Diastereoselective Friedel−Crafts Alkylation of Indoles with Chiral α-Phenyl Benzylic Cations. Asymmetric Synthesis of Anti-1,1,2-Triarylalkanes
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- 作者：John Y. L. Chung ; Danny Mancheno ; Peter G. Dormer ; Narayan Variankaval ; Richard G. Ball ; Nancy N. Tsou
- 刊名：Organic Letters
- 出版年：2008
- 出版时间：July 17, 2008
- 年：2008
- 卷：10
- 期：14
- 页码：3037 - 3040
- 全文大小：220K
- 年卷期：v.10,no.14(July 17, 2008)
- ISSN：1523-7052
文摘
The reactions of chiral benzyl carbocations bearing α-phenyl substituents with N-sulfonylated indoles afford 1,1,2-triarylalkanes with anti-selectivities. This outcome is a reversal of facial diastereoselectivity relative to Bach’s α-alkyl-bearing benzyl cations. The reactions are promoted by either a Brønsted acid (TFA) or Lewis acid (BF3·OEt2), offering differential diastereoselectivities and reactivities. The electronic properties of both reacting partners strongly influence the reaction rates and the product diastereoselectivities and appear to operate under kinetic control. This chemistry provides an efficient access to sterically congested tetrasubstituted ethanes.