A Practical Solution to Stereodefined Tetrasubstituted Olefins

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• 作者：Jianxin Dai ; Minyan Wang ; Guobi Chai ; Chunling Fu ; Shengming Ma
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：March 2, 2016
• 年：2016
• 卷：138
• 期：8
• 页码：2532-2535
• 全文大小：323K
• ISSN：1520-5126

文摘

Olefins, compounds with a carbon–carbon double bond, are of fundamental importance, and stereodefined construction of tetrasubstituted carbon–carbon double bond is a significant challenge. Here we show a unique and practical method for the preparation of stereodefined, fully substituted olefins via conjugate addition of organozinc reagents to readily available 2,3-allenals. Through mechanistic studies, it is confirmed that the geometry of the newly formed double bond is controlled by unique regiospecific oxygen-protonation of the enolate intermediates, generating 1,3-alkadienols. Such alkadienols would undergo a concerted 1,5-H-transfer reaction via a six-membered transition state to ensure the configuration of the carbon–carbon double bond in the final products. Using the readily available organozinc reagents and 2,3-allenals provides a very rapid access to a wide range of tetrasubstituted olefins with defined stereochemistry, bearing an extremely versatile aldehyde functionality.