2.7- Dihydrothiepin-1,1-dioxide

The first synthesis of thiepin 1,1-dioxide (131) was performed by Mock in 1967 75>. With exess bromine in chloroform 2,7-dihydrothiepin 1,1-dioxide (129), prepared by 1,6-addition of sulfur dioxide to m-hexatriene, gave a dibromide 130 which, on treatment with two equivalents of triethylamine, afforded 131. Upon catalytic reduction, 131 rapidly absorbed three molar equivalents of hydrogen to yield hexahydrothiepin 1,1-dioxide (132). The 1,1-dioxide 131 is a fairly stable compound ... 

A further example of a concerted thermal elimination reaction of a thiepane derivative was the formation of c/s-hexatriene and the extrusion of sulfur dioxide from heating 2,7-dihydrothiepin 1,1-dioxide (116) (67JA1281). That this reaction was under orbital symmetry control was deduced from the results obtained by heating cis- (117) and trans-... 

A double nucleophilic substitution reaction on 1,6-dibromohexane with sodium sulfide has been found to give an acceptable yield (59%) of the thiepane (35 equation 62) (81SC409). The reversible 1,6-addition of sulfur dioxide to ds-hexatriene (equation 63) provides a convenient synthetic route to the 2,7-dihydrothiepin 1,1-dioxide (116) (67JA1281). 

CycloaddUion. Sulfur dioxide reacts with c -3-hexatriene (1) (20°, several weeks) to form 2,7-dihydrothiepin 1,1-dioxide (2). This cycloaddition appears to be general indeed substituted co-3-hexatrienes react more readily... 

Dihydrothiophene 1,1-dioxides from 1,3-dienes s. 6, 615 2,5-dienc-2,5-dihydro-thiophene 1,1-dioxides from conjugated diallenes s. K. Kleveland and L. Skatteb0l, Acta Chem. Scand. B 29, 827 (1975) 2,7-dihydrothiepin 1,1-dioxide ring s. W. L. Mock and J. H. McCausland, J. Org. Chem. 41, 242 (1976)... 

With trienes, the extrusion process dominates and the ring opens in a con-rotatOTy fashion. This indicates that in this reaction, one of the components is acting in an antarafacial manner. For example, cis- and [Pg.241]

The stereochemical consequences of orbital symmetry control and the mechanism of the reversible addition of sulphur dioxide to hexatrienes, which yields 2,7-dihydrothiepin 1,1-dioxides, have been examined, and the scope of the reaction has been explored. "... 

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