Stereoselectivity of 6-Exo Cyclization of α-Carbamoyl Radicals

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• 作者：Liyan Song ; Xinqiang Fang ; Zijia Wang ; Kun Liu ; Chaozhong Li
• 刊名：Journal of Organic Chemistry
• 出版年：2016
• 出版时间：March 18, 2016
• 年：2016
• 卷：81
• 期：6
• 页码：2442-2450
• 全文大小：410K
• ISSN：1520-6904

文摘

The stereoselectivity in the 6-exo cyclization of α-carbamoyl radicals was investigated experimentally and theoretically. The BEt₃/O₂-initiated iodine-atom-transfer radical cyclization reactions of substituted N-(but-3-en-1-yl)-N-(tert-butyl)-2-iodoalkanamides were carried out, which led to the predominant formations of 3,4-cis, 4,5-trans, or 4,6-trans substituted δ-lactams. Density functional calculations at the B3LYP/6-31G* level revealed that the 6-exo radical cyclization proceeds via boat-conformational transition states. Furthermore, a mechanistic insight into the stereoselectivity was provided and the calculation results were in excellent agreement with the experimental observations.