Thiane oxides synthesis

A method for the stereospecific synthesis of thiolane oxides involves the pyrolysis of derivatives of 5-t-butylsulfinylpentene (310), and is based on the thermal decomposition of dialkyl sulfoxides to alkenes and alkanesulfenic acids299 (equation 113). This reversible reaction proceeds by a concerted syn-intramolecular mechanism246,300 and thus facilitates the desired stereospecific synthesis301. The stereoelectronic requirements preclude the formation of the other possible isomer or the six-membered ring thiane oxide (equation 114). Bicyclic thiolane oxides can be prepared similarly from a cyclic alkene301. 

Thiadiazoline S-oxides, synthesis of 275 Thiane dioxides formula of 382 synthesis of 468 Thiane oxides 750-752 conformational analysis of 465-467 formula of 382... 

In this synthesis the geometry of the acyclic double bonds is controlled through their formation as part of the thiane ring. Thiacyclohexanone (711) was converted to 4-thia-l-methylcyclohexene by reaction with methylmagnesium iodide and subsequent dehydration. Metallation of (712) with s-butyllithium and alkylation of the anion with the epoxide (713) gave a tertiary alcohol which was dehydrated to yield (714). A second alkylation of (714) with trails-4-chloro-3-methyl-2-butene 1-oxide (715) completed the carbon skeleton of the Cis juvenile hormone. Reduction of (716) with lithium in ethylamine and then desulfurization with Raney nickel led to trienol (717), a product converted previously to (718). 

The best available methods for synthesis of the parent heterocycles are clearly (a) Pummerer rearrangement of thiane 1-oxide, followed by elimination, affording the 3,4-dihydro compound and (b) dehydration of thian-4-ol to give the 3,6-dihydro system (78JHC289). Preparation of the benzannelated compounds is covered in reviews (75AHC(18)59, 80AHC(26)115>. 

The chemistry of rran5-4-r-butyl(diphenyl)silyloxythiane oxide has been investigated by Simpkins in the synthesis of protected, substituted secondary alcohols. Simpkins has found that the anion of fra s-4-r-butyl(diphenyl) silyloxythiane oxide, when treated with trimethylsilyl chloride, can form a 2,4-disubstituted thiane in turn, this product may be easily desulfurized with Raney nickel to liberate (S)-3-r-butyl(diphenyl)silyloxy-l-trimethylsilylpentane in good yield (Scheme 4.49) [101]. 

Thiolans, Thians, Thiepans, Thiocans, and their Oxides and Dioxides Synthesis.—The intramolecular trapping of a sulphenic acid by a carbon-carbon double bond constitutes a new stereospecific route to cw-2-substituted thiolans and thian 1-oxides. Thus 5-t-butylsulphinylpent-l-ene (1), when heated at... 

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