Efficient and Practical Ag-Catalyzed Cycloadditions between Arylimines and the Danishefsky Diene
作者:Nathan S. Josephsohn、Marc L. Snapper、Amir H. Hoveyda
DOI:10.1021/ja030033p
日期:2003.4.1
An efficient Ag-catalyzed method for asymmetric addition of the Danishefsky diene to various aryl imines to afford cycloadducts in > or =89% ee and > or =85% isolated yield is reported. Reactions are effected with 0.1-1 mol % catalyst (4 degrees C), and the chiral ligand is readily prepared from commercially available materials, including the inexpensive i-Leu. These catalytic asymmetric cycloadditions can be carried out without the use of solvent or with undistilled THF in air. A first generation supported chiral catalyst that effectively promotes the cycloaddition reaction and can be recycled (five cycles) is described.
作者:Václav Jurčík、Kenzo Arai、Matthew M. Salter、Yasuhiro Yamashita、Shū Kobayashi
DOI:10.1002/adsc.200700615
日期:2008.3.25
Niobium-based chiral Lewis acid was found to be highly effective catalyst for aza-Diels–Alderreactions of imines with Danishefsky‘s dienes. The reactions proceed in high yield with high enantioselectivity for both aromatic and aliphatic imines. The developed methodology was applied to total synthesis of (+)-anabasine.