Tandem Polar/Radical Crossover Sequences for the Formation of Fused and Bridged Bicyclic Nitrogen Heterocycles Involving Radical Ionic Chain Reactions, and Alkene Radical Cation Intermediates, Perform
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- 作者：David Crich ; Krishnakumar Ranganathan ; Santhosh Neelamkavil ; and Xianhai Huang
- 刊名：Journal of the American Chemical Society
- 出版年：2003
- 出版时间：July 2, 2003
- 年：2003
- 卷：125
- 期：26
- 页码：7942 - 7947
- 全文大小：200K
- 年卷期：v.125,no.26(July 2, 2003)
- ISSN：1520-5126
文摘
It is demonstrated that phosphorylated forms of 
-nitro alcohols provide an excellent means ofentry into -(phosphatoxy)alkyl radicals on exposure to tributyltin hydride and AIBN in benzene at reflux.These radicals then undergo heterolytic cleavage of the phosphate group to yield alkene radical cation/phosphate anion contact ion pairs which are trapped intramolecularly in a tandem polar/radical crossoversequence involving radical ionic chain reactions by allylic and propargylic amines. The substitution patternof the alkene radical cation dictates the cyclization mode, and this may be engineered to form fused ringsystems by an initial exo-mode nucleophilic cyclization or bridged bicyclic systems when the nucleophilicattack takes place in the endo-mode.
-nitro alcohols provide an excellent means ofentry into -(phosphatoxy)alkyl radicals on exposure to tributyltin hydride and AIBN in benzene at reflux.These radicals then undergo heterolytic cleavage of the phosphate group to yield alkene radical cation/phosphate anion contact ion pairs which are trapped intramolecularly in a tandem polar/radical crossoversequence involving radical ionic chain reactions by allylic and propargylic amines. The substitution patternof the alkene radical cation dictates the cyclization mode, and this may be engineered to form fused ringsystems by an initial exo-mode nucleophilic cyclization or bridged bicyclic systems when the nucleophilicattack takes place in the endo-mode.