The silylium (Me₂EtSi⁺) catalyzed condensative cyclization of persilylated linear or cyclic sugars has been examined as a selective route to monoanhydro sugars. The silylium could be generated either from the sequential addition of [Ph₃C⁺][B(C₆F₅)₄^–] and R₃SiH (where Si is the silyl protecting group (either trimethylsilyl (TMS) or Me₂EtSi)) or by abstracting a primary silyl ether with the Lewis acid catalyst B(C₆F₅)₃. This latter method forms [R₃SiO–B(C₆F₅)₃^–] and a silylium-coordinated product. This reactive pair eventually converts to L–B(C₆F₅)₃ (L = THF-like product) and the condensate (R₃Si)₂O. The L–B(C₆F₅)₃ is a much less potent form of the catalyst. Under the silylium catalyzed conditions, linear sugars (C_nO_n, n = 5, 6) and biomass-derived tetraols (C₆O₄) afford a diverse collection of diastereomerically pure THFs in good to excellent yields (50–99%). Persilylated 1,6-anhydrogalactofuranose is provided in a single step from persilylated galactose (85% isolation yield after silyl deprotection) and the corresponding 1,6-anhydroglucoses are available from mono-, di-, tri, and oligo-gluco-saccharides.

中文翻译：

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硅（R ₃ Si ⁺）催化缩合环化合成脱水糖。

已经研究了甲硅烷基（Me ₂ EtSi ⁺）催化的全硅烷基化直链或环状糖的缩合环化反应，作为制备单脱水糖的选择性途径。可以通过依次添加[Ph ₃ C ⁺ ] [B（C ₆ F ₅）₄ ^– ]和R ₃ SiH（其中Si是甲硅烷基保护基（三甲基甲硅烷基（TMS）或Me ₂ EtSi ））或通过路易斯酸催化剂B（C ₆ F ₅）₃提取伯甲硅烷基醚。后一种方法形成[R ₃ SiO–B（C ₆ F₅）₃ ^– ]和甲硅烷基配位产物。该反应性对最终转换到L-B（C ₆ ˚F ₅）₃（L = THF状产物）和冷凝物（R ₃ Si）的₂ O的L-B（C ₆ ˚F ₅）₃是一个更催化剂的有效形式。在甲硅烷基催化的条件下，直链糖（C _n O _n，n = 5，6）和生物质衍生的四醇（C ₆ O ₄）以良好或优异的收率（50–99％）提供了各种非对映体纯的THF。只需一步即可从全硅烷基化的半乳糖中获得全硅烷基化的1，6-脱水半乳糖呋喃糖（甲硅烷基脱保护后的分离产率为85％），相应的1，6-脱水葡萄糖可从单糖，二糖，三糖和寡糖获得。