[3, 3]Sigmatropic Ring Expansion of Cyclic Thionocarbonates. IV. Relatioship between Ring Size of Cyclic Thionocarbonates and Geometry of Created Double Bond in Medium- and Large-Membered Thiolcarbonates

Medium- and large-membered cyclic thiolcarbonates containing an (E)- or (Z)-double bond were synthesized by two methods using [3, 3]sigmatropic ring expansion of cyclic thionocarbonates. The [3, 3]sigmatropic ring expansion proceeds exclusively via the transition state bearing the chain tethered in a cis relationship when the cyclic thionocarbonates are 8-membered or smaller. Importantly, the ring size of the cyclic thionocarbonate determines the double bond geometry of the thiolcarbonate.Conversion of the cyclic thiolcarbonates into (E)- or (Z)-allylic sulfides is also described.