Compounds Structurally Related to 6a-Thiathiophthen

The 4 -thiapyran-4-thione route to thiathiophthens has been modified so as to yield 6a-selenahthiopthens (35). The intermediate selenoketones (38) are unstable, but react satisfactorily with sodium sulphide in aqueous dimethyl sulphoxide to give dianions which are oxidized, as in the original synthesis, with ferricyanide. N.m.r. data on 6a-selenathiophthen, and on its 3,4-dimethyl and 2,5-diphenyl derivatives, indicate real or time-averaged 

Cj symmetry. An JT-ray study on the parent compound gives the bond lengths shown (39). The Se—S bonds, like the S—S bonds in 6a-thia-thiophthen, are longer (by ca. 10%) than would be expected for a normal covalent bond. This is also true for the Se—Se bonds in 6a-selena-selenophthen (40).  

4-diaza-6a-thiathiophthens, (41) and (42), have been studied by the crystallographic method. The slightly differing values for the S—S bond lengths (2.319 and 2.328 A) in the 2,5-diphenyl compound may result from different degrees of twist (2.9 and 7.0°) of the phenyl groups. The 2,5-bisanilino-compound is of interest because of the possibility of 

Various routes to 1,2-dithiolylidene ketones (45) have been described. These include the reaction of 3-methylthio-l,2-dithiolium salts with sodium benzoylacetate, the treatment of 3-phenacylthio-l,2-dithiolium salts (43 = R = Ph, R = H) with triethylamine and decomposition of 

Studies of the i.r. spectra of dithiolylidene ketones in which the oxygen is enriched in 0 have identified the carbonyl stretching bands which appear in the region 1550—1595 cm , depending on the substitution pattern and the conditions of measurement.  

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