[Development of new reactions utilizing feature of sulfur atom and the applications].

Several novel reactions utilizing the latent feature of sulfur atoms have been developed. We found that chiral p-toluenesulfinyl groups on olefines control the stereochemistry in highly diastereoselective manners as show in the following three types of reactions: 1) intramolecular Michael addition reactions, 2) Pummerer-type reactions, and 3) cyclopropanation reactions. These chiral auxiliary groups are also very efficient for the asymmetric desymmetrization of sigma-symmetric diols via diastereoselective acetal fission. In addition, it was revealed that an aryl sulfide group on the cyclopropyl ring triggers single electron transfer reactions via cation radical species, resulting in the following reactions: 1) tandem oxidative ring cleavage-cyclization reactions and 2) intramolecular [3 + 2] cycloaddition reactions. These reactions have been applied to the syntheses of natural products.