The presence of water improves reductive openings of benzylidene acetals with trimethylaminoborane and aluminium chloride
作者:Andrei A. Sherman、Yuri V. Mironov、Olga N. Yudina、Nikolay E. Nifantiev
DOI:10.1016/s0008-6215(03)00015-6
日期:2003.4
efficient for the reductive openings of the cyclic benzylidene acetals with Me(3)N x BH(3) in tetrahydrofurane than the AlCl(3) alone. Under proposed conditions, the dioxane-type 4,6-O-bezylidene acetals of hexopyranosides give regioselectively the corresponding 4-hydroxy,6-O-benzyl derivatives in excellent yields. Reductive openings of the dioxolane-type 3,4-O-benzylidene acetals of galactopyranoside are
由无水AlCl(3)和H(2)O以3:1比例原位形成的酸性试剂比四氢呋喃中Me(3)N x BH(3)还原环亚苄基乙缩醛的效率高得多单独的AlCl(3)。在提出的条件下,己吡喃糖苷的二恶烷型4,6-O-亚苄基乙缩醛以优异的产率选择性地给出相应的4-羟基,6-O-苄基衍生物。半乳糖吡喃糖苷的二氧戊环型3,4-O-亚苄基乙缩醛的还原开口也非常有效且具有区域选择性,可生成3-O-苄基衍生物(来自3,4-O-外亚苄基乙缩醛)或4-O-苄基衍生物(来自3,4-O-内-亚苄基缩醛)取决于缩醛碳原子的构型。