Development of Synthetic Radical Reactions of Cyclic Compounds based on Characteristics of Silicon.

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1.1-Allyloxy-2-bromo-1-phenylsilacyclopentane was synthesized by a ring-enlargement reaction of 1-allyloxy-1-phenylsilacyclobutane with LiCHBr_2. The treatment of 1-allyloxy-2-bromo-1-phenylsilacyclopentane with n-Bu_3SnH in the presence of a catalytic amount of Et_3B provided 2-oxa-1-silabicyclo [3.3.0] octane, which was converted into 1,3,6-triol by an oxidative cleavage of silicon-carbon bonds with H_2O_2. An intermolecular radical addition of 2-iodosilacyclopentane to acetylenic compounds afforded the corresponding iodoalkenes.2.Treatment of ethyl benzoate or isopropyl formate with tert-butyldimethylsilyldibromomethyllithium gave alkyl silyl mixed acetal via 1,3-rearrangement of silyl group from carbon to oxygen. The reaction of the mixed acetals with allylsilane in the presence of Lewis acid afforded allylated ethers.3.Treatment of 2-halo-2-trimethysilyloxirane with metal salts such as ZnCl_2, ZnBr_2, NaI,and AgBF_4 gave the corresponding alpha-haloacylsilanes in good yields. An addition of triethylborane to haloacylsilane provided boron enolate which reacted with aldehydes to give aldol type adducts with high stereoselectivity.