Development of Novel Selective Reactions Using Neighboring Group Effect of a Sulfenyl Group.

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This reserch project is concerned with the development of selective reactions applying the neighboring group effect of a sulfenyl group. First, we tried remote asymmetric induction by the neighboring group participation of a sulfenyl group toward the delta-position. As result, 2-[1-(mesitylthio) alkyl]benzaldehydes and their dimethyl acetals reacted with silylated carbon nucleophiles under Lewis acidic conditions to give the corresponding aldol adducts with high diastereoselectivity, and in some cases, the product was obtained as almost a single diastereomer.Next, the reaction of episulfonium ions generated via neighboring group participation was investigated. Episulfonium ions with an appropriate intramolecular nucleophilic olefin part gave cyclized products, 5-or 6-membered ring carbocycles, with high diastereoselectivity. This reaction is useful for the synthesis of terpenes and steroids.The reaction of glycidyl sulfides, which have a sulfenyl group, participating only at C-2, with trialkylaluminum showed definite C-2 selectivity for uncleophilic ring-opening and gave C-2 alkylated products exclusively with the complete retention of the configuration at the C-2. Upon applying the present reaction, an aggregation pheromone of African Palm Weevil was stereoselectively synthesized in short steps.Amino groups are also known to participate to the neighboring cationic center. Then, similar reactions were carried out with glycidyl amines ; alkylation, alkynylation, and hydride reduction occurred regioselectively at the C-2 position with the retention of the configuration at the C-2.