1.3- Dithietane-1,1,3,3-tetraoxide

The cyclic disulfone, 1,3-dithietane 1,1,3,3-tetraoxide 83, underwent Knoevenagel and substitution reactions to form a new class of unsaturated disulfenes. Thus, its treatment with isobutyraldehyde in the presence of a catalyst gave 84 bearing unsaturated vinylic moieties, the double bonds of which were resistant to all typical olefin reactions. Deprotonation of 84 and subsequent silylation with C4F9-S02-0SiMe3 yielded 2,4-disilylated product 85 (Scheme 9) <1996CB161>. 

The lithiation of the seven-membered sultone 217 with lithium iV,./V-diisopropylamide at -78 °C led to the rapid formation of the 1,3-dithietane 1,1,3,3-tetraoxide 218 in 55% yield, via the intermediate 219 (Scheme 26) <2003SL667>. 

Tetrasubstitution of 1,3-dithietane 1,1,3,3-tetraoxide occurs in the presence of tetramethylammonium fluoride in acetonitrile by Michael addition of activated olefins (RCH=CH2, where R is electron withdrawing) (93ZOR574). 

Thermolysis of the dicarbamic acid silyl ester (CH2 N[SiMe3]C02SiMe3)2) gives the 1,3-diazetane derivative 26 <96JOM93>. Alkylation of the 1,3-dithietane tetraoxide 27 with a,co-dihaloalkanes yields the dispiro compounds 28 (n = 1-4) <95ZOR589>. The first 1,2-dithiete S-oxide 29 is reported <95TL8583>. 

The parent 1,3-dithietane tetraoxide (76JA5715) as well as the tetrafluoro, tetrachloro and tetrabromo derivatives (80LA1981) have all had X-ray structures determined. IR, UV and NMR spectral data are also reported for these planar, almost square, rings <80AG(E)203). 

Dithietane tetraoxide, called disulfene, is completely stable to acids even though it is very reactive towards base. It exchanges readily with D20 and forms a tetrabromide with bromine (Scheme 55) (69AG(E)73>. 

The in situ generation of sulfene gives rise to an interesting dimer, 1,3-dithietane tetraoxide <69AG(E)73), which readily brominates and exchanges with D20 (Scheme 111). 

Lithiation of sultone 238 with LDA in THF at — 78 °C gave the rapid formation of the 1,3-dithietane tetraoxide 239 in 55% isolated yield in the apparent form of a 60 40 mixture of trans/cis-diastereomers bearing double bonds with the (Z)-configuration <2006T9017>. The authors explained the formation of the 1,3-dithietane 239 by the transformation of the a-lithiated sultone into the corresponding sulfene, which dimerized to give dithietane 239 (Scheme 28). 

The geometric structural parameters of a number of A-oxides generated from 1,3-dithietane and keto and thioketo derivatives generated from 2,2,4,4-tetrafluoro-l,3-dithietane have been recently calculated at the Hartree-Fock (HF)/6-31-G level, within the molecular orbital (MO) theory framework <1999JMT(466)111>. Structures shown here show the optimized geometries of the parent 1,3-dithietane 1, its mono- and bis-oxides 2-4, l,l -dioxide 5, l,3,3 -trioxide 6, and l,l, 3,3 -tetraoxide 7, whereas Table 1 lists the selected bond distances and angles for these compounds. 

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