Organolanthanide-Catalyzed Hydroamination/Cyclization. Efficient Allene-Based Transformations for the Syntheses of Naturally Occurring Alkaloids
作者:Victor M. Arredondo、Shun Tian、Frank E. McDonald、Tobin J. Marks
DOI:10.1021/ja984305d
日期:1999.4.1
organolanthanide complexes efficiently mediate highly diastereoselective intramolecular hydroamination/cyclization (IHC) reactions under mild conditions. The turnover-limiting step in these catalytic cycles is proposed to be intramolecular insertion into the Ln−N bond of the proximal allenic CC linkage, followed by rapid protonolytic cleavage of the resulting Ln−C bond. The rate and selectivity of the insertion
描述了吡咯烷生物碱 (+)-197B (1) 和吡咯里西啶生物碱 (+)-xenovenine (2) 的全合成。该策略涉及氨基丙二烯 (5S,8S)-5-amino-trideca-8,9-diene (3) 和氨基丙二烯-烯烃 (5S)-5-amino-pentadeca-1,8 的对映选择性合成, 9-三烯 (4),然后在有机镧系元素预催化剂 Cp'2LnCH(TMS)2 和 Me2SiCp''(tBuN)LnN(TMS)2 (Cp' = η5-Me5C5; Cp' ' = η5-Me4C5;Ln = 镧系元素;TMS = Me3Si)。这些反应性有机镧系化合物在温和条件下有效地介导高度非对映选择性的分子内加氢胺化/环化 (IHC) 反应。这些催化循环中的转换限制步骤被认为是分子内插入到近端丙二烯 CC 键的 Ln-N 键中,随后是所得 Ln-C 键的快速质子裂解。插入过程的速率和选择性对底物的空间要求高度敏感。