A Combined DFT and NMR Investigation of the Zinc Organometallic Intermediate Proposed in the Syn-Selective Tandem Chain Extension鈥揂ldol Reaction of 尾-Keto Esters
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- 作者：Karelle S. Aiken ; Wilhelm A. Eger ; Craig M. Williams ; Carley M. Spencer ; Charles K. Zercher
- 刊名：The Journal of Organic Chemistry
- 出版年：2012
- 出版时间：July 20, 2012
- 年：2012
- 卷：77
- 期：14
- 页码：5942-5955
- 全文大小：588K
- 年卷期：v.77,no.14(July 20, 2012)
- ISSN：1520-6904
文摘
The tandem chain extension鈥揳ldol (TCA) reaction of 尾-keto esters provides an 伪-substituted 纬-keto ester with an average syn:anti selectivity of 10:1. It is proposed that the reaction proceeds via a carbon鈥搝inc bound organometallic intermediate potentially bearing mechanistic similarity to the Reformatsky reaction. Evidence, derived from control Reformatsky reactions and a study of the structure of the TCA intermediate utilizing DFT methods and NMR spectroscopy, suggests the 纬-keto group of the TCA intermediate plays a significant role in diastereoselectivity observed in this reaction. Such coordination effects have design implications for future zinc mediated reactions.