[3,3]sigmatropic rearrangement of cyclic thionocarbonates of medium ring-size

Highly stereoselective synthesis of (Z)- or (E)-double bonds in 10-membered thiolcarbonates is achieved by the [3,3]sigmatropic rearrangement of 8-membered thionocarbonates which proceed through the chairlike vs. boatlike transition states. The formation of the 8-membered intermediates followed by their [3,3]-sigmatropic rearrangements were investigated by experiment and theoretical calculation. The utility of this method has been demonstrated by the unique and stereoselective synthesis of (-)-yellow scale pheromone. Moreover, medium-sized heterocyclic allenes were synthesized by this method. The structure and reactivity of a new type of strained 8-membered allene were also examined. By this method combined with a novel application of the newly developed SmI2-HMPA reduction of the cyclic allene, the antifungal constituent of a Sapium japonicum was synthesized.