Danheiser成环反应

Danheiser成环反应（Danheiser annulation），又称Danheiser TMS-环戊烯成环反应（Danheiser TMS-Cyclopentene annulation）[1][2][3][4][5][6]

α,β-不饱和酮与三烃基硅基（如三甲基硅基、三异丙基硅基）丙二烯在路易斯酸存在下发生反应，生成三烃基硅基环戊烯。


Danheiser成环反应
Danheiser成环反应


α,β-不饱和醛太活泼，反应会生成大量副产物；而α,β-不饱和酯则太不活泼，反应速度慢，产率低；环状和开链的酮都可以用作反应底物。这个反应是同面反应，具有高度立体选择性。

反应机理

路易斯酸四氯化钛首先活化α,β-不饱和酮的羰基，得到烯丙位碳正离子中间体，然后被三烃基硅基丙二烯进攻得到乙烯基碳正离子中间体A；临近的硅原子可以稳定乙烯基碳正离子（中间体B），或者可以发生1,2-重排反应得到中间体C；接下来钛烯醇化物进攻中间体C的碳正离子就可以得到环戊烯。有时中间体A也会生成副产物D–F。

Danheiser成环反应机理
Danheiser成环反应机理

参见

参考资料
  1. "TMS-Cyclopentene Annulation: A Regiocontrolled Approach to the Synthesis of Five-Membered Rings", R. L. Danheiser, D. J. Carini, and A. Basak, J. Am. Chem. Soc. 1981, 103, 1604.
  2. "Scope and Stereochemical Course of the (Trimethylsilyl)cyclopentene Annulation", R. L. Danheiser, D. J. Carini, D. M. Fink, and A. Basak, Tetrahedron 1983, 39, 935.
  3. "The Reaction of Allenysilanes with α,β-Unsaturated Acylsilanes: New Annulation Approaches to Five and Six-Membered Carbocyclic Compounds", R. L. Danheiser and D. M. Fink, Tetrahedron Lett. 1985, 26, 2513.
  4. "A General [3+2] Annulation: cis-4-Exo-isopropenyl-1,9-dimethyl-8-(trimethylsilyl)bicyclo-[4.3.0]non-8-en-2-one", R. L. Danheiser, D. M. Fink, and Y. -M. Tsai, Organic Syntheses 1988, 66, 8.
  5. "Organic Syntheses Based on Name Reactions", By Alfred Hassner and C. Stumer, Elsevier, p. 78, 2002
  6. "Name Reactions: A Collection of Detailed Reaction Mechanisms", By Jie Jack Li, Springer, p. 102, 2003
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