Stereospecific Asymmetric N-Heterocyclic Carbene (NHC)-Catalyzed Redox Synthesis of Trifluoromethyl Dihydropyranones and Mechanistic Insights
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- 作者：Alyn T. Davies ; James E. Taylor ; James Douglas ; Christopher J. Collett ; Louis C. Morrill ; Charlene Fallan ; Alexandra M. Z. Slawin ; Gwydion Churchill ; Andrew D. Smith
- 刊名：Journal of Organic Chemistry
- 出版年：2013
- 出版时间：September 20, 2013
- 年：2013
- 卷：78
- 期：18
- 页码：9243-9257
- 全文大小：661K
- 年卷期：v.78,no.18(September 20, 2013)
- ISSN：1520-6904
文摘
N-Heterocyclic carbene (NHC)-catalyzed redox asymmetric hetero-Diels鈥揂lder reactions of 伪-aroyloxyaldehydes with 尾-trifluoromethyl enones generates synthetically useful dihydropyranones containing a stereogenic trifluoromethyl substituent in good yields (up to 81%) and excellent diastereoselectivity and enantioselectivity (up to >95:5 dr and >99% ee). The process is stereospecific, with use of either (E)- or (Z)-尾-trifluoromethyl enones forming syn- or anti-dihydropyranone products, respectively. Mechanistic studies through in situ kinetic analysis of the reaction reveal key differences in reactivity between chiral NHC precursor 1 and an achiral NHC precursor.