1.4- Dithiepanes

Joining two heteroatoms to a ring by radical combination is not presently a common route to heterocycles. It might become more important if the art of metal-catalyzed redox reactions keeps advancing at the present pace. Current examples are the conversion of 1,5-dithiols to 1,2-dithiepanes by oxidants such as FeCla, and the oxidation of 1,3-propane-bis-hydrazines to 1,2,3,4-tetrazepines (Sections 5.18.4.1 and 5.18.10.1). 

Dithiepane can be oxidized to its 1,1-dioxide by hydrogen peroxide and this is further oxidized to the 1,1,2,2-tetraoxide by hydrogen peroxide in the presence of tungstic acid. 

Fully saturated 1,3-dithiepins can be prepared by the Lewis acid-catalyzed exchange reactions of 1,4-butanedithiol with the appropriate diethyl acetal, and l,3-dithiepan-2-one is obtained as an unstable oil via the reaction of 1,4-dichlorobutane with alkali trithiocarbon-ates (72HC(26)573, p. 616). 

The fully saturated 1,4-dithiepane system can be prepared by reactions of propane-1,3-dithiol with 1,2-dibromoethane, and of ethane-1,2-dithiol with 1,3-dihalopropanes (72HC(26)598, p. 619). 

An attempt to extend this approach to the preparation of the oxetan-3-one system, i.e. use of an aldehyde in place of an epoxide, failed. Instead, a 2-acyl-3-substituted-l,4-dithiepane derivative was obtained. 

Reactivity of (Nonartemisinin) Nonconjugated 1,2-Dioxepanes, 1,2-Oxathiepanes, and 1,2-Dithiepanes... 

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