[3,3]Sigmatropic ring expansion of cyclic thionocarbonates. 8. highly stereoselective synthesis of (Z- or (E)-double bonds by controlling chairlike-boatlike transition states in the [3,3]sigmatropic rearrangement of 8-membered thionocarbonates
synthesis of (Z)- or (E)-double bonds in 10-membered thiolcarbonates (3) was successfully conducted by controlling the chairlike-boatlike transition states in the [3,3]sigmatropicrearrangement of 8-membered thionocarbonates (2). The geometry of the product appeared to be highly dependent on the substituent pattern in the allylic system of the substrates (1). The 10-membered thiolcarbonates (3) were readily