Heterocycles with two sulfur atoms

Heterocycles with two sulfur atoms obtained from sulfur monochloiide, for example, 1,2-dithioles, 1,2,3-dithiazoles and 1,2-dithiines, are the most anticipated compounds because they are obtained by a direct insertion of two sulfur atoms during heterocyclic molecule construction. But even in that case some... 

Four-Membered Sulfur Heterocycles with Two Sulfur Atoms and Two Heteroatoms. 658... 

XXXXII. FOUR-MEMBERED SULFUR HETEROCYCLES WITH TWO SULFUR ATOMS AND TWO HETEROATOMS... 

Four-Membered Sulfur Heterocycles With Two Sulfur Atoms... 

The iron-catalyzed reaction of 1,3-dimethoxybenzene with sulfur monochloride in dilute chloroform gave two polysulfur heterocycles 245 and 246 with six sulfur atoms in the molecule, yields were very low (1979JCS(P1)1712 Scheme 131). 

The reactions described show that sulfur monochloride is an important reagent for the synthesis of heterocycles with various numbers of sulfur atoms and even without sulfur. An important feature of this reagent is that it can add not only two sulfur atoms to the molecule, as might be expected, but also one, three, four, five or even more atoms, and the structure of the final compound often depends on its stability. Recent developments in the use of sulfur monochloride include the discovery of its ability to form complexes with organic bases and of the significant difference in reactivity of these complexes from S2CI2. A selective synthesis of particular heterocycles requires accurate conditions (temperature, solvent, catalyst and base). 

Sulfur heterocycles, including those with more than two sulfur atoms, are used for optical materials <2000JPP2002040201>. The molecular third-order optical nonlinearity 7R (Second hyperpolarizability or nonlinear refractive index) was measured for pentathiepinethiafulvalene <1999PCA6930>. 

Heterocycles with two oxygen or sulfur atoms in one of the rings, i.e., dioxane and dioxolanes as well as their thia analogues have not been considered in this chapter many such ring systems are in the carbohydrate series in the form of acetals. 

Five-membered heterocycles with two vicinal chalcogen atoms in the ring system can be used as stable precursors for sulfur as well as for selenium-containing hetero-1,3-dienes in cycloaddition reactions. Consequently, 3//-1,2,4-thiaselenazoles have been used for the in situ formation of 4,4-bis(trifluoromethyl)-l-thia-3-azabuta-1,3-dienes, which exist at room temperature only as 4,4-bis(trifluoromethyl)-2//-l,3-thiazetes. This strategy was applied to the synthesis of the first stable selenophosphorane from bis(trifluoromethyl)-substituted 3//-diselenazol and 2-methoxy-1,3,2-dioxaphospholan [78AG(E)774] (Scheme 83). 

A heterocyclic carbene complex (285) results when cyclohexasulfur is allowed to react with the ylide complex 284. The cyclization involves the incorporation of two sulfur atoms (189). 

The present review includes data on the synthesis and chemical properties of the fluorine containing derivatives of furan, thiophene, selenophene, phospholene, and hve-membered heterocycles with two or more oxygen and sulfur atoms pubhshed prior 2007. Every section starts with discussion on the synthetic methods for unsaturated heterocycles (furan, thiophene etc.) and is followed by synthesis and transformations of dihydro and tetrahydro derivatives. 

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