Thietane 1,1-dioxides photolysis

The photolysis of various substituted thiete dioxides under similar conditions resulted in the formation of the unsaturated ketones (255)264, most probably via a vinyl sulfene intermediate followed by a loss of sulfur monoxide as shown in equation 96. The same results were obtained in the thermolysis of 6e (R1 = R3 = Ph R2 = R4 = H)231, which further demonstrates that similar mechanisms are operative in thermolyses and pho-tolyses of thietane dioxides and thiete dioxides. 

The first diradical intermediate is the same as that involved in the photolysis and thermolysis of thietane l,l-dioxides ° and interconversion of the y-sultine and thietane dioxide often accompanies cyclopropane formation. In flash-vacuum pyrolysis, formation of the alkene may compete with the desired cyclopropane-forming reaction. Examples of this reaction are summarized in Table 11. 

Thermolysis and Photolysis of Thietan Dioxides. These reactions frequently lead non-stereospecifically to cyclopropanes and olefins, the relative yields of which vary markedly with the constitution of the thietan... 

Photolysis of thietan dioxides is a preparatively useful synthesis of cyclopropanes, particularly since stabilization of an cf-carbanion by a sulphonyl group allows wide latitude for manipulation. Thietan dioxide (101) gives (102) in 95% yield upon photolysis. Trimethylene sulphone gives trimethylene biradicals... 

Thermolysis of 4-benzoyl-3-phenyl-l,2-dithiolane 2,2-dioxide at 230° in a sealed tube gives 3-benzoyl-2-phenylthietane in 55% yield. ° Photolysis of 1,2-dithiolanes gives low yields of thietanes. ... 

Other work on four-membered heterocycles containing one sulphur atom includes a study of the vacuum-u.v. photodecomposition of thietan 1,1-dioxide and the formation of a thietanone from a xanthate and diphenylketen, and reports of several thiets. There is evidence that photolysis of (107) in a matrix at 77 K leads to the o-thiobenzoquinone (108), which is interconvertible with the... 

Alkylation of anions (88) and (89), followed by pyrolysis, provides novel methods of synthesis of carbonyl compounds and polycyclic hydrocarbons (including steroids), respectively. A synthesis of polycyclic hydrocarbons related to that based on the anion (89) involves alkylation of a benzocyclobutenyl-sulphonyl carbanion. Alkylation of a thietan 1,1-dioxide carbanion (90), followed by photolysis of the product, affords cyclopropanes. ... 

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