光学活性アリルシランの合成と反応 (有機合成指向有機金属化学<特集>)
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概要
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Optically active allylsilanes (up to 95 %ee) which contain an asymmetric carbon atom directly bonded to the silicon atom have been prepared by asymmetric cross-coupling of α- (trimethylsilyl) - benzyl or 1- (trialkylsilyl) ethyl Grignard reagent with alkenyl bromides in the presence of a chiral ferrocenylphoshine-palladium complex ((<I>R</I>) - (<I>S</I>) -PPFA-Pd) as a catalyst. Palladium-catalyzed asymmetric hydrosilylation of 1, 3-dienes also gave optically active allylsilanes. Reaction of the allylsilanes with various electrophiles (<I>t</I>-BuCl/TiCl<SUB>4</SUB>, MeCOCl/AlCl<SUB>3</SUB>, trioxane/TiCl<SUB>4</SUB>, CF<SUB>3</SUB>COOD, MCPBA, and palladium (II)) was found to proceed with anti stereochemistry, the electrophiles attacking the double bond selectively anti with respect to the leaving trimethylsilyl group. Reaction of the optically active allylsilanes with aldehydes in the presence of titanium chloride gave optically active erythro homoallylic alcohols with over 90 % enantio- and diastereoselectivities.
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