Dithiepanes, oxidation

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. 

Potassium permanganate adsorbed on copper sulfate pentahydrate oxidizes dithiol 112 into 1,2-dithiepane 113 (Equation 35) <1998S1587>. 

Dithiepanes and 1,3-oxathiepanes are readily oxidized to give the corresponding h -oxides. For example, oxidation of l,3-dithia-5,6-benzocycloheptenes 66 with w-chloroperbenzoic acid afforded l,3-dithia-5,6-benzocyclo-heptene 1-oxides 67 (cf. also compounds 42 and 43, Section 13.11.4). In the oxidation of the isopropyl derivative 66d, /ra t-2-isopropyl-l,3-dithia-5,6-benzocycloheptene 1,3-dioxide 68 was isolated as a byproduct (Scheme 10) <2001JGU960, 2004JST(688)191>. For the conformation of 67 and 68, see Section 13.11.4. 

Simple 1,2-dithiepanes are prepared by the oxidation of, -alkanedithiols using hydrogen peroxide, iodine, oxygen, or other oxidants . For example, potassium permanganate adsorbed on copper sulfate penta-hydrate oxidizes 1,5-pentanedithiol into 1,2-dithiepane 198 <1998S1587>. 

A tin-directed cyclization technique was introduced for a selective formation of the monomer. This mild, template-driven ring closure gave a good yield of the desired monomer <86TL44i>. Thus, high yield preparations of cyclic disulfides, including 1,2-dithiolanes, 1,2-dithiane, 1,2-dithiepane, and up to 1,2-dithiacyclodecane, by this oxidative cyclization with bromine or iodine from the... 

Oxidations of 1,3-dithiolanes, unsubstituted and 2-substituted 1,3-dithianes, and 1,3-dithiepanes by H2O2 in the presence of aluminium salalen complex (114) are highly... 

---