the cantilever are the reference, counter, and working electrodes, respectively) and combined AFM device used to measure the bending by detecting a laser beam reflected off of the cantilever s surface...

Leinamycin 412 is a unique natural antibiotic product isolated from Streptomyces sp. S-140, which targets DNA. The DNA damage is achieved by the attack of the thiol on the l,2-dithiolan-3-one 1-oxide heterocycle of the molecule <2002JOC9054>. 

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